High power budget-practical 140 Mb/s FSK coherent system

The author reviews the design of a 140 Mb/s optical coherent system. Following a look at the design philosophy behind the system, he goes on to describe the DFB laser transmitter, PIN diode receiver and AFC/LO board. The equipment has a 60 dB or greater section loss and fits in a standard exchange shelf. The design includes automatic start-up and polarisation control. This development, funded by GEC Plessey Telecommunications at Plessey Research Caswell and GEC Hirst Research Centre Wembley, takes coherent technology out of the laboratory and into the working environment as a practical system