Abstract

It is today commonly acknowledged that the optical switch will be a key component in future optical communications networks [1,2,3]. Apart from requirements such as high flexibility and transparency to bit rate and format, optical switches must be able to support wavelength division multiplexed (WDM) networks and already existing components as especially erbium doped fibre amplifiers (EDFA’s). Several designs have been suggested and implemented including both lithium-niobate [4] and semiconductor based [5] devices. Among the latter, loss-compensating components [6,7] are believed to be advantegeous, since the switch architectures will probably get rather extended. The main disadvantage compared to switches without amplification is that a limited dynamic range is obtained due to the semiconductor gain medium. The switch evaluated here (see fig 1) is a monolithic strictly non-blocking device based on semiconductor optical amplifier (SOA) gates in InGaAsP/InP, operated in the 1550 nm window [8]. Publications of optical switches have so far mainly dealt with unpackaged components. Performance has often been measured with a cw source as to achieve gain optimisation. In this paper, extensive bit error rate (BER) measurements on fully packaged InP switches are presented concerning dynamic range and dependence upon polarisation of the incoming signal. The system has been optimised for low BER rather than maximum gain. Furthermore, cascading of several switches and a WDM experiment demonstrate the usefulness of this component in future optical WDM networks, and theoretical simulations investigate dependence of reflections and bit rate.

© 1995 Optical Society of America