Centralized in-service OTDR testing in a CWDM business access network

This paper describes "virtual common space", an access architecture that uses inexpensive "coarse" wavelength-division-multiplexing (CWDM) technology to extend the advantages of wavelength-division multiplexing (WDM) to business access applications. This new approach suggests new operations and diagnostic requirements. A wavelength-selective optical time-domain reflectometer using CWDM sources is demonstrated for such procedures. Some of the potential impairments that could arise from in-service monitoring on these systems are quantified.     

The Monolithic Integration of a Wavelength-Demultiplexer With Evanescently Coupled Uni-Traveling-Carrier Photodiodes

In this letter, we discuss a novel integration of a wavelength demultiplexer with a pair of uni-traveling-carrier photodiodes (UTC-PDs). With this integrated module, we could separate incoming wavelengths of 1530 and 1550 nm, which are near the wavelengths utilized for digital and analog signal transmission in coarse wavelength-division multiplexing (CWDM) systems. The integrated UTC-PDs exhibited the following advantages: a wide 3-dB bandwidth (25 GHz), a reasonable responsivity (0.35 A/W), and a high-saturation-current (>17 mA). A low level of radio frequency crosstalk between the two photodiodes (less than -15 dB) could also be achieved for a wide frequency range (near DC to 40 GHz). This is low enough for the multichannel receivers in a WDM broadcast system. In addition, by use of our module, we demonstrated digital/analog signals co-transmission and demultiplexing with speeds of 2.5 Gb/s at optical wavelengths of 1530 and 1550 nm.     

Plasma-enhanced chemical-vapor deposition oxide prepared at low-flow conditions for course wavelength-division multiplexing optical-waveguide devices

Silicon oxide (SiO_x) films grown by plasma-enhanced chemical-vapor deposition (PECVD) were investigated for applications in a course wavelength-division multiplexing (CWDM) network. The SiO_x films were deposited on 4-in. silicon wafers based on the reaction of N₂O/SiH₄ precursors. After postdeposition annealing at 1,150°C, the transmission spectra of the films prepared at different flow rates of the precursor were compared. We found that the transmission spectrum of the films deposited at the low-flow conditions can be flattened to a ripple of less than 0.5 dB ranging from visible up to 1,470 nm. In addition, the material losses at wavelengths around 1,500 nm caused by absorption of Si-H and N-H bonds were significantly reduced.     

Competitive Analysis of Online Traffic Grooming in WDM Rings

This paper addresses the problem of traffic grooming in wavelength-division multiplexing (WDM) rings where connection requests arrive online. Each request specifies a pair of nodes that wish to communicate and also the desired bandwidth of this connection. If the request is to be satisfied, it must be allocated to one or more wavelengths with sufficient remaining capacity. We consider three distinct profit models specifying the profit associated with satisfying a connection request. We give results on offline and online algorithms for each of the three profit models. We use the paradigm of competitive analysis to theoretically analyze the quality of our online algorithms. Finally, experimental results are given to provide insight into the performance of these algorithms in practice.      

粗波分复用及其扩容技术

分析比较了粗波分复用(CWDM)技术与密集波分复用(DWDM)技术的异同,总结了CWDM技术的优点与不足之处,针对CWDM系统扩容性差的缺陷,给出了目前的一些解决方案: 全波段CWDM、CWDM内嵌DWDM波长、提高单位通道传输容量.     

粗波分复用在远程备份系统中的应用

CWDM(粗波分复用)技术以其在系统成本、性能及可维护性等方面的优势,正逐渐成为城域网的主流技术。文中在对比和分析DWDM(密集波分复用)和CWDM技术特点的基础上,提出了采用CWDM替代基于DWDM实现远程备份的新方法,并设计了CWDM接口和基于CWDM远程备份应用的体系结构,对CWDM链路的可靠性和数据传输率进行了分析。     

10-Gb/s upgrade of bidirectional CWDM systems using electronic equalization and FEC

We discuss options for upgrading coarse wavelength-division multiplexed (CWDM) optical access links over standard single-mode fiber (SSMF) by increasing per-channel data rates from 2.5 to 10 Gb/s. We identify electronic equalization and forward error correction (FEC) as the enabling technologies to overcome the dispersion limit of SSMF. In addition, we show how FEC enhances the tolerance to in-band crosstalk, and paves the way toward fully bidirectional CWDM transmission. Due to the lack of CWDM sources rated for 10-Gb/s operation, we demonstrate full-spectrum (1310 to 1610 nm) 10-Gb/s CWDM transmission over standard-dispersion fiber using uncooled, directly modulated lasers specified for 2.5 Gb/s. All 16 CWDM channels could be transmitted over more than 40 km, yielding a capacity-times-distance product of 6.4 Tb/s/km. The longest transmission distance (80 km) was achieved at 1610 nm, equivalent to 1600 ps/nm of chromatic dispersion.     

