Noise figure monitoring of optical amplifiers via backward amplified spontaneous emission

A new configuration of an optical amplifier is proposed that provide in-service noise figure (NF) monitoring. It is difficult to determine the NF of traditional optical amplifiers in operation because the amplified spontaneous emission (ASE) power cannot be measured separately from the output signal power. The proposed technique measures the NF from the backward ASE power. The discrepancy between the NF measured from forward ASE (using the traditional technique) and backward ASE (proposed technique) is found to be less than 1.0 dB at input powers below /spl minus/6.2 dBm. A prototype optical amplifier is successfully used as a linear repeater, in a 10 Gbit/s 200 km transmission experiment.<>