The future development of optical communication systems

The routes to higher transport capacity are clear. i. Increase the TDM rate up to the electronic limit (10-40 Gbit/s) ii. Move to the optical domain to achieve higher per fibre transport a. using multiple wavelength channels (DWDM) b. using optical TDM. Both routes have their attractions. If we now wish to carry out all-optical routing, we have a variety of options. i. Access the underlying digital data structure and operate in the manner of an electronic router or digital switch. This seems unrealistic for optics. ii. Route complete wavelength channels in the DWDM system after demultiplexing them, possibly with wavelength shifting at nodes, and probably using some form of space switch. iii. Time demultiplex the OTDM data stream, space switch the discrete channels and then recombine them using some form of time-slot interchange processor.