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Electro-optical time gating based on Mach-Zehnder modulator for multiple access interference elimination in optical code-division multiple access networks

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optical ENGINEERING 2014年第5期53卷 1-5页

作者： Chen, Yinfang Wang, Rong Fang, Tao Pu, Tao Xiang, Peng Zheng, Jilin Zhu, Huatao PLA Univ Sci & Technol Inst Commun Engn Nanjing 210007 Jiangsu Peoples R China

An electro-optical time gating technique, which is based on an electrical return-to-zero (RZ) pulse driven Mach-Zehnder modulator (MZM) for eliminating multiple access interference (MAI) in optical code-division multiple access (OCDMA) networks is proposed. This technique is successfully simulated in an eight-user two-dimensional wavelength-hopping time-spreading system, as well as in a three-user temporal phase encoding system. Results show that in both systems the MAI noise is efficiently removed and the average received power penalty improved. Both achieve error-free transmissions at a bit rate of 2.5 Gb/s. In addition, we also individually discuss effects of parameters in two systems, such as the extinction ratio of the MZM, the duty cycle of the driven RZ pulse, and the time misalignment between the driven pulse and the decoded autocorrelation peak, on the output bit error rate performance. Our work shows that employing a common MZM as a thresholder provides another probability and an interesting cost-effective choice for a smart size, low energy, and less complex thresholding technique for integrated detection in OCDMA networks. (C) 2014 Society of Photo-optical Instrumentation Engineers (SPIE)

关键词： optical code-division multiple access multiple access interference electro-optical time gating wavelength-hopping time spreading time phase en/decoding

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Performance analysis of 2D asynchronous hard-limiting optical code-division multiple access system through atmospheric scattering channel

Performance analysis of 2D asynchronous hard-limiting optica...

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Conference on Satellite Data Compression, Communications, and Processing IX

作者： Zhao, Yaqin Zhong, Xin Wu, Di Zhang, Ye Ren, Guanghui Wu, Zhilu Harbin Inst Technol Sch Elect & Informat Engn Harbin 150001 Heilongjiang Peoples R China

ISBN: (纸本)9780819497215

optical code-division multiple access (OCDMA) systems usually allocate orthogonal or quasi-orthogonal codes to the active users. When transmitting through atmospheric scattering channel, the coding pulses are broadened and the orthogonality of the codes is worsened. In truly asynchronous case, namely both the chips and the bits are asynchronous among each active user, the pulse broadening affects the system performance a lot. In this paper, we evaluate the performance of a 2D asynchronous hard-limiting wireless OCDMA system through atmospheric scattering channel. The probability density function of multiple access interference in truly asynchronous case is given. The bit error rate decreases as the ratio of the chip period to the root mean square delay spread increases and the channel limits the bit rate to different levels when the chip period varies.

关键词： optical code-division multiple access atmospheric scattering channel asynchronous hard-limiting multiple access interference

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Multiservice transmissions in optical code-division multiple access networks of spectral amplitude coding based on hypothesis testing and multiple chip decoding

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optical ENGINEERING 2022年第9期61卷 096105-096105页

作者： Chen, Kai-Sheng Nanfang Coll Guangzhou Sch Elect & Comp Engn Guangzhou Peoples R China

I propose a multiservice scheme in optical code-division multiple access (OCDMA) networks by adapting hypothesis testing to a receiver design of multiple chip decoding. Each transmitted bit of a single user is divided into several time-domain chips carrying an identical spectral amplitude coding (SAC) signature. Multiservice transmissions are achieved by assigning the users with different chip numbers based on the user classes. Hypothesis testing is employed to derive the required chip number supporting the desired bit-error rate (BER) performance. Numerical results have shown that efficient BER classifications are achieved among distinctive classes for multiple conditions of user numbers and power levels. The proposed multiservice scheme can be transparently applied to SAC-OCDMA systems with existing optical codes and various user class numbers. (C) 2022 Society of Photo-optical Instrumentation Engineers (SPIE)

关键词： multiservice transmissions optical code-division multiple access spectral amplitude coding hypothesis testing

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Suppression of phase noises with residual-spectra eliminator in circulator-free fiber-grating optical code-division multiple-access network coder/decoder

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optical ENGINEERING 2006年第6期45卷 065006-1-065006页

