Super-dense WDM transmission technology in the zero-dispersion region employing distributed Raman amplification

This paper describes a practical system design and the transmission performance of high-capacity super-dense-wavelength-division-multiplexing (SD-WDM) transmission in the zero-dispersion region employing distributed Raman amplification (DRA). By combining several semiconductor laser diodes (LDs) of different wavelengths, gain-flattened DRA can be achieved. We quantitatively clarify the relation between the pump power and the maximum input signal power that can be injected into a transmission fiber by taking into account gain saturation due to pump depletion. Based on these analytical results and computer simulations on transmission performance, an SD-WDM transmission experiment is conducted. By employing four-wavelength, backward-pumped DRA and forward-error correction, we successfully demonstrate 1-Tb/s (100 /spl times/ 10 Gb/s) SD-WDM transmission with 25-GHz channel spacing (0.4-b/s/Hz spectral efficiency) in the C-band (zero-dispersion region) over 4 /spl times/ 80 km of dispersion-shifted fiber. These results show that DRA is a powerful technology in realizing high-capacity SD-WDM transmission, particularly in the zero-dispersion region.     

A product-coded WDM coding system

Forward error correction is a feasible approach for reducing the bit error floor of lightwave systems, arising from the fact that a simple single-error-correcting code can reduce the error floor from O(P _e) to O(P_e²). We propose a novel wavelength demultiplexer (WDM) coding system using a product code to improve the performance of WDM systems with an error floor caused by fiber dispersion or system noise     

Multistage WDM access architecture employing cascaded AWGs

Here we propose passive/active arrayed waveguide gratings (AWGs) with enhanced performance for system applications mainly in novel access architectures employing cascaded AWG technology. Two technologies were considered to achieve space wavelength switching in these networks. Firstly, a passive AWG with semiconductor optical amplifiers array, and secondly, an active AWG. Active AWG is an AWG with an array of phase modulators on its arrayed-waveguides section, where a programmable linear phase-profile or a phase hologram is applied across the arrayed-waveguide section. This results in a wavelength shift at the output section of the AWG. These architectures can address up to 6912 customers employing only 24 wavelengths, coarsely separated by 1.6 nm. Simulation results obtained here demonstrate that cascaded AWGs access architectures have a great potential in future local area networks. Furthermore, they indicate for the first time that active AWGs architectures are more efficient in routing signals to the destination optical network units than passive AWG architectures.     

基于空时编码的高效星地数据传输技术

为提升星地数据传输效率,多采用时间域变速率传输模式,但改善程度有限。文中从空间域角度着手,提出基于空时编码的高效星地数据传输技术,通过空时预编码将多个混叠的数据流分离开来,形成多个编码通道同时传输多路并发数据,并且能够在空间域上收集散射、反射路径功率,从而充分利用有限的链路功率。分析与仿真结果显示,采用星上2天线对2个用户的传输模式,相比传统点对点的传输模式其频谱效率可提升0.5～1 b?s~(-1)?Hz~(-1)。     

An AWG-based WDM-PON architecture employing WDM/TDMA transmission for upstream traffic with dynamic bandwidth allocation

In this article, we examine a candidate architecture for wavelength-division multiplexed passive optical networks (WDM-PONs) employing multiple stages of arrayed-waveguide gratings (AWGs). The network architecture provides efficient bandwidth utilization by using WDM for downstream transmission and by combining WDM with time-division multiple access (TDMA) for upstream transmission. In such WDM-PONs, collisions may occur among upstream data packets transmitted simultaneously from different optical networking units (ONUs) sharing the same wavelength. The proposed MAC protocol avoids such collisions using a request/permit-based multipoint control protocol, and employs a dynamic TDMA-based bandwidth allocation scheme for upstream traffic, called minimum-guaranteed maximum request first (MG-MRF), ensuring a reasonable fairness among the ONUs. The entire MAC protocol is simulated using OPNET and its performance is evaluated in terms of queuing delay and bandwidth utilization under uniform as well as non-uniform traffic distributions. The simulation results demonstrate that the proposed bandwidth allocation scheme (MG-MRF) is able to provide high bandwidth utilization with a moderately low delay in presence of non-uniform traffic demands from ONUs.     

