This document discusses transmission characteristics of optical fibers, including:
- Attenuation losses such as absorption and scattering losses that reduce signal strength.
- Dispersion which causes pulses to spread, interfering with each other (intersymbol interference) and limiting bandwidth. Types of dispersion include material dispersion and waveguide dispersion.
- Single mode fibers which only propagate a single mode and have low dispersion. Dispersion can be optimized by designing the refractive index profile, such as in dispersion shifted or flattened fibers.
Hello everyone. This is a short presentation on path loss and shadowing. I have not covered all the topics but a brief idea is given on path loss and wireless channel propagation models.
Hope you find it useful.
Thanks
Signal Degradation In Optical Fiber
Losses in an optical fibre:-
The types of losses in a optical fibre are
Attenuation loss
Absorption
Scattering
Bending loss
Dispersion loss
Coupling loss
Unit II- TRANSMISSION CHARACTERISTIC OF OPTICAL FIBER tamil arasan
Attenuation - Absorption losses, Scattering losses, Bending Losses, Core and Cladding losses, Signal Distortion in Optical Wave guides-Information Capacity determination -Group Delay-Material Dispersion, Wave guide Dispersion, Signal distortion in SM fibers-Polarization Mode dispersion, Intermodal dispersion, -Design Optimization of SM fibers-RI profile and cut-off wavelength.
The attached narrated power point presentation attempts to explain the methods of computation of total power loss and system rise time in a fiber optic link. The material will be useful for KTU final year B Tech students who prepare for the subject EC 405, Optical Communications.
Hello everyone. This is a short presentation on path loss and shadowing. I have not covered all the topics but a brief idea is given on path loss and wireless channel propagation models.
Hope you find it useful.
Thanks
Signal Degradation In Optical Fiber
Losses in an optical fibre:-
The types of losses in a optical fibre are
Attenuation loss
Absorption
Scattering
Bending loss
Dispersion loss
Coupling loss
Unit II- TRANSMISSION CHARACTERISTIC OF OPTICAL FIBER tamil arasan
Attenuation - Absorption losses, Scattering losses, Bending Losses, Core and Cladding losses, Signal Distortion in Optical Wave guides-Information Capacity determination -Group Delay-Material Dispersion, Wave guide Dispersion, Signal distortion in SM fibers-Polarization Mode dispersion, Intermodal dispersion, -Design Optimization of SM fibers-RI profile and cut-off wavelength.
The attached narrated power point presentation attempts to explain the methods of computation of total power loss and system rise time in a fiber optic link. The material will be useful for KTU final year B Tech students who prepare for the subject EC 405, Optical Communications.
LEDs are of interest for fibre optics because of five inherent characteristics..
How it works?
Spectrum of an LED
Modulation of LED
LED Vs. Laser diode
disadvantages of LED
Non Linear Effects in Fiber Optic SystemsAtul Nanal
This is the presentation of my project thesis at Conslusion of my 2 year Mater of Technology course in Opto Electronics and Optical Communications at IIT Delhi
The project studied the effects of non linear effects of Self and Cross Phase Modulation in presence of Dispersion in an Optical Fiber.
Optical fiber communication Part 1 Optical Fiber FundamentalsMadhumita Tamhane
Optical fiber systems grew from combination of semiconductor technology, which provided necessary light sources and photodetectors and optical waveguide technology. It has significant inherent advantages over conventional copper systems- low transmission loss, wide BW, light weight and size, immunity to interferences, signal security to name a few. One principle characteristic of optical fiber is its attenuation as a function of wavelength. Hence it is operated in two major low attenuation wavelength windows 800-900nm and 1100-1600nm . Light travels inside optical fiber waveguide on principle of total internal reflection. Fiber is available as single mode and multiple mode, step index and graded index depending on applications and expenditures. Principle of fiber can be understood by ray theory or mode theory. ...
As we know Optical communication Network offers
very high potential bandwidth and flexibility. In terms of high
bit-rate transmission. However, their performance slows down
due to some parameter like dispersion, attenuation, scattering. In
long haul application, dispersion is the main parameter which
needs to be compensated in order to provide better service. Fiber
Braggs Grating (FBG) is one of the most widely used element to
compensate it, however its performance slows down with the
increase in distance.
