Multichannel CPFSK coherent optical communications systems
Abstract
A detailed theoretical analysis of multichannel coherent CPFSK communications systems is presented. The analysis accounts for the crosstalk between adjacent channels, the intersymbol interference and correlation between noise samples stemming from the limited IF bandwidth, the nonGaussian statistics of the noise at the decision gate, and the impact of the laser phase noise. It is found that the IF bandwidth needed to avoid intersymbol interference is 2.2 bit rates for a modulation index m = 1; it is larger for other modulation index values. For m = 1, receiver sensitivity is within 1 dB of the shotnoise limit, and the electrical domain channel spacing can be as small as 2.05 bit rates with 1dB sensitivity penalty. These conclusions are valid for a negligibly narrow linewidth; the degradation due to phase noise is shown to be modest as long as the linewidth does not exceed 1 percent of the bit rate if m = 1. Larger linewidth can be tolerated if the modulation index is larger than unity.
 Publication:

Journal of Lightwave Technology
 Pub Date:
 June 1989
 DOI:
 10.1109/50.32366
 Bibcode:
 1989JLwT....7..972K
 Keywords:

 Crosstalk;
 Frequency Shift Keying;
 Intersymbolic Interference;
 Multichannel Communication;
 Optical Communication;
 Phase Shift Keying;
 Bandwidth;
 Bit Error Rate;
 Low Pass Filters;
 Noise Spectra;
 Transfer Functions;
 Communications and Radar