WDM coding for high-capacity lightwave systems

An interchannel parallel coding scheme in the wavelength domain-the WDM coding system-is proposed. The system differs from the usual serial coding systems and provides many advantages. First, data channels are completely unaltered in the coding process, rendering it very suitable for practical lightwave systems with standard bit rate. Second, parallel encoding/decoding systems are simpler than those of serial coding systems, being easier to be implemented in high-speed optical systems. Third, compared with serial coding, WDM coding is able to reduce heavily the number of encoding/decoding pairs. For example, a (15, 11) Hamming coded WDM system reduces the number from 12×11=132 to 1 at the line rate of STS-12. Fourth, the WDM coding system could offer infinite coding gain in dispersion-limited lightwave systems. Finally, WDM coding systems could correct single-channel burst error. The system performance was evaluated and the system limitation imposed by bit-skew among wavelength channels was analyzed. The results indicated that a 15-channel Hamming coded WDM system can reduce the uncoded BER from 10^-9 to 3×10^-17 and the distance limitation imposed by bit-skew is 250 km if a dispersion-shifted fiber is used and a channel span of 30 nm is assumed     

A 90-nm logic technology featuring strained-silicon

A leading-edge 90-nm technology with 1.2-nm physical gate oxide, 45-nm gate length, strained silicon, NiSi, seven layers of Cu interconnects, and low-/spl kappa/ CDO for high-performance dense logic is presented. Strained silicon is used to increase saturated n-type and p-type metal-oxide-semiconductor field-effect transistors (MOSFETs) drive currents by 10% and 25%, respectively. Using selective epitaxial Si/sub 1-x/Ge/sub x/ in the source and drain regions, longitudinal uniaxial compressive stress is introduced into the p-type MOSEFT to increase hole mobility by >50%. A tensile silicon nitride-capping layer is used to introduce tensile strain into the n-type MOSFET and enhance electron mobility by 20%. Unlike all past strained-Si work, the hole mobility enhancement in this paper is present at large vertical electric fields in nanoscale transistors making this strain technique useful for advanced logic technologies. Furthermore, using piezoresistance coefficients it is shown that significantly less strain (/spl sim/5 /spl times/) is needed for a given PMOS mobility enhancement when applied via longitudinal uniaxial compression versus in-plane biaxial tension using the conventional Si/sub 1-x/Ge/sub x/ substrate approach.     

基于网络编码的水下传感器可靠传输技术

网络编码技术可以极大的提高网络的吞吐量,同时能提高网络的鲁棒性。为了提高水下传感器网络数据传输的可靠性,利用网络编码对消息的备份性进行能量收集。该方案节省了电池能量,提高水下传感器节点的生存周期。     

A secure WDM ring access network employing silicon micro-ring based remote node

A secure and scalable wavelength-division-multiplexing (WDM) ring-based access network is proposed and demonstrated using proof-of-concept experiments. In the remote node (RN), wavelength hopping for specific optical networking unit (ONU) is deployed by using silicon micro-ring resonators (SMR). Using silicon-based devices could be cost-effective for the cost-sensitive access network. Hence the optical physical layer security is introduced. The issues of denial of service (DOS) attacks, eavesdropping and masquerading can be made more difficult in the proposed WDM ring-based access network. Besides, the SMRs with different dropped wavelengths can be cascaded, such that the signals pass through the preceding SMRs can be dropped by a succeeding SMR. This can increase the scalability of the RN for supporting more ONUs for future upgrade. Here, error-free 10 Gb/s downlink and 1.25 Gb/s uplink transmission are demonstrated to show the feasibility of the proposed network.     

Optimizing subcarrier-multiplexed WDM transmission links

We present an analytic approach to optimizing the information capacity of a subcarrier-multiplexed wavelength-division-multiplexed optical communication link. Receiver and relative-intensity noise, clipping distortion, and crosstalk between wavelength channels due to optical nonlinearities in the fiber are the signal impairments considered.     

WDM coding system with single parity-check channel

We propose a modified WDM coding system with a single parity-check channel to achieve an efficient and flexible WDM coding system. The system provides most of the advantages of the original WDM coding system with just one parity-check channel. The bit rate and the data sequences are unaffected by the coding processes, making it very attractive for practical lightwave systems with standard rates. Compared to serial coding systems, it is able to reduce the number of encoding/decoding pairs in an m-channel WDM transmission system operated at STS-N from m×N to one. We have evaluated the system performance and analyzed the performance of frame synchronization needed for the modified WDM coding system. An example shows that the WDM coding can reduce the error floor of a four-channel dispersion-limited WDM system from 10^-10 to 10^-19 with reliable frame synchronization     

2×10 Gbit/s WDM 1310-nm optical transmission over 63.5-kmstandard single-mode fiber using optical preamplifiers

