Equalization in coherent lightwave systems using a fractionally-spaced equalizer

The performance of a fractionally spaced analog trapped delay line equalizer that has the advantages of being adaptive, being capable of equalizing other linear distortions such as polarization dispersion and nonideal receiver response, and eliminating chromatic dispersion over any distance if a sufficient number of taps are used is discussed. It is shown how this equalizer can be implemented at intermediate frequencies (IF) and at baseband (for homodyne detection). Results show that an N-tap equalizer increases the maximum bit rate distance, B ²L, approximately (N-1)/2-fold (e.g., a threefold increase in distance with a seven-tap equalizer)