Reduction of Frequency offset Using Joint Clock for OFDM Based Cellular Syste...IJRST Journal
This project addresses the problem of clock synchronization between a base station (BS) and a mobile station (MS). A conventional technique for clock synchronization is that the MS clock is derived from the downlink signal originated from a base station. In cellular systems, a base station and mobile stations need to be synchronized before data exchange. Since the base station clock reference is more accurate, a mobile station typically derives its clock reference from the base station. But the carrier frequency offset due to Doppler shift may have harmful effects on the local clock derivation. This project proposes a joint clock and frequency synchronization technique between a base station and a mobile station, which is effective even with Doppler shift. We derive the joint estimation algorithm by analyzing the phase and the amplitude distortion caused by the sampling frequency offset and the carrier frequency offset. Simulation results showing the effectiveness of the proposed algorithm will also be presented.
In this paper, the performances of adaptive noise cancelling system employing Least Mean Square (LMS) algorithm are studied considering both white Gaussian noise (Case 1) and colored noise (Case 2)
situations. Performance is analysed with varying number of iterations, Signal to Noise Ratio (SNR) and tap size with considering Mean Square Error (MSE) as the performance measurement criteria. Results show that the noise reduction is better as well as convergence speed is faster for Case 2 as compared with Case 1. It is also observed that MSE decreases with increasing SNR with relatively faster decrease of MSE in Case 2 as compared with Case 1, and on average MSE increases linearly with increasing number of filter
coefficients for both type of noise situations. All the experiments have been done using computer
simulations implemented on MATLAB platform.
Abstract
Terahertz sub-surface imaging offers an effective solution for surface and 3D imaging because of minimal
sample preparation requirements and its ability to “see” below the surface. Another important property is the ability
to inspect on a layer-by layer basis via a non-contact route, non-destructive route. Terahertz 3D imager designed
at Applied Research and Photonics (Harrisburg, PA) has been used to demonstrate reconstructive imaging with a
resolution of less than a nanometer. Gridding with inverse distance to power equations has been described for 3D
image formation. A continuous wave terahertz source derived from dendrimer dipole excitation has been used for
reflection mode scanning in the three orthogonal directions. Both 2D and 3D images are generated for the analysis
of silver iodide quantum dots’ size parameter. Layer by layer image analysis has been outlined. Graphical analysis
was used for particle size and layer thickness determinations. The demonstrated results of quantum dot particle
size checks well with those determined by TEM micrograph and powder X-ray diffraction analysis. The reported
non-contact measurement system is expected to be useful for characterizing 2D and 3D naomaterials as well as for process development and/or quality inspection at the production line.
This presentation gives a overview about the microvolume UV/VIS spectroscopy. Instrumentation , working ,merits, demerits, cleaning of the sample platform. mainly explains about the measurement of sample using nano or micro volume samples.
Derivative spectroscopy and applications of uv vis spectroscopyNayeemaKhowser
The main obejectives of derivative spectroscopy
Derivative spectra and its measurements
Orders of derivative spectra
Noise to signal ratio
Instrumentation of derivative spectroscopy
Advantages and disadvantages of derivative spectroscopy
Applications of Derivative and UV-Vis spectroscopy
Reduction of Frequency offset Using Joint Clock for OFDM Based Cellular Syste...IJRST Journal
This project addresses the problem of clock synchronization between a base station (BS) and a mobile station (MS). A conventional technique for clock synchronization is that the MS clock is derived from the downlink signal originated from a base station. In cellular systems, a base station and mobile stations need to be synchronized before data exchange. Since the base station clock reference is more accurate, a mobile station typically derives its clock reference from the base station. But the carrier frequency offset due to Doppler shift may have harmful effects on the local clock derivation. This project proposes a joint clock and frequency synchronization technique between a base station and a mobile station, which is effective even with Doppler shift. We derive the joint estimation algorithm by analyzing the phase and the amplitude distortion caused by the sampling frequency offset and the carrier frequency offset. Simulation results showing the effectiveness of the proposed algorithm will also be presented.
In this paper, the performances of adaptive noise cancelling system employing Least Mean Square (LMS) algorithm are studied considering both white Gaussian noise (Case 1) and colored noise (Case 2)
situations. Performance is analysed with varying number of iterations, Signal to Noise Ratio (SNR) and tap size with considering Mean Square Error (MSE) as the performance measurement criteria. Results show that the noise reduction is better as well as convergence speed is faster for Case 2 as compared with Case 1. It is also observed that MSE decreases with increasing SNR with relatively faster decrease of MSE in Case 2 as compared with Case 1, and on average MSE increases linearly with increasing number of filter
coefficients for both type of noise situations. All the experiments have been done using computer
simulations implemented on MATLAB platform.
Abstract
Terahertz sub-surface imaging offers an effective solution for surface and 3D imaging because of minimal
sample preparation requirements and its ability to “see” below the surface. Another important property is the ability
to inspect on a layer-by layer basis via a non-contact route, non-destructive route. Terahertz 3D imager designed
at Applied Research and Photonics (Harrisburg, PA) has been used to demonstrate reconstructive imaging with a
resolution of less than a nanometer. Gridding with inverse distance to power equations has been described for 3D
image formation. A continuous wave terahertz source derived from dendrimer dipole excitation has been used for
reflection mode scanning in the three orthogonal directions. Both 2D and 3D images are generated for the analysis
of silver iodide quantum dots’ size parameter. Layer by layer image analysis has been outlined. Graphical analysis
was used for particle size and layer thickness determinations. The demonstrated results of quantum dot particle
size checks well with those determined by TEM micrograph and powder X-ray diffraction analysis. The reported
non-contact measurement system is expected to be useful for characterizing 2D and 3D naomaterials as well as for process development and/or quality inspection at the production line.
This presentation gives a overview about the microvolume UV/VIS spectroscopy. Instrumentation , working ,merits, demerits, cleaning of the sample platform. mainly explains about the measurement of sample using nano or micro volume samples.
Derivative spectroscopy and applications of uv vis spectroscopyNayeemaKhowser
The main obejectives of derivative spectroscopy
Derivative spectra and its measurements
Orders of derivative spectra
Noise to signal ratio
Instrumentation of derivative spectroscopy
Advantages and disadvantages of derivative spectroscopy
Applications of Derivative and UV-Vis spectroscopy
Photoacoustic technology for biological tissues characterizationjournalBEEI
The existing photoacoustics (PA) imaging systems showed mixed performance in imaging characteristic and signal-to-noise ratio (SNR). This work presents the use of an in-house assembled PA system using a modulating laser beam of wavelength 633 nm for two-dimensional (2D) characterization of biological tissues. The differentiation of the tissues in this work is based on differences in their light absorption, wherein the produced photoacoustic signal detected by a transducer was translated into phase value that corresponds to the peak amplitude of optical absorption of tissue namely fat, liver and muscle. This work found fat tissue to produce the strongest PA signal with mean ± standard deviation (SD) phase value = 2.09 ± 0.31 while muscle produced the least signal with phase value = 1.03 ± 0.17. This work discovered the presence of stripes pattern in the reconstructed images of fat and muscle resulted from their structural properties. In addition, a comparison is made in an attempt to better assess the performance of the developed system with the related ones. This work concluded that the developed system may use as an alternative, noninvasive and label-free visualization method for characterization of biological tissues in the future.
