The document discusses optical sources and detectors used in fiber optic communication systems. It describes light emitting diodes (LEDs) and laser diodes as optical sources and their operating principles. It also discusses different types of photodetectors - PN detectors, PIN detectors, and avalanche photodiodes (APDs). The key characteristics and operating principles of these optical components are explained in detail. Various applications of lasers are also mentioned.
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
Optical fiber communication Part 2 Sources and DetectorsMadhumita Tamhane
For optical fiber communication, major light sources are hetero-junction-structured semiconductor laser diode and light emitting diodes. Heterojunction consists of two adjoining semiconductor materials with different bandgap energies. They have adequate power for wide range of applications. Detectors used are PiN diode and Avalanche Photodiode. Being very small in size and feeding to small core optical fiber, it is very important to study emission characteristics of sources and their coupling to fiber. As it can operate for low power over a long distance, received power is very small, hence study of noise characteristics of detectors is very essential...
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
Optical fiber communication Part 2 Sources and DetectorsMadhumita Tamhane
For optical fiber communication, major light sources are hetero-junction-structured semiconductor laser diode and light emitting diodes. Heterojunction consists of two adjoining semiconductor materials with different bandgap energies. They have adequate power for wide range of applications. Detectors used are PiN diode and Avalanche Photodiode. Being very small in size and feeding to small core optical fiber, it is very important to study emission characteristics of sources and their coupling to fiber. As it can operate for low power over a long distance, received power is very small, hence study of noise characteristics of detectors is very essential...
The following ppt gives overview about Optical Communication and the underlying principle with the general overview of all the contents for optical communication
The attached narrated power point presentation explores the different methods of modulation of light such as direct modulation and external modulation. The material will immensely benefit KTU final year B Tech students who prepare for the subject EC 405, Optical Communications.
The attached narrated power point presentation attempts to explain the working principle, types, classifications, merits, demerits, applications,safety and deployment issues related to Raman Amplifiers. The material will be useful for KTU final year B Tech students who prepare for the subject EC 405, Optical Communications.
A Klystron is a vacuum tube that can be used either as a generator or as an amplifier or as an oscillator, at microwave frequencies.The Klystron is a linear beam device; that is, the electron flow is in a straight line focused by an axial magnetic field.
The attached narrated power point presentation attempts to explore the various semiconductor injection laser diode structures. The material will be useful for KTU final year B tech students who prepare for the subject EC 405, Optical Communications.
An electron gun generates an electron beam that is interacting with a slow-wave structure.
It sustains the oscillations by propagating a traveling wave backwards against the beam
. The generated electromagnetic wave power has its group velocity directed oppositely to the direction of motion of the electrons.
The output power is coupled out near the electron gun.
Photo Diode as a Light sensor .Photo diode as an Electronic Device. V-I curve of Photo Diode.Advantage ,Disadvantage of Photodiode.Application of Photodiode.Types of Photodiode.
The following ppt gives overview about Optical Communication and the underlying principle with the general overview of all the contents for optical communication
The attached narrated power point presentation explores the different methods of modulation of light such as direct modulation and external modulation. The material will immensely benefit KTU final year B Tech students who prepare for the subject EC 405, Optical Communications.
The attached narrated power point presentation attempts to explain the working principle, types, classifications, merits, demerits, applications,safety and deployment issues related to Raman Amplifiers. The material will be useful for KTU final year B Tech students who prepare for the subject EC 405, Optical Communications.
A Klystron is a vacuum tube that can be used either as a generator or as an amplifier or as an oscillator, at microwave frequencies.The Klystron is a linear beam device; that is, the electron flow is in a straight line focused by an axial magnetic field.
The attached narrated power point presentation attempts to explore the various semiconductor injection laser diode structures. The material will be useful for KTU final year B tech students who prepare for the subject EC 405, Optical Communications.
An electron gun generates an electron beam that is interacting with a slow-wave structure.
It sustains the oscillations by propagating a traveling wave backwards against the beam
. The generated electromagnetic wave power has its group velocity directed oppositely to the direction of motion of the electrons.
The output power is coupled out near the electron gun.
Photo Diode as a Light sensor .Photo diode as an Electronic Device. V-I curve of Photo Diode.Advantage ,Disadvantage of Photodiode.Application of Photodiode.Types of Photodiode.
This ppt will explain the basic operation, advantages, disadvantages, applications of LED and operation, characteristics and applications of varactor diodes.
A p-n junction diode which emits spontaneous emission of radiation in the visible and IR regions when forward biased is called Light Emitting Diode.
This converts the input electrical energy into optical energy in the visible or IR spectrum depending on the semiconductor material
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
1. Optical Sources and Detectors
Subject Teacher
Mrs. Pallavi Mahagaonkar
Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
2. To understand the principles of fiber optic communication
system.
