Routing scheme, permutation properties, and optical implementation of a four-shuffle-exchange-based Omega network

The routing scheme and some permutation properties of a four-shuffle-exchange-based Omega network are discussed. The corresponding optical setup, which is composed of 2-D phase spatial light modulators and calcite plates, is proposed and demonstrated through mapping the inputs to a 2-D array. Instead of one shuffle-exchange followed by one switching operation as in ordinary Omega networks, in our presented system, the shuffle interconnection embraced in the switches is accomplished simply by varying the switching structure of each stage. For the proposed polarization-optical modules, the system is compact in structure, efficient in performance, and insensitive to the environment. (C) 1997 Society of Photo-Optical Instrumentation Engineers.

Highly stable, diode-pumped Nd : YLF regenerative amplifier

We present the design and experimental results for a diode pumped Nd:YLF regenerative amplifier applied to amplify a nanosecond laser pulse. Numerical simulation shows that the maximum output energy and the best stability can be obtained when the regenerative amplifier operates in a saturated mode for all pulse duration and temporal profiles. Using extra post-pulse is a good method to decrease the square-pulse distortion caused by gain saturation effect. The amplifier shows output energy of 4.2mJ with a total energy gain of more than 107 and output energy stability of better than 1% rms. When extra post-pulse is added, square-pulse distortion is decreased from 1.33 to 1.17 for the amplifier that is seeded with an optical pulse of 3 ns.

Efficient diode-pumped Tm : YALO(3) laser with a pump recycling scheme

By using a pump recycling configuration, the maximum power of 8.1 W in the wavelength range 1.935-1.938 mu m is generated by a 5-mm long Tm:YAlO3 (4 at. %) laser operating at 18 degrees C with a pump power of 24 W. The highest slope efficiency of 42% is attained, and the pump quantum efficiency is up to 100%. The Tm:YAlO3 laser is employed as a pumping source of singly-doped Ho(l%):GdVO4 laser operating at room temperature, in which continuous wave output power of greater than 0.2 W at 2.05 mu m is achieved with a slope efficiency of 9%.

Diode-pumped Q-switched Tm:YAP laser with a pump recycling scheme

We reported on a diode end-pumped AO Q-switched Tm:YAP laser at 1937 nm. The average output power was 3.9 W, with a slope efficiency of 29.4% and optical-optical conversion efficiency of 21.6% at a 5-kHz repetition rate. The temperature dependency of the output power and the pulse width at different repetition rates were investigated in details.

Design of novel three port optical gates scheme for the integration of large optical cavity electroabsorption modulators and evanescently-coupled photodiodes

This paper presents a novel scheme to monolithically integrate an evanescently-coupled uni-travelling carrier photodiode with a planar short multimode waveguide structure and a large optical cavity electroabsorption modulator based on a multimode waveguide structure. By simulation, both electroabsorption modulator and photodiode show excellent optical performances. The device can be fabricated with conventional photolithography, reactive ion etching, and chemical wet etching.

Crosstalk analysis of a fiber laser sensor array system based on digital phase-generated carrier scheme

A detailed study on analyzing the crosstalk in a wavelength division multiplexed fiber laser sensor array system based on a digital phase generated carrier interferometric interrogation scheme is reported. The crosstalk effects induced by the limited optical channel isolation of a dense wavelength division demultiplexer (DWDM) are presented, and the necessary channel isolation to keep the crosstalk negligible to the output signal was calculated via Bessel function expansion and demonstrated by a two serial fiber laser sensors system. Finally, a three-element fiber laser sensor array system with a 50-dB channel-isolation DWDM was built up. Experimental results demonstrated that there was no measurable crosstalk between the output channels.

A novel butt-joint scheme for the preparation of electro-absorptive lasers

A 1.55 mu m InGaAsP/InGaAsP multiple-quantum-well electro-absorption modulator (EAM) monolithically integrated with a distributed feedback laser (DFB) diode has been realized based on a novel butt-joint scheme by ultra-low metal-organic vapour phase epitaxy for the first time. The threshold current of 25 mA and an extinction ratio of more than 30 dB are obtained by using the novel structure. The beam divergence angles at the horizontal and vertical directions are as small as 19.3 degrees x 13 degrees, respectively, without a spot-size converter by undercutting the InGaAsP active region. The capacitance of the ridge waveguide device with a deep mesa buried by polyimide was reduced down to 0.30 pF.

Quantum master equation scheme of time-dependent density functional theory to time-dependent transport in nanoelectronic devices

In this work a practical scheme is developed for the first-principles study of time-dependent quantum transport. The basic idea is to combine the transport master equation with the well-known time-dependent density functional theory. The key ingredients of this paper include (i) the partitioning-free initial condition and the consideration of the time-dependent bias voltages which base our treatment on the Runge-Gross existence theorem; (ii) the non-Markovian master equation for the reduced (many-body) central system (i.e., the device); and (iii) the construction of Kohn-Sham master equations for the reduced single-particle density matrix, where a number of auxiliary functions are introduced and their equations of motion (EOMs) are established based on the technique of spectral decomposition. As a result, starting with a well-defined initial state, the time-dependent transport current can be calculated simultaneously along with the propagation of the Kohn-Sham master equation and the EOMs of the auxiliary functions.

