Patent ID: 6900929

Claim:
A noise figure measuring system comprising: a first optical amplifier whose noise figure is to be measured; a plurality of light sources for outputting a plurality of optical signals having different wavelengths, respectively; an optical multiplexer for wavelength division multiplexing said plurality of optical signals output from said light sources to obtain WDM signal light; a second optical amplifier for amplifying said WDM signal light output from said optical multiplexer; an optical spectrum measuring unit; switch means for selectively inserting said first optical amplifier in an optical transmission line between said second optical amplifier and said optical spectrum measuring unit; a power deviation detecting unit for detecting a deviation in power between said optical signals of said WDM signal light amplified by said second amplifier and to be input into said first amplifier; a light source power control unit connected to said power deviation detecting unit and said light sources for controlling said light sources so that the powers of said optical signals of said WDM signal light to be input into said first optical amplifier becomes substantially equal to each other; and a noise figure computing unit for computing the noise figure of said first optical amplifier according to measured data obtained by said optical spectrum measuring unit.