This paper presents an investigation on Pulse distortions due to
the third-order dispersion (TOD) on very high speed long
distance single mode optical fiber communication system using
OptiSystem. Presence of the TOD introduces broadening on the
propagating pulse. The impact of TOD is observed at the
receiving end of transmission line considering the variation of
different factors such as transmission reach, bit rate, duty
cycle.BER performance are also considered here.
LEDs are of interest for fibre optics because of five inherent characteristics..
How it works?
Spectrum of an LED
Modulation of LED
LED Vs. Laser diode
disadvantages of LED
Non Linear Effects in Fiber Optic SystemsAtul Nanal
This is the presentation of my project thesis at Conslusion of my 2 year Mater of Technology course in Opto Electronics and Optical Communications at IIT Delhi
The project studied the effects of non linear effects of Self and Cross Phase Modulation in presence of Dispersion in an Optical Fiber.
Optical fiber communication Part 1 Optical Fiber FundamentalsMadhumita Tamhane
Optical fiber systems grew from combination of semiconductor technology, which provided necessary light sources and photodetectors and optical waveguide technology. It has significant inherent advantages over conventional copper systems- low transmission loss, wide BW, light weight and size, immunity to interferences, signal security to name a few. One principle characteristic of optical fiber is its attenuation as a function of wavelength. Hence it is operated in two major low attenuation wavelength windows 800-900nm and 1100-1600nm . Light travels inside optical fiber waveguide on principle of total internal reflection. Fiber is available as single mode and multiple mode, step index and graded index depending on applications and expenditures. Principle of fiber can be understood by ray theory or mode theory. ...
As we know Optical communication Network offers
very high potential bandwidth and flexibility. In terms of high
bit-rate transmission. However, their performance slows down
due to some parameter like dispersion, attenuation, scattering. In
long haul application, dispersion is the main parameter which
needs to be compensated in order to provide better service. Fiber
Braggs Grating (FBG) is one of the most widely used element to
compensate it, however its performance slows down with the
increase in distance.
This paper presents an investigation on Pulse distortions due to
the third-order dispersion (TOD) on very high speed long
distance single mode optical fiber communication system using
OptiSystem. Presence of the TOD introduces broadening on the
propagating pulse. The impact of TOD is observed at the
receiving end of transmission line considering the variation of
different factors such as transmission reach, bit rate, duty
cycle.BER performance are also considered here.
Enhancing the Data Transmission Capability on Optical Fiber Communication Lin...IOSRJECE
Explosive growth of broadband multimedia applications, such as high-definition television (HDTV), video on demand (VOD) and interactive games imposed a huge demand for bandwidth on the access network. The potential bandwidth of optical communication system is driving force behind the worldwide development and deployment of light wave system but dispersion limits the system performance in terms of high speed optical communication. In this paper different dispersion compensation methods are discussed, which are based on Chirped Fiber Grating (CFG), Dispersion Compensation Fibers (DCF), Self Phase Modulation (SPM ) resulting from Kerr nonlinearity to overcome pulse broadening effect of Group Velocity Dispersion (GVD), which eventually have direct implication on the data transmission capability on optical fiber communication link.
Twenty Essential Knowledge of Optical Cable.pdfHYC Co., Ltd
An article about basic knowledge of optical fiber cable, including the wavelength, dispersion of optical fiber, insertion loss, return loss, fiber core diameter, types of optical fiber etc. Including What is the mode field diameter (MFD), What is Numerical Aperture (NA), What is the cutoff wavelength and so on.
