Patent ID: 8041211
Filing Date: 2011-10-18
Classification: G01J,H04B

Abstract:
1. An optical signal quality monitoring apparatus comprising: a sampling optical pulse generation unit which emits a sampling optical pulse having a period Ts different from a predetermined offset time ΔT to integral N multiplication of a clock period Tc of a data signal modulating an optical signal of a monitoring target; an optical sampling unit which supplies an optical pulse signal obtained by sampling the optical signal of the monitoring target using the sampling optical pulse emitted from the sampling optical pulse generation unit; a photoelectric converter which receives the optical pulse signal supplied 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 optical signal of the monitoring target based on the electric signal from the photoelectric converter, wherein the optical sampling unit includes: an electroabsorption optical modulator which has two optical terminals used to input and output light, and a power supply terminal imparting an electric field to an optical path connecting the two optical terminals, the electroabsorption optical modulator having a characteristic in which an absorption index is changed with respect to the light propagating through the optical path according to a level of the electric field, the electroabsorption optical modulator receiving the optical signal of the monitoring target at one of the two optical terminals; a direct-current power supply which applies a predetermined direct-current voltage to the power supply terminal of the electroabsorption optical modulator, the electroabsorption optical modulator exhibiting a high absorption index with respect to the optical signal of the monitoring target at the predetermined direct-current voltage; and a photocoupler which receives the sampling optical pulse emitted from the sampling optical pulse generation unit of the optical signal sampling apparatus to input the sampling optical pulse into another of the two optical terminals of the electroabsorption optical modulator, and receives the optical signal of the monitoring target emitted from the other of the two optical terminals of the electroabsorption optical modulator to input the optical signal as the optical pulse signal into the photoelectric converter, wherein when the sampling optical pulse is supplied, the absorption index is lowered by a mutual absorption saturation characteristic of the electroabsorption optical modulator, and the optical signal of the monitoring target is passed onto a side of the other of the two optical terminals of the electroabsorption optical modulator to perform sampling.