Demonstration of an optical self-clocked time-division switch

A novel architecture for an optical time-division switch is investigated and demonstrated at a bit rate of 625 Mbit/s. The self-clocked configuration eliminates some of the limitations found in previous optical implementations of time-division switches: the switch operation is asynchronous, no read gate is required, and an optimal number of delay lines is used. Furthermore, this paper reports the first experimental demonstration of optical space-sorting demultiplexing.     

Use of WDM technique in SDH networks

This paper proposes the introduction of the multiwavelength technique in the three layers of a SDH-based network. In the trunk layer, wavelength division multiplexing (WDM) takes advantage of the optical parallelism in a single fiber. Cross-connection can be achieved either passively (i.e., with tunable filters) or by means of wavelength converters. The latter solution, which offers high flexibility, was implemented in a 4 × 4 optical routing element. In the junction network the feasibility of a three-station WDM self-healing ring was demonstrated. Finally, in the access network, synchronous burst access and time and wavelength division multiplexing (T/WDM) switching is proposed to offer service flexibility to the subscribers.     

250-Gb/s self-clocked optical TDM with a polarization-multiplexed clock

In this paper we report the first demonstration of all-optical time demultiplexing at 250 Gb / s with self-clocking using polarization multiplexing of the clock and data. To achieve such high speed, an ultra high-speed device known as the Teruhertz Optical Asymmetric Demultiplexer (TOAD) is used. We also demonstrate self-clocked address recognition and routing control of a photonic switch at 250 Gb / s. The bit-error rate at the switch output was measured to be less than 10 -⁹.     

Wavelength division multiplexed loop buffer memory based optical packet switch

Photonic all-optical switching is widely considered as one of the technique to utilize the enormous optical bandwidth. Optical packet switching provides high speed, data rate transparency, data format transparency, efficient use of bandwidth and flexibility. To resolve the conflict during contention, packets are needed to be buffered. Due to the lack of optical RAM, fiber delay lines (FDLs) are the most suited option to buffer the packets. This paper proposes new optical packet switch architecture alongwith feedback shared buffer utilizing the advantage of WDM loop buffer memory. The loop buffer module used in this switch architecture is a new approach towards WDM buffering of packets. The mathematical modeling is done to validate the results obtained from simulation.     

WDM光网络安全生存机制研究

针对WDM光网络安全生存性问题的故障的发现、定位和恢复三个重要环节之中的恢复问题,提出了一种WDM光层中的安全保护与恢复方案。采用了恢复路由选择算法和恢复波长分配算法,提出了一种混合的多层恢复机制,从而构建了一种从故障的发现、定位到故障恢复的覆盖各环节的连续性光网络安全生存机制,并在理论上进行了性能比较。     

Sub-nanosecond optical switch based on silicon racetrack resonator

<正>We experimentally demonstrate a small-size and high-speed silicon optical switch based on the free carrier plasma dispersion in silicon.Using an embedded racetrack resonator with a quality factor of 7400,the optical switch shows an extinction ratio exceeding 13 dB with a footprint of only 2.2×10~(-3)mm~2.Moreover,a novel pre-emphasis technique is introduced to improve the optical response performance and the rise and the fall times are reduced down to 0.24 ns and 0.42 ns respectively,which are 25%and 44%lower than those without the pre-emphasis.     

光梯度力驱动的纳米硅基光开关

通过一道光改变另一道光的传输路线是光子集成网络中重要而长远的目标, 然而, 由于硅材料的光学非线性较弱, 在硅材料上实现开关的全光控制难以实现. 因此本文提出了一种由光梯度力驱动的纳米硅基光开关, 实现了硅基光开关的全光控制. 该光开关由一个部分悬空的微环谐振器和一个交叉波导结构构成, 当通入一道控制光时, 悬空的微环谐振器在光梯度力的作用下发生弯曲, 微环谐振器的谐振波长随之发生变化, 从而实现光信号的传输路线发生改变. 该光开关利用纳米光子制造技术在标准绝缘体上硅晶圆上制造, 实验数据得出其最小消光比为10.67 dB, 最大串扰为 -11.01 dB, 开关时间分别为180 ns和170 ns. 该光开关具有尺寸小, 响应速度快, 低损耗和可拓展等优点, 在片上集成光路、高速信号处理以及下一代光纤通信网络中具有潜在应用.     

