全光中继光纤传输系统中掺铒光纤放大器监控的研究

文章对全光中继光纤传输系统中掺铒光纤放大器(EDFA)作为提升放大器、线路放大器和前置放大器的监控问题进行了探讨,提出了利用相干光时域反射仪与本地控制单元监测和控制线路EDFA的增益与主备用倒换的方案,该方案可实现对上行和下行的线路EDFA的单端全光监测。     

Optical cross-connect system in broad-band networks: system conceptand demonstrators description

A network robust to future evolution in network topologies or transmission formats and bit rates, which would be achieved by introducing an all-optical transparent layer in the transport network hierarchy is considered. The transparency would permit use of physically common fiber lines and nodes for different transmission hierarchies and/or formats. A transparent network could be achieved by combining photonic switching with electronic switching technology in the network nodes. A combination of wavelength routing and space-division switching in the optical layer would increase the capacity, as well as the flexibility in a network, allowing routing with higher granularity within the optical layer. Two optical cross-connect demonstrators have been set up. One demonstrates protection switching and restoration of traffic in a future transport network, and the other demonstrates routing of subscriber signals to different service switches in a local exchange. Space switches, tunable lasers and filters are the key technologies used to obtain enhanced flexibility     

Integrated Broad-Band Communication Using Optical Networks--Results of an Experimental Study

This paper reports on an experimental system of an integrated communication network built with components representing the state-of-the-art in the area of optical fiber transmission and large-scale integration of logic functions. These components make it possible to apply new concepts for signal processing, transmission, and switching in the experimental system. The large bandwidth of optical channels allows the transmission of all kinds of communication services including data, audio, and video, while semiconductor technology offers low cost realization and mass production of complex signal processing and switching functions to handle all these services within one network. The concept of the system is presented and results on system components and subsystems are given.     

光线路自动倒换保护(OLP)系统建设方案

为有效地预防和压缩光缆传输系统故障,提高光通信网抗阻断、高可靠、安全、抗灾害能力,提高长途光缆维护质量,光纤自动监测倒换系统是实现这一责任目标的重要的现代化维护手段。实现光缆网的自动监测倒换系统,从而在通信光缆线路设备大幅度增加,原有的线路维护技术人员又不能同幅增员的情况下,确保巨额投资建成的光缆传输网高质、高效、安全地运行。     

Optical network design with mixed line rates

Future telecommunication networks employing optical wavelength-division multiplexing (WDM) are expected to be increasingly heterogeneous and support a wide variety of traffic demands. Based on the nature of the demands, it may be convenient to set up lightpaths on these networks with different bit rates. Then, the network design cost could be reduced because low-bit-rate services will need less grooming (i.e., less multiplexing with other low-bit-rate services onto high-capacity wavelengths) while high-bit-rate services can be accommodated on a wavelength itself. Future optical networks may support mixed line rates (say over 10/40/100 Gbps). Since a lightpath may travel a long distance, for high bit rates, the effect of the physical impairments along a lightpath may become very significant (leading to high bit-error rate (BER)); and the signal’s maximum transmission range, which depends on the bit rate, will become limited.In this study, we propose a novel, cost-effective approach to design a mixed-line-rate (MLR) network with transmission-range (TR) constraint. By intelligent assignment of channel rates to lightpaths, based on their TR constraint, the need for signal regeneration can be minimized, and a “transparent” optical network can be designed to support all-optical end-to-end lightpaths. The design problem is formulated as an integer linear program (ILP). A heuristic algorithm is also proposed. Our results show that, with mixed line rates and maximum transmission range constraints, one can design a cost-effective network.     

Video-Service-Overlaid Wavelength-Division-Multiplexed Passive Optical Network

We propose and demonstrate a novel wavelength- division-multiplexed passive optical network (WDM-PON) with multicast overlay. By superimposing an inverse return-to-zero multicast signal onto a nonreturn-to-zero point-to-point signal, simultaneous transmission is realized for both services. At the optical network unit (ONU), only one photodiode is required to detect both signals. No complex receiver is demanded. Multicast control is realized through a switch for each wavelength at the optical line terminal. We successfully demonstrate the proposed WDM-PON.      