Design and Implementation of All Optical Tunable Delay by the Combination of ...ijtsrd
In this paper we have designed and implemented an all optical tunable delay element using the combination of wavelength conversion and fiber dispersion. We present wavelength conversion method that show with FWM. The characteristics of the proposed all optical based techniques for tunable delay element are discussed theoretically and demonstrated experimentally. This element operates near 1550nm and generates delay time range is 2430ps. Pyae Phyo Swe | Tin Tin Ohn "Design and Implementation of All-Optical Tunable Delay by the Combination of Wavelength Conversion and Fiber Dispersion" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd27874.pdfPaper URL: https://www.ijtsrd.com/engineering/electrical-engineering/27874/design-and-implementation-of-all-optical-tunable-delay-by-the-combination-of-wavelength-conversion-and-fiber-dispersion/pyae-phyo-swe
NOISE REMOVAL TECHNIQUES FOR MICROWAVE REMOTE SENSING RADAR DATA AND ITS EVAL...cscpconf
Microwave Remote Sensing data acquired by a RADAR sensor such as SAR(Synthetic Aperture Radar) is affected by a peculiar kind of noise called speckle. This noise not only renders the
data ineffective for classification, texture analysis, segmentation etc. which are used for image analysis purposes, but also degrades the overall contrast and radiometric quality of the image. Here we discuss the various noise removal techniques which have been widely used by scientists all over the world. Different filtering methods have their pros and cons, and no single method can give the most satisfactory result. In order to circumvent those issues, better and better methods are being attempted. One of the recent methods is that based on Wavelet technique. This paper discusses the denoising techniques based on Wavelets and the results from some of those methods. The relative merits and demerits of the filters and their evaluation is also done.
Noise removal techniques for microwave remote sensing radar data and its eval...csandit
Microwave Remote Sensing data acquired by a RADAR sensor such as SAR(Synthetic Aperture
Radar) is affected by a peculiar kind of noise called speckle. This noise not only renders the
data ineffective for classification, texture analysis, segmentation etc. which are used for image
analysis purposes, but also degrades the overall contrast and radiometric quality of the image.
Here we discuss the various noise removal techniques which have been widely used by scientists
all over the world. Different filtering methods have their pros and cons, and no single method
can give the most satisfactory result. In order to circumvent those issues, better and better
methods are being attempted. One of the recent methods is that based on Wavelet technique.
This paper discusses the denoising techniques based on Wavelets and the results from some of
those methods. The relative merits and demerits of the filters and their evaluation is also done.
Presented by Yonas Asmare, ILRI, at the Workshop on Identifying Investment Opportunities for Livestock Feed Resources Development in the Eastern Africa Sub-Region, ILRI Addis, 13–15 December 2017
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
El Ejército; la palabra y la espada
EMB. Enrique Campos Menéndez [Página 5]
El Cabildo de Santiago y los apercibimientos para la Guerra de Arauco
Dn. Javier González Echeñique [Página 12]
El General Francisco Javier Díaz Valderrama
MGL. Manuel Barros Recabarren [Página 22]
Ramón Cañas Montalva, un General visionario
Gral.(C) René Peri Fargerstrom. [Página 33]
El perfil del soldado
GDB. Jorge Court Moock [Página 37]
El Presidente Ríos y el Ejército
Sr. Alejandro Pizarro Soto [Página 44]
Notas sobre Concepción (Perú) a propósito del Combate
Msñor. Joaquín Matte Varas [Página 58]
Visión político-militar del Gral. Carrera y su tiempo
BGR. Juan de Dios Barriga Muñoz [Página 62]
Las fortificaciones de la Defensa de la Costa del Reino de Chile
Dn. Isidoro Vásquez de Acuña [Página 90]
El Servicio de Intendencia
CRL. Rafael Pizarro Barahona [Página 111]
Photoacoustic technology for biological tissues characterizationjournalBEEI
The existing photoacoustics (PA) imaging systems showed mixed performance in imaging characteristic and signal-to-noise ratio (SNR). This work presents the use of an in-house assembled PA system using a modulating laser beam of wavelength 633 nm for two-dimensional (2D) characterization of biological tissues. The differentiation of the tissues in this work is based on differences in their light absorption, wherein the produced photoacoustic signal detected by a transducer was translated into phase value that corresponds to the peak amplitude of optical absorption of tissue namely fat, liver and muscle. This work found fat tissue to produce the strongest PA signal with mean ± standard deviation (SD) phase value = 2.09 ± 0.31 while muscle produced the least signal with phase value = 1.03 ± 0.17. This work discovered the presence of stripes pattern in the reconstructed images of fat and muscle resulted from their structural properties. In addition, a comparison is made in an attempt to better assess the performance of the developed system with the related ones. This work concluded that the developed system may use as an alternative, noninvasive and label-free visualization method for characterization of biological tissues in the future.
Design and Implementation of All Optical Tunable Delay by the Combination of ...ijtsrd
In this paper we have designed and implemented an all optical tunable delay element using the combination of wavelength conversion and fiber dispersion. We present wavelength conversion method that show with FWM. The characteristics of the proposed all optical based techniques for tunable delay element are discussed theoretically and demonstrated experimentally. This element operates near 1550nm and generates delay time range is 2430ps. Pyae Phyo Swe | Tin Tin Ohn "Design and Implementation of All-Optical Tunable Delay by the Combination of Wavelength Conversion and Fiber Dispersion" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd27874.pdfPaper URL: https://www.ijtsrd.com/engineering/electrical-engineering/27874/design-and-implementation-of-all-optical-tunable-delay-by-the-combination-of-wavelength-conversion-and-fiber-dispersion/pyae-phyo-swe
NOISE REMOVAL TECHNIQUES FOR MICROWAVE REMOTE SENSING RADAR DATA AND ITS EVAL...cscpconf
Microwave Remote Sensing data acquired by a RADAR sensor such as SAR(Synthetic Aperture Radar) is affected by a peculiar kind of noise called speckle. This noise not only renders the
data ineffective for classification, texture analysis, segmentation etc. which are used for image analysis purposes, but also degrades the overall contrast and radiometric quality of the image. Here we discuss the various noise removal techniques which have been widely used by scientists all over the world. Different filtering methods have their pros and cons, and no single method can give the most satisfactory result. In order to circumvent those issues, better and better methods are being attempted. One of the recent methods is that based on Wavelet technique. This paper discusses the denoising techniques based on Wavelets and the results from some of those methods. The relative merits and demerits of the filters and their evaluation is also done.
Noise removal techniques for microwave remote sensing radar data and its eval...csandit
Microwave Remote Sensing data acquired by a RADAR sensor such as SAR(Synthetic Aperture
Radar) is affected by a peculiar kind of noise called speckle. This noise not only renders the
data ineffective for classification, texture analysis, segmentation etc. which are used for image
analysis purposes, but also degrades the overall contrast and radiometric quality of the image.
Here we discuss the various noise removal techniques which have been widely used by scientists
all over the world. Different filtering methods have their pros and cons, and no single method
can give the most satisfactory result. In order to circumvent those issues, better and better
methods are being attempted. One of the recent methods is that based on Wavelet technique.
This paper discusses the denoising techniques based on Wavelets and the results from some of
those methods. The relative merits and demerits of the filters and their evaluation is also done.
