OPTICAL REPEATER MONITORING SYSTEM

PROBLEM TO BE SOLVED: To provide an optical repeater monitoring system in which whether or not an interpolation optical signal is received by a linear repeater while distinguishing the low frequency component from an ASE noise power and a fault point location and an automatic level interruption function in the linear repeater are easily realized and each wavelength of a wavelength multiplex signal is monitored by superimposing a low frequency signal onto an information optical signal sent from an optical transmitter and using the linear repeater to detect the low frequency component. SOLUTION: A light from a light source 11-1 with a wavelength λ1 is finely modulated by an electric signal (a) from a low frequency oscillator 12-1 in an optical transmitter 10-1 and the modulated signal is given to an optical modulator 13-1 as an optical carrier (b). The optical carrier (b) is modulated by an information signal (c) to be an information optical signal (d) and amplified and outputted by an optical amplifier 14-1. The processing above is similar in other optical transmitter 10-n. The sets of information signals (e) of wavelength bands λ1-λn outputted from optical transmitters 10-1-10-m are synthesized by an optical synthesizer 15 and sent to an optical fiber transmission line 1 as a transmission line optical signal (f).