A novel frequency-hop (FH) scheme is proposed for optical code division multiple access (OCDMA) system. According to the characteristics of FH-OCDMA system, an upper bound on the code size is deduced and the quadratic congruence-hop codes (QCHC) which achieves this bound is presented, with examples given. On the basis of it, a novel scheme for FH-OCDMA system with fiber Bragg grating array based encoder/decoder and QCHC is designed. Furthermore, a detailed performance analysis of the system is given. The results reveal that such a new scheme for FH-OCDMA system is not only easy to plan, but also has a large number of simultaneous users and low bit error rate.