A new bandwidth efficient scheme for applying error-correcting codes in fiber-optic CDMA systems

In this paper, we consider using practical low-rate error-correcting codes in fiber-optic code division multiple-access (CDMA) communication systems. To this end, a new method of low-rate channel coding is proposed. As opposed to the conventional coding schemes, this method does not require any further bandwidth expansion for error correction. The low-rate channel codes that are used for demonstrating the capabilities of the proposed method, are super orthogonal codes (SOC). These codes are near optimal and have a relatively low complexity. We evaluate upper bounds on the bit error probability of the proposed coded system assuming both on-off keying and binary pulse position modulation schemes. It is shown that the proposed method significantly outperforms the uncoded systems for various receiver structures such as a correlator with and without hard-limiter and chip-level detector. Furthermore, the performance of the proposed method is also evaluated in the presence of different values of dark current.