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

Reviews the design and testing of a 140 Mbit/s coherent system. A demonstration system has been completed by GEC-Marconi Limited, Plessey Research Caswell and GEC-Marconi Limited, Hirst Research Centre Wembley, funded by GEC Plessey Telecommunications. The equipment has a 59.7 dB section loss and fits in a standard exchange shelf. The design includes automatic start up and polarisation control. The production system now under development will fit in a type 88 shelf, support a usable 60 dB section loss and provide laser shutdown. Provision of an optical amplifier will increase the usable section loss to greater than 70 dB