Full form related to optical communication

Optical communication related full form :

AON - All-optical network
APD - Avalanche photodiode
ASE - Amplified spontaneous emission
ATM - Asynchronous transfer mode
BER - Bit error rate
BH - Buried heterostructure
CNR - Carrier to noise ratio
CVD - Chemical vapor deposition
DBR - Distributed Bragg reflector
DFB - Distributed feedback
EDFA - Erbium-doped fiber amplifier
FDDI - Fiber distributed data interface
FP - Fabry Perot
FWHM - Full width at half maximum
GVD - Group velocity dispersion
HBT - Heterojunction bipolar transistor
HFD - Hybrid fiber co-axial
IMD - Intermodulation distortion
IMP - Intermodulation product
ISI - Intersymbol interference
LEAF - Large effective area fiber
LED - Light-emitting diode
LO - Local oscillator
MCVD - Modified chemical vapor deposition
MEMS - Micro electro mechanical system
MOCVD - Metal-organic chemical vapor deposition
MONET - Multi-wavelength optical network
NA - Optical carrier
OTDM - Optical time division multiplexing
OVD - Outside vapor deposition
PIC - Photonic integrated circuit
PON - Passive optical network
RDF - Reverse dispersion fiber
RIN - Relative intensity noise
RMS  - Root mean square
RZ - Return to zero
SCM - Subcarrier multiplexing
SDH - Synchronous digital hierarchy
SONET - Synchronized optical network
STM - Synchronous transport module
STS - Synchronous transport signal
TDM -  Time division multiplexing
TE - Transverse electric
TW - Transverse magnetic
VAD - Vapor axial deposition
VPE - Vapor phase epitaxy
WDM - Wavelength division multiplexing
WDMA - Wavelength division multiple access
YAG - Yttrium aluminium garnet
YIG - Yttrium iron garnet
ZDWL - Zero-dispersion wavelength

Characteristics of avalanche photo diode

Avalanche photodetector construction and also have current-voltage characteristics curve with, depicts avalanche region to shown in the figure.

This allows each of photo-generated carrier to be multiplied by avalanche breakdown. This effect is known as the avalanche break down effect.

Resulting internal gain within the photodiode, which increases the effective responsibility of the device.



Application of Avalanche photo diode

An avalanche photodiode is a semiconductor device. It is a very similar structure to that of PIN or PN photodiode types. These diodes are specially designed to work in the reverse breakdown area. In an avalanche photodiode is basically two terminal namely anode and cathode. It is similar or looks like Schottky photodiode. Avalanche multiplication of the holes and electrons created by photon impact. Here is some application of avalanche photodiode.
  • High-speed laser scanner 
  • Speed gun
  • PET scanner
  • Data communication
  • White noise generators
  • Sources in radio gears
  • Confocal microscopy
  • Fault location
  • Ultrasensitive fluorescence 
  • Particle detection
  • Optical range finding and Optical fiber

Advantages and disadvantages of avalanche photo diode

An avalanche photodiode is a one type of diode. It is specially designed to work in the reverse breakdown region. In an avalanche photodiode is basically two-terminal namely anode and cathode. It is basically PN junction diode that operates in the avalanche break down the region. This article gives information about the advantages and disadvantages of avalanche photodiode to know more details about it.

Advantages of avalanche photodiode :
  • Includes a greater level of sensitivity
  • High performance
  • Fast response time
Disadvantages of avalanche photodiode :
  • The much higher operating voltage required
  • The output is not linear
  • A much higher level of noise
  • Not as widely used due to low reliability
  • Requires high reverse bias for operation 

Avalanche photo diode

What is an avalanche photodiode?

An avalanche photodiode is one kind of semiconductor device specially designed to work in the reverse breakdown region. The symbol, of this diode, is actually same to a Zener diode. The avalanche diode comprises two terminals namely anode and cathode. The symbol is alike to the normal diode but with turn edges of the vertical bar that is shown in the following figure.

Avalanche photodiode basics :

 An avalanche photodiode is a semiconductor device types of a diode, it looks like as PN photodiode or PIN photodiode. An avalanche photodiode specially designed to work in the reverse breakdown region. In an avalanche photodiode is basically two terminal namely anode and cathode. It is similar or looks like Schottky photodiode. Avalanche multiplication of the holes and electrons created by photon impact.