作者： Huang, Jen-Fa Tsai, Chen-Mu Huang, Chun-Ming Natl Cheng Kung Univ Taiwan Adv Optoelect Technol Ctr Dept Elect Engn Inst Comp & Commun Tainan 701 Taiwan

In this work, transmissive spectral characteristics of fiber Bragg gratings (FBGs) are applied to construct a circulator-free scheme of an optical code-division multiple-access (OCDMA) network coder/decoder (codec). The unnecessary spectra would accompany the coding chips to arrive at the photodetectors (PDs) to induce higher phase-induced intensity noise (PIIN) and multiple-access interference (MAI). A residual-spectra eliminator (RSE) between OCDMA encoder and decoder modules is employed to remove the unnecessary spectral parts of data so that the PIIN and MAI can be reduced. A simple experiment performed on the basis of transmissive spectral characteristics of FBGs together with RSE is demonstrated to verify the capability of suppressing residual-spectra noise at the PDs. Performance evaluations indicate that using RSE between network codecs can remarkably lower the PIIN effects in the receiver PDs. (c) 2006 Society of Photo-optical Instrumentation Engineers.

关键词： optical code-division multiple access spectral-amplitude coding fiber Bragg gratings phase-induced intensity noise multiple-access interference residual-spectra eliminator

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Above the nominal limit performance evaluation of multiwavelength optical code-division multiple-access systems

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optical ENGINEERING 2009年第3期48卷 035003-1-035003-9页

作者： Inaty, Elie Raad, Robert Fortier, Paul Shalaby, Hossam M. H. Univ Balamand Fac Engn Elkoura Lebanon Univ Laval Fac Engn Quebec City PQ G1K 7P4 Canada Univ Alexandria Dept Elect Engn Fac Engn Alexandria 21544 Egypt

We provide an analysis for the performance of a multiwave-length optical code-division multiple-access (MW-OCDMA) network when the system is working above the nominal transmission rate limit imposed by passive encoding-decoding operation. We address the problem of overlapping in such a system and how it can directly affect the bit error rate (BER). A unified mathematical framework is presented under the assumption of one-coincidence sequences with nonrepeating wavelengths. A closed form expression of the multiple access interference limited BER is provided as a function of different system parameters. Results show that the performance of the MW-OCDMA system can be critically affected when working above the nominal limit, an event that can happen when the network operates at a high transmission rate. In addition, the impact of the derived error probability on the performance of two newly proposed medium access control (MAC) protocols, the S-ALOHA and the R(3)T, is also investigated. It is shown that for low transmission rates, the S-ALOHA is better than the R(3)T, while the R(3)T is better at very high transmission rates. In general, it is postulated that the R(3)T protocol suffers a higher delay mainly because of the presence of additional modes. (C) 2009 Society of Photo-optical Instrumentation Engineers. [DOI: 10.1117/1.3099613]

关键词： multiwavelength optical code-division multiple access fiber Bragg grating multirate overlapping coefficient one-coincidence sequences S-ALOHA R(3)T

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Optimum threshold detection in real-time scalable high-speed multi-wavelength optical code-division multiple-access LANs

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IEEE TRANSACTIONS ON COMMUNICATIONS 2002年第5期50卷 778-784页

作者： Ng, EKH Sargent, EH Trop Networks Inc Ottawa ON K2M 2E9 Canada Univ Toronto Dept Elect & Comp Engn Toronto ON M5S 3G4 Canada

We examine the properties and applications of a general class of multi-wavelength optical code-division multiple access codes in high-speed optical local area networks. We demonstrate that multiple pulse per row codes with optimum threshold detection admit maximization of the number of simultaneous users and spectral efficiency. The code design problem is also greatly simplified when the optimum threshold detection is employed. Based on our results, we propose a simple and low-cost receiver to enable true real-time network optimization.

