The flexible cross correlation (FCC) code algorithm for optical code division multiple access (OCDMA) systems has been developed. The FCC approach has advantages, such as flexible cross-correlation property at any given number of users and weights, as well as effectively suppressed the impact of phase-induced intensity noise (PIIN) and multiple-access interference (MAI) cancellation property. The results revealed that the FCC code can accommodate 150 users, where FCC code offers 66%, 172%, 650% and 900% improvement as a contrast to 90, 55, 20 and 15 numbers of users for Dynamic Cyclic Shift (DCS), Modified Double Weight (MDW), Modified Frequency Hopping (MFH) and Hadamard codes respectively, for a permissible bit error rate (BER) of  10⁻⁹.