Double Weight Code Research Articles

Spectral/spatial optical CDMA code based on Diagonal Eigenvalue Unity

Abstract A new two dimensional Diagonal Eigenvalue Unity (2D-DEU) code is developed for the spectral⧹spatial optical code division multiple access (OCDMA) system. It has a lower cross correlation value compared to two dimensional diluted perfect difference (2D-DPD), two dimensional Extended Enhanced Double Weight (2D-Extended-EDW) codes. Also, for the same code length, the number of users can be generated by the 2D-DEU code is higher than that provided by the others codes. The Bit Error Rate ( BER ) numerical analysis is developed by considering the effects of shot noise, phase induced intensity noise (PIIN), and thermal noise. The main result shows that BER is strongly affected by PIIN for the higher source power. The 2D-DEU code performance is compared with 2D-DPD, 2D-Extended-EDW and two dimensional multi-diagonals (2D-MD) codes. This comparison proves that the proposed 2D-DEU system outperforms the related codes.

Construction and Analysis of a Novel SAC-OCDMA System with EDW Coding using Direct Detection Technique

Abstract Spectral amplitude coding optical code division multiple access (SAC-OCDMA) is a promising innovation for burst and asynchronous environment. This paper endeavors to analyze the efficacy of the proposed optimum SAC-OCDMA system by utilizing enhanced double-weight (EDW) code for six users operating at a bit rate of 60 Gb/s (10×6 Gb/s). Also, an algorithm is designed for EDW code with mapping technique for any weight that can be greater than two. The EDW code is analyzed for bit error rate (BER) and Q-factor using direct detection technique. Further, the system is compared with three dispersion compensating techniques (pre, post and symmetrical). The results indicate that by using symmetrical compensation the maximum usable distance increases to more than twice as compared to without compensation for the targeted BER (10−9), whereas by using p- and post-compensation the BER value increases to 10−13 as compared to without compensation whose BER value is 10−5. The comparison results show acceptable performance improvement.

High Performance with Avalanche Photodiode in Wavelength/Time Optical Code Division Multiple Access

In order to increase the number of users as increasing the data rate and transmission distance, then to reduce the impact of multi-access interference (MAI) and the effect of phase-induced intensity noise (PIIN). This study proposed the utilizing of an avalanche photodiode (APD) on two-dimension optical code division multiple access (2-D OCDMA). APD detector is more sensitive than positive-intrinsic-negative (PIN) photodiode, due to its inherent gain that increases the signal to noise ratio (SNR) of the system by amplifying the received signal prior to proceeding to next stage. In this research, an improvement of realizable system capacity APD performance of different gain applied for Wavelength/Time modified double weight (MDW) code for cardinality, bit error rates (BER) and noise interference are analyzed. MATLAB is utilized as a software for theoretical results to study the APD gain effect upon the probability density function (PDF) and SNR performance. The results in very good approval indicate that 95.45% cardinality improvements compare to 2-D MDW code with PIN at 1.25 Gbps data bit rate. The Psr = -14 dBm for 500 active users by using APDs with gain =5, but 5 dBm effective receive power for PIN error floor 10-9 for 500 users. The usage of APD over (PIN) photodiode provides a high performance for a long transmission distance and high data bit rate that improved in the simulation for real environment by using the Optiwave software version 11.0. Seemingly, the system supports more no. of users, less bit error rate, and large data rate transmission.

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.

Performance analysis of SAC-OCDMA in free space optical medium using DDW code

Spectral amplitude coded Optical code division multiple access technique (SAC-OCDMA) has become a major area of research in optical communication. OCDMA allows multiple users to access a medium simultaneously without any contention. It has ability to operate asynchronously, provide privacy and security and reduce multiple user interference. In this paper performance of SAC-OCDMA with Diagonal double weight (DDW) code with FSO communication system is presented and compared under different conditions of rain and haze. 10 simultaneous users with 5Gbps data rate are evaluated in the system. Effect of transmitted power and beam divergence is also studied. Results have been formulated based upon eye diagrams and values of Q- factor and BER. Maximum distance covered is 10 Km with BER of 10−25 under clear weather. Simulation results show that DDW code is able to perform well at low power values also.

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.

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

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 Review on Spectral Amplitude Coding Optical Code Division Multiple Access

AbstractThis manuscript deals with analysis of Spectral Amplitude Coding Optical Code Division Multiple Access (SACOCDMA) system. The major noise source in optical CDMA is co-channel interference from other users known as multiple access interference (MAI). The system performance in terms of bit error rate (BER) degrades as a result of increased MAI. It is perceived that number of users and type of codes used for optical system directly decide the performance of system. MAI can be restricted by efficient designing of optical codes and implementing them with unique architecture to accommodate more number of users. Hence, it is a necessity to design a technique like spectral direct detection (SDD) technique with modified double weight code, which can provide better cardinality and good correlation property.

