Patent ID: 7508889
Filing Date: 2009-03-24
Classification: H04B,H04L

Abstract:
1. A soft decision circuit for determining a most likely data content of a differential phase-shift keying (DPSK) modulated optical signal from three differentially detected intermediate signals that are based on comparisons between pairs of a series of three contiguous data bits of the DPSK modulated optical signal, the soft decision circuit comprising: a plurality of comparators, each comparator comparing two of the three intermediate signals and generating a digital signal in accordance with the comparison; and digital logic, the digital logic determining a most likely data content based on the comparator signals, wherein: where A represents a first of the intermediate signals based on a comparison between the first and second of the series of three contiguous data bits, B represents a second of the intermediate signals based on a comparison between the second and third of the series of three contiguous data bits, C represents a third of the intermediate signals based on a comparison between the first and third of the series of three contiguous data bits, and G represents the most likely data content.