Hi,
The margin, or the difference between the received signal-to-noise ratio (SNR) and the SNR required to maintain a given bit error
ratio (BER), is important to the design and operation of optical amplifier transmission systems.
The margin
in an optical amplifier system is the decibel difference between the received SNR and the SNR required to maintain the system error
rate specification. The received SNR, and therefore the margin, is
set by optical noise and waveform degradations accumulating over the entire length of the system.
Thanks,
Rajguru