R. Welter

Wide-linewidth phase diversity homodyne receivers

The use of phase diversity homodyne receivers, which have excellent performance even when the laser linewidth is of the same order of magnitude as the bit rate, to construct coherent systems with semiconductor lasers and moderate bandwidth receivers is considered. Theoretical, experimental, and computer simulation results of a study of a linewidth homodyne phase-diversity receiver is presented. A 150-Mb/s system with an IF linewidth of more than 50% of the bit rate is investigated in depth and is experimentally shown to operate within 1.8 dB from its theoretical limit. >

Conversion of laser phase noise to intensity noise in single-mode fiber-optic components

We have recently observed that the Fabry-Perot cavities formed by index discontinuities in connectors and other fiber-optic components convert the intrinsic phase noise of semiconductor lasers into excess intensity noise which can significantly impact both direct detection and coherent communication systems. The level of this noise can be higher than −100 dB/Hz and can result in bit-error-rate (BER) floors.

Recent progress of coherent lightwave systems at Bellcore

The progress in selected areas of coherent lightwave systems technology at Bellcore over the past year is reviewed. Studies of the demodulator portion of a polarization diversity receiver show that a polarization sensitivity of less than 0. 5 dB can be achieved and that squaring circuits with wide dynamic range and very high sensitivity can be realized. We also report the results of frequency stability measurements made on packaged DFB laser transmitters over an extended time period. Four-wave-mixing (FWM) experiments show that high power in the range of 5 to 10 mW launched into dispersion shifted fiber can cause FWM crosstalk. Reports of FWM in a semiconductor optical amplifier are also reported. 1. )