Utilization of four WDM channels with signal remodulation of OFDM-QAM for 10 Gb/s uplink passive optical networks

In this investigation, we experimentally investigate an extended reach (ER) time-division-multiplexed passive optical network (TDM-PON) using four wavelength-multiplexed channels to achieve 16 Gb/s downlink and 10 Gb/s uplink traffic. Each downlink signal uses the highly spectral efficient 4 Gb/s OFDM-QAM, and each uplink signal is generated by signal remodulating the downlink signal via a reflective semiconductor amplifier (RSOA) at 2.5 Gb/s non-return-to-zero (NRZ). In addition, the performance of the proposed ER TDM-PON has also been analyzed and discussed.     

基于光时分复用技术的高速成像系统

提出了一种基于光时分复用技术的高速成像系统。飞秒激光器中心波长1557 nm,脉冲宽度90 fs,对USAF-1951分辨率板线性扫描成像,扫描频率为38.88 MHz。在连续时间序列编码放大显微成像技术的基础上,运用光时分复用技术,复制光脉冲信号并携带检测物体相同的空间信息。原光脉冲和复制光脉冲以相同的采样率分别采样,通过相应的数据处理将两次采样数据整合在一起还原图像。实验结果表明,与传统的超快成像方法相比,成像系统利用10 GHz的数字采样设备可以达到20 GHz的采样率,采样点数是传统超快成像方法的两倍。该方法有效克服了成像系统采样率不足的问题,提高了成像系统的空间分辨率。与此同时,该系统算法复杂程度不高,有利于进一步促进超高速成像技术的发展。     

Survivability in IP-over-WDM Networks: WDM Lightpath Protection versus IP LSP Protection

Abstract

This article compares the performance of WDM lightpath protection and IP LSP protection schemes for IP-over-WDM networks. A mathematical formulation of the maximum throughput problem is presented and analytical expressions for recovery time are derived for both schemes. The throughputs and recovery times are analyzed and compared. Results show that the IP LSP protection scheme presents higher throughputs then WDM lightpath protection. The IP LSP protection scheme, providing individual IP LSP protection has, however, scalability problems. This scheme presents high recovery times when a failure affects many lightpaths and many hops are allowed for the primary routes of IP LSPs.     

Demonstration of an all-optical switching operation using an optical fiber grating coupler

An optical fiber grating coupler (FGC) is a fused optical fiber coupler with a tapered region in which refractive index-modulated gratings are written. In the FGC, the light with specific wavelength satisfying the Bragg condition of the grating can be dropped to one output port and other lights are transmitted to another output port when lights with various wavelengths are launched into the input port. The FGC can operate as an all-optical switch by controlling the Bragg wavelength of the grating using a third order nonlinear optical effect caused by a control light that are launched with a signal light. In this paper, an all-optical switching operation due to a third order nonlinear optical effect in an FGC is first demonstrated for a signal light with 1.55 μm-wavelength to be changed from one port of the FGC to another one by the 720 W peak of a control light from a Nd:YAG laser with 1.06 μm-wavelength. The switching efficiency obtained was 7%. It was clarified that a longer pulse length of the control light compared to the grating length is required to obtain a large Bragg wavelength shift for the switching. It was also clarified that the Bragg wavelength shift is caused by a third order nonlinear effect and a photothermal effect. A contribution of the photothermal effect was estimated. We also estimated the switching efficiency for pump power in the FGC switch.     

Survivability in IP-over-WDM Networks: WDM Lightpath Protection versus IP LSP Protection

This article compares the performance of WDM lightpath protection and IP LSP protection schemes for IP-over-WDM networks. A mathematical formulation of the maximum throughput problem is presented and analytical expressions for recovery time are derived for both schemes. The throughputs and recovery times are analyzed and compared. Results show that the IP LSP protection scheme presents higher throughputs then WDM lightpath protection. The IP LSP protection scheme, providing individual IP LSP protection has, however, scalability problems. This scheme presents high recovery times when a failure affects many lightpaths and many hops are allowed for the primary routes of IP LSPs.     

