Patent ID: 7035538
Filing Date: 2006-04-25
Classification: H04B

Abstract:
1. A method for monitoring optical dispersion in a modulated optical signal produced by modulating light at an optical carrier frequency at a signal bit rate of digital bits of a digital signal to produce the first and second sidebands at opposite sides of the carrier frequency to carry the digital signal, comprising: optically filtering the modulated optical signal at a carrier frequency that has first and second sidebands at opposite sides of said carrier frequency with at least one optical bandpass filter centered at a frequency away from said carrier frequency less than the signal bit rate to produce a first optical signal having a first spectral range that covers said carrier frequency and said first sideband to include a first portion of a baseband signal in said modulated optical signal and a second optical signal having a second, different spectral range that covers said carrier frequency and said second sideband to include a second portion of said baseband signal in said modulated optical signal that partially overlaps with said first portion; measuring a parameter in the first portion of the baseband signal from said first optical signal to obtain a first result; measuring said parameter in the second portion of the baseband signal from said second optical signal to obtain a second result; and obtaining a difference between said first and said second results to extract frequency-dependent information in said modulated optical signal, wherein said frequency-dependent information includes optical chromatic dispersion.