Design of Symmetric dispersion compensated, long haul, Single and Multichanne...IOSR Journals
Abstract: Here we propose a model on Enhanced- Large Effective Area Fiber (E-LEAF) and Dispersion Compensation Module (DCM) with precise designed Dispersion Compensation Fiber (DCF). The Model is implemented in a long haul Single and Multichannel Optical telecommunication systems with E-LEAF as data transmission Fiber (NZ-DSF) of 1700Km (85 Km SMF×20 loops) length. The DCM is proposed in Symmetric Compensation fashion consisting of 20Km (2Km×20spans) length DCF in Pre-Compensation and Post-Compensation totally comprising of 40Km length DCF for complete Compensation of total Optical Link. Thereby, we study the effect of various Line Coding Schemes like NRZ, RZ, CS-RZ, DUOBINARY and MODIFIED DUOBINARY in single and multichannel optical link with our designed DCM and concluded the suitable line coding scheme for our proposed model. This paper focus on the theoretical background, design procedures, technical terms and finally a simulation model is experimented with proposed parameters to realize the foresaid concepts with various modulation formats.
Macro-Bending Loss of Single-Mode Fiber beyond Its Operating WavelengthTELKOMNIKA JOURNAL
A standard telecommunication-grade single-mode optical fiber is designed to have a
low macro-bending loss in its entire operating wavelengths to comply with the ITU-T
Recommendation G.652. In this paper, we described the potential use of such a fiber as an
intensity-based sensor due to the macro-bending loss as an alternative to using a bendingsensitive
fiber. We calculated the macro-bending loss of several single-mode optical fiber
patchcords using the classical Marcuse equation at several wavelengths, and measured its
transmission loss due to bending using an optical spectrum analyzer. For each type of fibers
there is a wavelength with a significant macro-bending loss of the LP11 mode when the Vnumber
of the fiber lies between 2.4 and 4, and that of the LP01 mode when the V-number of the
fiber lies between 1 and 2.4. This work shows a thorough mathematical and experimental
analysis for the posibility in using standard telecommunication fibers for intensity based-fiber
sensor taking the benefit of bending loss phenomenon using commercial light sources.
Performance Analysis of Dispersion Compensation in Long Haul Optical Fiber wi...IOSR Journals
Abstract : In this paper, We investigate post, pre and symmetrical/mix dispersion compensation methods for 40
Gb/s non-return to zero link using standard and dispersion compensated fiber through FBG compensator to
optimize high data rate optical transmission. The influence of dispersion of FBG compensator and increases in
the power of CW laser has been studied to evaluate the performance of optical communication systems. The
simulation model of the WDM based on the Optisystem 11.0 is presented according to the above principle. The
simulation results are validated by analysing the Q-factor and Bit error rate (BER) in the numerical simulator.
It is found that post compensation performance is best and the input fiber power is taken as 5-10dB, the
corresponding BER performance is better.
Keywords - BER, Dispersion compensation, Q-factor, WDM.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Quality defects in TMT Bars, Possible causes and Potential Solutions.PrashantGoswami42
Maintaining high-quality standards in the production of TMT bars is crucial for ensuring structural integrity in construction. Addressing common defects through careful monitoring, standardized processes, and advanced technology can significantly improve the quality of TMT bars. Continuous training and adherence to quality control measures will also play a pivotal role in minimizing these defects.
