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. ...
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. ...
A spectrophotometer is an instrument that measures the amount of light absorbed by a sample. Spectrophotometer techniques are used to measure the concentration of solutes in solution by measuring the amount of the light that is absorbed by the solution in a cuvette placed in the spectrophotometer .
The tunable single-frequency (SF) narrow-linewidth fiber laser with all-fiber complex cavity structure is designed, which is composed of an optical fiber tunable filter, a high-precision ring filter, and a fiber loop mirror. A 980-nm semiconductor laser is used as the pumping source, and the ytterbium-doped fiber is employed as the gain medium and saturable absorber, then a wide-spectrum tunable single-frequency narrow-linewidth laser output from 1030 nm to 1090 nm is successfully realized. When the pump power is up to 300 mW, the output power is 18.5 mW and the slope efficiency is 7.95% at the wavelength of 1070 nm. There is no mode hopping phenomenon within 1 h, and the standard deviation of power stability is less than 1 %. When the pump power is 200 mW, the linewidth is measured by the delay self-heterodyne method, and the average line width in the wavelength tuning range is 8.7 kHz, and the relaxation oscillation frequency is 64 kHz.
What is the Structure and Working Principle of WDM Devices.pdfHYC Co., Ltd
TFF and AWG are the two most commonly used WDM technologies. This article will introduce the structure and working principle of TFF WDM devices. The structure of a three-port WDM device includes a dual-fiber collimator, a single-fiber collimator, and a TFF filter.
2013 University of Virginia's W.M. Keck FRET Workshop: Basic Filter Considera...Jeff Carmichael
This was part of an in-person, live presentation at the 2012 annual University of Virginia's Keck FRET workshop. The presentation covered basic optical filter considerations for FRET microscopy, including the basics of how optical interference filters work. Filter set combinations for different approaches to FRET imaging are proposed.
How to Create Map Views in the Odoo 17 ERPCeline George
The map views are useful for providing a geographical representation of data. They allow users to visualize and analyze the data in a more intuitive manner.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
The Art Pastor's Guide to Sabbath | Steve ThomasonSteve Thomason
What is the purpose of the Sabbath Law in the Torah. It is interesting to compare how the context of the law shifts from Exodus to Deuteronomy. Who gets to rest, and why?
We all have good and bad thoughts from time to time and situation to situation. We are bombarded daily with spiraling thoughts(both negative and positive) creating all-consuming feel , making us difficult to manage with associated suffering. Good thoughts are like our Mob Signal (Positive thought) amidst noise(negative thought) in the atmosphere. Negative thoughts like noise outweigh positive thoughts. These thoughts often create unwanted confusion, trouble, stress and frustration in our mind as well as chaos in our physical world. Negative thoughts are also known as “distorted thinking”.
3. Optical Filters
Optical filters are used for example to separate a single of
multiple optical signals from a WDM signal
Optical filters are also widely used to reject out-of-band ASE
noise imposed on the desired signals
Some of the desirable features of an optical filter are:
1. A high out-of-band signal rejection,
2. Temperature independent operation,
3. Low insertion loss,
4. Compact size and
5. low cost
4. Optical Filters
In this course, we will discuss the four most common optical
filters used in communications namely:
1. Grating Based Filter
2. Arrayed Waveguide Grating Filter
3. Fabry-Perot Filters
4. Fiber Bragg Grating Filter
5. Grating Filters
Grating filters exploit the phenomenon of light-diffraction to
different wavelengths of an input optical signal
It uses a diffraction grating, which is essentially a glass having
a rectangular cross-section and multiple slits or groves
When light composed of different wavelengths impinges on
such a grating, it passes through the narrow slits and spreads
out at the output due to diffraction
Hence each slit effectively acts like a separate source of light
7. Grating Filters
An important quality of diffraction grating is that for a unique set
of discrete angles, the light diffracted from the multiple slits
facing in different directions are in phase
This coherent phase relationship results in constructive
interference among various diffracted wavefronts at spatially
separate points at the opposite side of the diffraction grating
The condition for constructive interference to occur for a grating
having a uniform slit spacing of d between two consecutive slits
and an incident light of wavelength λ is given by:
8. Grating Filters
Where m is the diffraction order and θ is the diffraction angle
The operating principle of a grating filter based on a diffraction
grating can be understood from the simplified diagram
The optical signal to be filtered impinges on a diffraction
grating, which results in a diffraction pattern at the opposite side
The diffraction pattern is composed of multiple bright spots of
light at different wavelengths separated spatially
9. Grating Filters
The spatial distance among the different bright spots depends
both upon:
1. The slit spacing of the grating and
2. The distance of the screen used for observing the pattern
