15-01-2013, 03:14 PM
Optical receiver operation
Optical receiver.pptx (Size: 316.64 KB / Downloads: 29)
Introduction of receiver operation
basic and general operation of the optical receiver is:
To convert the optical energy from end of a fiber into electrical signal
Circuit used in optical receiver
1-photodetector.
2-front end amplifier.
3-filter equalizer.
4-sampling circuit.
5-decision circuit.
6-clock recovery.
Elementary operation
1-Photodetector : it may be either pin or avalanche which produces electric current proportional to optical power level.
2-Front end amplifire : it boosts the low level signal .
3-Filter and equlizer : filter removes the noise and equlizer can reshape the distorted signal or can say to remove ISI.
Error sources
Errors can be takes place from various noises and disturbance sources.
Noise disturbs the transmission of the signals
It may be external (atmospheric) and internal (fluctuation of electrical signal).
Internal noise may be of two type:
1- Shot noise- it arises in electronic devises due to discrete nature of current flow in device.
2-Thermal noise- it is due to random motion of electron in conductor.
Diagram discription
Photon detection quantum noise arises due to Poisson fluctuation.
Photo detector noise arises due to bulk of dark current, surface leakage current staticalgain fluctuation.
Thermal noise arising from the detector load resistor
Due to effect of all noise amplifier noise occurs.