Generalized optical code construction for enhanced and Modified Double Weight like codes without mapping for SAC–OCDMA systems

Abstract Double Weight (DW) code family is one of the coding schemes proposed for Spectral Amplitude Coding–Optical Code Division Multiple Access (SAC–OCDMA) systems. Modified Double Weight (MDW) code for even weights and Enhanced Double Weight (EDW) code for odd weights are two algorithms extending the use of DW code for SAC–OCDMA systems. The above mentioned codes use mapping technique to provide codes for higher number of users. A new generalized algorithm to construct EDW and MDW like codes without mapping for any weight greater than 2 is proposed. A single code construction algorithm gives same length increment, Bit Error Rate ( BER ) calculation and other properties for all weights greater than 2. Algorithm first constructs a generalized basic matrix which is repeated in a different way to produce the codes for all users (different from mapping). The generalized code is analysed for BER using balanced detection and direct detection techniques.

Design of double-weight code for synchronous OCDMA systems with power control

Double-weight optical code division multiple access (OCDMA) systems are proposed for studying differentiated quality-of-service transmission. Based on quadratic congruence code (QCC), we construct a one-dimensional double-weight code family, which can be well utilized in incoherent synchronous double-weight OCDMA networks. By introducing algebraic transformation to code sequences of QCC in level 1, we obtain multiple double-weight codes with cross-correlation 1. Under the same-bit-power assumption, the performance of low-weight codes can be significantly improved and is always superior to that of high-weight codes in double-weight OCDMA systems with power control. This property is contrary to previous conclusions under the same-chip-power assumption.

Enhanced Performance of SAC-OCDMA System based on SPD Detection Utilizing EDFA for Access Networks

In this paper, we present the impact of an EDFA (Erbium Doped Fibre Amplifier) for high data rate in Spectral Amplitude Coding Optical Code Division Multiple Access (SAC-OCDMA) networks. A Single photodiode (SPD) detection structure for SACOCDMA system is presented. The SPD detection can be flexibly constructed for any weight and number of users by using a single photodiode. Several advantages of using EDFA for simultaneous noise suppression and improved the signal quality. Thus, these features show the SPD combined with EDFA be a solution to enhance the overall system performance of SAC-OCDMA access networks. Based on the theoretical and simulation evaluation, Modified Double Weight (MDW) code is shown to provide a much better performance compared to existing SAC-OCDMA codes. The ability of the MDW code based SAC-OCDMA system utilizing EDFA to support simultaneous transmissions at different data rate has been successfully established through the simulated results of the (622 Mbps×3 users) at bit error rate of 10. 

Performance Analysis of Hybrid OCDMA/WDM System for Metro Area Network

In this study a hybrid spectral amplitude coding for optical code division multiple access (i.e., called OCDMA) over wavelength division multiplexing (WDM) network is proposed to support large number of subscribers. The proposed system combines two different techniques, namely OCDMA and WDM. The modified double weight (MDW) code is used as a signature address for designing the system. This code has numerous advantages such as this code can accommodate more number of simultaneous active users under considerable standard bit error rate (e.g. ≤ 10-9) and shorter code length. The proposed system can enhance the network capability to support high number of users. Therefore, this system can be considered as a promising solution for Metro Area Network (MAN).

Channel Spacing Effect on SAC-OCDMA System Based Modified-AND Subtraction Detection Scheme

This paper focuses on the performance of different channel spacing with AND as well as modified-AND subtraction detection techniques emphasizing the spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. Modified double-weight (MDW) codes are used as the signature codes for SAC-OCDMA systems. This study has been carried out through simulation of a real-like SAC-OCDMA system by using OptiSystem software from optiwaveTM. It has been found that the modified-AND subtraction detection technique able to provide a good transmission of 0.8nm that close to 1nm channel spacings performance thus show that it is a good solution which able to provide bandwidth efficiency factor to the incoherent SAC-OCDMA system that can cut down 25% of the bandwidth usage.

