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Due to power restriction of some laser sources, the use of same power (per bit duration) in optical codes in incoherent optical code-division multiple-access multimedia networks with variable quality-of-services was previously studied. In those studies, the performance of double-weight codes with the maximum cross-correlation function λc=1 was exactly analyzed, but an approximation was only applied to the codes with λc > 1 due to mathematical complexity. In this paper, an exact analytical model of double-weight codes with an arbitrary λc ≥ 1 is formulated and validated with computer simulation. This general, more accurate performance model is also useful for power-sensitive applications, such as in-service monitoring and fiber-fault surveillance in optical networks and sensor-identification in fiber-sensor systems using optical codes for address or user identification. [ABSTRACT FROM PUBLISHER]

In this paper, the extended Reed-Solomon codes are modified to construct a new family of 2-D codes for asynchronous optical code-division multiple access (O-CDMA). In addition of having expanded and asymptotically optimal cardinality, these 2-D asynchronous optical codes can be partitioned into multiple tree structures of code subsets, in which code cardinality is a function of the (periodic) cross-correlation value assigned to the subset. The performance of these 2-D optical codes is analyzed and compared with that of the multilevel prime codes. Our results show that the unique partition property of the new optical codes supports a trade-off between code cardinality and performance for meeting different system requirements, such as user capacity and throughput. In addition, the multiple tree structures of the new codes potentially support applications that require rapid switching of many codewords, such as in O-CDMA-network gateway or in strategic environments where code obscurity is essential. [ABSTRACT FROM PUBLISHER]

Due to power restriction of some laser sources, the use of same optical power in every bit duration (i.e., same bit power) of double-weight codes in optical code-division multiple access (O-CDMA) with differential quality-of-service (QoS) was previously studied and analyzed with approximated performance. In this paper, an exact analytical model is formulated and validated with computer simulation, establishing accurate relationships of code weight, chip power, and bit power with code performance. Besides better understandings the role of power control in variable-weight O-CDMA with differential QoS, such accurate analytical model is important for power-sensitive applications, such as in-service monitoring and fiber-fault surveillance in optical networks and sensor-identification in fiber-sensor systems with the use of optical codes. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) wavelength-time coding schemes have recently been studied for optical code-division multiple access. In this paper, we propose a new family of 2D codes, which use "synchronized" quadratic congruence sequences for wavelength hopping and (n,w,2,2) optical orthogonal codes for time spreading. The new 2D codes provide larger (asymptotically optimal) code cardinality than other 2D codes by relaxing the maximum cross-correlation function from one to two. Our study shows that the heavier code weight supported by our 2D codes results in better code performance than some of previously proposed 2D codes (of the maximum cross-correlation functions of one and two). The new codes potentially support more subscribers and heavier bursty asynchronous traffic with gradual performance degradation as traffic load increases. [ABSTRACT FROM AUTHOR]

To provide differential quality-of-service in optical code-division multiple access, variable-weight codes were proposed and analyzed under a conventional assumption of identical power in every optical pulses (i.e., same chip power). To account for power limit of some laser sources, we assume the use of same optical power in each bit duration (i.e., same bit power) in this paper. For illustration, we focus our study on double-weight codes under both same-chip-power and same-bit-power assumptions. A new and better approximate performance-analytical model for double-weight codes is developed and validated with computer simulation. We show that heavy-weight codes do not always perform better than light-weight codes under the same-bit-power assumption, contrary to previous findings under the same-chip-power assumption. [ABSTRACT FROM AUTHOR]