We have constructed a series of new code families for the spectral-amplitude-coding optical code-division multiple-access (CDMA) system, and proposed new transmitter and receiver structures based on tunable chirped fiber Bragg gratings (FBGs). The proposed system has been analyzed by taking into account the effects of phase-induced intensity noise, shot noise, and thermal noise. We have also compared the performance of this system with that of a former system where a Hadamard code is used. It has been shown that the new code families can suppress the intensity noise effectively and improve the system performance significantly. When the effective power is large (i.e., >-10 dBm), the intensity noise is the main factor that limits the system performance. When the effective power is not sufficiently large, thermal and shot noise sources become the main limiting factors and the effect of thermal noise is much larger than that of shot noise.

A new detector for optical code-division multiple- access (CDMA) communication systems is proposed. This detec- tor is called the chip-level receiver. Both ON-OFF keying (OOK) and pulse-position modulation (PPM) schemes, that utilize this receiver, are investigated in this paper. For OOK, an exact bit error rate is evaluated taking into account the effect of both multiple-user interference and receiver shot noise. An upper bound on the bit error probability for pulse-position modulation (PPM)-CDMA system is derived under the above considerations. The effect of both dark current and thermal noises is neglected in our analysis. Performance comparisons between chip-level, correlation, and optimum receivers are also presented. Both correlation receivers with and without an optical hardlimiter are considered. Our results demonstrate that significant improvement in the performance is gained when using the chip-level receiver in place of the correlation one. Moreover the performance of the chip-level receiver is asymptotically close to the optimum one. Nevertheless, the complexity of this receiver is independent of the number of users, and therefore, much more practical than the optimum receiver.

The asymptotic performance of a multiterminal detection system comprising a central detector and two remote sensors that have access to discrete, spatially dependent, and temporally memoryless observations is discussed. It is assumed that prior to transmitting information to the central detector, each sensor compresses its observations at a rate which approaches zero as the sample size tends to infinity, and that, on the basis of the compressed data from both sensors, the central detector seeks to determine whether the true distribution of the observations belongs to a null class II or an alternative class Xi . Under the criterion that stipulates minimization of the type-II error rate subject to an upper bound epsilon on the type-I error rate, it is shown that, in the case of simple distribution classes ( mod Pi mod = mod Xi mod =1), the error exponent achievable by such a system has a simple characterization, is independent of the value of epsilon , and is insensitive to changes in compression rate as long as the asymptotic rate on one of the sensors is zero.<>

Direct-detection optical synchronous code-division multiple-access (CDMA) systems with M-ary pulse-position modulation (PPM) signaling are investigated. Optical orthogonal codes are used as the signature sequences of our system. A union upper bound on the bit error rate is derived taking into account the effect of the background noise, multiple-user interference, and receiver shot noise. The performance characteristics are then discussed for a variety of system parameters. Another upper bound on the probability of error is also obtained (based on Chernoff inequality). This bound is utilized to derive achievable expressions for both the maximum number of users that can communicate simultaneously with asymptotically zero error rate and the channel capacity. Our results show that under average power and bit error rate constraints, there always exists a pulse position multiplicity that permit all the subscribers to communicate simultaneously.

A new code structure for spectral amplitude coding optical code division multiple access (CDMA) is proposed and analysed. It is shown that such codes can effectively suppress the intensity noise and in turn increase the number of active users and improve the bit error rate performance.

A series of new code families are constructed for spectral-amplitude-coding optical code division multiple access (CDMA) systems. Then structures of both the transmitter and the receiver in such a system are also proposed based on tunable chirped fiber Bragg gratings. Our analysis shows that the proposed new code families can suppress the intensity noise effectively and, hence, improve the overall system performance.