Performance analysis of multiple interference suppression over asynchronous/synchronous optical code-division multiple-access system based on complementary/prime/shifted coding scheme
نویسندگان
چکیده
A complete complementary/prime/shifted prime (CPS) code family for the optical code-division multiple-access (OCDMA) system is proposed. Based on the ability of complete complementary (CC) code, the multiple-access interference (MAI) can be suppressed and eliminated via spectral amplitude coding (SAC) OCDMA system under asynchronous/synchronous transmission. By utilizing the shifted prime (SP) code in the SAC scheme, the hardware implementation of encoder/decoder can be simplified with a reduced number of optical components, such as arrayed waveguide grating (AWG) and fiber Bragg grating (FBG). This system has a superior performance as compared to previous bipolar-bipolar coding OCDMA systems. C Subject terms: optical code-division multiple access; complete complementary code; shifted prime code; wavelength-hopping time-spreading; multiple-access interference. 1 Introduction In optical code-division multiple-access (OCDMA) systems using one-dimension coding, there are several ways to reduce the multiple-access interference (MAI), such as extending the length of the code or increasing the cardinality of codes. Recently , wavelength-hopping/time spreading (WH/TS) codes have been proposed and thoroughly investigated. The WH/TS code can be represented by an M×N matrix, where M denotes the number of available wavelengths and N the number of time slots (or code length). In Refs. 1–3, the two-dimensional (2D) WH/TS codes have been proposed by using different sequences in the TS and WH codings, the codes used in the TS coding being prime code, optical orthogonal code (OOC), extended quadratic congruence (EQC) code, carrier hopping prime code (CHPC), etc. In general, the proposition of these codes has three motivations: (1) Increase the cardinality of the codes, (2) limit the cross-and auto-correlation values, and (3) find a trade-off between hardware implementation complexity and number of simultaneous users. In Refs. 4–6, a new bipolar-bipolar code has been proposed by Yang et al. The bipolar-bipolar code in Ref. 4 is obtained from the combination of a modified m-sequence, a prime sequence, and a barker code in SAC, WH, and TS scheme, respectively. This composite code is named m-sequence/prime/barker (MPB) code in this paper and has some fundamental properties, especially regarding the cardinality of the MPB code. MPB is p 2 for a prime number p and the cross-correlation of any two distinct codewords for the MPB code is at most one in an asynchronous OCDMA system. Another bipolar-bipolar code has been proposed in Ref. 5 and the difference between the codes in
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