NO1 Uk best vashikaran specialist in delhi vashikaran baba near me online vas...Amil Baba Dawood bangali
Contact with Dawood Bhai Just call on +92322-6382012 and we'll help you. We'll solve all your problems within 12 to 24 hours and with 101% guarantee and with astrology systematic. If you want to take any personal or professional advice then also you can call us on +92322-6382012 , ONLINE LOVE PROBLEM & Other all types of Daily Life Problem's.Then CALL or WHATSAPP us on +92322-6382012 and Get all these problems solutions here by Amil Baba DAWOOD BANGALI
#vashikaranspecialist #astrologer #palmistry #amliyaat #taweez #manpasandshadi #horoscope #spiritual #lovelife #lovespell #marriagespell#aamilbabainpakistan #amilbabainkarachi #powerfullblackmagicspell #kalajadumantarspecialist #realamilbaba #AmilbabainPakistan #astrologerincanada #astrologerindubai #lovespellsmaster #kalajaduspecialist #lovespellsthatwork #aamilbabainlahore#blackmagicformarriage #aamilbaba #kalajadu #kalailam #taweez #wazifaexpert #jadumantar #vashikaranspecialist #astrologer #palmistry #amliyaat #taweez #manpasandshadi #horoscope #spiritual #lovelife #lovespell #marriagespell#aamilbabainpakistan #amilbabainkarachi #powerfullblackmagicspell #kalajadumantarspecialist #realamilbaba #AmilbabainPakistan #astrologerincanada #astrologerindubai #lovespellsmaster #kalajaduspecialist #lovespellsthatwork #aamilbabainlahore #blackmagicforlove #blackmagicformarriage #aamilbaba #kalajadu #kalailam #taweez #wazifaexpert #jadumantar #vashikaranspecialist #astrologer #palmistry #amliyaat #taweez #manpasandshadi #horoscope #spiritual #lovelife #lovespell #marriagespell#aamilbabainpakistan #amilbabainkarachi #powerfullblackmagicspell #kalajadumantarspecialist #realamilbaba #AmilbabainPakistan #astrologerincanada #astrologerindubai #lovespellsmaster #kalajaduspecialist #lovespellsthatwork #aamilbabainlahore #Amilbabainuk #amilbabainspain #amilbabaindubai #Amilbabainnorway #amilbabainkrachi #amilbabainlahore #amilbabaingujranwalan #amilbabainislamabad
Courier management system project report.pdfKamal Acharya
It is now-a-days very important for the people to send or receive articles like imported furniture, electronic items, gifts, business goods and the like. People depend vastly on different transport systems which mostly use the manual way of receiving and delivering the articles. There is no way to track the articles till they are received and there is no way to let the customer know what happened in transit, once he booked some articles. In such a situation, we need a system which completely computerizes the cargo activities including time to time tracking of the articles sent. This need is fulfilled by Courier Management System software which is online software for the cargo management people that enables them to receive the goods from a source and send them to a required destination and track their status from time to time.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Vaccine management system project report documentation..pdfKamal Acharya
The Division of Vaccine and Immunization is facing increasing difficulty monitoring vaccines and other commodities distribution once they have been distributed from the national stores. With the introduction of new vaccines, more challenges have been anticipated with this additions posing serious threat to the already over strained vaccine supply chain system in Kenya.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
Oc unit 2 - Part II - Transmission Characteristics
1. R.M.K. COLLEGE OF ENGINEERING AND TECHNOLOGY
Puduvoyal,Chennai.
DEPARTMENT OF ECE
OPTICAL COMMUNICATION
UNIT II
TRANSMISSION CHARACTERISTIC OF OPTICAL FIBER
Dr.K.Kannan
ASP/ECE
2. Attenuation Losses
Absorption Losses
Scattering Losses
Linear and Non Linear Scattering losses
Bending Losses
Micro and Macro bending losses
Core and Cladding Losses
Signal Dispersion
Inter Symbol Interference and Bandwidth
Intra Model Dispersion
Material Dispersion and Waveguide Dispersion
Polarization Mode Dispersion
Intermodal Dispersion
Dispersion Optimization of Single Mode Fiber
Characteristics of Single Mode Fiber
RI Profile
Cutoff wave length
3. Signal Degradation in the Optical Fiber
SignalAttenuation
Signal Distortion/Dispersion
signal strength
10. INTER SYMBOL INTERFERENCE AND BANDWIDTH
Dispersion (intramodal and intermodal) affects the transmission of optical signal in
case of both analog and digital transmission of optical signal.
Dispersion causes overlapping of spread pulses making them unrecognizable and
resulting into Inter Symbol Interference (ISI). This overlapping finally leads to errors
in making decisions regarding 1’s and 0’s
A large ISI may lead to increased number of errors. The error in digital optical
communication is measured in terms of Bit-Error-Rate (BER), which is measured in
terms of the number of errors incurred in a given bit stream
ISI restricts bit rate and Bit rate may be viewed as the analogue of bandwidth in the
case of analog optical communication. Similarly, the bit-error-rate and signal-to-
noise ratio are also related to each other. The exact relationship depends on the
characteristics of the channel (fiber).
11. In order to avoid the effect of Intersymbol interference one must control the rate
at which the bits are being transmitted.