Multichannel optical filters using birefringent planar opticalplatforms

Multichannel optical filters are proposed for wavelength-division multiplexing communication systems. The proposed filters utilize the multireflection property of optical beams, have stable wavelengths, and can select arbitrary channels with arbitrary transmittance. We show seven-channel filter module with 1-nm channel spacing as a feasibility study     

Precisely and rapidly wavelength-switchable narrow-linewidth1.5-μm laser source for wavelength division multiplexing applications

We report the design and demonstration of a novel narrow-linewidth fiber laser that is switchable (at microsecond speeds) to precise predesignated wavelengths. This simple multiwavelength source, based on off-the-shelf components (fiber Bragg gratings (FBGs) and fiber Fabry-Perot filters), appears very promising for wavelength-division multiplexing     

基于熔融拉锥技术的全光纤粗波分复用器

介绍了使用熔融拉锥技术(FBT)制作粗波分复用器(CWDM)中无源器件的过程,并且测试了制作的粗波分复用器无源器件的性能参数。同时我们比较了用熔融拉锥技术制作的粗波分复用器无源器件和用薄膜技术制作的粗波分复用器以及密集波分复用器的无源器件的性能。     

光子晶体电光调制和粗波分复用集成器件研究

提出了一种用于电光调制和粗波分复用的片上集成器件。该集成器件的电光调制器模块和粗波分复用器模块都是由硅基光子晶体波导和L3型谐振腔组成,两个模块间采用硅基光子晶体波导连接。该器件根据等离子体色散效应,采用L3型谐振腔和PN结实现了对波长的调制;根据微腔与波导的直接耦合理论,采用L3型谐振腔结构实现了滤波。利用基于三维时域有限差分法(3D-FDTD)的Lumerical软件对其进行仿真分析,结果表明该集成器件在工作波长1530 nm和1550 nm下均可以先完成各自的电光调制再进行双通道波长的复用。该器件在工作波长1530 nm和1550 nm下的插入损耗分别为0.70 dB和0.95 dB,消光比分别为20.97 dB和22.05 dB,调制深度均为0.99,信道串扰分别为-29.05 dB和-27.59 dB,器件尺寸仅为17.83μm×17.3μm×0.22μm。该集成器件结构紧凑,易于集成,可应用于高速大容量波分复用光通信系统。     

Multihop packet scheduling in WDM/TDM networks with nonnegligibletransceiver tuning times

This paper addresses the design of packet transmission schedules in photonic slotted wavelength-division multiplexing/time-division multiplexing broadcast-and-select networks with W wavelengths and N nodes. Nodes are equipped with one tunable-wavelength transmitter with nonnegligible tuning times and one fixed-wavelength receiver. A new scheduling algorithm that exploits multihop packet transfer to shorten the duration of scheduling periods is first proposed. A single-hop scheduling algorithm that performs slightly better than previous proposals is then described. A simulation-based analysis of the two algorithms shows that they jointly lead to significant improvements in both throughput and delay with respect to previous single-hop schedules     

Optimization of wavelength assignment for QoS multicast in WDMnetworks

This paper discusses quality-of-service (QoS) multicast in wavelength-division multiplexing (WDM) networks. Given a set of QoS multicast requests, we are to find a set of cost suboptimal QoS routing trees and assign wavelengths to them. The objective is to minimize the number of wavelengths in the system. This is a challenging issue. It involves not only optimal QoS multicast routing, but also optimal wavelength assignment. Existing methods consider channel setup in WDM networks in two separate steps: routing and wavelength assignment, which has limited power in minimizing the number of wavelengths. In this paper, we propose a new optimization method, which integrates routing and wavelength assignment in optimization of wavelengths. Two optimization algorithms are also proposed in minimizing the number of wavelengths. One algorithm minimizes the number of wavelengths through reducing the maximal link load in the system; while the other does it by trying to free out the least used wavelengths. Simulation results demonstrate that the proposed algorithms can produce suboptimal QoS routing trees and substantially save the number of wavelengths     

Widely tunable chaotic fiber laser for WDM-PON detection

A widely tunable high precision chaotic fiber laser is proposed and experimentally demonstrated. A tunable fiber Bragg grating （TFBG） filter is used as a tuning element to determine the turning range from 1533 nm to 1558 nm with a linewidth of 0.5 nm at any wavelength. The wide tuning range is capable of supporting 32 wavelength-division mul- tiplexing （WDM） channels with 100 GHz channel spacing. All single wavelengths are found to be chaotic with 10 GHz bandwidth. The full width at half maximum （FWHM） of the chaotic correlation curve of the different wave- lengths is on a picosecond time scale, thereby offering millimeter spatial resolution in WDM detection.     

