This paper presents a bipolar en/decod ing optical code division multiple access (OCDMA) system based on chaotic sequen ces,whose en/decoder is superstructure f iber Bragg grating (SSFBG).The three-order Chebyshev map can generate bipolar chaotic sequences which are appropriate for asynchronous CDMA s ystem.With an initial condition and repeating application of the three-order Ch ebyshev map,chaotic sequences with a certain length can be obtained.According to the characteristics of address code and through control of refractive index distribution of fiber grating,the SSFBG can be fabricated which can generate bipolar chaotic sequences,so SSFBG can be used as the en/decoder of th e OCDMA system.The performance of this system is tested by the quantitative an alysis.In the case of asynchronization,the formulas of SNR and BER are derived and the curves of BER versus the number of simultaneous transmissions are simulated.Our numerical simu lations show that with the increase of code length,the system has a lower BER with identical number of users,and the sy stem based on chaotic spreading sequences performs better than that using Gold sequences.