Performance analysis of direct-detection optical asynchronous CDMA systems with double optical hard-limiters

Performance of optical asynchronous CDMA systems with double optical hard-limiters is analyzed under the assumption of Poisson shot noise model for the receiver photodetector where the noise due to the detector dark currents exists. The performance is analyzed in the chip synchronous case and thus the derived performance results in the upper bounds. The results show that the optical asynchronous CDMA systems with double optical hard-limiters have much better performance than other conventional asynchronous CDMA systems with and without the optical hard-limiter even when the number of simultaneous users is large, which is different from the case of optical synchronous CDMA systems