Signal bit rate and performance measurement for optical channel signals

Abstract

Methods and apparatus for determining channel signal bit rate and measuring channel signal performance in a wavelength division multiplexed (WDM) optical network or other optical communication system. A selected channel signal modulated by a pseudorandom non-return-to-zero (NRZ) data stream is detected in a front-end receiver or photodetector and converted to an electrical signal. An autocorrelator receives the detected channel signal, and generates an autocorrelation function for the corresponding electrical signal, from which the channel signal bit rate can be determined. The autocorrelator separates the electrical signal into a first part and a second part, introduces a delay between the first and second parts, multiplies the first and second parts in a multiplier, and integrates the result of the multiplication over a designated time period to provide the autocorrelation function. The bit rate may be determined by measuring the width of a peak in the autocorrelation function. Once the bit rate is determined, the bit-error rate performance of the channel signal can be measured by setting the delay between the first and second parts of the electrical signal to the corresponding bit period, and counting the number of times the multiplier output voltage falls within a specified range. The autocorrelator may be part of a receiver which uses the determined bit rate to generate a clock for recovering the channel signal data.