An Improved Technique for Suppression of Intrachannel Four-Wave Mixing in 40-Gb/s Optical Transmission Systems

This letter presents an efficient method for testing the efficiency of modulation techniques for countering the effects of intrachannel four-wave mixing by calculating the sum of all the contributors at a given resonance position (the position affected by the surrounding pulses). In addition to this method, we are proposing a modulation technique that shows a significant Q-factor improvement of up to 7.5 dB (depending on the number of spans and the phase sequence implemented) over the uncoded return-to-zero on-off keying. Although the implementation of this phase modulation technique is simple, it is still very efficient in extending the nonlinearity tolerance and enhancing the performance of a high-speed optical transmission system     

PES News

This letter proposes a model reference adaptive system (MRAS)-based algorithm for simultaneous stator resistance (R/sub s/) and rotor speed (/spl omega/) identification of position sensorless induction motor to accurately estimate /spl omega/ at low speeds without affecting drive performance. The R/sub s/ has to be estimated concurrently with the /spl omega/ estimation to compensate for the fluctuation in R/sub s/. The reference model and adjustable model are interchangeable for concurrent /spl omega/ and R/sub s/ estimation. For stator resistance identification, the two models switch roles. Extensive computer simulation and experimental investigation prove the effectiveness of the proposed solution.     

Generalized low-density parity-check codes for optical communication systems

This paper is concerned with investigating the performance of regular and irregular, randomlike and structured generalized low-density parity-check (GLDPC) codes for long-haul transmission. The proposed GLDPC codes outperform currently known turbo and low-density parity-check (LDPC) coding schemes with comparable parameters utilized in optical communication systems. For a GLDPC coding scheme with 23.6% redundancy, the largest so far reported coding gain of at least 11dB (at 40 Gb/s) is demonstrated.     

Aging of the over-voltage protection elements caused by over-voltages

The aim of this work is examining the influence of the number of the activation––over-voltage pulses to the aging of over-voltage protection elements. Both non-linear (gas-filled surge arresters (GFSA), varistors, over-voltage diodes) and linear (capacitors––constituents of filters) over-voltage protection elements were tested. The instruments employed allow reliable measurements, 1000 consecutive activation were tested. The double-exponential current pulse (amplitude I₁^max=13 A, I₂^max=16 A, rise time T₁=8 μs, fall time T₂=20 μs) for non-linear elements and a double-exponential over-voltage pulse (rise time T₁=1.2 μs, fall time T₂=50 μs) of the amplitude U₁^max=320 V, U₂^max=480 V and U₃^max=640 V for capacitors were used. The experimental results show that the over-voltage diodes are the most reliable elements in view of characteristic modifications that are consequence of aging. However, it was observed that varistors, GFSA and capacitors undergo noticeable changes in characteristics.     

交流调速电梯中的电能质量

因为人们越来越多地使用非线性负载，电网中就存在电源质量问题。在交流传动系统中广泛使用功率变换器，由于其非线性的工作运行状态，导致电压发生畸变，从而影响敏感设备的性能。本文试图分析由功率变换器供电的电梯交流传动系统对电源质量的影响。敏感电气设备和电梯交流传动系统都连接到0．4kV输电线路上。因功率逆变器导致的电压畸变能够导致系统故障甚至电气设备中部分元件的损坏。     

Procedure for setting up the drying regime that is consistent with the nature and properties of the clay raw material

Over the past three decades, traditional ceramic facilities, such as chamber and tunnel dryers, are improved. Better thermotechnical equipment, operational strategies, and reliable scale-up methodologies have lead to higher quality of the dried clay roofing tiles. Although there has been a progress, up to this study, there is no universally or even widely applicable criterion, which could be used to precisely define the change of drying air parameters (humidity, temperature, and velocity) during the drying process. The objective of this study was to specify the variable air parameters that should be used during the drying process to approach as much as possible to the theoretically defined optimal drying process.     

MacNeish-Mann theorem based iteratively decodable codes for optical communication systems

A novel family of low-density parity-check codes is proposed based on MacNeish-Mann theorem for construction of mutually orthogonal Latin squares. Codes from this family have high code rate, girth at least six, large minimum distance, and significantly outperform conventional forward error correction schemes based on Reed-Solomon (RS) and turbo codes.     

Combinatorial constructions of optical orthogonal codes for OCDMA systems

Two novel classes of optical orthogonal code (OOC) based on balanced incomplete block designs are proposed: OOC based on mutual orthogonal Latin squares/rectangles and the codes based on finite geometries. Both OOC families can be applied to synchronous and asynchronous incoherent optical CDMA, and are compatible with spectral-amplitude-coding (SAC), time-spreading encoding and fast frequency hopping schemes. Large flexibility in cross-correlation control makes those OOC families interesting candidates for applications that require a large number of users. Novel fiber Bragg grating decoding scheme for canceling the multi-user interference from SAC-signals with nonfixed in-phase cross-correlation is proposed as well.     

Multi-weight unipolar codes for multimedia spectral-amplitude-coding optical CDMA systems

A novel balanced detection scheme for multi-access interference cancellation in multimedia spectral-amplitude-coding optical code-division multiple-access system is proposed. The receiver is capable of handling both equal and unequal in-phase cross correlation of optical orthogonal codes. A novel class of constant-length variable-weight optical orthogonal codes able to support multimedia services with different quality-of-service requirements is proposed as well. The construction is based on the pairwise balanced designs, or more specifically, on an incidence structure defined on an integer sub-lattice.     

Combinatorial constructions of low-density parity-check codes for iterative decoding

This paper introduces several new combinatorial constructions of low-density parity-check (LDPC) codes, in contrast to the prevalent practice of using long, random-like codes. The proposed codes are well structured, and unlike random codes can lend themselves to a very low-complexity implementation. Constructions of regular Gallager codes based on cyclic difference families, cycle-invariant difference sets, and affine 1-configurations are introduced. Several constructions of difference families used for code design are presented, as well as bounds on the minimal distance of the codes based on the concept of a generalized Pasch configuration.