| 摘要 |
PROBLEM TO BE SOLVED: To improve optical power measurement accuracy. SOLUTION: An oscillator 20 is oscillated at a reference frequency fr and a reference signal optical transmitter 22 generates a light (reference signal light) with a wavelength λr deeply intensity-modulated by an output of the oscillator 20. A frequency divider 24 applies 1/N frequency division to the output of the oscillator 20 and provides an output of a tone signal with a measurement frequency of fs. An output of the frequency divider 24 is fed selectively to any of optical transmission signal transmitters 18-1-n via switches 26-1-n to apply shallow intensity modulation to the corresponding optical transmission signal. Branching devices 32a, 32b provide an output of most of output lights of optical amplifiers 30a, 30b to optical fiber transmission lines 14a, 14b toward terminal stations 12, 10 and apply only a small amount of the lights to measurement circuits 34a, 34b. The measurement circuits 34a, 34b use a reference frequencies fr obtained from a reference signal light with a wavelength λr to apply synchronization detection to a component of the received light with a measurement frequency fs. Modulation circuits 36a, 36b modulate shallowly the amplification factor of the optical amplifiers 30a, 30b according to the measurement result of the measurement circuits 34a, 34b. |
