Channel interference cancellation using electrooptic switch and optical hard-limiters for direct-detection optical CDMA systems

This paper proposes new channel interference cancellation technique using an electrooptic (EO) switch and optical hard-limiters for direct-detection optical CDMA systems. In the proposed system the channel interference in a reference path is reduced by double optical hard-limiters. The output of a reference path drives the EO switch to reduce the effect of the channel interference in a signal path. When the reference signal is larger than or equal to the threshold of the driver circuit, the EO switch is turned on and the signal in a signal path is passed to an avalanche photodiode (APD); otherwise, the EO switch is turned off and the signal is not passed to the APD. It is shown that the proposed system is effective to reduce the effect of the channel interference when the received optical power is large.