Optical amplifier evaluating method and optical amplifier evaluating apparatus

An optical amplifier evaluating apparatus comprising:

• a first light source for outputting signal light;
• a first optical modulator for modulating the signal light into a rectangular optical signal which is turned on and off at a predetermined period;
• a second light source for outputting probe light, and an optical multiplexer for multiplexing the probe light and optical signal output from said modulator and selectively outputting multiplexed light to an input terminal of an optical fiber amplifier as an object to be measured;
• optical path switching means for switching connection states of the input terminal and an output terminal of said optical fiber amplifier;
• a second optical modulator for extracting the signal light switched by said optical path switching means and output from the output terminal of said optical fiber amplifier;
• and
• a controller for controlling said first optical modulator, said second optical modulator, and said optical path switching means, and analyzing means for obtaining a light intensity in a region where the signal light is in an OFF period and the probe light is output, a light intensity in a region where the signal light is in the OFF period and the probe light is not output, and a light intensity of an input signal of the probe light to said optical fiber amplifier, thereby obtaining a gain and noise figure as wavelength characteristics of said optical fiber amplifier.

An optical amplifier evaluating method comprising the steps of:

• outputting rectangular signal light which is turned on and off at a predetermined period from a first light source device;
• outputting probe light from a second light source device;
• multiplexing the probe light and the signal light output from said first light source device by an optical multiplexer and outputting multiplexed light to an optical fiber amplifier as an object to be measured;
• extracting, by an optical modulator, an output signal in an OFF period of the signal light from an output from an output terminal of said optical fiber amplifier;
• measuring an intensity of input light to an input terminal by a light intensity measuring device;
• switching optical paths between said optical multiplexer, said optical fiber amplifier, said optical modulator, and the input terminal of said light intensity measuring device by optical switching means;
• and
• switching said optical switching means by a controller such that said light intensity measuring device measures a light intensity (Pout) in a region where the output signal light from said optical fiber amplifier is in an OFF period and the probe light is output, a light intensity (Pase) in a region where the signal light is in the OFF period and the probe light is not output, and a light intensity (Pin) of an input signal of the probe light to said optical fiber amplifier, thereby obtaining a gain of said optical fiber amplifier from values of the measured light intensities.