If Tb is the duration of a single pulse, a conservative estimate of the maximum bit
rate that can be obtained on an optical channel without overlapping of bits as
The above estimation is based on the assumption that spreading of the pulses
due to dispersion in the channel is also Tb.
Thus the optical bandwidth can be written as
In terms of bit rate,
32. Polarization Mode dispersion
Polarization mode dispersion (PMD) is a source of pulse broadening which results from fiber
birefringence
It is a random effect due to both intrinsic (caused by noncircular fiber core geometry and residual
stresses in the glass material near the core region) and extrinsic (caused by stress from
mechanical loading, bending or twisting of the fiber) factors which in actual manufactured fibers
result in group velocity variation with polarization state.
33. Two modes have different phase propagation constants βx and βy they exhibit different
specific group delays In the time domain for a short section of fiber, the differential group delay
(DGD), Δτ = δτgL, is defined as the group delay difference between the slow and the fast modes
over the fiber lengths as indicated in Figure
The differential group delay per unit length is referred to as the polarization mode dispersion
(PMD) of the fiber and is usually expressed in units of picoseconds per kilometer of fiber
34. DISPERSION OPTIMIZATION OF SINGLE MODE FIBER
The pulse broadening in single-mode fibers results almost entirely from chromatic or intramodal dispersion as only a
single-mode is allowed to propagate
Hence the bandwidth is limited by the finite spectral width of the source.
The transit time or specific group delay τg for a light pulse propagating along a unit length of single-mode fiber may be
given, following
where c is the velocity of light in a vacuum,
β is the propagation constant for a mode within the fiber core of refractive index n1 and
k is the propagation constant for the mode in a vacuum.
The total first-order dispersion parameter or the chromatic dispersion of a single-mode fiber, DT, is given by the derivative
of the specific group delay with respect to the vacuum wavelength λ as
The material dispersion parameter it is usually expressed in units of ps nm−1 km−1. When the variable λ is replaced by ω,
then the total dispersion parameter becomes:
The fiber exhibits intramodal dispersion when β varies nonlinearly with wavelength.
The total first-order dispersion DT in a practical single-mode fiber as comprising:
which is simply the addition of the material dispersion DM, the waveguide dispersion DW and the profile dispersion DP
components.
35. However, the overall dispersion of single mode fibers is much less than that of multimode fibers. Therefore,
single mode fibers are widely used for high-speed long-haul optical communication systems
The single mode fibers do not suffer from intermodal dispersion. The overall dispersion of the fiber is thus
determined by the intramodal dispersion which has two components, e.g., material dispersion and waveguide
dispersion.
Out of these two components, the material dispersion of the fiber cannot be changed much.
On the other hand, the waveguide dispersion component can be varied significantly by changing the refractive
index profile from the conventional step-index profile to a more complex index profiles
36. Different Refractive index structures that give different waveguide dispersion and they can be added with
material dispersion which is constant for selected material.
1. Standard single mode fiber (1300 nm optimized)
2. Dispersion flattened fiber
3. Dispersion shifted fiber
RI profile design to optimize dispersion
Zero material dispersion(ZMD) point occurs in 1.27 μm. However it can be shifted by designing
different core cladding interface refractive index (RI) profiles.
At wavelengths longer than the ZMD point in most common fiber designs, the DM and DW
components are of opposite sign and can therefore be made to cancel at some longer wavelength.
Hence the wavelength of zero first-order chromatic dispersion can be shifted to the lowest loss
wavelength for silicate glass fibers at 1.55 μm to provide both low dispersion and low-loss fiber.
This may be achieved by such mechanisms as a reduction in the fiber core diameter with an
accompanying increase in the relative or fractional index difference to create so-called dispersion-
shifted single-mode fibers (DSFs)
The step index profile illustrated in Figure gives a shift to longer wavelength by reducing the core
diameter and increasing the fractional index difference.
37. In graph, various design combinations of refractive index profile and dispersion variation with
wavelength are shown.