In this diode when a P-N junction diode is applied with high reverse bias break down can occur by two separate mechanisms direct ionization of the lattice atoms devices, it is a Zener break down and also its is high-velocity carriers causing impact ionization of the lattice atoms called avalanche break down. APD uses has its avalanche break down phenomena for its operation. Here this articles also gives the difference between these two types of a diode; PIN photodiode versus avalanche photodiode.
The avalanche photodiode has its internal gain which increases its responsibility. Shows the figure schematic structure of an APD. By virtue of the doping concentration and physical construction of the N-P  junction, The electric field is high enough to cause of impact ionization.

Under normal operating bias, the I-layer is completely depleted. This is known as reach through condition, hence APDs are also known as reach through APD or reverse APDs.

The avalanche action enables the gain of the diode to be too much increased many times and providing a very much greater level of sensitivity.


APD schematic and variation of E - field across the diode


A breakdown voltage of diode :

The avalanche diode breakdown voltage totally depended on the density of doping. When rising the density of doping will reduce the breakdown voltage of the diode.

                          



Avalanche diode modules :

Avalanche photodiode are available as part of modules which apart from the photodiode also contain additional different electronic components. In particular, there can be a current amplifier integrated into the package, which can not only reduces the number of parts required on a circuit board but also it can also improve the noise performance and results in a better combination of bandwidth and responsivity. Some modules have been specially optimized use for an optical fiber communication system and fiber coupled.


Application of avalanche photodiode :
  • It can be used as white noise generators
  • This diode is more protecting the circuit against unwanted voltages
  • This diode is produced RF noise, they are generally used as noise sources in radio gear
  • It can be also used to generate microwave frequency
For detailed information :
This article also gives the various types of diode listed below:

What is photo diode

What does photodiode mean?

 A photodiode is a device that helps in conversion of light electric current. It is a made of semiconductor material and containing a P-N junction and also it is designed to function in revere bias. Reverse bias means that the p - side of the photodiode is connected to the negative terminal of the battery and n - side means is connected to the positive terminal of the battery. It is also sometimes referred as a photodiode detector, photo sensor or light detector. Photodiode technology has been successfully and widely used due to its low-cost rugged structure.

 A photodiode is very sensitive to light so when light or photons fall on the photodiode it easily converts light into electric current. A solar cell is also known as large area photodiode because it converts solar energy or light energy into electric energy. However solar cell works in bright light.

 Photodiode symbol :

 The schematic symbol of a photodiode is given below.  This diode is in order to convert the modulated electrical light back into an electrical signal type, Photodiode is one type of light detector.
Schematic symbol of a photodiode 
Photodiode looks like a light emitting diode. They have two terminal, one is a smaller end and other is a longer end. The longer end of the diode is the anode terminal while smaller end of the diode is cathode terminals. The characteristics of a photodiode are operated in a reverse bias mode.
The main feature of photodiode includes the  following ways :
  • Long life
  • Quick response
  • The linearity of the diode is too much good with respect to incident light 
  • Noise is very low
  • High Gain
  • Low cost
  • Long lifeline
  • Smaller size
  • Low sensitivity to temperature
  • High response speed
  • Small output current
  • Lightweight
  • Output change with respect to temperature change
  • Wide spectral responseApplied reverse voltage  be low
  • It will be always operated in reverse bias condition
Types of photodiode :

 There are different types of photodiode such as :

 There are many numerous types of photodiode available in the market.  They all work on the same basic principle, but working on different types of photodiode work in a slightly different way. A photodiode can be classified based on its construction are as follows given below :
  • PN photodiode - It is the first type of photodiode to be developed but not as widely used as others due to better performance parameters of other types of photodiodes.
  • PIN photodiode - It is one of the most widely used photodiodes, It generally offers lower capacitance and efficiently collects light photons better than PN photodiodes.
  • Avalanche photodiode -  It provides very high gain levels but comes with high noise levels
For detailed information :
Read more >>
Application of Photodiode :
  • An optical fiber communication system
  • Automotive devices
  • Solar cell panels
  • Medical devices
  • Demodulation
  • Camera light meters
  • Street lights
  • Logic circuit
  • Photodetection circuits
  • Character recognition circuit
  • Televisions and remote control in VCRs
  • Measurement of the intensity of light in science and industry
More detailed information 

Working of photo diode

In the photodiode, convert the modulated light back into an electrical signal. As the intensity of an optical signal at the receiver is very low, the detector has to meet high-performance specifications.

