Patent ID: 9154226
Filing Date: 2015-10-06
Classification: H04B

Abstract:
1. An optical signal quality monitoring apparatus, comprising: an optical detector for directly receiving an optical signal modulated in an optical path and converting the optical signal to an electric signal; an asynchronous sampling unit for asynchronously sampling the electric signal of the optical detector at a speed lower than a symbol speed of the optical signal; and a digital signal processor for monitoring an optical signal quality by finding a synchronized amplitude histogram of data sampled in the asynchronous sampling unit, wherein the asynchronous sampling unit comprises: a sample-and-hold amplifier for sampling the electric signal outputted from the optical detector; and an analog-to-digital converter for converting an analog signal sampled in the sample-and-hold amplifier to a digital signal, and wherein the digital signal processor comprises: a clock signal extracting unit for extracting a clock signal using a software-based synchronization method; a retiming-and-arranging unit for retiming and arranging sampled data using a clock frequency estimated by the clock signal extracting unit such that the sampled data are inserted into a single symbol period; an amplitude histogram acquiring unit for acquiring a synchronized amplitude histogram using the sampled data positioned at a central region of a symbol while excluding a sample acquired in a region where symbol conversion occur; and a quality calculating unit for calculating a parameter indicating an optical signal quality by analyzing a distribution of the synchronized amplitude histogram acquired in the amplitude histogram acquiring unit.