VCSE laser transmitters for parallel data links

The major issues associated with using vertical cavity surface emitting laser (VCSEL)-based transmitter arrays for parallel data links are examined. An assumption is made that only limited optimization of the individual links is permitted, and to the extent that the required circuits are shared by many channels. An analysis of bit-error ratios, based on measured laser parameter variations across the array, and their theoretical effect on noise margins indicates that a 5-dB penalty may be expected. This leads to a tradeoff between laser tolerances and receiver complexity. Experimental work towards a VCSEL-CMOS transmitter is described. A 622-Mb/s operation is demonstrated with a small hybrid transmitter array. Power dissipation and electrical crosstalk problems are assessed. Block coding of data before transmission significantly improves some aspects of laser transmitter performance. A statistical treatment of crosstalk noise is presented and compared to experimental results