Multiwavelength Optical Orthogonal Codes Research Articles

Study of fiber optic code division multiple access Code families for Application in Optical Communication based on weight and bit error rate

This paper investigates on fiber optic code division multiple access (FOCDMA) code families using different sets of parameter. The different code families considered here are generalized multi-wavelength Reed-Solomon code (GMWRSC), complete row-wise orthogonal pairs (CRWOP), row-wise orthogonal pairs (RWOP) and Multiwavelength Optical Orthogonal Code (MWOOC). The parameters under investigation in this work chosen to be number of maximum users (Nmax),Bit error rate(BER),Spreading Factor(Sf),Weight(K’),Number of Wavelengths(WI) and number of time chips(T). By using suitable mathematical formula, computation is made for above said parameters using aforementioned methods At the end a healthy comparison was made to identify efficient one among them just by estimating cardinality of each result. The comparison result revealed that row wise orthogonal pairs (RWOP) code family gives high performance.

Performance Analysis of Variable-Weight Multilength Optical Codes for Wavelength–Time O-CDMA Multimedia Systems

To support multimedia services with different discrete bit-rate requirements, families of multilength optical codes, such as the carrier-hopping prime code (CHPC), extended CHPC, and multiwavelength optical orthogonal code, were recently constructed for wavelength-time optical code-division multiple-access (O-CDMA). In this paper, the performance of these multilength optical codes in a multimedia O-CDMA system with a variable-weight operation are analyzed. Our study shows that short-length codes generate stronger interference than long-length codes. This supports services prioritization in O-CDMA. Our study also shows that code weight is a more important factor than code length in determining code performance (i.e., quality of service).

Performance Analysis of Variable-Weight, Multilength Optical Codes for Wavelength-Time O-CDMA Multimedia Systems

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> To support multimedia services with different discrete bit-rate requirements, families of multilength optical codes, such as the carrier-hopping prime code (CHPC), extended CHPC, and multiwavelength optical orthogonal code, were recently constructed for wavelength-time optical code-division multiple-access (O-CDMA). In this paper, the performance of these multilength optical codes in a multimedia O-CDMA system with a variable-weight operation are analyzed. Our study shows that short-length codes generate stronger interference than long-length codes. This supports services prioritization in O-CDMA. Our study also shows that code weight is a more important factor than code length in determining code performance (i.e., quality of service). </para>

2‐Dimensional code design for an optical CDMA system with a parallel interference cancellation receiver

AbstractThe objective of this paper is to design a two‐Dimensional Optical Code Division Multiple Access system (2D‐OCDMA) for application in access networks, with coding and decoding functions performed by electronic devices. We present a new construction method of Multi‐Wavelength Optical Orthogonal Codes (MWOOC), which permits a high flexibility in the code parameters choice. This work evaluates in the noiseless case, the MWOOC potentialities for two receiver structures: a Conventional Correlation Receiver (CCR) and a Parallel Interference Cancellation receiver (PIC). We show that with a PIC receiver, it is possible to design two‐Dimensional codes that respect the access specifications. Copyright © 2007 John Wiley &amp; Sons, Ltd.

2-Dimensional optical CDMA system performance with parallel interference cancellation

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

Modified multi-wavelength optical orthogonal code for spectral efficiency improvement in two-dimensional optical CDMA system

Classical multi-wavelength optical orthogonal code (MWOOC) constructions impose several conditions on the code parameters. These limit the optical code division multiple access (OCDMA) system potentialities in terms of performance and practical implementation. A modified MWOOC construction is used to overcome these limitations. Indeed, this method permits the design of 2D codes with a low temporal code length value and a low number of wavelengths. Considering a multi-user receiver named parallel interference cancellation, the number of users and the data rate per user the system can provide for a low bit error rate value are evaluated. For a given performance, it is shown that the spectral efficiency using the modified MWOOC is significantly improved. Thus, the simplicity of the modified code design and the spectral efficiency increase constitute an advantage for practical implementation of OCDMA network.

Polarization-assisted OCDMA using fiber Bragg gratings written in highly birefringent fibers

A new polarization-assisted method for the implementation of multiwavelength optical orthogonal codes for optical code-division multiple-access is presented. It is based on fiber Bragg gratings written in highly birefringent fibers. The advantages of the technique include the reduction of the interference between users and the reduction of the number of coders and decoders needed.

Multilength two-dimensional codes for optical CDMA system

A newe class of multilength, constant-weight and two-dimensional multiwavelength optical orthogonal code (2D MWOOCs) with large capacity and good correlation properties is constructed based on multilength one-dimensional (1D) OOCs. The performance of these newe MWOOCs in an OCDMA network with double-services is analyzed. The result shows that media with the shorter codeword performs much better than the media with longer codeword, and OCDMA system with these new multilength MWOOCs performs well. These features allow multimedia transmission of large capacity in OCDMA

Comparison of diverse optical CDMA codes using a normalized throughput metric

A new method of comparing optical CDMA codes of different families, sizes and weights is described. We outline why the traditional performance metric of bit-error rate versus number of simultaneous users is lacking and propose a new performance measure - the peak throughput normalized with respect to the size of the code. This new metric is used to show that optical-orthogonal codes (OOCs) with a weight of 4 perform best at low offered loads while OOCs with weight 5 should be used at higher offered loads. By applying the technique across different families of codes, we demonstrate that multi-wavelength OOCs (MWOOCs) perform better than both OOCs (by a factor of approximately 1.25) and asymmetric prime-hop codes (by a factor of approximately 3.5), over a wide range of offered loads.

