Optical CDMA System Research Articles

Two-Dimensional Optical CDMA System Parameters Limitations for Wavelength Hopping/Time-Spreading Scheme based on Simulation Experiment

Abstract A new family of two-dimensional optical hybrid code which employs zero cross-correlation (ZCC) codes, constructed by the balanced incomplete block design BIBD, as both time-spreading and wavelength hopping patterns are used in this paper. The obtained codes have both off-peak autocorrelation and cross-correlation values respectively equal to zero and unity. The work in this paper is a computer experiment performed using Optisystem 9.0 software program as a simulator to determine the wavelength hopping/time spreading (WH/TS) OCDMA system performances limitations. Five system parameters were considered in this work: the optical fiber length (transmission distance), the bitrate, the chip spacing and the transmitted power. This paper shows for what sufficient system performance parameters (BER≤10−9, Q≥6) the system can stand for.

High performance mixed optical CDMA system using ZCC code and multiband OFDM

In this paper, we have proposed a high performance network design, which is based on mixed optical Code Division Multiple Access (CDMA) system using Zero Cross Correlation (ZCC) code and multiband Orthogonal Frequency Division Multiplexing (OFDM) called catenated OFDM. In addition, we also investigate the related changing parameters such as; effective power, number of user, number of band, code length and code weight. Then we theoretically analyzed the system performance comprehensively while considering up to five OFDM bands. The feasibility of the proposed system architecture is verified via the numerical analysis. The research results demonstrated that our developed modulation solution can significantly enhanced the total number of user; improving up to 80% for five catenated bands compared to traditional optical CDMA system, with the code length equals to 80, transmitted at 622 Mbps. It is also demonstrated that the BER performance strongly depends on number of weight, especially with less number of users. As the number of weight increases, the BER performance is better.

The effect of total noise on two-dimension OCDMA codes

In this research, we evaluate the performance of total noise effect on two dimension (2-D) optical code-division multiple access (OCDMA) performance systems using 2-D Modified Double Weight MDW under various link parameters. The impact of the multi-access interference (MAI) and other noise effect on the system performance. The 2-D MDW is compared mathematically with other codes which use similar techniques. We analyzed and optimized the data rate and effective receive power. The performance and optimization of MDW code in OCDMA system are reported, the bit error rate (BER) can be significantly improved when the 2-D MDW code desired parameters are selected especially the cross correlation properties. It reduces the MAI in the system compensate BER and phase-induced intensity noise (PIIN) in incoherent OCDMA The analysis permits a thorough understanding of PIIN, shot and thermal noises impact on 2-D MDW OCDMA system performance. PIIN is the main noise factor in the OCDMA network.

Cardinality enhancement utilizing Sequential Algorithm (SeQ) code in OCDMA system

Optical Code Division Multiple Access (OCDMA) has been important with increasing demand for high capacity and speed for communication in optical networks because of OCDMA technique high efficiency that can be achieved, hence fibre bandwidth is fully used. In this paper we will focus on Sequential Algorithm (SeQ) code with AND detection technique using Optisystem design tool. The result revealed SeQ code capable to eliminate Multiple Access Interference (MAI) and improve Bit Error Rate (BER), Phase Induced Intensity Noise (PIIN) and orthogonally between users in the system. From the results, SeQ shows good performance of BER and capable to accommodate 190 numbers of simultaneous users contrast with existing code. Thus, SeQ code have enhanced the system about 36% and 111% of FCC and DCS code. In addition, SeQ have good BER performance 10-25 at 155 Mbps in comparison with 622 Mbps, 1 Gbps and 2 Gbps bit rate. From the plot graph, 155 Mbps bit rate is suitable enough speed for FTTH and LAN networks. Resolution can be made based on the superior performance of SeQ code. Thus, these codes will give an opportunity in OCDMA system for better quality of service in an optical access network for future generation's usage

Withdrawn article: Simulation Realization of 2-D Wavelength/Time System Utilizing MDW Code for OCDMA System

This paper presented a realization of Wavelength/Time (W/T) Two-Dimensional Modified Double Weight (2-D MDW) code for Optical Code Division Multiple Access (OCDMA) system based on Spectral Amplitude Coding (SAC) approach. The MDW code has capability to suppress Phase-Induce Intensity Noise (PIIN) and minimizing the Multiple Access Interference (MAI) noises. At the permissible BER 10 -9 , the 2-D MDW (APD) had shown minimum effective received power (P sr ) = -71 dBm that can be obtained at the receiver side as compared to 2-D MDW (PIN) only received -61 dBm. The results show that 2-D MDW(APD) has better performance in achieving same BER with longer optical fiber length and with less effective received power (P sr ). Also, the BER from the result shows that MDW code has capability to suppress PIIN ad MAI.

