Performance improvement of hybrid subcarrier multiplexing optical spectrum code division multiplexing system using spectral direct decoding detection technique

In this paper a Variable Weight OCDMA (VWOCDMA) system using KS code with Direct Decoding (DD), Complementary Subtraction (CS) and AND subtraction detections is proposed. System performance is analyzed using mathematical approximation and software simulation. In mathematical analysis, the effects of Phase-Induced Intensity Noise, shot noise and thermal noise are taken into account. Bit Error Rate of different users is plotted as a function of received optical power per chip with varying the bit rates and number of active users. It has been shown that for different bit rates and number of users, system using DD has better performance than the system applying CS and AND detection. Using DD scheme, the number of active users are 100 while this value is 27 and 25 in case of using CS and AND detection, respectively, when the received optical power per chip is –10 dBm.

Variable-weight optical code division multiple access system using different detection schemes

A new optical orthogonal frequency division multiplexing technique with spectrum amplitude coding optical code division access (SAC-OCDMA) system is developed to enhance the channel data rate, reduce power, and increase the number of SAC-OCDMA system users. The average received signal-to-noise ratio with inter-modulation distortion of subcarriers is derived. Theoretical results are evaluated based on bit error rate, number of users, data rate, and amount of power saved. The proposed system is then compared with the traditional hybrid sub-carrier multiplexing (SCM)/SAC OCDM. The results show that the proposed system reduces approximately −8 dBm of power and doubles the number of users at a higher data rate than the SCM/SAC-OCDMA system. Proof-of-principle simulations of the proposed system are successfully implemented. Overall, the proposed system performed better than the SCM/SAC-OCDMA system. The system is designed based on modified double weight code, which provides better performance than Hadamard and modified frequency-hopping codes.

A new model to enhance the QoS of spectral amplitude coding-optical code division multiple access system with OFDM technique

Development of OCDMA system based on Flexible Cross Correlation (FCC) code with OFDM modulation

This paper demonstrates the transmission performance of a hybrid subcarrier multiplexing over optical CDMA for a point-to-point network design. The system is designed based on the Zero Cross Correlation (ZCC) code in the Spectral amplitude coding (SAC)-OCDMA because of its ability to suppress the Multiple Access Interference (MAI) using code sequences with fixed in-phase cross correlation. The performance of this hybrid system is shown through simulative experiment results of bit error rate (BER) and eye patterns for various numbers of subcarrier channels and frequencies. The simulation is done using Optisys version 7.0. It has been observed from the simulation results that up to eight RF channels can be added up in one optical channel for a successful transmission of 45km. It is also shown that higher subcarrier frequencies contribute to a better BER performance. We compared the hybrid system with a purely all-optical system utilizing the same code. This new hybrid system is proven to provide better bandwidth efficiency by accommodating larger number of simultaneous users with fewer optical channels and thus their code lengths, hence lowering the implementation cost. Thus, this system could be one promising solution to the symmetric high-capacity access network with high spectral efficiency, cost effective, good flexibility and enhanced security, which makes an attractive candidate for next-generation broadband access network. .

http://www.aicit.org/JCIS/ppl/04_JCISS1-004%20.pdf

Performance of Hybrid Subcarrier Multiplexing Over Optical CDMA Network Based on Zero Cross Correlation Code

This paper describes the application of the microwave subcarrier multiplexing technique (SCM) in an optical frequency division multiplexing (OFDM) system which employs an optical FM direct detection scheme. Direct frequency modulation of a laser diode offers the advantages of compact optical spectrum and simple driving circuit; it also permits a more effective utilisation of optical channel capacity. The carrier-to-noise ratio performance of each subcarrier channel is evaluated. The effect of laser diode phase noise and relative intensity noise as well as the intermodulation product of subcarrier channels on the overall system performance is analysed and the results presented.

L. Chao

Papers

Effect of laser diode characteristics on the performance of an SCM–OFDM direct detection system