Presented by Yonas Asmare, ILRI, at the Workshop on Identifying Investment Opportunities for Livestock Feed Resources Development in the Eastern Africa Sub-Region, ILRI Addis, 13–15 December 2017
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
El Ejército; la palabra y la espada
EMB. Enrique Campos Menéndez [Página 5]
El Cabildo de Santiago y los apercibimientos para la Guerra de Arauco
Dn. Javier González Echeñique [Página 12]
El General Francisco Javier Díaz Valderrama
MGL. Manuel Barros Recabarren [Página 22]
Ramón Cañas Montalva, un General visionario
Gral.(C) René Peri Fargerstrom. [Página 33]
El perfil del soldado
GDB. Jorge Court Moock [Página 37]
El Presidente Ríos y el Ejército
Sr. Alejandro Pizarro Soto [Página 44]
Notas sobre Concepción (Perú) a propósito del Combate
Msñor. Joaquín Matte Varas [Página 58]
Visión político-militar del Gral. Carrera y su tiempo
BGR. Juan de Dios Barriga Muñoz [Página 62]
Las fortificaciones de la Defensa de la Costa del Reino de Chile
Dn. Isidoro Vásquez de Acuña [Página 90]
El Servicio de Intendencia
CRL. Rafael Pizarro Barahona [Página 111]
This work measured experimentally, and calculated theoretically using the existing Friis Fomula, the Attenuation of 92.1 MHz (Ajilete FM) Signals along Gambari(Lat 8o291N; Long 4o291) – Oyo-Road(Lat 7o501N; Long 3o561E), Oyo State Nigeria. The two results were compared. The experimental Measurement campaign was achieved by using an appropriate design dipole antenna, well matched to (810 GSP Analyser), to determine the attenuation. The calculated results correlated very well with the measurements (Correlation Coefficient Value R2=1). But, they are not accurate when compared with the measurements (Chi- square values equal zero for received power, measured attenuation). The inaccuracies of the results for the existing formula with the measurements may be due to hills, valleys, trees and bends along the links. Hence the accuracy of the model used can only be effectively confirmed in areas free of the obstacles mentioned above. By applying LEAST SQUARE fit method to the experimental measured data, the analytical models, P(x)= 0.0154x2-1.3575x-38.7620 and A(x)= 0132x2 -1.2464x-104.8487, in the form of polynomial of degree two, were obtained respectively for received power and measured attenuation. The analytical model obtained is therefore recommended for use in an area characterised with bends, valleys, hills and trees, since the model has taken into consideration all these factors. In addition, repeater stations should be installed for effective transmission and for wider coverage in forested and valley areas. Moreover, transmitter of higher value like ten kilowatts should be employed for long distance transmission
A mitigation of channel crosstalk effect in dispersion shifted fiber based on...IJECEIAES
In fiber optics the Four Wave Mixing (FWM) has the harmful effect of an optical transmission system that can severely limit Wavelength Division Multiplexing (WDM) and reduce the transmission aptness. This work preset the durability of the different modulation format was tested to FWM by using Dispersion Shifted Fiber (DSF). Moreover, the performance of the proposed system is surveyed by changing the fiber length and applying an information rate of 200 Gb/s. The experimental results show that the FWM capacity has decreased significantly by more than 14 dB when applying Return to Zero (RZ) modulation form. In addition, in terms of the propsed system performance in the first channel and with 700 km distance, it was observed that the lower Bit Error Rate (BER) in the normal RZ modulation is equal to 1.3×10 -13 . As well as it is noticeable when applied the Non Return to Zero (NRZ), the Modified Duobinary Return to Zero (MDRZ) and Gaussian modulation, the system performance will be quickly changed and getting worse, where the BERs increased to 1.3×10 consecutively at same channel and for the same parameters. -4 , 1.3×10 -6 and 1.3×10 -2
Available online at [www.ijeete.com]EFFECT OF DISPERSION AND FIBER LENGTH ON ...Ankur Bindal
This paper introduces the non linear optical effect known as four wave mixing (FWM). In wavelength division multiplexing (WDM) systems four wave mixing can strongly affect the transmission performance on an optical link. As a result it is important to investigate the impact of FWM on the design and performance of WDM optical communication systems. The main objective of this paper is to analyze the FWM power for different values of fiber length and dispersion by designing and simulating a model in Optisim. In this paper, we have simulated the FWM design for three waves. The results obtained show that when the optical fiber length and dispersion value is increased FWM effect reduces. This result confirms that the fiber nonlinearities play decisive role in the WDM.
High-Sensitivity HydrophoneBased on Fiber Grating Laser And Acorrugated Diaph...IJRESJOURNAL
ABSTRACT: In this work, we present afiber optic hydrophones based on dual-frequency fiber grating lasers and a corrugated diaphragm. The laser is employed as sensing element and an elastic corrugated diaphragm is used to translate acoustic pressure P intolateral point loadNon the laser cavity. Experimental result shows the fiber laser hydrophone has a working bandwidth over 1 kHz with sub100 μPa/Hz1/2minimum detectable pressure at 1 kHz
Digital signal processing techniques for lti fiber impairment compensationeSAT Journals
Abstract Coherent detection is one of the active research areas for the development of high speed, high spectral efficient optical communication network. Digital signal processing is the important technique for compensating the fiber transmission impairments because of number of advantages such as signal can be amplified, delayed, splitted and manipulated without degrading the signal quality. This paper presents DSP compensation algorithms for linear time invariant (LTI) impairment such as chromatic dispersion (CD) and polarization mode dispersion (PMD) in optical fiber communication. We presented a mathematical framework for compensation of LTI fiber impairments. This paper also focuses the different compensation methods both in time and frequency domain for chromatic dispersion compensation. These DSP techniques confirm that coherent detection with high data rates will become feasible in future for compensating transmission impairments. Keywords: Coherent Detection, Chromatic Dispersion, Polarization Mode Dispersion
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
UNDER WATER NOISE REDUCTION USING WAVELET AND SAVITZKY-GOLAYcsandit
A precise, linear indication of the depth of water in a specific part of water body is what always
required. Presently there are a wide variety of ways to produce a signal that tracks the depth of
water.The Ultrasonic signal is most commonly used for the depth estimation. This signal is
affected by various underwater noises which results in inaccurate depth estimation. The
objective of this paper is to provide noise reduction methods for underwater acoustic signal.In
present work, the signal processing is done on the data collected using TC2122 dual frequency
transducer along with the Navisound 415 echo sounder. There are two signal processing
techniques which are used: The first method is denoising algorithm based on Stationary wavelet
transform (SWT)and second method is Savitzky-Golay filter. The results are evaluated based on
the criteria of peak signal to noise ratio and 3D Surfer plots of the dam reservoir whose depth
estimation has to be done.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Integrated ring resonator system analysis to Optimize the soliton transmissionPremier Publishers
The chaotic signals can be generated within the microring resonator (MRR) system when the Gaussian pulse with input power of 120 mW is inserted into the system. Generation of chaotic signals respect to the ring's radius has been studied. The coupling coefficient affects the output power significantly, thus in order to generate signals with higher output power, the smaller coupling coefficient can be used. Here the output power of the system is characterized with respect to the different coupling coefficients of the system.A series of MRRs connected to an add/drop filter system in order to anaylize the soliton signals. The nonlinear refractive index of the MRR is n2=2.2 x 10-17 m2/W. The capacity of the output signals can be increased through generation of peaks with smaller full width at half maximum (FWHM). Here, we generate and characterize the ultra-short optical soliton pulses respect to the ring's radius and coupling coefficients variation of the system. As result, soliton pulses with FWHM and free spectral range (FSR) of 50 pm and 1440 pm are generated.
Decimal Convertor Application for Optical Wireless Communication by Generatin...University of Malaya (UM)
Two systems consist of microring resonators (MRRs) and an add/drop filter are used to generate signals as localized multi wavelengths. Quantum dense encoding
can be performed by output signals of selected wavelengths incorporated to a polarization control system. Therefore dark and bright optical soliton pulses
with different time slot are generated. They can be converted into digital logic quantum codes using a decimal convertor system propagating along a wireless networks. Results show that multi soliton wavelength, ranged from 1.55 m to 1.56 m with FWHM and FSR of 10 pm and 600 pm can be generated respectively. Keywords- Micro Ring Resonator, Quantum Dense Coding (QDC), Wireless network communication system.
Analysis and Estimation of Harmonics Using Wavelet TechniqueRadita Apriana
The paper develops an approach based on wavelet technique for the evaluation and estimation of
harmonic contents of power system waveform. The proposed algorithm decomposes the signal waveforms
into the uniform frequency sub-bands corresponding to the odd harmonic components of the signal. The
proposed implementation of algorithm determines the frequency bands of harmonics which retain both the
time and frequency relationship of the original waveforms and uses a method to suppress those
harmonics.Thewaveletalgorithm is selected to obtain compatible output bands with the harmonic groups
defined in the standards for power-supply systems. A comparative analysis will be done with the input and
the results obtained from the wavelet transform (WT) for different measuring conditions and Simulation
results are given.
