Redusedcal fibre is an example of guided media or connection oriented media. It is suitable for long distance communication. Let's discuss about it.
Optical fibre basic features :
- Transmission of signal is in optical form.
- It is made of glass or plastics.
- Efficiency high.
- Bandwidth very high.
- Diameter small.
- Noise immunity high.
- Highly expensive.
- Weight light
- Transmission speed is high.
Application :
1.
Medical : It is used as light guides, imaging tools and also as lasers for surgeries.
2.
Telecommunication : Fiber is used for transmitting and receiving purpose.
3.
Data storage : It is used for data transmission.
Special properties of Optical fibre :
1. Optical fibre transmits a signal encoded beam of light by means of total internal reflection.
Lets discuss what is Total Internal Reflection??
When the incident angle is greater than the critical angle, the light is reflected back to medium 1.
There will not be any light transmission in medium 2.
This is called Total Internal Reflection.
There are two conditions for Total Internal reflection. What are they??
- The medium from which light is incident, must be optically denser than the medium to which it is incident.
- The angle of incidence in the denser medium must be greater than the critical angle of the denser medium with respect to the rarer medium.
2. It act as waveguide for frequency of 10^14 to 10^15 Hz.
3.
There are three transmission modes:
- Step index multimode
- Graded index multimode
- Single mode
4.
Two types of light sources:
- Light Emitting Diode (LED)
- Injection Laser Diode (ILD)
5.
WDM:
Multiple beams of light at different frequency see transmitted on the same fibre. This is a form of FDM.
Need of Optical Fibre Communication:
- Optical fibre is used by many telecommunication companies.
- It has extremely high data rates which allows extremely high data rates.
- It has high bandwidth.
- It has very low loss.
- It has the potential for transmission over long distances.
- It is suitable for long distance transmission.
What are the elements of optical fibre??
Fig: Block diagram of optical fibre communication
Optical fibre is made of three main elements :
- Transmitter
- Transmission channel
- Receiver
- Transmitter :
Transmitter is that device /node that sends data.
- An electric signal is applied to the optical transmitter. The optical transmitter consists of driver circuit, light source and fibre flyer.
- Driver circuit drives the light source.
- Light source converts electrical signal to optical signal.
- Fibre flylead is used to connect optical signal to optical fibre.
2.
Transmission channel :
Transmission channel consists of a cable that provides mechanical and environmental protection to the optical fibre.
- Each optical fibre acts as an individual channel.
- Optical splice is used to join Two individual optical fibres.
- Optical connector is for temporary joining between two individual fibres.
- Optical coupler provides signal to other devices.
- Repeater converts optical signal into electrical signal and passes it to electronic circuit. Here the signal is reshaped and amplified as it get redused and distorted with increasing distance. This signal is then again converted into optical signal by optical transmitter.
3.
Reciever:
Receiver is that receives data from transmitter.
- Optical signal is applied to the optical receiver. It consists of photo detector, amplifier and signal restorer.
- Photo detector converts the optical signal to electrical signal.
- Signal restorers and amplifiers are used to improve signal to noise ratio of the signal as there are chances of noise to be introduced in the signal due to the use of photo detectors.
For short distance communication only main elements are required :
Source: LED
Fibre: Multimode step index fibre
Detector : PIN detector
For long distance communication along with main elements there should be couplers, Beam splitters, repeaters, optical amplifier.
Source : LASER diode
Fibre: Single mode fibre
Detector : Avalanche photo diode(APD)
These are the Concept of Optical fibre. We'll be glad if you share your valuable information with us regarding this topic, then it will be a golden oppertunity for all of us to improve ourselves and know more. Comment below!!
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