To learn measure different parameter of optical fibers
To understand essential optical components of Fiber Optic
Communication
To study the applications of fiber optic communication
systems
Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
3. LED and LASER diode
Principles of operation
Concepts of line-width, phase noise, switching and modulation
characteristics-typical LED and LD structures
PN detector
PIN detector
Avalanche photodiode-principles of operation,
Concepts of responsivity
Sensitivity
Quantum efficiency
Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
4. Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
High
intensity
output
Easy
Modulation
Size &
configuration
LED
&
LASER
Monochromatic
Highly
reliable &
Low noise
Coupling
From One
fiber to other
Cost
Effective Optical
source
7. Light Amplification by Stimulated Emission of
Radiation
Applications – Medical, Scientific and Commercial
laser printers
barcode scanners
DNA sequencing instruments
fiber-optic
semiconducting chip manufacturing
free-space optical communication
laser surgery and skin treatments
cutting and welding materials
Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
8. Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
CHARACTERISTICS REQUIRED:
Capability to sense light power and convert to corresponding
varying current
Very high efficiency required to convert all of weak input power to
desired signal
High response or sensitivity in desired wavelength.
Minimum noise
Fast response speed and high bandwidth
Insensitive to temperature variation
Physically compatible dimension of optical fiber
Low cost and long life
9. Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
Photomultipliers –
Photocathode and electron multiplier in vacuum tube
High gain, low noise
Large size and high voltage required
Pyro-electric crystals –
Photon to heat conversion
Variation in dielectric constant gives change in capacitance
Cooling arrangements required
Semiconductor photo detectors –
Size is large
Photodiodes
10. Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
Small size
Suitable material
High sensitivity
Fast response time
Types of photo diodes –
PiN diode
Avalanche Photodiode APD
11. Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
A photodiode is a PN-junction diode that consumes light energy to
produce electric current.
Sometimes it is also called as photo-detector, a light detector, and
photo-sensor.
These diodes are particularly designed to work in reverse bias
condition, it means that the P-side of the photodiode is associated
with the negative terminal of the battery and n-side is connected
to the positive terminal of the battery.
12. Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
When a photon of ample energy strikes the diode, It makes a
couple of an electron-hole This mechanism is also called as the
inner photoelectric effect
If the absorption arises in the depletion region junction then the
carriers are removed from the junction by the inbuilt electric field
of the depletion region
The holes in the region move toward the anode, and electrons
move toward the cathode, and a photocurrent will be generated
The entire current through the diode is the sum of the absence of
light and the photocurrent So the absent current must be reduced
to maximize the sensitivity of the device
13. Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
A PIN diode is a diode with a wide, lightly doped 'near' intrinsic
semiconductor region between a p- type semiconductor and an n-type
semiconductor region.
The p-type and n-type regions are typically heavily doped because they
are used for ohmic contacts.
The wide intrinsic region is in contrast to an ordinary PN diode. The wide
intrinsic region makes the PIN diode an inferior rectifier (one typical
function of a diode), but it makes the PIN diode suitable for attenuators,
fast switches, photo detectors, and high voltage power electronics
applications.
The speed of the PIN diode is limited by variation in the time it takes
electrons to pass through the device. This time spread can be spread in
two ways: By increasing the bias-voltage By reducing the thickness of
intrinsic layer
TYPES: Metal-Semiconductor PIN diode Hetero junction PIN diode
14. Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
A microwave PIN diode is a semiconductor device that operates as
a variable resistor at RF and Microwave frequencies.
A PIN diode is a current controlled device in contrast to a varactor
diode which is a voltage controlled device.
When the forward bias control current of the PIN diode is varied
continuously, it can be used for attenuating, levelling, and
amplitude modulating an RF signal.
15. Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
It is used as a Photo Detector for most fiber optic application
They are used in electronic pre-amplifier to boost sensitivity
They are used as a variable resistor in at RF and microwave
frequency
Widely used in RF modulator circuit to control RF intermediation
distortion
In a phase shifter circuit considered as a lumped variable-
impedance microwave circuit element
PIN diodes are utilized as series or shunt connected switches in
phase shifter designs
The switched elements are either lengths of transmission line or
reactive elements
16. Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
INTRODUCTION:
The performance of Avalanche photo diode depends upon the
efficiency.
It convert light energy in to electrical signal.
Designed to operate in reverse bias condition
Photo electric effect:
17. Prepared By Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)
High gain due to avalanche multiplication effect
Increased noise
Si-InGaAs APD often used(diagram on right) n + p + pi
Electricfield Depletion region
High resistivity p-doped layer increases electric field across
absorbing region
High-energy electron-hole pairs ionize other sites to multiply the
current Leads to greater sensitivity
