2D code construction using DW code families for SAC-OCDMA systems

We proposed newly two-dimensional (2- D ) spectral amplitude coding optical code division multiple access (OCDMA) scheme using modified double weight (MDW) code capable of suppressing phase-induced intensity noise (PIIN). The architecture of the spectral/spatial MDW OCDMA system with the property of multi-access interference cancellation is presented. The proposed code exhibits good cross-correlation property. At the optimized data transmission rate of 0.745 Gbps, 2-D MDW, M = 63, N = 3, reaches maximum cardinality of 200% increases compared to 2- D perfect difference code, M = 57, N = 3. The performance is severely deteriorated if the data rate further increases above 0.745 Gbps. The proposed code meets the optical transmission requirements at 10−9 bit error rate error floor, with lowest effective transmitted power ( P sr), −17.5 dBm, in comparison to the others through minimizing interference noise that result in PIIN suppression. The proposed system reaches optimum requirements performance in terms of cardinality, data transmission rate, and low effective transmitted power.

Double Weight (DW) code families are constructed with different algorithms and fixed value of users at basic code matrix. A single code construction algorithm is proposed for DW code families in which, number of users for basic code matrix depends on the code weight and on a constant value. Mapping is used to provide the greater number of users. Affect of basic matrix (used in mapping) on Bit Error Rate (BER) and code length is analyzed. The properties of proposed code construction algorithm are easy code construction, any positive integer value of weight is used for code construction, design of different code set by varying size of basic matrix. Ex-OR function is used in balanced detection technique at receiver. Numerical results are calculated using MATLAB.

In this paper the Double Weight code (DW) family which is used as a proposed code in optical spectral code division multiple access system (OSCDMA) has been studied using the Modified Double Weight code (MDW) which has across correlation value equals to one. By eliminating the intersection columns of this code we can reduce the cross correlation value from one to zero. This code is named Zero Cross-correlation Code (ZCC) [1]. Therefore, the Multiple Access Interference (MAI) can be reduced. Also, a general equation is used to generate the basic matrix of the code with the cross correlation equal zero instead of that in the existing construction technique. In this paper, we also show the advantages of this equation. All of these studies concentrate on the basic matrix of modified double weight code with zero cross correlation value.

This paper organizes the performance of twodimensional (2-D) Modified Double Weight (MDW) code for Optical Code Division Multiple Access (OCDMA) system by employing Avalanche Photodiodes (APD) as a gain. To accomplish the perfection system capacity, their cardinality, bit error rates (BER) and noise interferences are analyzed. With 2-D MDW with APD able to recovered the cardinality at least 61%, which able to reduce the BER of 10−9 Obviously, the proposed system maximally suppressed PIIN and shot noise which is a major factor affecting BER at high effective received power (Psr). Thus, this system shows an improvement of the system by applying APD instead of PIN diodes.

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We proposed the multipolar inserting zeros (MIZ) code for direct-sequence optical code division multiple access (OCDMA) systems. This code is designed to correspond with the judgment based on linear convolution. Simulation results showed that it can provide a lower multiuser interference than the conventional Gold sequence. With the same number of users, the bit error rate in the OCDMA system coded by MIZ can be reduced by several decuples than that coded by Gold, and the source power needed to reach a BER of 1×10?9 can also be reduced by several decibels. So the performance of OCDMA can be improved.

In this paper, we investigate the feasibility of a 2 Dimensional Optical Code Division Multiple Access system (2DOCDMA), with electronic coding and decoding functions. We present a modified construction method of Multi-Wavelength Optical Orthogonal Codes (MWOOC) which permits high flexibility for the code parameters choice. Our objective is to evaluate the 2D code performance, with a Conventional Correlation Receiver (CCR) and a more complex one named Parallel Interference Cancellation receiver (PIC). For example, for a Bit Error Rate (BER)10-9, 30 simultaneous users and an electrical implementation, we show that contrary to the CCR, the use of a PIC receiver leads to workable 2D code solutions.

This 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.

This paper the construction of the double weight (D\V) code family, one the recent codes for spectral amplitude coding (SAC) is studied. The DW code family is constructed using a matrix construction technique and a mapping scheme to increase the number of users. To obtain a single user's codeword the whole matrix must be constructed. In this paper a simplified equation based construction technique for the DW code family is proposed. This new simplified construction scheme depends on the three basic building blocks for the DW code family. General equations for the codeword construction and code length are given.

