Impact of the phase noise generated from semiconductor optical amplifiers on the size of optical space switches

Optical space switch matrices can be designed by interconnecting properly multiple 2/spl times/2 switches based on semiconductor optical amplifiers (SOAs). The size of these switching structures is limited by many phenomena, including phase noise generated by SOAs, which can be a serious drawback if coherent modulation schemes are used in the network. This paper examines this problem, for a DPSK direct detection system. It is found that there is an optimum level for the switch input power, and the phase noise limits the number of 2/spl times/2 switches, which can be cascaded, to about 200, for a bit rate in the gigabit/s range.