Simulation realization of 2-D wavelength/time system utilizing MDW code for OCDMA system

This paper presents a realization of Wavelength/Time (W/T) Two-Dimensional Modified Double Weight (2-D MDW) code for Optical Code Division Multiple Access (OCDMA) system based on Spectral Amplitude Coding (SAC) approach. The MDW code has the capability to suppress Phase-Induce Intensity Noise (PIIN) and minimizing the Multiple Access Interference (MAI) noises. At the permissible BER 10-9 , the 2-D MDW (APD) had shown minimum effective received power (Psr ) = -71 dBm that can be obtained at the receiver side as compared to 2-D MDW (PIN) only received -61 dBm. The results show that 2-D MDW (APD) has better performance in achieving same BER with longer optical fiber length and with less received power (Psr ). Also, the BER from the result shows that MDW code has the capability to suppress PIIN ad MAI.

Two dimension MDW OCDMA code cross-correlation for reduction of phase induced intensity noise

In this paper, we first review 2-D MDW code cross correlation equations and table to be improved significantly by using code correlation properties. These codes can be used in the synchronous optical CDMA systems for multi access interference cancellation and maximum suppress the phase induced intensity noise. Low Psr is due to the reduction of interference noise that is induced by the 2-D MDW code PIIN suppression. High data rate causes increases in BER, requires high effective power and severely deteriorates the system performance. The 2-D W/T MDW code has an excellent system performance where the value of PIIN is suppressed as low as possible at the optimum Psr with high data bit rate. The 2-D MDW code shows better tolerance to PIIN in comparison to others with enhanced system performance. We prove by numerical analysis that the PIIN maximally suppressed by MDW code through the minimizing property of cross correlation in comparison to 2-D PDC and 2-D MQC OCDMA code.scheme systems.

FWM behavior in 2-D time-spreading wavelength-hopping OCDMA systems

Abstract A new formula for the signal-to-four-wave mixing (FWM) crosstalk in 2-D time-spreading wavelength-hopping (TW) optical code division multiple access (OCDMA) systems is derived. The influence of several system parameters on the signal-to-FWM crosstalk ratio (SXR) is analyzed, including transmitted power per chip, code length, the number of active users, code weight, wavelength spacing, and transmission distance. Furthermore, for the first time, a closed-form expression for the total number of possible FWM products employing symmetric TW codes with equal wavelength spacing is investigated. The results show that SXR is sensitive to minor variations in system parameters, especially the launched power level and the code length while the wavelength spacing has a less impact on the level of the generated FWM power.

Performance enhancement of OCDMA systems for LAN consideration

In this study, the performance of optical code-division-multiple-access (OCDMA) systems using 2D optical codes, taking into account an optical channel in local area network context is investigated. The authors demonstrate that one can enhance the 3-dB multi-mode fibre baseband bandwidth up to 4 GHz by exciting only two mode groups with the optimal axial launching. It has been demonstrated, that the OCDMA system performance can achieve a very low bit-error-rates in the range of −9 dBm. Furthermore, a large number of simultaneous users can be supported. In the authors’ treatment, the effect of both multiple access interference and modal dispersion are considered. Nonetheless, an OCDMA successive interference cancellation receiver is used to foster a better system performance.