The conversion efficiency must be very high at the operating wavelength. The speed of the response must be high enough to ensure that the signal distortion does not occur. It must be possible to operated continuously over a wide range of temperature for many years.

At present, these requirements are met by a reverse biased p-n photodiode. In these devices, the semiconductor material will absorbs a photon of light, which excites an electron from the valence band to the conduction band.

The photogenerated electron leaves behind it a hole, and so each photon generates two change carriers. This increases the material conductivity so-called photo conductivity resulting in an increase in the diode current. 

V-I characteristics of photodiode :

The characteristics of the photodiode are shown in clearly in the following figure. A photodiode is operated in a reverse bias mode. To show in figure photocurrent is nearly independent of reverse bias voltage which is applied. For zero luminance, the photocurrent is almost zero excluding for small dark current to shown in the figure.
V-I characteristics of a photodiode

Application of photo diode

Photo diode generally used to convert the light into current or voltage based on the mode of operation of the device. So photo diode used in various industries. Now you can check the application of photo diode one by one below :

Application of photo diode :
  • Light detector. 
  • Used in demodulates.
  • Encoders.
  • Optical communication system.
  • High speed counting and switching circuits. 
  • Computer punching cards and tapes.
  • Light operated switches.
  • Sound track films.
  • Cameras.
  • Electronic control circuits. 
  • Used in cameras.
  • Medical devices.
  • Digital signal processing.
  • Safety equipment.
  • Position sensors. 
  • Bar code scanners.
  • Automotive devices.
  • Compact disk player.
  • Smoke detector.
  • Position sensor.
  • Surveying equipment.

PIN photo diode

What is the PIN diode?

 The PIN photodiode is a one type photodetector, it is used to convert an optical signal into an electrical signal. A photodiode in general and in this case PIN photodiode will respond to different light wavelength. It is generally the thickness of top p-type region one of the key parameters in determining the response sensitivity.

Basically, the PIN diode is a one types of a photodetector. This diode can be diagrammatical as being a PN junction. but in PIN diode intrinsic layer between the PN and layers. It converts an optical signal into an electrical signal. 

The PIN diode comprises three regions:
  1.  P - region
  2.  I - region
  3.  N-region 
In PIN diode both the P and N region are heavily doped and the region between the P and N layer where there are no majority carriers
Structure of  PIN diode
PIN diode operates in the exact same way as a normal diode. but the only difference is that depletion region, It normally exists between the P and N region in the reversed diode is larger. A region between the P and N region contains no charge carriers.

P and N region are heavily doped, P region has been doped holes and N region has been doped to contain excess electron. so the region between P and N region contain no charge carrier as any electrons or holes combine, so the depletion region has no charge carriers it acts as an insulator.

When the diode is forward biased, the carrier concentration, holes and electron is very much higher than the intrinsic level carrier concentration. 

This article also gives the various types of diode listed below:

Advantages and disadvantages of photodiode

A photodiode can convert light into either current or voltage depending upon the mode of operation. In general, a photodiode is designed to operate in reverse bias. It is one type of photodetector. In this article, you can check it out the advantages and disadvantages of knowing more about it. 

Advantages of photodiode :

  • The photodiode is linear
  • Low resistance
  • A very good spectral response
  • Better frequency response
  • Low dark current
  • Fastest photodetector
  • Long lifetime
  • Low noise
  • High quantum efficiency
  • It is highly sensitive to the light
  • Compact and lightweight
  • No high voltage requires
  • Ruggedized the mechanical stress
  • Using photodiode the speed of operation is very high

Disadvantages of photodiode :

  • Require increases in  the dark current 
  • It depends on the temperature
  • Small active area
  • Normal PN junction photodiode has a very high response time
  • It has very low sensitivity
  • Light sensitive device
  • Poor temperature stability
  • Change in current is very small,  hence may not be sufficient to drive the circuit
  • It need offset voltage 

Application of PIN diode

A PIN diode is used in a variety of different applications from low to high radiofrequency. PIN diodes are very good for RF switching and photodiode. Here is some application related to the PIN diode to know more details about PIN diode 

Application of Photodiode

  • A PIN diode is used as a photodetector for most fiber optic applications.
  • There are used as a variable resistor in at RF and microwave frequency.
  • They are used in electric Pre - Amplifier to boost sensitivity.
  • It used as a high voltage rectifier.
  • Audio CD players, Computer CD drive, DVD players.
  • In a phase shifter circuit considered as a lumped variable impedance microwave circuit element.
  • Nuclear radiation detector.
  • It can be also used limiter circuit and modulator.
  • PIN diodes are utilized as series or shunt connected switches in a phase shifter design.