Twenty Gbit/s transmission over 63.5 km SMF at 1310 nm is reported by using two channel 10 Gbit/s wavelength (de)multiplexing (Δλ=1.5 nm). Two 1310 nm SL-MQW semiconductor optical amplifiers are utilized for loss compensation and sensitivity improvement. For the 1310 nm wavelength domain, a record bitrate x distance product of 1.27 Tbit/s.km has been obtained. Crosstalk penalties are identified, and the feasibility of an extension up to at least four, 10 Gbit/s channels is discussed     

Proposal for simplified WDM transmission configuration

A new WDM (wavelength division multiplexing transmission configuration for local communications is proposed. In this configuration, the demultiplexing function is performed using narrow spectral sensitivity optical detectors and a demultiplexer is not required, allowing economical and simple WDM transmission. Dual-wavelength WDM transmission of 0.86 ?m and 0.73 ?m over 2 km on GI fibre is experimentally confirmed, using commercially available LEDs for both optical sources and detectors.     

Network coding based all-optical multicast in WDM networks

Wavelength division multiplexing(WDM) has been becoming a promising solution to meet the rapidly growing demands on bandwidth. Multicast in WDM networks by employing free wavelength is an efficient approach to saving bandwidth and cost. However, the free wavelength may not identical between different hops in a multicast light-path, particularly in heavy load optical WDM networks. In order to implement multicast applications efficiently, a network coding(NC) technique was introduced into all-optical WDM multicast networks to solve wavelength collision problem between the multicast request and the unicast request. Compared with the wavelength conversion based optical multicast, the network coding based optical multicast can achieve better multicast performance with paying lower cost.     

Chaotic transmission strategies employing artificial neuralnetworks

Two novel chaotic coding and decoding methods based on artificial neural networks (ANNs) are reported which employ the unimodal logistic map (LM) as an example. Coding is carried out by either modulating the LM or by generating the chaotic sequence with ANNs. In simulations speech has been coded and the resulting SNR_sig for the decoded speech has been evaluated. The results demonstrate that the two proposed methods offer a SNR_sig improvement of 4 and 20 dB over the SNR_sig obtained by using the LMS for decoding     

610-nm band AlGaInP single quantum well laser diode

The short-wavelength limits of AlGaInP visible laser diodes with Al_0.5In_0.5P cladding layers, and Ga_xIn _1-xP single quantum well (QW) active regions are investigated. Good performance is maintained throughout the 620 nm band, but the characteristics rapidly degrade in the 610 nm band. Biaxial-compression and -tension were compared, with the case of tension yielding slightly better performance. Using a 25 Å Ga_0.45 In_0.55P QW, a wavelength of 614 nm was obtained, while a 50 Å Ga_0.6In_0.4P QW emitted at 620 nm with a threshold current density of 0.8 kA/cm². These results with thin single QWs indicate the effectiveness of using an Al_0.5In_0.5P cladding layer to reduce electron leakage     

Advanced data modulation techniques for WDM transmission

This article discusses the various schemes for generating typical advanced modulation formats in terms of configuration and cost, and particularly presents some recently proposed configurations for optical data generation with better performance or reduced components, including pulsed multichannel source generation for return-to-zero (RZ)-based WDM application, multichannel dual-mode pulse source for carrier-suppressed RZ (CSRZ)-based WDM application, CSRZ and CSRZ differential phase shift keyed (DPSK) signal generation using a single Mach-Zehnder modulator (MZM) together with an electrical mixer, chirped RZ generation with reduced modulator number, and RZ/CSRZ-DPSK generation using a single dual-drive MZM and optical minimum shift keying (MSK).     

Broadband high-density WDM transmission using superluminescent diodes

Fibre-loop architectures employing high-density WDM for passive routing have been demonstrated using both DFB-laser and LED transmitters. The latter approach is known as 'spectrum slicing'. The first demonstration of broadband spectrally sliced transmission is reported. superluminescent diodes were used to transmit 150 Mbit/s on each of 10 WDM channels, or 50 Mbit/s on each of 16 WDM channels.<>     

Laser based WDM multichannel video transmission system

The results of a WDM experiment involving the transmission of three video channels using AM-VSB modulation on each of three lasers in the 800?900 nm range are presented. A weighted video signal/noise ratio greater than 40 dB was achieved at each wavelength for a laser modulation index of 0.3 over a 1.1 km link.     

WDM系统传输容量的仿真研究

基于Optisystem详细讨论如何构建一个完整的WDM仿真系统,分别给出4波长和8波长WDM系统在传输距离为340km和500km的合波器与分波器输出信号及其仿真眼图,并进行比较分析.结果表明此仿真系统能够很好的模拟WDM长距离传输系统,为进一步对WDM传输系统进行平滑升级扩容提供参考.