High-Speed Optical Time-Division Multiple-Access (OTDMA) Networks Using Optical Signal Processing

In this paper, we design high-speed optical fiber networks based on the time-division multiple-access (TDMA) technique. To achieve an ultrahigh throughput, optical signal processing should be used in the network. We present a feasible scheme to implement optical TDMA networks, with the emphasis on optical clock distribution, synchronization, and optical time demultiplexing. Since the proposed network uses two wavelengths to carry optical TDMA and clock signals respectively, at each TDMA receiver slot synchronization is feasibly achieved by using simple optical delay lines to process the separated optical clock and TDMA signals. This in turn allows us to build a large-scale distribution network which is attractive for future HDTV broadcasting applications. Using the proposed scheme also allows to implement a high-capacity broadcast and select optical TDMA network for real-time data communications.     

A simple broad-band coherence multiplexed optical access networkand its scalability

This paper proposes a novel and simply configured broad-band optical access network that uses coherence multiplexing (CM) and half-duplex bidirectional transmission. It allows the on-demand use of broad bandwidth on existing fiber-to-the-home (FTTH) access lines. The design of the proposed CM network considers degradation factors in CM systems. This paper introduces two analyses. The first one is a numerical simulation to optimize the tradeoff between available user number and fiber dispersion degradation, and the second estimates acceptable access-line loss in the network. These analyses show that 16 users×100 Mb/s (or 12 users×155 Mb/s) bandwidth Is possible on a standard single-mode fiber access line whose loss and length are under 9 dB and 10 km (and 7 km), respectively. The feasibility and scalability of the proposed network are verified by an experiment in which eight-channel 155-Mb/s half-duplex optical packet transmission is successfully demonstrated on a 7-km standard fiber access line with bit error rates better than 1×10^-9. This study shows that the capacity of existing FTTH access lines that employ star couplers can be significantly enhanced     

An optical surveillance technique based on cavity mode analysis of SL-RSOA for GPON

An optical in-service surveillance technique based on cavity mode analysis of self-injection locked reflective semiconductor optical amplifier (SL-RSOA) for gigabit-capable passive optical network (GPON) is proposed. At each optical network unit (ONU), an upstream transmitter utilizing SL-RSOA can generate both upstream data signal and surveillance signal due to presence of external cavity. We can able to detect both upstream data and surveillance signals from all ONUs simultaneously at the optical line terminal (OLT) by assigning a distinct cavity mode frequency to each upstream transmitter. We also estimate the power penalty induced by the surveillance signals on the upstream data channel during simultaneous detection mechanism. Further, we propose an alternative method to detect the surveillance signals by allocating a separate monitoring time slot in upstream GPON transmission convergence (GTC) frame so as to reduce the influence of surveillance signals on the upstream data channel.     

Optical networks for local loop applications

Some of the options for optical technology within the local loop environment are examined. In particular, passive shared access networks have been considered in some detail. These networks show great promise for delivering existing telephone services to small to medium business customers (4-30 lines) economically by the early 1990s. Extending fiber to the home will also be possible by virtue of a similar passive network infrastructure for customers requiring new broadband services beyond the single telephone line. For one-line plain old telephone service (POTS) customers, an intermediate approach of terminating the fiber network at the final network distribution point, with copper retained for the final leg, may be used prior to the provision of broadband services. A key feature of the passive optical network architecture is the use of wavelength-division multiplexing (WDM) as an upgrade strategy, allowing graceful upgrading from telephone services to multichannel high-definition television (HDTV) on gigabit/second bearers and full two-way switched broadband services employing wavelength routing across the network     

A New Optical Fiber Line Testing Function for Service Construction Work That Checks for Optical Filters Below an Optical Splitter in a PON

In this paper, we propose a new function for construction work undertaken to install optical fiber lines for services in a passive optical network (PON). This paper describes a novel measurement technique designed to check for optical filters located in front of an optical network unit in branched optical fiber regions in PONs with outside optical splitters. The purpose is to determine whether an optical fiber is ldquoliverdquo or ldquounused.rdquo The features of our proposed technique are the use of test lights operating at two different wavelengths and a nondestructive macrobending technique. By comparing the difference between the reflected powers of the two wavelengths, we can determine the presence of a filter at the end of a fiber line. Furthermore, we describe an enhanced estimation analysis method that uses two photodetectors installed symmetrically in the detection part and an analysis procedure for detecting only a test light reflected from the fiber end. We also demonstrate the performance of the enhanced analysis method experimentally and confirm that it can be employed to detect an optical filter installed at the end of an optical fiber line.     