Advantages and disadvantages of PIN diode

A PIN diode is used in a variety of different applications from low to high radiofrequency. PIN diodes are very good for RF switching and photodiode. So now check it out the advantages and disadvantages of PIN diode to know more details about PIN diode.


Advantages of PIN diode :

  • Low noise
  • Low dark current
  • Low bias voltage
  • Higher reverse voltages to be tolerated
  • High-speed response
  • Low junction capacitance 
  • Large depletion region 

Disadvantages of PIN diode :

Fiber optic cable advantages

A fiber optic cable is a flexible and transparent fiber made by drawing plastic or glass to a diameter slightly thicker than that of a human hair. Optical fiber cable is generally used most often as a means to transmit light between the two ends of the fiber and also find wide usage in the fiber optic communication system. So now let use check about the advantages and of fiber optical cable to know more details about fiber optic cable.

Advantages of fiber optic cable :

  • Fiber optic cable has a much greater bandwidth than metal cables
  • Optical fiber capability has a bandwidth capability of 400 MHz/km or greater
  • Longer lasting
  • Thinner 
  • Faster speed
  • Less signal degradation
  • Light signal
  • Long lifespan
  • Extremely high bandwidth
  • Crosstalk immunity
  • High carrying capacity
  • Reduced size and weight cable
  • An optical fiber can provide data transmission performance up to 10 Gbps
  • Resistance to corrosion and temperature variations.
  • High resistance ever-dropping
  • Immunity to electrical noise
  • Greater cable distance without a repeater
  • An industry standard for high-speed networking
  • Low power losses
  • an optical fiber is generally made of silica band, raw materials abundant compared with copper
  • Low-security risk
  • Less expensive than copper cable

Fiber optic cable disadvantages

The main features of fiber optic cable are that it is a flexible, transparent fiber made by drawing plastic or glass to a diameter as a means to transmit light between the two ends of the fiber and also find wide usage in fiber-optic communication. So now let use check about the disadvantages of optical fiber cable to know more details about fiber optic cable. 

Disadvantages of fiber optic cable :


  • Special training required to attach the connector to the cable
  • Difficult to splice
  • Can't be curved
  • Low power
  • The distance between the transmitter and receiver should keep short or repeater are needed to boost the signal
  • Difficult to work with and difficult to install
  • Higher initial cost installation
  • More expensive to repair or maintain
  • Interfacing cost
  • Connector problem
  • Highly susceptible
  • Expensive in comparison with conventional electrical cables
  • Limited application
  • More vulnerable damage compare to copper wires
  • Cost is higher than copper cable
  • Require specific skills
  • Affected by chemical

Fiber optic cable color code

Fiber color code:

In optical fiber terms inside the cable each tube in a loose tube cable, Individual fiber will be color-coded for different identification. So now in optical fiber communication, the fiber allows the convention created for telephone wire except fiber are identified individually, not pairs. Color fiber is spliced to ensure continuity of color codes throughout a cable run. The figure shows the color coding in optical fiber communication.


Fiber color codes

Connector color codes :


The earliest days of fiber optics cable like, orange, black or gray was multimode and yellow single mode. However, the advent of metallic connectors like the FC and ST mode connector color coding difficult, so colored strain relief boots were often used.

Fiber optic cable bandwidth

Introduction : 

In general, bandwidth is referred to as the range of a particular fiber optic cable. In reality, different cable has a different bandwidth capacity of transmitting data from one point to another. The bandwidth of fiber optic cable determines the maximum speed of the data pulses to the fiber cable can handle it. We know that the bandwidth is normally stated in terms of megahertz-kilometers.  For instance, there those which are most suitable is carrying large quantity data over long distances within a short time. Consequently, there are those most suited in transmitting a large quantity of data over short distances. In this case, the cable made to transmit data over very long distance cannot be used to transmit the same data over a short distance and if that is done, then the frequency will too much lower. For that reason, it is very important to study that bandwidth of particular fiber optic cable.

As the length of the fiber cable is increased, the bandwidth decreases in propagation. In general, a common 62.5/125 micrometer cable has a bandwidth in the 100 to 300 MHz-km range.

 The speed of optical fiber cable while in using a single mode fiber cable can run from a few meters to 40 kilometers Where a multimode fiber optic cable is used for much shorter ranges.