플라스틱 광섬유를 사용한 통신망에서 OCDMA의 성능 분석

본 논문은 플라스틱 광섬유(POF)를 연결한 네트워크에서 광 부호분할다중접근(OCDMA)기술의 성능을 분석한다. 최근에 POF는 무게가 가볍고, 중심선의 직경이 크며, 유연하고, 쉽게 설치할 수 있는 특성이 있기 때문에 POF를 이용한 광전송은 커다란 주목을 받고 있다. 특히 POF의 광대역(broad band) 특성은 OCDMA기술에 기초한 네트워크 연결 전송매체로서 각광을 받고 있다. 일반적인 OCDMA 시스템은 전송로의 수량이 BER특성에 의해서 단지 제한된 단위만을 동시에 연결하고 전송할 수 있다. 이러한 문제를 해결하기 위하여 본 논문에서는 새로운 다우선 예약프로토콜을 제안하였다. 이 프로토콜과 분산 조정 알고리듬을 이용하여, 통신로 내부와 목표지로 가는 정보의 충돌을 피할 수 있다. 이 프로토콜은 시간지연이 서로 다른 다매체정보의 전송을 효과적으로 지원할 수 있다. 데이터 분석과 모의실험을 실행하여, 여러 시스템 매개변수에 의존하는 네트워크 출력과 평균지연을 조사했다. 그 결과, OCDMA기술에 근거한 POF를 네트워크를 사용하는 다우선 예약 프로토콜이 효율적이라는 것을 확인할 수 있었다. In this paper, the performance of the optical code-division multiple access (OCDMA) technology on a plastic optical fiber (POF) access network, which had received much attention due to its low weight, large core diameter, flexibility, easy installation, and especially its high bandwidth, is analyzed. Recently, POF was a very attractive candidate for transmission media in an access network based on OCDMA technology. But the conventional OCDMA system only allows finite units to transmit and access simultaneously according to the number of channels which are restricted by BER, and so, in this paper, to resolve this problem a novel multi-priority reservation protocol is also proposed. By using this reservation scheme and a distributed arbitration algorithm, channel collision and destination conflict could be avoided. And this protocol can efficiently support the transmission of multimedia messages that require the different time-delay. The network throughput and average delay using various system parameters have been investigated by numerical analysis and simulation experiments. These results shows that the multi-priority reservation protocol in this POF access network based on OCDMA technology is valid and efficient.

A Novel Technique to Detect Code for SAC-OCDMA System

Abstract The main task of optical code division multiple access (OCDMA) system is the detection of code used by a user in presence of multiple access interference (MAI). In this paper, new method of detection known as XOR subtraction detection for spectral amplitude coding OCDMA (SAC-OCDMA) based on double weight codes has been proposed and presented. As MAI is the main source of performance deterioration in OCDMA system, therefore, SAC technique is used in this paper to eliminate the effect of MAI up to a large extent. A comparative analysis is then made between the proposed scheme and other conventional detection schemes used like complimentary subtraction detection, AND subtraction detection and NAND subtraction detection. The system performance is characterized by Q-factor, BER and received optical power (ROP) with respect to input laser power and fiber length. The theoretical and simulation investigations reveal that the proposed detection technique provides better quality factor, security and received power in comparison to other conventional techniques. The wide opening of eye in case of proposed technique also proves its robustness.

Numerical construction of generalized matrix partitioning code for spectral amplitude coding optical CDMA systems

A new code construction algorithm for Spectral Amplitude Coding Optical Code Division Multiple Access (SAC-OCDMA) is proposed to reduce multiple access interference (MAI) and mitigate the influence of Phase Induced Intensity Noise (PIIN) arising in photodetecting process effectively. The new family of code called Generalized Matrix Partitioning Code (GMPC) has many advantages such as simplicity in code construction using the concept of the sequence of numbers, no upper and lower bounds restrictions and it is valid for all natural numbers. The performance analysis shows that the proposed GMP code family can suppress phase induced intensity noise effectively and improve the system performance significantly.

New optimal $(v, \{3,5\}, 1, Q)$ optical orthogonal codes

Variable-weight optical orthogonal code (OOC) was introduced by Yangfor multimedia optical CDMA systems with multiple quality of service(QoS) requirements. It is proved that optimal $(v, \{3, 5\}, 1,(1/2, 1/2))$-OOCs exist for some complete congruence classes of $v$.In this paper, for $Q\in \{(2/3,1/3), (3/4,1/4)\}$, by using skewstarters, it is also proved that optimal $(v, \{3,5\}, 1, Q)$-OOCsexist for some complete congruence classes of $v$.

Two Dimensional Tunable Optical-CDMA System

<p>In this work an experimental demonstration is proposed to implement the synchronous optical code division multiple access system using two dimensional wavelength hopping and time spreading optical prime code is presented. An optical CDMA system is configured on latest version of optisystem by optiwave for the 20 users (Prime Number = 5) connected in a network operating at a bit rate 10 Gbps each. Tunability is achieved by using a MATLAB based delay selector which serves as the source of control signal for optical delay lines. The encoded optical signal of each user has been assigned a particular mode. The resulting optical signal is then transmitted over parabolic index multimode optical fiber. The received signal can successfully be retrieved at the decoder, when the encoder and decoder are configured for the same user. The performance of Optical CDMA system is evaluated in terms of the autocorrelation and cross correlation function, BER, Q factor, eye diagram and compared with 1D code for a given prime number. </p>

Spectrally Efficient SAC-OCDMA System Using a New Two-Code Keying Scheme

This paper introduces a new two-code keying scheme for increasing the spectral efficiency (SE) of spectral-amplitude-coding optical code-division multiple-access (SAC-OCDMA) system. The analytical expression is derived for the SE of SAC-OCDMA system based on the proposed scheme utilizing multi-diagonal (MD) code. The theoretical results demonstrate that the suggested scheme has an improved SE performance over the conventional unipolar encoding with direct detection technique. This SE enhancement is verified in simulation experiments.