The image coding scheme based on neural network and SVM

This paper applies data coding thought, which based on the virtual information source modeling put forward by the author, to propose the image coding (compression) scheme based on neural network and SVM. This scheme is composed by "the image coding (compression) scheme based oil SVM" embedded "the lossless data compression scheme based oil neural network". The experiments show that the scheme has high compression ratio under the slightly damages condition, partly solve the contradiction which 'high fidelity' and 'high compression ratio' cannot unify in image coding system.

Lossless data compression scheme based on neural network and SVM

First, the compression-awaited data are regarded Lis character strings which are produced by virtual information source mapping M. then the model of the virtual information source M is established by neural network and SVM. Last we construct a lossless data compression (coding) scheme based oil neural network and SVM with the model, an integer function and a SVM discriminant. The scheme differs from the old entropy coding (compressions) inwardly, and it can compress some data compressed by the old entropy coding.

A differential recursive scheme for suppression of Peak to average power ratio for OFDM

A differential recursive scheme for suppression of Peak to average power ratio (PAPR) for Orthogonal frequency division multiplexing (OFDM) signal is proposed in this thesis. The pseudo-randomized modulating vector for the subcarrier series is differentially phase-encoded between successive components in frequency domain first, and recursion manipulates several samples of Inverse fast Fourier transformation (IFFT) output in time domain. Theoretical analysis and experimental result exhibit advantage of differential recursive scheme over direct output scheme in PAPR suppression. And the overall block diagram of the scheme is also given.

New finite-difference scheme for simulations of step-index waveguides with tilt interfaces

A new finite-difference scheme is presented for the second derivative of a semivectorial field in a step-index optical waveguide with tilt interfaces. The present scheme provides an accurate description of the tilt interface of the nonrectangular structure. Comparison with previously presented formulas shows the effectiveness of the present scheme.

A two-step backoff scheme for improving the performance of the IEEE 802.11 distributed coordination function

This paper describes the binary exponential backoff mechanism of 802.11 distributed coordination function (DCF), and introduces some methods of modifying the backoff scheme. Then a novel backoff scheme, called Two-step Backoff scheme, is presented and illustrated. The simulation process in OPNET environment has been described also. At last, the analysis and simulation results show that the Two-step backoff scheme can enhance the performance of the IEEE 802.11 DCF.

A power-saving scheme for IEEE 802.11 Ad hoc networks

In the Wireless Local Area Networks (WLANs), the terminals are often powered by battery, so the power-saving performance of the wireless network card is a very important issue. For IEEE 802.11 Ad hoc networks, a power-saving scheme is presented in Medium Access Control (MAC) layer to reduce the power consumption by allowing the nodes enter into the sleep mode, but the scheme is based on Time-Drive Scheme (TDS) whose power-saving efficiency becomes lower and lower with the network load increasing. This paper presented a novel energy-saving mechanism, called as Hybrid-Drive Scheme (HDS), which introduces into a Message.-Drive Scheme (MDS) and combines MDS with the conventional TDS. The MDS, could obtain high efficiency when the load is heavy; meanwhile the TDS has high efficiency when the network load is small. The analysis shows that the proposed HDS could obtain high energy-efficiency whether the network load is light or heavy and have higher energy-saving efficiency than conventional scheme in the IEEE 802.11 standard.

Proposed scheme for parallel 10Gb/s VSR system and its Verilog HDL realization

This paper proposes a novel and innovative scheme for 10Gb/s parallel Very Short Reach (VSR) optical communication system. The optimized scheme properly manages the SDH/SONET redundant bytes and adjusts the position of error detecting bytes and error correction bytes. Compared with the OIF-VSR4-01.0 proposal, the scheme has a coding process module. The SDH/SONET frames in transmission direction are disposed as follows: (1) The Framer-Serdes Interface (FSI) gets 16x622.08Mb/s STM-64 frame. (2) The STM-64 frame is byte-wise stripped across 12 channels, all channels are data channels. During this process, the parity bytes and CRC bytes are generated in the similar way as OIF-VSR4-01.0 and stored in the code process module. (3) The code process module will regularly convey the additional parity bytes and CRC bytes to all 12 data channels. (4) After the 8B/10B coding, the 12 channels is transmitted to the parallel VCSEL array. The receive process approximately in reverse order of transmission process. By applying this scheme to 10Gb/s VSR system, the frame size in VSR system is reduced from 15552x12 bytes to 14040x12 bytes, the system redundancy is reduced obviously.