Both the LED and LD have attenuation low Optic Receiver. Two types of semiconductor receiver used in fiber optic communication system:

1. PIN (P-Intrinsic-N).
2. APD ( Avalanche Photo Diode).

As well as the optical transmitter, the optical material also consists of semiconductor. Combined with a transmitter Gallium Arsenide (GaAS), quartz and silica fiber (SiO2) and silica (Si) receiver.

PIN diode
In the PIN diode, optical fiber is placed so that the light received a fall on the intrinsic layer of semiconductor material that placed between the layers and the types of N-type and P-type. Junction diode is formed by coating a layer, this reverse-biased and the amount of cash that flows through junction is determined by intensity light (photon number) in the entry intrinsic layer. Variations in cash that flows through the PIN diode as a result of variations in the intensity of the optical signal is received is very small so that the need strengthening.































Receiver Optical Wave
PIN semiconductor FO
Semiconductor PIN diode
Avalanche photo diode
Have a similar construction and operate the same way PIN diode. However, APD does not need a brace effect on the field in the module recipient. Internal gain of APD to create more sensitive, obtained through the use of reverse-biased voltage on the diode junction high. This produce an electric field in the layer of high intrinsic diode.
















APD diodeAt the time an electron removed because of a photon into the intrinsic layer, electric field will cause electrons to move along the layer and a high speed impact with another molecules and release more electrons, which then move along layer with a high speed. This process is called avalanche breakdown. Benefits of the use of avalanche breakdown is increased sensitivity compared with the PIN diode.