A parallel combinatory (PC)-hybrid pulse interval modulation-optical code division multiple access (hPIM-OCDMA) system is proposed. In the PC-hPIM-OCDMA system, a user chooses e among K code sequences assigned to the user and sends e2b-ary PIM symbols for a given frame, where b is the number of bits per PIM symbol. The PC-hPIM-OCDMA system can offer higher bit rate than hPIM-OCDMA systems, and then it can reduce the effect of MAI, without reducing the bit rate. The bit error rate (BER) of PC-hPIM-OCDMA is derived, by considering that the dominant interference is MAI, which is caused by cross-correlation of strict optical orthogonal codes (SOOCs). Numerical results show that the PC-hPIM-OCDMA system can offer lower BER and accommodate more users than hPIM-OCDMA systems.

In this paper, we are proposing a detection scheme known as spectral direct detection technique implemented with fiber bragg grating (FBG) act as encoder/decoder. This FBG based is used to encode and decode the spectral amplitude coding namely modified double weight (MDW) code in optical code division multiple access (OCDMA). This code is used due to its flexibility where its weight can be any even number that greater than two. Moreover, it can maintain the cross-correlation parameter equal to one. The performance of spectral direct detection technique against AND-subtraction technique which is both implemented with FBG based encoder/decoder is compared via simulation in downstream and upstream access network at point to multipoint (P2MP) configuration. The simulation will be carried out using OptiSystem version 6.0 and the performance is characterized through bit error rate (BER) and power received at various bit rate.

In this paper, three code families for spectral amplitude coding optical code division multiple access (SAC-OCDMA) systems in terms of performance are compared to each other under the impact of group velocity dispersion (GVD). The investigated code families are m-sequence, Walsh-Hadamard and modified quadratic congruence (MQC). The performance of these codes is evaluated for three types of transmission media such as single-mode fiber (SMF), dispersion shifted fiber (DSF) and nonzero dispersion shifted fiber (NZ-DSF). Results show that in each of the three transmission media m-sequence code family offers the best performance among the investigated code sets under the impact of GVD. Systems which employ m-sequence codes can achieve longer transmission length compared to those using Walsh-Hadamard and MQC codes. In addition, a chirped fiber Bragg grating (CFBG) is designed as a compensating element to compensate the impact of GVD in a SAC-OCDMA system. Employing the designed grating in the system results in a wide opening in the eye diagram as well as improved bit error rate (BER) of the system which indicate that the impact of GVD is effectively compensated.

The atmospheric two-dimensional optical code-division multiple-access (CDMA) systems using pulse-position modulation (PPM) and Turbo-coded were presented. We analyzed the bit-error rate (BER) of the proposed system using pulse-position modulation (PPM) with considering the effects of the scintillation, avalanche photodiode noise, thermal noise, and multi-user interference. We showed that the atmospheric two dimensional (2D) optical PPM CDMA systems can realize high-speed communications when the logarithm variance of the scintillation is less than 0.1, and the turbo-coded atmospheric optical CDMA system has better bit error rate(BER) performance than the atmospheric optical PPM CDMA systems without turbo-coded. We also showed that the turbo-coded system has better performance than the multi-user detection system.

Chromatic and temperature induced dispersion can both severely affect incoherent high data rate communications in optical fibre. This is certainly also true for incoherent optical code division multiple access (OCDMA) systems with multi-wavelength picosecond code carriers. Here, even a relatively small deviation from a fully dispersion compensated transmission link can strongly impact the overall system performance, the number of simultaneous users, and the system cardinality due to the recovered OCDMA auto-correlation being strongly distorted, time-skewed, and having its full width at half maximum (FWHM) value changed. It is therefore imperative to have a simple tunable means for controlling fibre chromatic or temperature induced dispersion with high sub-picosecond accuracy. To help address this issue, we have investigated experimentally and by simulations the use of a semiconductor optical amplifier (SOA) for its ability to control the chirp of the passing optical signal (OCDMA codes) and to exploit the SOA ability for dispersion management of a fibre link in an incoherent OCDMA system. Our investigation is done using a 19.5 km long fibre transmission link that is exposed to different temperatures (20 °C and 50 °C) using an environmental chamber. By placing the SOA on a transmission site and using it to manipulate the code carrier’s chirp via SOA bias adjustments, we have shown that this approach can successfully control the overall fibre link dispersion, and it can also mitigate the impact on the received OCDMA auto-correlation and its FWHM. The experimental data obtained are in a very good agreement with our simulation results.

The encoding/decoding scheme based on Fiber Bragg Grating (FBG) for Optical Code Division Multiple Access (OCDMA) system is analyzed and the whole process from transmitting end to receiving end is researched in detail. The mathematical mode including signal transmission, summing, receiving and recovering are established respectively. One of the main sources of Bit Error Rate (BER) of OCDMA system based on FBGs is the unevenness of signal power spectrum, which leads to the chip powers unequal with each other. The Signal to Interfere Ratio (SIR) and BER performance of the system are studied and simulated at the case with uneven distribution of chips’ powers.