OPTICAL FIBERS IN COMMUNICATION SYSTEM
Because of wide bandwidth, more long distant communication, less weight and security etc., optical fibers play an important role in a communication system. The basic mechanism used in the communication system is understood by the following block diagram.
The optical fiber communication system mainly consists of three parts. They are
1. Transmitter
2. Optical fiber
3. Receiver.
1. Transmitter:
The transmitter section consists of a modulator, encoder, light source, drive circuits and couples. Initially, AF signal like voice, data which is in analogue form is given to the input of the encoder in the transmitter section. The encoder is an electronic system used to convert analogue information into binary information. this binary data comes out as stream electric pulses and these pulses are again converted into pulses of optical power by modulating the light emitted by the light source. That means the laser drive circuit directly modulates the intensity of the semiconductor laser with the encoded digital signal.
This digital optical signal is launched into the optical fibre cable. And the signal is propagated through optical fiber due to the principle called total internal reflection.
As the signal propagates in the fiber, then it suffers attenuation. Attenuation means loss of optical power due to absorption and scattering of photons. So, to retrieve the signal or overcome attenuation a repeater is added at the end of the optical fiber.
2. Optical fiber:
The optical fiber is used to send an optical signal to the receiver section. It is possible due to total internal reflection.
3. Receiver:
The receiver section converts the optical signal into a corresponding electric signal. And is amplified and recast in the original form using an electrical generator. Also, the receiver consists of a light detector which is used to convert binary data into an analogue form