Bandwidth density optimization of misaligned optical interconnectsIJECEIAES
In this paper, the bandwidth density of misaligned free space optical interconnects (FSOIs) system with and without coding under a fixed bit error rate is considered. In particular, we study the effect of using error correction codes of various codeword lengths on the bandwidth density and misalignment tolerance of the FSOIs system in the presence of higher order modes. Moreover, the paper demonstrates the use of the fill factor of the detector array as a design parameter to optimize the bandwidth density of the communication. The numerical results demonstrate that the bandwidth density improves significantly with coding and the improvement is highly dependent on the used codeword length and code rate. In addition, the results clearly show the optimum fill factor values that achieve the maximum bandwidth density and misalignment tolerance of the system.
Similar to An investigation and reduction of electro optical noise in tunable diode laser (20)
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
Essentials of Automations: The Art of Triggers and Actions in FMESafe Software
In this second installment of our Essentials of Automations webinar series, we’ll explore the landscape of triggers and actions, guiding you through the nuances of authoring and adapting workspaces for seamless automations. Gain an understanding of the full spectrum of triggers and actions available in FME, empowering you to enhance your workspaces for efficient automation.
We’ll kick things off by showcasing the most commonly used event-based triggers, introducing you to various automation workflows like manual triggers, schedules, directory watchers, and more. Plus, see how these elements play out in real scenarios.
Whether you’re tweaking your current setup or building from the ground up, this session will arm you with the tools and insights needed to transform your FME usage into a powerhouse of productivity. Join us to discover effective strategies that simplify complex processes, enhancing your productivity and transforming your data management practices with FME. Let’s turn complexity into clarity and make your workspaces work wonders!
A tale of scale & speed: How the US Navy is enabling software delivery from l...sonjaschweigert1
Rapid and secure feature delivery is a goal across every application team and every branch of the DoD. The Navy’s DevSecOps platform, Party Barge, has achieved:
- Reduction in onboarding time from 5 weeks to 1 day
- Improved developer experience and productivity through actionable findings and reduction of false positives
- Maintenance of superior security standards and inherent policy enforcement with Authorization to Operate (ATO)
Development teams can ship efficiently and ensure applications are cyber ready for Navy Authorizing Officials (AOs). In this webinar, Sigma Defense and Anchore will give attendees a look behind the scenes and demo secure pipeline automation and security artifacts that speed up application ATO and time to production.
We will cover:
- How to remove silos in DevSecOps
- How to build efficient development pipeline roles and component templates
- How to deliver security artifacts that matter for ATO’s (SBOMs, vulnerability reports, and policy evidence)
- How to streamline operations with automated policy checks on container images
GraphRAG is All You need? LLM & Knowledge GraphGuy Korland
Guy Korland, CEO and Co-founder of FalkorDB, will review two articles on the integration of language models with knowledge graphs.
1. Unifying Large Language Models and Knowledge Graphs: A Roadmap.
https://arxiv.org/abs/2306.08302
2. Microsoft Research's GraphRAG paper and a review paper on various uses of knowledge graphs:
https://www.microsoft.com/en-us/research/blog/graphrag-unlocking-llm-discovery-on-narrative-private-data/
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
Do you want to learn how to model and simulate an electrical network from scratch in under an hour?
Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
UiPath Test Automation using UiPath Test Suite series, part 5DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 5. In this session, we will cover CI/CD with devops.
Topics covered:
CI/CD with in UiPath
End-to-end overview of CI/CD pipeline with Azure devops
Speaker:
Lyndsey Byblow, Test Suite Sales Engineer @ UiPath, Inc.
Why You Should Replace Windows 11 with Nitrux Linux 3.5.0 for enhanced perfor...SOFTTECHHUB
The choice of an operating system plays a pivotal role in shaping our computing experience. For decades, Microsoft's Windows has dominated the market, offering a familiar and widely adopted platform for personal and professional use. However, as technological advancements continue to push the boundaries of innovation, alternative operating systems have emerged, challenging the status quo and offering users a fresh perspective on computing.
One such alternative that has garnered significant attention and acclaim is Nitrux Linux 3.5.0, a sleek, powerful, and user-friendly Linux distribution that promises to redefine the way we interact with our devices. With its focus on performance, security, and customization, Nitrux Linux presents a compelling case for those seeking to break free from the constraints of proprietary software and embrace the freedom and flexibility of open-source computing.
Securing your Kubernetes cluster_ a step-by-step guide to success !KatiaHIMEUR1
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An investigation and reduction of electro optical noise in tunable diode laser
1. Advances in Physics Theories and Applications
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
Vol.25, 2013
www.iiste.org
An Investigation and Reduction of Electro-Optical Noise in
Tunable1 Diode Laser
2
3
Samira Mahdi* , Youhua Chen , Gary Anderson
1. Department of Applied Science, University of Arkansas at Little Rock, AR 72204,
Faculty member in the Physics Department, College of Science, Babylon University, Babylon, Iraq.
2. Graduate Institute of Technology, University of Arkansas at Little Rock, AR 72204
3. Department of Systems Engineering, University of Arkansas at Little Rock, AR 72204,
* E-mail of the corresponding author: samahdi@ualr.edu
Abstract
A double FFT (DFFT) procedure is developed to reduce the effect of 1/f noise in the spectrum of Distribution
FeedBack (DFB) tunable diode laser. Simulations and experimental results are preformed. An obvious
effectiveness of the double FFT on the 1/f noise spectrum has been observed. The 1/f noise was monitored in the
three terminals. A linear fitting of the 1/f was verified for Single FFT (SFFT) and (DFFT) to calculate the
Frequency Exponent Factor (FEF) α and the amplitude of 1/f noise.
Keywords: Fast Fourier transformation, tunable diode laser, Double Fast Fourier Transform.
Introduction
Near infrared InGaAs-InP distributed feedback (DFB) tunable diode laser which can be designed to emit almost
anywhere in the spectral range between 1μm and 2μm. These diode lasers are compact and low power
consumption, and more importantly, they can operate at room temperature and compatible with commercial
optical fiber. As such, tunable diode laser (TDL) is considered a key component in many applications such as
high resolution spectroscopy, optical telecoms, and metrology. However, its light power spectrum suffers from
having a large 1/f noise component. The TDL wavelength is “tuned” either by changing the injection current of
the diode laser or by varying the temperature of the junction region (p-n junction) of the diode. This injection
current is a source of 1/f noise due to the generation recombination process of charge carriers (electrons and
holes) [1]. Also, the noisier injected current to the diode laser will generate noisier stream photons from the laser
diodes [2]. The 1/f spectra from intensity fluctuations in the optical spectrum and current noise of the diode laser
Hz.
were first noted by Tenchio [3], in the range of
A cross- correlation between the electrical noise and optical fluctuations was also monitored [4, 5]. Moreover,
Dandridge and Taylor observed a correlation between l/f intensity fluctuations and frequency fluctuations in the
optical emission [6, 7]. 1/f noise is actually observed in frequency noise spectra which would expand the linewidth of the laser light [8-12]. The the 1/f noise spectrum is one of the most important contributors in the
sampling data that has been measured to evaluate reliability and stabilizing of TDL [13-18]. Therefore, the1/f
noise is considered an important aspect of diode lasers to investigate.
