Patent ID: 8019218
Filing Date: 2011-09-13
Classification: H04B

Abstract:
1. An optical signal monitoring apparatus comprising: an optical interference unit which includes: an optical brancher which branches a monitoring object optical signal into two optical paths, the monitoring object optical signal being input to be monitored and being phase-modulated at a predetermined symbol rate; a delay device which imparts delay corresponding to an integral multiple of one symbol to an optical signal, the optical signal being branched in one optical path of the two optical paths by the optical brancher; an optical phase adjuster which makes an adjustment such that an optical signal emitted from the delay device and an optical signal are brought into a predetermined optical phase difference, the optical signal being branched in another optical path of the two optical paths by the optical brancher; and an optical multiplexer which multiplexes optical signals, the optical signals being adjusted so as to be brought into the predetermined optical phase difference by the optical phase adjuster, wherein the optical interference unit converting the phase modulated monitoring object optical signal into intensity-modulated light to supply the intensity-modulated light, the monitoring object optical signal being supplied from the optical multiplexer; a sampling optical pulse generation unit which produces a sampling optical pulse having a period Ts different from a predetermined offset time ΔT to integral multiplication N of a symbol clock period corresponding to the predetermined symbol rate; an optical sampling unit which samples the intensity-modulated light using the sampling optical pulse to supply an optical pulse signal, the intensity-modulated light being emitted from the optical interference unit, the sampling optical pulse being produced by the sampling optical pulse generation unit; a photoelectric converter which receives the optical pulse signal emitted from the optical sampling unit, and converts the optical pulse signal into an electric signal to supply the electric signal; and a computation unit which computes a value indicating quality of the monitoring object optical signal based on the electric signal supplied from the photoelectric converter, the monitoring object optical signal being phase-modulated at the predetermined symbol rate.