A narrow bandwidth of light can be filtered out by using an exit
slit located at some distance from the diffraction grating
The bandwidth retained depends upon the size of the exit slit
10. Grating Filters
In order to construct a tunable grating filter, the diffraction
grating is mounted on a mechanical structure that can be
rotated externally
When the diffraction grating rotates, the diffraction pattern on
the screen also shifts, resulting in different retained
wavelengths exiting the exit slit
11. Arrayed Waveguide Grating Filter
The grating filter described in the previous section uses a
diffraction grating for achieving spatial dispersion of the input
optical signal
Now we discuss the Arrayed Waveguide Grating (AWG) filter,
which uses optical waveguides for achieving a spatial
separation similar to the grating filter
AWG filters rely on the principle of optical interferometers
12. Arrayed Waveguide Grating Filter
The simplest interferometer is the Mach-Zehnder
Interferometer (MZI)
MZI is composed of two optical couplers connected by two
separate waveguides in order to filter a single wavelength, in a
fashion that is reminiscent of the MZM
Similarly, the AWG is composed of two optical couplers that are
connected by more than two waveguides in order to filter
multiple wavelengths
14. Arrayed Waveguide Grating Filter
Observe that the AWG consists of input and output
waveguides, two slab waveguides and a set of arrayed
waveguides, which are made up of silica
When the optical signal passing through the input waveguide
enters the first slab waveguide, it diverges in the free
propagation region of the slab waveguide
The signal that spreads in the first slab waveguide is captured
by the set of arrayed waveguides which function as dispersive
elements and are arranged to have a constant length-difference
between the adjacent waveguides
15. Arrayed Waveguide Grating Filter
The length of each waveguide is chosen by ensuring that a
particular wavelength undergoes the same dispersion in each
waveguide
Therefore, after travelling through the free propagation region
of the second slab waveguide, all the optical signals having a
particular wavelength constructively focus their output on a
single output waveguide
16. Arrayed Waveguide Grating Filter
The length-difference △L of the adjacent arrayed waveguides
required for achieving the constructive focusing of all the optical
signals having a particular wavelength can be written as:
Where m is the order and ng is the effective refractive index of
the arrayed waveguide
The central wavelength of the incident optical signal is
represented by λ𝑐
17. Fiber Bragg Grating Filter - Concept
From a practical standpoint, a diffraction grating is defined as
any optical element capable of imposing a periodic variation in
the amplitude or phase of light incident on it
Clearly, an optical medium whose refractive index varies
periodically acts as a grating since it imposes a periodic
variation of phase when light propagates through it
Such gratings are called index gratings
18. Bragg Diffraction
The diffraction theory of gratings shows that when light is
incident at an angle θi (measured with respect to the planes of
constant refractive index), it is diffracted at an angle θr such
that:
Λ is the grating period,
λ is the wavelength of the light inside the medium
𝑛 is the average refractive index
m is the order of the Bragg diffraction
19. Fiber Bragg Grating Filter
In the case of single-mode fibers, the incident and diffracted
light lie along the fiber axis
As a result, the diffracted light propagates backward
Therefore:
If m = 1, the period of the grating is related to the vacuum
wavelength as:
This condition is known as the Bragg condition
20. Fiber Bragg Grating Filter
A fiber grating acts as a reflector for a specific wavelength of
light for which the phase-matching condition is satisfied
21. Fiber Bragg Grating Filter
Gratings satisfying Bragg condition are referred to as Bragg
gratings
Physically, the Bragg condition ensures that weak reflections
occurring throughout the grating add up in phase to produce a
strong reflection
For a fiber grating reflecting light in the wavelength region near
1550 nm, the grating period is:
22. Fabry-Perot Filter
A Fabry-Perot (FP) filter exploits the interference of light in a
resonating cavity
The resonating cavity of the FP filter consists of two highly
reflective mirrors that are placed parallel to each other at a
distance L
The input light enters into the cavity through the left mirror and
after traveling a distance of L it falls on the reflective side of the
right mirror
23. Fabry-Perot Filter
A part of the light exits through the right mirror, while a part of it
is reflected back into the cavity
The percentage of light refracted or reflected depends upon the
reflectivity of the mirrors
The resonating cavity structure of the FP filter can be used to
filter out a particular wavelength by choosing the length of the
cavity to be an integer multiple of half the wavelength
That is L = mλ/2, where m is an integer and λ is the wavelength
to be retained
25. Fabry-Perot Filter
Light having a particular wavelength λ interferes constructively
after going through a round-trip inside the cavity, the resultant
high intensity light exits through the right facet
The power transfer function PTF of the filter in terms of
wavelength is given by:
A and R are the absorption loss and reflectivity of the each
mirror’s respectively and n is the refractive index of the cavity