Fiber types and bandwidth  :


Single mode - 100 Ghz-km
Graded index - 560 MHz-km at 1300 nm, 160 MHz-km at 850 nm 
Step index - 20 MHz-km

 Conclusion :

 The cost of fiber cables with the bandwidth capacity of fiber optic cable. You can have also found that fiber cable with efficiently and faster bandwidth capacity is more expensive than others. The greater the frequency and larger the bandwidth of fiber optic cable the more efficient is the cable. So and we already know that different people have got different reasons to purchase a fiber cable, the variation of bandwidth has indeed been beneficial to many. Therefore, the bandwidth capacity of fiber optic cable before purchasing it.

Fiber optic cable definition

A fiber optic cable is a flexible, high-speed data transmission medium, transparent fiber made by drawing plastic or glass to a diameter slightly thicker than that of a human hair. It is a high-speed data transmission medium.

The optical fiber cable is generally used as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communication. Digital data is transmitted through the cable via the rapid pulses of light. The receiving end of fiber optic transmission translates the light pulses into binary values, which can be read by a computer. Color fiber is spliced to ensure continuity of color codes throughout a cable run.

Since fiber optic cable provides fast transfer speed and large bandwidth, They are used for a large part of the internet backbone. For example, most transatlantic telecommunication cables between the U.S and Europe are fiber optic. In recent years, fiber optic technology has become increasingly popular for local internet connection as well. 
  • Fiber optic cable can be used as a medium for computer networking and telecommunication because it is flexible and can be bundled as cables
  • It also is used in telephone, military and space application
  • It can be used an easy, economical and attractive solution for a lighting project
  • It can be used to transmit power using a photovoltaic cell to convert the light into electricity. 

Fiber optic cable uses

A definition of fiber optic cable is a flexible, as well as transparent fiber made by drawing plastic or glass to a diameter slightly thicker than that of a human hair. Optical fiber cable can be generally used most often as a means to transmit light between the two ends of the fiber and find wide usage in the fiber optic communication system. So now let use check about where to uses of fiber optic to know more details about fiber optic cable.

Fiber optic cable can accommodate a variety of needs is given below :

  • It can be used in communication, fiber optic sensors, as well as illumination,
  • It is used a medical treatment like light guides, imaging tools and also as lasers for surgeries
  • It is used hydrophones seismic or SONAR application, submarines, like wiring in aircraft, and other vehicles and also for field networking
  • It used in computer networking, telephone, military as well as space application
  • It can provide an easy, economical and attractive solution for a lighting project
  • It is used for data transmission
  • It can be also used microscopy and biomedical research
  • It is used to transmit power using a photovoltaic cell to convert the light-electricity
  • It is used to connect in a variety of network settings 
  • And also help increase the speed and accuracy of data transmission
  • Broadcast/cable companies are using fiber optic cable for wirings like HDTV, CATV, internet, video on demand and other applications

Fiber optic cable speed

A fiber optic cable is a flexible, as well as transparent fiber made by drawing plastic or glass to a diameter as a means to transmit light between the two ends of the fiber and find wide usage in fiber optic communication system. allow data to be transmitted high speeds over a great distance.

There are two types of fiber :

  • Single mode fiber 
  • Multimode fiber.
The two types of fiber and speed from these two fibers are different. A single-mode fiber cable can run from a few meters to 40 kilometers While multimode fiber optic cable is used for too much shorter ranges. 

Speeds :

  
Fiber optic cable is generally in single mode fiber uses only (OS1) while in multimode uses different (OM1, OM2, OM3, OM4). Single mode fiber optic can reach speed up to 100GB whereas multimode fiber optic run at speed from 100 Mb to 10 GB.

In fiber optic cable transmit at different speed over varying length depending on the size is used.

OM1 - 275 m ,33 m (Gigabit range)
OM2  - 550 m, 82 m (Gigabit range)
OM3 - 800 m, 300 m, 100 m, 100 m (Gigabit range)
OM4 - 1100 m, 550 m, 150 m (Gigabit range)
OS1 - 40km (Gigabit range)

 Here we have to also compare the speed of Coaxial cable vs fiber optic cable. 

 Fiber optic cable is just flat out faster. Fiber optic cable speed up to 10 Gbps, symmetrical upload as well as download bandwidth.

While in cable internet speed vary by provider and range from 10 Mbps to 1Gbps download speed and upload speed from 3 Mbps to 50 Mbps.

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