CWDM(粗波分复用)技术在宽带城域网中的应用

在概述构筑宽带城域网(BIP-MAN)的重要性和必然性的基础上，阐述了粗波分复用(CWDM)的基本概念和技术特点，比较分析了CWDM用于BIP-MAN的技术优势和成本优势，研究讨论了CWDM技术在BIP-MAN中的应用地位。     

Wavelength requirements for multicasting in all-optical networks

Multicasting in a network is needed for a number of applications where a session requires connectivity between more than two participants. In this paper, we consider a wavelength-division multiplexing (WDM)-based all-optical network. We derive asymptotic upper bounds on the number of wavelengths needed to support multicasting capability in an all-optical network. The number of wavelengths in a WDM network continues to be a major constraint. The results derived here should be seen as the limit on scalability of all-optical networks that support multicasting. The derivation of the upper bound uses some properties of expander graphs     

CWDM Transmission in the S/C/L Bands over Standard Fibers with Total Capacity of 40 Gb/s

We present simulations of a 16 channels coarse wavelength division multiplexing (CWDM) system operating at 2.5 Gb/s transmitted over 55 Km of standard fiber. The channel space was optimized in order to improve the use of the operation spectrum and to avoid the water peak. The results demonstrate the feasibility of 40 Gbit/s total capacity CWDM system operation using the S, C and L bands with BER better than 10-9.     

Fiber to the Home Using a PON Infrastructure

Traffic patterns in access networks have evolved from voice- and text-oriented services to video- and image-based services. This change will require new access networks that support high-speed (> 100 Mb/s), symmetric, and guaranteed bandwidths for future video services with high-definition TV quality. To satisfy the required bandwidth over a 20-km transmission distance, single-mode optical fiber is currently the only practical choice. To minimize the cost of implementing an FTTP solution, a passive optical network (PON) that uses a point-to-multipoint architecture is generally considered to be the best approach. There are several multiple-access techniques to share a single PON architecture, and the authors addressed several of these approaches such as time-division multiple access, wavelength-division multiple access, subcarrier multiple access, and code-division multiple access. Among these multiple techniques, they focus on time-division multiplexing (TDM)-PON and wavelength-division multiplexing (WDM)-PON, which will be the most promising candidates for practical future systems. A TDM-PON shares a single-transmission channel with multiple subscribers in time domain. Then, there exists tight coupling between subscribers. A WDM-PON provides point-to-point optical connectivity using a dedicated pair of wavelengths per user. While a TDM-PON appears to be a satisfactory solution for current bandwidth demands, the combination of future data-rate projections and traffic patterns coupled with recent advances in WDM technology may result in WDM-PON becoming the preferred solution for a future proof fiber-based access network     

非统一多量子阱波长可选DFB激光器

报道了一种单片集成的串联DFB激光器芯片,在合适工作条件下,可以在疏波分复用(CWDM)的两个信道波长激射。芯片通过非统一多量子阱有源区拓宽材料增益谱,给DFB激光器的纯折射率光栅引入弱增益耦合,提高DFB激光器的动态单模特性。芯片采用普通DFB激光器的制备工艺制备,工艺简单成本低,重复性高。测试结果表明,芯片能够在1.51μm和1.53μm两个波长激射,出光功率均能达到6mW以上,边模抑制比均达到40dB。     

Wavelength-division integration of services in fibre-optic networks

A flexible fibre-optic network architecture for the integration of multiple services is proposed and demonstrated. The traffic requirements of each service are addressed by using distinct wavelengths and multiple-access schemes. The separation of services by wavelength eliminates the need for complex bandwidth allocation and multiplexing techniques. As a consequence of wavelength-division, the network can be seen as consisting of a collection of subnetworks, each carrying a different service. Different data rates and signal formats are easily accommodated. To the user, however, the integration appears complete.