Wavelength conversion in optical transport networks

The introduction of optical technology in the path layer of a transport network is analyzed; in particular, the impact of all-optical wavelength conversion is examined. Two basic optical cross-connect schemes based on space switching and on wave-length switching, respectively, and two types of wavelength converters are considered. The wavelength converters are, respectively, based on four-wave miring (FWM) in semiconductor optical amplifiers (SOAs) and on cross-phase modulation (XPM) obtained by two SOAs put in an interferometric configuration. An analysis of transmission performances of optical transport networks employing both types of wavelength conversion and both the node architectures is reported. The performances are evaluated by means of a system modeling that facilitates considering physical phenomena occurring during transmission and all the important transmission impairments. The analysis reveals that both the types of converters can be employed with different features and limitations, according to the considered network and switching architecture.     

Total internal reflection optical switch with injection region isolated by oxygen ion implantation

The characteristics of InGaAsP/InP total internal reflection optical switches were improved by adopting Oxygen ion implantation in forming electrical isolation, which can confine injected carriers successfully and obtain good perpendicular reflective 'wall” whose transparency is controlled by injected carriers. Operating at 1.3-μm wavelength, the extinction ratio at the reflected port of the optical switch is 18.5 dB at a low injection current of 26 mA and the off-state crosstalk is -18.8 dB.     

Wavelength assignment algorithms for WDM optical networks

In this paper, we have proposed an efficient wavelength assignment algorithm for dynamic provisioning of lightpath. This proposed algorithm is based on most-used wavelength assignment algorithm. We have also suggested a mathematical model for WDM optical networks for minimization of blocking probability. The results of proposed algorithm and suggested model are then compared with the conventional wavelength assignment algorithms such as first-fit, best-fit, random and most-used wavelength assignment algorithms. These proposed approaches are very effective for the minimization of blocking probability of optical WDM networks.     

Demonstration of an optical pipeline adder and design concepts for its microintegration

A fully functional optical pipeline adder based on systolic arrays and optical symbolic substitution (OSS) is demonstrated. By pupil division four OSS-rules are applied to a dataplane in one single optical path. The design concept includes the possibility of microintegration by adapting the modular system design to features of typical micro-optical devices.     

Investigations on burst length in optical burst switched networks

In this paper, we investigate the performance of optical burst switched networks for erbium-doped fiber amplifiers (EDFAs) and semiconductor optical amplifiers (SOAs). We show that EDFAs are more suitable for burst switching as compared to SOAs. We further investigate the burst length for 18, 24.6 and 55 km optical switched network. It is observed that burst length should neither be very small nor very large. If the burst length is small, throughput will be less, and if the burst length is very large, delay will be very large. This is due to higher wait times incurred when packets are formed into larger bursts causing additional overall delay. It is observed that performance decreases up to a small burst length of 1500 μs, which is the minimum burst length required for the creation of the burst. Once this burst is created, there is significant improvement in the quality factor up to 3000 μs. After this burst length, the performance again degrades. Hence the burst length can be optimized for the best quality factor in optical burst switched networks. We further show that by increasing EDFA gain, the quality deteriorates as increasing the EDFA gain results in increased levels of additive phase noise, which can further induce nonlinearities.     

Atom-loss-induced quantum optical bi-stability switch

We investigate the nonlinear dynamics of a system composed of a cigar-shaped Bose-Einstein condensate and an optical cavity with the two sides coupled dispersively.By adopting discrete-mode approximation for the condensate,taking atom loss as a necessary part of the model to analyze the evolution of the system,while using trial and error method to find out steady states of the system as a reference,numerical simulation demonstrates that with a constant pump,atom loss will trigger a quantum optical bi-stability switch,which predicts a new interesting phenomenon for experiments to verify.     

数字光开关网络中四功能交换开关光学Omega网络

本文提出了一种用于数字光开关网络中，四功能交换开关光学Ｏｍｅｇａ网络。文中详细地阐述了用液晶空间光调制方法实现光学四功能交换开关，和Ｏｍｅｇａ互连网络的原理，并给出了光学系统和实验结果。     

Robust wavelength division multiplexed local area networks

The wavelength division multiplexing (WDM) network architectures, in general, are based on transmitters and/or receivers that can be precisely and speedily tuned to predetermined, fixed wavelengths. These requirements are not easy to meet in practice. Robust WDM, the subject of this paper, has been introduced as a technique to implement WDM in the local area. The strength of this novel approach is that it does not rely on wavelength-sensitive devices that are required to perform with extreme stability. This paper describes the basis of this approach and presents two types of medium access control (MAC) protocols that are suitable for Robust WDM local area networks (LANs). The performance of networks based on these protocols is discussed in detail. It is shown that the new approach has considerable promise for WDM networks in the local area.