38. Several of the graded refractive index profile DSF types are illustrated in Figure 2.15. The triangular profile
shown in Figure 2.15 (a) is the simplest and was the first to exhibit the same low loss (i.e. 0.24 dB km−1) at a
wavelength of 1.56 μm (i.e. λ0) as conventional non shifted single-mode fiber.
In the basic triangular profile design the optimum parameters giving low loss together with zero dispersion
at a wavelength of 1.55 μm cause the LP11 mode to cut off in the wavelength region 0.85 to 0.9 μm.
Thus the fiber must be operated far from cutoff, which produces sensitivity to bend-induced losses (in
particular micro bending) at the 1.55 μm wavelength.
One method to overcome this drawback is to employ a triangular index profile combined with a depressed
cladding index, as shown in Figure
39. An alternative modification of the dispersion characteristics of single-mode fibers involves the
achievement of a low-dispersion window over the low-loss wavelength region between 1.3 and 1.6 μm.
Such fibers are known as dispersion-flattened single-mode fibers (DFFs)
A typical W fiber index profile (double clad) is shown in Figure offers flat dispersion profile over a
wavelength region
Triple clad and quad cladding structures also used in DFF design which are shown here.
40. All fiber which are designed by designing different refractive index profile are exhibiting the low
dispersions which are compared in below graph.
41. Cutoff Wavelength
Single-mode operation only occurs above a theoretical cutoff wavelength λc given by:
where Vc is the cutoff normalized frequency. Hence λc is the wavelength above which a particular
fiber becomes single-moded.
Thus for step index fiber where Vc = 2.405, the cutoff wavelength is given by
Mode-field diameter and spot size
The MFD is an important parameter for characterizing single-mode fiber properties which takes into account
the wavelength-dependent field penetration into the fiber cladding.
The MFD is generally taken as the distance between the opposite 1/e = 0.37 field amplitude points and the
power 1/e2 = 0.135 points in relation to the corresponding values on the fiber axis, as shown in Figure 2.18.
42.
43.
44.
45.
46. Consider a 10km optical fiber link using a MMSI fiber with the following parameters: Core refractive index n1= 1.458, Relative
index deviation ∆= 0.002. Estimate the delay time difference between axial ray and most oblique ray. What is the value of rms
pulse broadening due to intermodal dispersion. Estimate the bandwidth and maximum bit rate of transmission assuming RZ
formatting and neglecting intramodal dispersion.
Solution:
The delay time difference between axial ray and most oblique ray can be estimated using
δTmod =
Ln1Δ
c
=
10X 103
X 1.458 X0.002
3X108
= 97.2 nS
(i) The rms pulse broadening due to intermodal dispersion can be calculated using
σmod =
Ln1Δ
2 3c
=
10X 103
X 1.458 X0.002
2 3 X 3X108
= 28 nS
(ii) The bandwidth of transmission can obtained using
B =
0.2
σmod
=
0.2
28 X 10−9
= 7.14MHz
(iii) The maximum bit rate can be obtained using
BT = 2 X B
= 2 X 7.14 MHz
= 14.28 Mbps
47. A multimode step index fiber as numerical aperture of 0.22 and a core refractive index of 1.458.the fiber
exhibits an overall intramodal dispersion of 200ps km-1. calculate overall value of the rms pulse broadening per
kilometer of the fiber when the LED source operating at 850nm has an rms spectral width of 40nm.estimate
the bandwidth of the 10km link based on this fiber.
Solution:
(i) The rms pulse broadening per kilometer due to material dispersion can be obtained as
σintra 1km = σmat = σλ L Dmat
= 40 X 1 X 200
= 80 nS km−1
(ii) The rms pulse broadening due to intermodal dispersion can be obtained as
σmodal 1km = L
NA 2
4 3 n1 c
= 103
X
0.22
4 3 X 1.458 X 3 X 108
= 15.97 nS km−1
(iii) The overall rms pulse broadening can be obtained as
σ = σintra2 + σmodal2
= 82 + 15.972
= 17.86 nS km−1
(iv) For a fiber link of 10km length, the total rms pulse broadening would be
σT = 17.86 X 10−9
X10
=178.6 nS