Several methods have been used to reduce the effect of 1/f noise of the laser diode light spectrum. For example,
an optical feedback from an off-axis confocal cavity has been used to narrow the linewidth of lasers to kHz level
[19] or using a single-mode fiber resonator [20]. Optimizing design parameters, such as cavity length, power,
and gratings have been conducted to reduce the linewidth of the extended cavity diode lasers (ECDL) below 100
kHz [21]. A frequency discriminator, such as a fiber interferometer [22–26] and narrow optical filter [27] which
converting the frequency fluctuation of lasers into intensity variations using electrical feedback methods has
been developed to reduce the linewidth of diode lasers. In order to measure the linewidth broadening of the diode
laser due to 1/f noise, the self-heterodyne linewidth method has been performed on the different types of diode
laser [28, 29] . However, this method is not fully characterized the linewidth broadening because it only
measures 3dB linewidth [30,31]. The delay self-heterodyne linewidth method with phase detection has also been
employed to measure the linewidth broadening of the DFB and SGDBR diode lasers [32].
The Fast Fourier Transform (FFT) is the one of the most important analysis methods used to investigate
information that is carried by a signal in the frequency domain. With Fast Fourier transform analysis, it is
necessary to sample the input signal with a sampling frequency that is at least twice the bandwidth of the
signal, due to the Nyquist limit [33,35]. A Fourier transform will then produce a spectrum containing all
frequencies from zero to
. A new method is developed to reduce the effect of 1/f noise using an FFT on
simulation data [36-38]. A DFFT (Double Fast Fourier Transform) of the 1/f noise spectrum converts the
spectrum to approximately flat [ | F (A/f) | = | -i π A sgn (f) | = A π], where | F (A/f) | is the magnitude of an FFT
22
2. Advances in Physics Theories and Applications
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
Vol.25, 2013
www.iiste.org
of the (A/fα) noise. An FFT procedure is demonstrated to evaluate the Power Spectral Density (PSD) of the noisy
components (e.g., electronics and optical devices) experimentally in the TDL. The relation between the injected
current to the tunable diode laser and α which represents the exponent parameter that determines the type of 1/f
noise spectrum (A/fα) was evaluated. Also, the relation between the injected current and the amplitude of the 1/f
noise which represent by the factor (A) was performed.
It is worth mentioning, a DFFT has been used in various applications [39-42]. However the double FFT
procedures employed in those applications differ from the purpose, method and application used in this work.
For example, a double Fourier integral analysis is used as an analytical approach to determine the phase-leg
switched voltage spectrum under conditions of natural sampling of a four-switch three-phase (B4) voltage source
inverter in [43]. In [44], a fast acquisition method was put forward for high dynamic DSSS signal catching based
on double layers of short FFTs. The first FFT layer was used for quick acquisition of code and carrier. It can only
give a coarse carrier frequency. The second FFT layer was used for accurate frequency calculation based on the
result of the first FFT layer. In [45], a double Fourier Transform process process was implemented in a
sequential form in a beam forming network using a Two-Dimensional Double Fast-Fourier-Transform BeamForming-Network (2D-Double-FFT-BFN) concept.
Theory of 1/f Noise in the Tunable Diode Laser
which describe the relation among the carrier number
The noise sources
optical phase
are presented by two rate expressions [46].
, photon number
and
(1)
(2)
(3)
where
is the modulated current of the diode laser; is the electron charge;
is the carrier lifetime;
is the
is the
photon lifetime; is the gain slope constant coefficient; is the nonlinear gain compression factor;
carrier number of transparency;
is the fraction of spontaneous emission coupled into the lasing mode;
is
the linewidth enhancement factor;
is the time-averaged carrier number.
The intensity noise and phase noise of diode laser are introduced mainly by Langevin noise forces ,
respectively [47]. The low frequency intensity noise governs by two factors, gain fluctuations (g) and
spontaneous emission related factor . These fluctuations were considered to be caused by tow assumptions: 1)
the fluctuations in the absorption coefficient, 2) the uncorrelated fluctuations in the density of mobile charge
(free electrons and holes) [48]. A voltage noise spectral density
represented by the following expression [49].
of Laser voltage fluctuations could be
(4)
where
is the white noise term and T (K) the absolute temperature. The 1/f noise between (1 Hz100 kHz) is presented in second term which relates to R, proportional to
.Its expression is given by Hooge's
relation [50]:
(5)
Herein, is the mean value of the instantaneous current
; is the spectral power density of the 1/f
noise of the resistance R; N is the total number of free charge carriers in the InGaAsP layer as show in Fig. 1; f is
frequency at which the measurement is performed;
Hooge’s parameter;
is the intrinsic spectral
exhibits noise
density of the laser junction ( : RMS noise voltage). In addition, the optical light power
fluctuations which relates to the fluctuations of monitoring photocurrent, and it given by the photocurrent
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3. Advances in Physics Theories and Applications
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
Vol.25, 2013
spectral density
www.iiste.org
.
(6)
where
is the apparent sensitivity of the photodiode.
Figure 1. InGaAsP DFB Diode Laser.
1/f Noise Reduction Using DFFT
Application of DFFT Process of The 1/f noise
Noise is a major factor limiting measurement sensitivity in many fields of science. Due to their quantum
properties, diode laser exhibit a large 1/f noise spectrum. Many systems try to minimize this effect by using high
frequency techniques, or use a huge number of data points so that the noise can cancel each other. However, the
requirements of our system make this difficult. We therefore are examining techniques to reduce the effects of 1/f
noise on measurements made at lower frequencies, e.g., 500 Hz.
A new method is developed to reduce the effect of 1/f noise by performing multiple Fourier Transforms (FFTs)
on the signal received at the photodetector. This method is then tested both in simulation and experiments. In
simulation, the 1/f noise signal is generated by calculating the complex numbers of the data points in the
profile, where is usually about
frequency domain [51]. The power of the FFT of 1/f noise ( ) follows a
a 1.0 and phase angle ( ) is generated randomly using Eq.7. After performing an inverse FFT, the noise data in
the time domain are then obtained.
(7)
If we set
follows:
and rewrite
as
, where
=
Where
, then its Fourier transform will be as
=
Is the sign function, and the magnitude of
is
(8)
If the noise spectrum follows a 1/f profile after performing an FFT on it, then performing a second FFT converts
this 1/f profile to approximately constant profile.
DFFT Procedure for Looking at 1/f Noise
The following Table 1 and flowchart in Figure 2 describes (the DFFT procedure that is performed on the raw
data of the 1/f noise in both simulation and on the experimental data.
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4. Advances in Physics Theories and Applications
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
Vol.25, 2013
www.iiste.org
Table 1. Describes the DFFT procedure on the simulation and experiment noise data.
a
Sample the signals from the external photodiode (PD). The data sequences are
X= {x (1), x (2)… x (M1)}, where the number of sampling points is M1.
b
Apply an FFT on the time domain data X to obtain the Power Spectrum Density (PSD), and then remove
the DC part of the whole signal of FFT Y1 = {y (2), y (3)… y (M2)}, where M2 is the length of the first
FFT computation.
c
Apply an FFT (power spectrum) on the half of the frequency domain data Y1 = {y (2), y (3)… y
(M2/2)}, and get DFFT Y2 = {y (2), y (3) … y (M3)}, where M3 is the length of the DFFT.
Figure 2. Flowchart of DFFT on the 1/f noise.
Internal Circuit of TDL
Figure 3a present the 14 pin package of the diode laser. Figure 3b shows the internal structure of this package.
The main device is an InGaAsP commercial Distribution Feed Back (DFB) butterfly (NLK1655STG) Laser
Diode (LD), with (1m) pigtail fiber optics. The nominal wavelength is 1543.75 nm, and the maximum fiber-optic
output power is 26.8 (mW). The laser is activated by applying a forward current exceeding the threshold value Ith
= 19 mA at a diode temperature of T = 22 oC. The internal circuit of the butterfly DFB consists of an InGaAs
PIN monitoring photodiode (internal PD), a thermistor to monitor the laser temperature, and a Peltier cooler to
control the temperature of the diode. In this work, this PD is called the internal photodiode and it is monitored to
measure the 1/f noise spectrum that is generated by the laser light. The PD is mounted with a tin-lead solder at
around 400 picometer from the rear facet of the laser with an angle of 30" to prevent optical feedback in the laser
cavity.