Noncoherent spectral optical CDMA system using 1-D subtracted square codes of all transmitters in one optical line terminal

We propose a family of one-dimensional subtracted square codes in the spectral amplitude coding optical code division multiple access system. The proposed codes perform the subtraction and multiplication operations to give one-to-one mappings function, which produces the code sequences of 1-D subtracted square codes. The proposed structure uses one optical line terminal to produce all of the transmitters. This proposed system overcomes the interference from other simultaneous users, known as multiuser interference, and the cross-correlations suppress the phase-induced intensity noise. In numerical simulations using the proposed 1-D subtracted square codes, we show that 83 simultaneous users can be supported at a bit error rate of \(10^{-9}\). This number of simultaneous users in the proposed system using the 1-D subtracted square codes is superior to that in the other systems using the 1-D M sequence codes, 1-D RSQC codes, and 1-D ESP codes. The proposed system using the 1-D subtracted square codes achieves a data transmission rate of 3.2 Gbps.

A Study of Dispersion Compensation of Polarization Multiplexing-Based OFDM-OCDMA for Radio-over-Fiber Transmissions.

Chromatic dispersion from optical fiber is the most important problem that produces temporal skews and destroys the rectangular structure of code patterns in the spectra-amplitude-coding-based optical code-division multiple-access (SAC-OCDMA) system. Thus, the balance detection scheme does not work perfectly to cancel multiple access interference (MAI) and the system performance will be degraded. Orthogonal frequency-division multiplexing (OFDM) is the fastest developing technology in the academic and industrial fields of wireless transmission. In this study, the radio-over-fiber system is realized by integrating OFDM and OCDMA via polarization multiplexing scheme. The electronic dispersion compensation (EDC) equalizer element of OFDM integrated with the dispersion compensation fiber (DCF) is used in the proposed radio-over-fiber (RoF) system, which can efficiently suppress the chromatic dispersion influence in long-haul transmitted distance. A set of length differences for 10 km-long single-mode fiber (SMF) and 4 km-long DCF is to verify the compensation scheme by relative equalizer algorithms and constellation diagrams. In the simulation result, the proposed dispersion mechanism successfully compensates the dispersion from SMF and the system performance with dispersion equalizer is highly improved.

Study of Multicode-Keying Incoherent Optical CDMA Without the Conventional Symbol-Synchronous Assumption

In this paper, the effect of removing the symbol-synchronous assumption in the multicode-keying incoherent optical code-division multiple access (O-CDMA) systems is studied. Under true symbol asynchronism, the multicode-keying modulation can create “two hits” in the periodic cross-correlation process even though “one-hit” optical codes are used. Three pulse-erasure methods of reducing the occurrence of two hits are studied. By applying optical orthogonal codes to permute the pulses in codewords, a method of constructing one-hit optical codes that can eliminate the occurrence of two hits in “symbol-asynchronous” multicode-keying O-CDMA and enlarge code cardinality is proposed. Performance analytical models for these three two-hit reduction methods and the new optical codes are formulated. Finally, numerical examples are given to compare their performances, and computer-simulation results are presented to validate the analytical models.

Energy efficient adaptive optical CDMA random access protocol based on particle swarm optimization

In this paper, an energy efficient adaptive optical code division multiple access (OCDMA) random access protocol based on particle swarm optimization (PSO) is described. This protocol is based on the S-ALOHA with power and rate allocation based on PSO. This scheme evaluates jointly optimal power and rate allocation PSO based under the random access protocol as a new and simplified scheme for high performance, high energy efficiency suitable for OCDMA systems. The aim is to maximize the aggregate throughput, subject to predetermined quality of service restrictions and energy efficiency constraint in terms of the signal-to-noise-plus interference ratio of each user class. Numerical results are discussed taking into account realistic network operation scenario.

Performance Analysis of Two New Code Families for Spectral-Amplitude-Coding Optical CDMA Systems

In this paper, we have proposed two new one-dimensional code families for spectral amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. They are referred as 1) partitioned diagonal code (PDC) and 2) partitioned modified quadratic congruence code (PMQCC). Simulation results show that both of codes can reduce phase-induced intensity noise and support more active users as compared with MQC. Our results show that for similar code length, PDC and PMQCC can support 11% and 14%, respectively, more simultaneous users as compared with MQC. Also, at each synchronous time, the autocorrelations of PDC and PMQCC reach to their peak values and their cross correlations remain one.