Improvement of the bit error rate of a non-coherent OCDMA system for FTTH network applications

In this paper, an optical code division multiple access (OCDMA) system was analysed to improve the bit error rate (BER) performance at 10 Gbps. The improvements to this system were based on a modified double weight code and a NAND subtraction technique and aimed to support the large number of active users in the fibre-to-the-home network. The system performance was investigated through extensive theoretical and numerical simulation analyses. The theoretical and simulation results revealed that the new detection technique exhibits improved BER performance compared to conventional techniques, such as complimentary subtraction techniques. The system performance was characterised by the signal-to-noise ratio, the bit error rate (BER), and various transmit powers (\(P_{sr} - 10\) dBm). The results show that the proposed system, which is based on a new detection technique, can achieve the optimal BER with a high number of users and maintains the error floor transmission rate \((\le 10^{-9})\).

Study of the OCDMA Transmission Characteristics in FSO-FTTH at Various Distances, Outdoor

Abstract It is important to apply the field Programmable Gate Array (FPGA), and Optical Switch technology as an encoder and decoder for Spectral Amplitude Coding Optical Code Division Multiple Access (SAC-OCDMA) Free Space Optic Fiber to the Home (FSO-FTTH) transmitter and receiver system design. The encoder and decoder module will be using FPGA as a code generator, optical switch using as encode and decode of optical source. This module was tested by using the Modified Double Weight (MDW) code, which is selected as an excellent candidate because it had shown superior performance were by the total noise is reduced. It is also easy to construct and can reduce the number of filters required at a receiver by a newly proposed detection scheme known as AND Subtraction technique. MDW code is presented here to support Fiber-To-The-Home (FTTH) access network in Point-To-Multi-Point (P2MP) application. The conversion used a Mach-Zehnder interferometer (MZI) wavelength converter. The performances are characterized through BER and bit rate (BR), also, the received power at a variety of bit rates.

Accurate Analysis of Double-Weight Codes with an Arbitrary Maximum Cross-Correlation Value for Two-Chip-Power Optical CDMA

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 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> = 1 was exactly analyzed, but an approximation was only applied to the codes with λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> > 1 due to mathematical complexity. In this paper, an exact analytical model of double-weight codes with an arbitrary λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ≥ 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.

Cardinality enhancement of spectral/spatial modified double weight code optical code division multi-access system by PIIN suppression

A new two-dimensional (2-D) optical code division multiple access (OCDMA) scheme to increase the achievable system capacity is proposed. The code exhibits good cross-correlation property time and wavelength shift. Performances are analyzed on code size and correlation properties affecting two important system parameters, bit error rate (BER) as a function of cardinality generated and optical power transmission requirement. The proposed system can effectively suppress phase-induced intensity noise (PIIN) and has multi-access interference (MAI) cancellation property. Results in a good agreement indicate that 2-D modified double weight (MDW) offers 163.7% and 336.2% larger cardinality compare to 2-D perfect difference code (PDC) and 2-D modified quadratic congruence (MQC) code. By increasing spatial code (N) and keeps similar code length system performance can be further optimized. 2-D MDW (M=45, N=18) accommodates 252.2% and 18.3% cardinality increment and low effective transmitted power (Psr) at −17.9dBm, compare to 2-D MDW (M=247, N=3) and (M=84, N=9) at 10−9 BER error floor. The architecture of the spectral/spatial MDW OCDMA system with property of MAI cancellation is presented.

Novel OCDMA Detection Technique based on Modified Double Weight Code for Optical Access Network

In this paper a new detection technique known as NAND subtraction scheme based on Modified Double Weight (MDW) code for spectral-amplitude coding OCDMA (SAC-OCDMA) is proposed. The MDW code is the modified version of double weight (DW) code family. The theoretical and simulation results show that the new detection technique can have more better BER performance than other conventional techniques such as the AND and Complimentary subtraction techniques. The system performance was characterized by the signal to noise ratio (SNR), bit error rate (BER), and different P sr (-10 dBm) . This study also shows that the new detection scheme can be achieved when the number of users are high and maintain the standard acceptable BER value ((≤10 -9 ). DOI: http://dx.doi.org/10.5755/j01.eee.18.8.2638

Performance enhancement of OCDMA system using NAND detection with modified double weight (MDW) code for optical access network

In this paper, we have extensively analyzed the OCDMA system performance using modified double weight (MDW) code with NAND detection technique as newly developed by the authors. In theoretical analysis, various noises and multiple-access interference (MAI) effect were taken into account. The system performance was characterized by the signal-to-noise ratio (SNR) and the bit-error-rate (BER). The analysis results obtained with NAND detection technique were compared with those as obtained with complementary and AND subtraction techniques. The comparison results revealed that the NAND detection technique with MDW code can support more number of active users and improve the system performance compared to complimentary and AND subtraction techniques. We also ascertained by simulation experiment that the BER performance of the system with NAND detection technique is greatly improved as compared to the complementary and AND subtraction technique.