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5. Advances in Physics Theories and Applications
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
Vol.25, 2013
www.iiste.org
Figure 3. Near-infrared tunable diode laser: package picture of TDL (left), internal circuit of TDL
(NLK1655STG) (right).
1/f Intensity Noise Measurements
Experiment Setup
Figure 4 shows the experimental setup of the 1/f intensity and wavelength noise measurements. A low noise
(
) laser driver (Wavelength Electronics LDTC1020) is employed to drive the diode laser; an
InGaAs PIN photodiode (Thorlabs SM05PD5A) with spectral response (800-1800nm), responsivity in nearinfrared region is about 1.2 A/W, and Noise Equivalent Power (NEP) is about
W/√Hz an electronic
PCB board that performs a voltage to current converter and amplification. The data acquisition System (DAC)
device has 16-bit analog input and output with a 250K Sample/sec maximum sampling rate. An InGaAs PIN
photodiode (external PD) - (Thorlabs SM05PD4A) with spectral response (800-1800nm) is used for the detector,
and its Noise Equivalent Power (NEP) is about
W/√Hz. The LabView signal Express was the
software that was used to collect the data from the external photodiode, internal photodiode, and the laser current
terminal. SpectraWiz was the software that used to collect the data from the NIR spectrometer.
Figure 4. Experimental Setup of 1/f Intensity and Wavelength Noise Measurements.
1/f Intensity Noise (Simulation data)
In this work, the 1/f intensity noise was created in the simulation. The simulation data noise was generated
according to the details of which are listed in section 3.1 (
, A= α =1). Figure 5a shows the typical simulated
1/f noise in the frequency domain after the Single Fast Fourier Transform (SFFT) while Figure 5b shows the
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6. Advances in Physics Theories and Applications
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
Vol.25, 2013
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DFFT of the 1/f spectrum. In the DFFT, the noise profile is converted from
the 1/f noise has less influence on the signal at low frequencies.
-4
-4
Sample Data
Linear fit
-5
log (Arbitrary Unit)
log (Arbitrary Unit)
-6
-7
-8
-9
-10
-11
-12
-14
1.5
Sample Data
Linear fit
-5
-6
-13
to approximately flat, such that
-7
-8
-9
-10
-11
-12
(a)
2
(b)
-13
2.5
3
3.5
4
4.5
-14
1.5
5
log (Frequency (Hz))
-4.5
log Frequency (Hz)
2
-4
-3.5
2.5
-3
-2.5
3
-2
3.5
4
4.5
-1.5
log Time
Figure 5. Comparison between SFFT and DFFT of the simulation data of (sec) noise spectrum:
1/f
a) The spectrum after SFFT, b) The spectrum after DFFT.
1/f Intensity Noise (Experimental Data)
Noise was measured at three points in the system: at the output of the external photodiode, the internal
photodiode, and the laser current terminal. External photodiode which measures the total fluctuations that are
generated from the following sources 1) the noise of the output light power of the diode laser, 2) the noise from
laser current, and 3) the noise of the electronic circuit. The total noise seen at the output of the external
photodiode is a combination of the noise that is in these three components. The power spectral density was
calculated at different driving currents of the diode laser. The amplitude A of 1/f noise was also calculated at 1Hz
and at 1 KHz also calculated. In addition, the Frequency Exponent Factor (FEF) α as shows in Eq. 9 was
calculated. For the 1/f power spectrum α has been reported as being (1.0 ± 0.1) [52].
(9)
Figure 6a shows the experimentally measured noise spectrum when the injected current iin= 141 (mA). The
SFFT spectrum from the external PD (optical + electronic noise) is composed of 1/f noise in the low-frequency
range (10Hz – 2KHz), with other noise sources (shot noise, white noise, and thermal noise ) appearing above
2KHz. Figure 6b displays the DFFT spectrum, which is approximately flat. The main advantage of the DFFT
procedure is to convert the 1/f noise profile to an approximately flat profile, the power of noise in SFFT equal
the power of noise in DFFT, according to the energy conservation law. However, the power of the noise keeps
the same the flat DFFT spectrum indicates noise is evenly distributed over the range of frequencies. Thus, a high
noise power at low frequency in the SFFT spectrum will be converted to a lower noise in the DFFTin the
measurement signal.
The Frequency Exponent Factor (FEF) of the 1/f α noise (0 < < 2) was calculated by performing a linear fitting
function of the SFFT spectrum, as shown in Figures 6a. Data was collected from the external photodiode
component in the low-frequency range (4 Hz < f < 2 KHz) according to the relation (9). In the same relation, (A)
represents the amplitude of the 1/f noise at specific frequencies. The amplitude of the intensity noise (A) was
determined by taking data and performing a linear fit to Eq. 9.
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7. Advances in Physics Theories and Applications
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Vol.25, 2013
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-5
-5
(a)
2KHz
-6.5
-7
-7.5
sample data of SFFT
Linear fitting of SFFT
(b)
-6
-6
log(PSD(A/sqrt(Hz)))
4Hz
-5.5
log(PSD( A/sqrt(sec) )
log(PSD(A/sqrt(Hz)))
-5.5
sample data
fitting curve
-6.5
0.05s
2KHz
0.2E-3s
4Hz
-7
-7.5
-8
-8.5
-9
-8
-9.5
-8.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
-10
5
log(Frequency(Hz))
log Frequency (Hz)
0
-4.5
0.5
-4
-3.5
1
1.5
2
2.5
3
3.5
4
4.5
-3 -2.5 log(Frequency(Hz))
-2 -1.5 -1 -0.5 0
log Time (sec)
Figure 6. Comparison between SFFT and DFFT of the1/f noise spectrum from a 1543 nm DFB diode laser.
a) The spectrum after SFFT showing 1/f noise, and b) The spectrum after DFFT showing a flat spectrum.
The raw data from External PD at iin= 141 (mA) and T =22Co.
Measurements of the1/f noise spectrum were repeated three times for every value of the injected current. Then,
the relation between and the injected current iin was obtained. For example, Figure 7a shows this relation for
the external PD. It shows three regions:
1. Under the threshold current region, of ith = 19 mA, where α < 0.2. This indicates, the value of the injected
current isn’t able to generate the laser light which consider the most contributor in 1/f noise spectrum. Thus,
the spectrum in this region is almost flat.
2. Near the threshold current region, where α is increasing as iin increases at 22 (mA). The beginning of the
laser operation, the laser power is very low and cannot induce a much more current carriers in the diode
laser that will produce 1/f noise spectrum. So that, the spectrum has also a flat characteristic.
3. The laser operation region, iin > 60 (mA), where α 0.9. It is worth mentioning that the α value stays
constant with increasing injected current after the threshold current is reached. That means the spectrum has
1/f noise characteristics especially, at the interesting point (inside the ellipse) where the value of injected
current 141 (mA) which was used to gas measurements were performed.
Figure 7b shows the relation between the amplitude of the noise in (mA) at 1Hz and the injected current. There
are also, three regions. Under the threshold current region, the amplitude is about 5E-8. Near the threshold
current region, the value is continue having approximately the same value. Laser operation region, the value
of the amplitude of noise is nearly independent of the injected current [2,7]. It reaches about 4E-7at 141mA
(ellipse point). Investigate the amplitude of 1/f noise at 141 mA is important. Because it is the desired current
value which make the absorption peak of ammonia gas be in the middle of the sine wave. As a result, the second
harmonic will be the intensive harmonic in the FFT spectrum of the absorption signal.
