Specifications

Ethernet Design Considerations
RADring
Installation & Operation Manual
7-8 Fiber Optic Design Considerations 3/11/98 12:25
Preventing Saturation of Optical Receivers
Optical receivers are optimized for operation at low optical power levels
(long cable runs). When the optical input power reaching the receiver is too
high, the receiver may saturate. Saturation causes pulse distortion, resulting
in very high bit error rate, high enough to disrupt data transmission. It is
therefore essential to prevent receiver saturation.
The dynamic range of the optical receivers used by the Fiber Optic Module
is 20dB, and their sensitivity is -32dBm. Therefore, the maximum optical
input power before saturation occurs is: -32dBm + 20dBm = -12dBm.
The saturation power is high enough to ensure that the Fiber Optic Module
receiver will never saturate when receiving the signal generated by another
Fiber Optic Module, even when operating with short 100/140 micron cable
having a very low attenuation.