Unipolar codes with ideal in-phase cross-correlation for spectral amplitude-coding optical CDMA systems

Unipolar codes with ideal in phase cross-correlation are important in spectral amplitude-coding optical code-division multiple-access (CDMA) systems since these codes eliminate multiuser interference and also suppress the effect of phase-induced intensity noise. However, very little research work has been done on such codes although codes with ideal cross-correlation have been studied for many years. In the paper by Zhou et al.(see Electron. Lett., vol.36, p.728-29, 2000), such a code has been introduced without a clear construction method. In this paper, we firstly review this old code, and then construct two new codes with ideal in-phase cross-correlation in algebraic ways. Both of the proposed new codes are obtained by modifying former codes with ideal cross-correlation. It has been shown that the system performance can be improved significantly by using codes with ideal in-phase cross-correlation instead of the Hadamard code. These codes can also be used in synchronous optical CDMA systems for multiuser interference cancellation.