| （英） |
The SIK (sequence inversion keyed) CDMA (code division multiple access) system was proposed as one of optical CDMA communication systems with unipolar codes, where correlation properties of corresponding bipolar codes can be utilized. In this paper, we introduce spreading codes with negative auto-correlation suitable for asynchronous CDMA communications. The spreading codes are based on NFSRs (nonlinear feedback shift registers) and chaos theory. Bit error rate (BER) performances of asynchronous SIK optical CDMA systems using the proposed spreading codes are evaluated by computer simulations. |