The same characteristics were also extracted from the DFFT spectrum (α and A value), especially between 0.3
ms - 0.05 s. On one hand, to compare between Figure 7a and Figure 8a, the α value has been shifted from about
0.9 in the SFFT to 0.03 in the DFFT. This indicates a flater noise spectrum in the DFFT, notice that α = 0
indicates a completely flat spectrum. On the other hand, the amplitude of the noise which appears in the Figure
7b and Figure 8b shows a noise amplitude reduction and by a factor of 100 at 1Hz. In addition, An interesting
point 141 (mA) which appears inside the ellipse, this is the point we take gas measurements at. From the two
figures, it can be verified that the DFFT procedure reduces the amplitude and the fluctuations of 1/f noise density
readings as shown in Table 2 (in the end of current section).
Furthermore, the amplitude of noise at 1KHz is also measured for the SFFT and DFFT processes. The intent
behind the calculation of the amplitude of noise at 1KHz is to show that the 1/f noise density is reduced after
applying the DFFT procedure. If so, the measurement of the absorption signal at the second harmonic (1KHz)
will become more reliable. Figure 9 displays the relation between the injected current and the spectral noise
amplitude at 1KHz for a SFFT and at 1ms for the DFFT. The circle marks refer to the SFFT and the cross ones
belong to DFFT procedure. At the typical operating laser current of (141 mA), the amplitude of the noise at 1 ms
is reduced by a factor of 10 after applying the DFFT procedure. Notice that the amplitude of the noise after the
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8. Advances in Physics Theories and Applications
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
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DFFT process has been normalized, so this is a true reduction. Also, the fluctuations in the amplitude of the
noise over three measurements is decreased. All the calculations that were described in this regard have been
implemented in Matlab code.
-7
6
1.2
(a)
1
Laser
Operation
Noise Amplitude (A))
Alpha (Unitless)
0.6
Threshold
Under
Threshold
0.2
Laser
Operation
4
Threshold
3
2
Under
Threshold
1
0
-0.2
(b)
5
0.8
0.4
x 10
0
0
20
40
60
80
100
120
140
160
0
20
40
60
80
100
120
140
160
Current I(mA)
Current(mA)
Figure 7a The relation between the injected current of the laser diode and alpha values process.
b-The relation between the injected current of the laser diode and the noise amplitude at 1s. When T= 22 Co uses the
SFFT process. The raw data were collected from the external photodiode.
-9
x 10
(a)
0.034
5
Noise Amplitude (A))
Alpha (Unitless)
4.5
Laser
Operation
0.03
0.028
Threshold
0.026
(b)
5.5
0.032
Under
0.024
Threshold
0.022
Laser
Operation
4
3.5
3
2.5
Threshold
Under
Threshold
2
0.02
1.5
0.018
0.016
1
0
20
40
60
80
100
120
140
0.5
160
0
20
40
60
Current(mA)
80
100
120
140
160
Current(mA)
Figure 8a The relation between the injected current of the laser diode and alpha values process. b-The
relation between the injected current of the laser diode and the noise amplitude at 1s. When T= 22 Co uses
the DFFT process. The raw data were collected from the external photodiode.
-8
10
x 10
SFFT
DFFT
9
Noise Amplitude (A))
8
7
Laser
Operation
6
5
Threshold
4
Under
Threshold
3
2
1
0
0
20
40
60
80
100
120
140
160
Current(mA)
Figure 9 Comparison between the amplitude of the noise as a function of the injected current to the
diode laser at 1KHz using SFFT and 1ms using the DFFT. The raw data were collected from the
external photodiode.
A photodiode embedded in the laser package (Internal Photodiode) was used to monitor the power spectrum of
the 1/f noise in the laser light intensity alone. This is different from noise in the external photodiode, which
includes noise from the laser electronic circuit, laser driver and power supply. The sample data was collected
from the internal photodiode (see Figure 3) using a pre-amplifier and current circuit. After the data were sent to
an analog to digital converter and then to the computer. LabView signal express is used to control the data
acquisition process. Then, the data were processed using Matlab.
29
9. Advances in Physics Theories and Applications
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Vol.25, 2013
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The interest of monitoring noise across laser diode is to identify the type of the noise. We can measure the noise
in the light intensity from within the laser diode package, and determined its spectrum when the normal driving
current of 141 (mA). Also, it is important to evaluate the amplitude of the noise at 1KHz of the SFFT spectrum
and compare the result with what obtain after applying DFFT process. Figure 10a shows the SFFT spectrum of
the data that was collected from the internal photodiode. It is obvious the SFFT spectrum is comprised mainly of
1/f noise between 16Hz-50KHz. This measurement was obtained at iin= 141mA and T= 22Co. The DFFT process
was then applied to the data, with the results shown in Figure 10b. As can be seen the whole spectrum has been
converted to the nearly flat spectrum between 0.3E-3s - 0.1s.
-4
-4
Noise Amplitude (A))
log(PSD( A/sqrt(sec) )
50KHz
-5.5
sample data
Linear fitting
(b)
-5
16Hz
-5
log(PSD(A/sqrt(Hz)))
sample data
fitting curve
(a)
-4.5
-6
-6.5
-7
-7.5
-8
0.3E-3s
16Hz
0.1s
4KHz
-6
-7
-8
-9
-8.5
-4.5
-9
0
-4
0.5
2
-3.5 -3 1-2.5 1.5 -1.5 -1 2.5
-2
-0.5
3
0
3.5
4
4.5
-10
5
0
0.5
1
log(Frequency(Hz))
z)
1.5
2
2.5
3
3.5
4
4.5
log(Frequency(Hz))
log Time (sec)
Figure 10. Comparison between SFFT and DFFT of the1/f noise spectrum from a 1543 nm DFB diode
laser. a) The spectrum after SFFT showing 1/f noise, and b) The spectrum after DFFT showing a flat
spectrum. The raw data from External PD at iin= 141 (mA) and T =22Co at Iin = 141 mA, T= 22 Co. The
raw data were collected from the internal photodiode. a) SFFT spectrum, and b) DFFT spectrum.
Figure 11a shows the alpha parameter from Eq. 9 as a function of the injected current. The graphs display the
three operating regions of the laser versus injected current. 1) Under threshold current; 2) Threshold current;
and 3) Laser operation. α fluctuates around (0.5) in the 1st , and 2nd region, while it varies from (0.6- 0.9) in the
3rd region. However, the exact value of alpha at the interesting point (141 mA) is about o.95. In addition, the
relation between the (A) parameter which represents the amplitude of the noise and the injected current was
plotted as illustrated in the Figure 11b. The amplitude of noise fluctuates around (0.4 E-6 Amp.) after the
threshold current is reached. However, it increases at iin = 141mA (ellipse point) to reach (0.75E-6 Amp. ).
-6
1.1
1
0.9
1
Laser
Operation
0.8
Laser
Operation
N o ise A m p litu d e (A ))
0.9
Threshold
Alpha (Unitless)
x 10
0.8
0.7
0.6
0.7
Threshold
0.6
0.5
0.4
Under
Threshold
0.3
0.5
0.2
0.4
Under
Threshold
0
0.1
(a)
20
40
60
80
100
120
140
0
160
Current(mA)
(b)
0
20
40
60
80
100
120
140
160
Current(mA)
Figure 11a The relation between the injected current of the laser diode and alpha values process. b-The
relation between the injected current of the laser diode and the noise amplitude at 1s. When T= 22 Co
uses the SFFT process. The raw data were collected from the internal photodiode.