New construction of multiwavelength optical orthogonal codes

We investigate multiwavelength optical orthogonal codes (MWOOCs) for optical code-division multiple access. Particularly, we present a new construction method for (mn,/spl lambda/+2,/spl lambda/) MWOOCs with the number of available wavelengths m, codeword length n, and constant Hamming weight /spl lambda/+2 that have autocorrelation and cross-correlation values not exceeding /spl lambda/. In the proposed scheme, there is no constraint on the relationship between the number of available wavelengths and the codeword length, and it is also possible to use an arbitrary /spl lambda/. We show that the constructed code is optimal, especially for /spl lambda/=1. Finally, we analyze the bit error rate of the new code and compare it with that of other optical codes.

Performance evaluation of PIN+OA and APD receivers in multi-wavelength CDMA and WaCDMA networks

In this paper, the performance of multi-wavelength optical orthogonal code division multiple access (MWOCDMA) communication network and hybrid wavelength code division multiple access (WaCDMA) network are investigated. In both the networks, transmitted signal is coupled into a dispersion shifted fiber (DSF) which in turn is coupled to either a PIN+OA or an APD receiver. The expression for probability of error for the above receiver configurations in MWOCDMA and WaCDMA networks are derived taking into consideration various sources of receiver noise, multiple user interference and four wave mixing (FWM) effects. It is observed that for a given number of users, MWOCDMA networks with PIN+OA receiver and WaCDMA networks with APD receiver are preferred to achieve a required performance. Further, the former give improved performance as compared to the latter with the level of improvement depending upon the number of users for which the network is to be designed. This is valid for all values of link loss. However, at higher values of link loss, FWM effect becomes dominant since the transmitted power is high and it leads to a smaller range of input transmitted power levels for a given number of users and performance requirement.

Analysis of multiwavelength optical orthogonal CDMA communication system

The concept of a multiwavelength was recently introduced in order to support a large number of simultaneous users in optical code-division multiple-access (CDMA) networks without the need for complicated optical signal processing. A number of multiwavelength optical orthogonal codes (MWOOC) have been developed, and these codes show better performance under heavy traffic load conditions. In this paper, a complete analysis of the multiwavelength OOCDMA communication system is presented, including the effects of avalanche photodiode (APD) noise, thermal noise, and multiple-user interference for a direct-detection receiver. The results of the analysis are compared with the performance of an optical orthogonal CDMA system that uses only one wavelength, i.e., single-wavelength optical orthogonal codes (SWOOC). Typically, for 825, 826.1, and 827.2 nm, with −60 dB laser power and 50 simultaneous users, Pe is 4.17×10−15 compared to 1.77×10−5 at 825 nm in a SWOOC system. In the presence of various noises, the MWOOC system exhibits improved error performance over the SWOOC system. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 182–188, 1999

Frequency-hopping codes for multimedia services in mobile telecommunications

In this paper, "multilength" frequency-hopping (FH) codes are constructed by modifying the generalized prime codes (GPCs). The new codes have asymptotically optimal cardinality as well as zero autocorrelation sidelobes and cross-correlation functions of no greater than one. They are suitable for the integration of multimedia services (e.g., data, voice, image, and video) with different quality-of-service (QoS) requirements and signaling rates in future telecommunication systems, such as third-generation cellular mobile radio systems, where rate and service quality are dynamically matched to users' needs through the assignment of different-length FH patterns. The use of the new codes in multirate multimedia systems with FH code-division multiple access (FH-CDMA) is illustrated. Providing frequency and time diversities, the applications of the GPCs to an FH time-division multiple-access (FH-TDMA) and FH/time-hopping TDMA (FH/TH-TDMA) system are also discussed. Finally, the use of the codes in optical CDMA systems as multiwavelength optical orthogonal codes is studied.

Performance comparison of multiwavelength CDMA and WDMA+CDMA for fiber-optic networks

A scheme has been proposed to support large numbers of subscribers and simultaneous users in optical code-division multiple-access (CDMA) networks without using very large bandwidth expansion or the need of complicated and not-yet-feasible optical processing. In this paper, multiwavelength optical orthogonal codes (MWOOCs), which consist of two-dimensional codewords (or matrices) with every pulse of a codeword encoded in a distinct wavelength, are constructed for this scheme. MWOOCs have larger cardinality than the one-dimensional codes used in the hybrid wavelength-division multiple-access (WDMA) and CDMA scheme. With the same hardware configuration, our analysis shows that the multiwavelength scheme, in general, performs better than the hybrid scheme, particularly when the traffic load is heavy. However, if a central controller (i.e., under the best scenario) is used to uniformly distribute all available wavelengths to simultaneous users in the hybrid scheme, both schemes have comparable performance for a medium traffic load and the hybrid scheme can theoretically achieve error-free transmission when the load is light. In addition, using multiple wavelengths, the requirements of fiber ribbons and multiple stars in temporal/spatial optical CDMA networks are eliminated.