关键词： correlation receiver optical code-division multiple access optical communication networks optimum threshold detection real-time scalable networks

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Dispersion in multiwavelength optical code-division multiple-access systems: Impact and remedies

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IEEE TRANSACTIONS ON COMMUNICATIONS 2002年第11期50卷 1811-1816页

作者： Ng, EKH Weichenberg, GE Sargent, EH Univ Toronto Dept Elect & Comp Engn Toronto ON M5S 3G4 Canada

Temporal skewing, a hitherto unexamined effect of chromatic dispersion on multiwavelength optical code-division multiple-access (MW-O-CDMA) systems, is explored through simulation of realistic networks. In addition, two novel methods for combating the deleterious effects of temporal skewing are proposed: optimum threshold detection and code-pattern preskewing. It is shown that for a practical system configuration with optimum threshold detection, MW-O-CDMA networks can maintain design bit error rate performance within an order of magnitude for link lengths of up to approximately 500 m. Our results show that the effect merits careful attention in the design and realization of any MW-O-CDMA system based on two-dimensional codes. code pattern preskewing presents the possibility of completely eradicating the impact of temporal skewing.

关键词： chromatic dispersion local-area networks multi-wavelength optical networks optical code-division multiple access temporal skewing

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Inclusive bit error rate analysis for coherent optical code-division multiple-access system

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optical ENGINEERING 2002年第6期41卷 1227-1231页

作者： Katz, G Sadot, D Ben Gurion Univ Negev Dept Elect & Comp Engn IL-84105 Beer Sheva Israel

Inclusive noise and bit error rate (BER) analysis for optical code-division multiplexing (OCDM) using coherence techniques is presented. The analysis contains crosstalk calculation of the mutual field variance for different number of users. It is shown that the crosstalk noise depends deeply on the receiver integration time, the laser coherence time, and the number of users. In addition, analytical results of the power fluctuation at the received channel due to the data modulation at the rejected channels are presented. The analysis also includes amplified spontaneous emission (ASE)-related noise effects of in-line amplifiers in a long-distance communication link. (C) 2002 society or Photo-optical Instrumentation Engineers.

关键词： optical code-division multiple access amplified spontaneous emission multipexing crosstalk frequency-shift keying

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Performance analysis of multiple interference suppression over asynchronous/synchronous optical code-division multiple-access system based on complementary/prime/shifted coding scheme

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optical ENGINEERING 2011年第8期50卷 085004-085004页

作者： Nieh, Ta-Chun Yang, Chao-Chin Huang, Jen-Fa Natl Cheng Kung Univ Dept Elect Engn Tainan 70101 Taiwan Kun Shan Univ Tainan Taiwan Natl Cheng Kung Univ Dept Electroopt Engn Tainan 70101 Taiwan

A complete complementary/prime/shifted prime (CPS) code family for the optical code-division multiple-access (OCDMA) system is proposed. Based on the ability of complete complementary (CC) code, the multiple-access interference (MAI) can be suppressed and eliminated via spectral amplitude coding (SAC) OCDMA system under asynchronous/synchronous transmission. By utilizing the shifted prime (SP) code in the SAC scheme, the hardware implementation of encoder/decoder can be simplified with a reduced number of optical components, such as arrayed waveguide grating (AWG) and fiber Bragg grating (FBG). This system has a superior performance as compared to previous bipolar-bipolar coding OCDMA systems. (C) 2011 Society of Photo-optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3609005]

关键词： optical code-division multiple access complete complementary code shifted prime code wavelength-hopping time-spreading multiple-access interference

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Performance enhancement of optical code-division multiple-access systems using transposed modified Walsh code

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optical ENGINEERING 2018年第2期57卷 026114-026114页

作者： Sikder, Somali Ghosh, Shila BP Poddar Inst Management & Technol Elect & Commun Engn Dept Kolkata W Bengal India St Thomas Coll Engn & Technol Kolkata W Bengal India

This paper presents the construction of unipolar transposed modified Walsh code (TMWC) and analysis of its performance in optical code-division multiple-access (OCDMA) systems. Specifically, the signal-tonoise ratio, bit error rate (BER), cardinality, and spectral efficiency were investigated. The theoretical analysis demonstrated that the wavelength-hopping time-spreading system using TMWC was robust against multipleaccess interference and more spectrally efficient than systems using other existing OCDMA codes. In particular, the spectral efficiency was calculated to be 1.0370 when TMWC of weight 3 was employed. The BER and eye pattern for the designed TMWC were also successfully obtained using OptiSystem simulation software. The results indicate that the proposed code design is promising for enhancing network capacity. (C) 2018 Society of Photo-optical Instrumentation Engineers (SPIE)

关键词： optical code-division multiple access optical orthogonal code multiple-access interference spectral-amplitude coding phase-induced intensity noise wavelength-hopping time-spreading

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