30
10. Advances in Physics Theories and Applications
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
Vol.25, 2013
www.iiste.org
-9
8
0.07
(a)
Threshold
0.05
Alpha (Unitless)
7
Laser
Operation
Noise Amplitude (A))
0.06
0.04
0.03
0.02
0.01
Laser
Operation
6
Threshold
5
4
3
Under
2 Threshold
Under
Threshold
0
x 10
(a)
20
40
60
80
100
120
140
(b)
1
0
160
20
40
60
Current(mA)
80
100
120
140
160
Current(mA)
Figure 3-12a The relation between the injected current of the laser diode and alpha values process. b-The
relation between the injected current of the laser diode and the noise amplitude at 1s. When T= 22 Co uses
the DFFT process. The raw data were collected from the internal photodiode.
The DC term of the SFFT was removed and a second FFT was performed on the data (DFFT). Then, alpha was
extracted from the linear fitting curve of Figure 10b. The relation between alpha values and the injected current
was plotted as shown in Figure 12a. It is obvious that the alpha value (α = 0.06 ) has significantly decreased to
an extent that can be totally assertion that the1/f noise spectrum has disappeared. Also, the amplitude of the noise
was extracted from the same fitting curve at 1Hz, and the relation between the amplitude of the noise and the
injected current was plotted, as shown in Figure 12b. The amplitude of the noise at 141mA (ellipse point) is
about 6.5E-9 Amps.
Figure 13 shows a comparison between a SFFT and the DFFT procedures, and the relation between the
amplitude noise and the injected current to the laser diode at 1KHz. The amplitude of 1/f noise at 141 mA
(ellipse point) is about 4E-8 Amp from the SFFT procedure (circle marks ) and 1E-9 Amp from DFFT (cross
points). This indicates that the DFFT procedure was reduced the amplitude of noise by a factor of 10. If we
compare between the value of the amplitude of noise from a SFFT at 1Hz and the DFFT procedure. This value is
reduced by a factor of 100 after the DFFT process. For more details see Table 2 (in the end of current section).
5
x 10
-8
SFFT
DFFT
4.5
Threshold
4
Noise Amplitude (A))
Laser
Operation
3.5
3
2.5
2
1.5
1
Under
Threshold
0.5
0
0
20
40
60
80
100
120
140
160
Current(mA)
Figure 13 Comparison between the density of the 1/f noise as a function of the injected current to
the diode laser at1KHz using SFFT and at 1ms using DFFT. The raw data were collected from the
internal photodiode.
Laser current. The laser current terminal which feeds to the laser chip from the laser driver (as shown in
Figure 3) was monitored. The current contains an amount of noise however, the kind of noise that is in the laser
current does not exhibit 1/f spectrum. Figure 14a shows the noise spectrum after the SFFT process, and it
appears the noise might follow a 1/f spectrum. But, after the value of alpha was calculated (see Figure 15a ), it
became clear that the type of noise isn’t purely 1/f noise. This partially explains the reason that why the noise
spectrum after the DFFT process, isn’t a completely flat spectrum. Although , there are a lot fluctuations around
the linear fitting of the sample data from the DFFT spectrum, the value of alpha from that fitting has still been
reduced significantly, as shown in Figure 16a.
31
11. Advances in Physics Theories and Applications
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
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-5
-5
-5.2
sample data
fitting curve
(a)
4Hz
-5.5
log(PSD( A/sqrt(sec) )
-5.4
2KHz
-5.6
log(PSD(A/sqrt(Hz)))
log(PSD(A/sqrt(Hz)))
sample data
Linear fitting
(b)
-5.8
-6
-6.2
-6.4
-6.6
0.1s
2KHz
-6
4 4Hz
E-4s
-6.5
-7
-7.5
-6.8
-7
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
-8
5
0
0.5
-4.5
log(Frequency(Hz))
-4
1
-3.5 -3
-2.5
1.5
2
2.5
3
3.5
4
4.5
-2 -1.5 -1 -0.5
0
log(Frequency(Hz))
log Time(sec)
Figure 3-14. Comparison between SFFT and DFFT of the1/f noise spectrum of the raw data from laser
current terminal at iin= 141 (mA) and T =22Co a) The spectrum after SFFT, and b) The spectrum after DFFT.
-6
0.8
5
4.5
0.7
Laser
Operation
0.5
Threshold
0.4
0.3
Under
Threshold
3.5
3
2.5
Under
Threshold
20
40
60
80
100
120
(b)
0.5
0
0
Threshold
2
1.5
1
(a)
0.1
0
Laser
Operation
4
Noise Amplitude (A))
A lp h a (U n itless)
0.6
0.2
x 10
140
160
0
20
40
60
80
100
120
140
160
Current(mA)
Current(mA)
Figure 15a The relation between the injected current of the laser diode and alpha values process. bThe relation between the injected current of the laser diode and the noise amplitude at 1s. When T=
22 Co uses the SFFT process. The raw data were collected from the laser diode current terminal.
The amplitude of the noise was calculated from the linear fitting of the SFFT process and the DFFT process.
Figure 15b and Figure 16b show the 1/f noise amplitude at 1Hz vs. the injected current to the laser diode for
SFFT and in the DFFT process, respectively. This value has been reduced significantly after DFFT process by a
factor of 100. In addition, the amplitude of the noise was also calculated at 1KHz for the SFFT spectrum and at
1ms for the DFFT spectrum as appear in Figure 17.
-7
3
0.08
0.07
2.5
N o ise A m p litud e (A ))
A lp h a (U n itless)
(a)
Laser
Operation
0.06
x 10
0.05
Threshold
0.04
0.03
Threshold
1.5
1
Under
Threshold
0.02
(b)
Laser
Operation
2
Under
Threshold
0.5
0.01
0
0
20
40
60
80
100
120
140
0
160
0
20
40
60
80
100
120
140
160
Current(mA)
Current(mA)
Figure 16a The relation between the injected current of the laser diode and alpha values process. b-The
relation between the injected current of the laser diode and the noise amplitude at 1s. When T= 22 Co
uses the DFFT process. The raw data were collected from the laser diode current terminal.
32
12. Advances in Physics Theories and Applications
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Vol.25, 2013
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-7
8
x 10
SFFT
DFFT
7
Laser
Operation
Noise Amplitude (A))
6
Threshold
5
4
3
Under
Threshold
2
1
0
0
20
40
60
80
100
120
140
160
Current(mA)
Figure 17 A comparison between the density of noise as a function of the injected current to the
diode laser at1KHz using SFFT and at 1ms using DFFT. The raw data were collected from
internal photodiode.
The results have been shown a reduction in the amplitude of the noise after DFFT process by a factor of 100 at
1Hz. However, the amplitude of noise decreases by a factor of 10 at 1KHz, The values of the amplitude of noise
at 1Hz and 1KHz for a SFFT, also at 1s and 1ms for the DFFT were listed in Table 2.
Table 2. The comparison between the amplitude of noise density at 1Hz and 1KHz from the SFFT process,
also at 1s and 1ms from the DFFT process.
Domain (Frequency or
Time)
1Hz
1KHz
1s
1ms
Amplitude of Noise Density (Amps.)
Procedure
SFFT
DFFT
External
Photodiode
4E-7
1E-8
4E-9
4E-9
Internal
Photodiode
2E-6
2E-8
5E-9
5E-9
Laser Driver
Current
2E-6
3E-7
8E-8
6E-8
Conclusion
In this work a DSP technique was used by performing a DFFT procedure on the sample data. Several
conclusions can be listed in the following steps.
1. The results showed that 1/f noise has multiple contributing sources, including the injected current and
the laser light generated by the diode. The noise profile can determine by the value of α, which should
be 1 < α < 2 . α varies with the amount of the current injected into the diode laser. For example, in case
of external photodiode, the α value of a 141mA injection current was about 0.9, indicating a strong 1/f
noise component.
2. The intensity noise was manipulated using a Double Fast Fourier (DFFT) procedure after performing a
Single FFT (SFFT) procedure. The DFFT procedure reduced the power of 1/f noise, especially in the
low frequency ranges (4Hz-4KHz).
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