Enhanced Dynamic Bandwidth Allocation Algorithm in Ethernet Passive Optical Networks

As broadband access is evolving from digital subscriber lines to optical access networks, Ethernet passive optical networks (EPONs) are considered a promising solution for next generation broadband access. The point‐to‐multipoint topology of EPONs requires a time‐division multiple access MAC protocol for upstream transmission. In this paper, we propose a new enhanced dynamic bandwidth allocation algorithm with fairness called EFDBA for multiple services over EPONs. The proposed algorithm is composed of a fairness counter controller and a fairness system buffer in the optical line terminal. The EFDBA algorithm with fairness can provide increased capability and efficient resource allocation in an EPON system. In the proposed EFDBA algorithm, the optical line termination allocates bandwidth to the optical network units in proportion to the fairness weighting counter number associated with their class and queue length. The proposed algorithm provides efficient resource utilization by reducing the unused remaining bandwidth made by idle state optical network units.     

FTTH用光纤光缆分析

光纤到户(FTTH)网络系统是光通信发展的必然趋势.随着社会信息化建设步伐的加快,FTTH已经成为通信网络建设的重点.因此,FTTH用光纤、光缆等产品也越来越受到人们的关注.本文对FTTH所用的光纤、光缆的应用现状及发展趋势进行了分析与探讨.     

光网络发展展望

光网络的具体含义到底是什么，这是一个仁者见仁，智者见智的问题。但有一点是取得了共识的，即未来的光网络应该是一个应用灵活、可靠、性能稳定的网络。它应该满足传输各种信号，如SDH、ATM、IP等的所有基本要求（即灵活性、可升级性和系统生存性应能独立于比特率和协议）。这样一个网络应该能够对各种信号进行有效的传输、调度、保护和管理。因此，如果我们希望能对光网络今后的发展做一点预测的话，必须综合考虑传输技术、光网络产品、光网络设计以及光标准研究等方面的发展情况，才能尽量避免偏颇。     

FTTH模式下城中村接入的分光建设方案

在宽带接入驻地网大建设时期,FTTH建设中涉及的问题较多,只有在实践中慢慢总结,综合考虑用户类型、线路状况等,才能使FTTH建设具有较好的经济和技术效益。FTTH系统的基本组成包括FTTH光线路终端(OLT)、光分配网(ODN)、FTTH光网络单元(ONU)三大部分组成。去年以来,随着FTTH建设规模进一步扩大,各种ODN建设场景和产品需求层出不穷,各种场景的接入方式成为讨论的热点。本文介绍了城中村场景下的几种分光方式,并对其进行了比较分析。     

Mixed-line-rate optical network design with wavebanding

To cope with ever increasing and more heterogeneous traffic demands, today’s optical backbone networks are expected to support mixed line rates (MLR) over different wavelength channels. MLR networks can be designed to provide flexible rate assignments to low-bit-rate services and high-bit-rate services in a cost-effective manner. But with increasing number of wavelengths in the network, aggregating wavelengths into wavebands can further reduce the network cost.In this study, we incorporate the idea of waveband switching in MLR network design. Wavebanding or grouping of optical paths reduces the optical switch size at the optical cross-connects (OXCs). When several lightpaths share several common links, they can be grouped together and routed as a single waveband. For optical bypass at a transit node, only two optical ports are required for each waveband, hence reducing the port cost. It can be a challenge for an MLR network to waveband wavelengths of different line rates that have different transmission reaches. In our design, we present a suitable switching architecture and propose an efficient and cost-effective approach for wavebanding in an MLR network. The design problem is formulated as a mixed integer linear program (MILP) where the objective is to minimize transponder cost and port cost. A heuristic algorithm for wavebanding in MLR networks is provided. To further optimize our solution, we also present a Simulated Annealing algorithm for wavebanding. Our results show a significant improvement in cost savings compared to single-line-rate (SLR) networks with wavebanding and an MLR network employing only wavelength switching.     

Subscriber Stations in Service Integrated Optical Broad Band Communications Systems

Subscriber stations in service integrated communications systems can be implemented in many different ways. Within the HHI Broad-Band Communications System two extremely different solutions have been realized: on the one hand, subscriber stations in a conventional star type network with central exchange and analog transmission, and on the other hand, subscriber stations in a digital, loop-structured network employing distributed control. In both cases, the same services (telephone, data, videophone, TV, and stereo broadcasting) are carried to the subscriber via one single optical fiber. This paper describes these different realizations of service integrated subscriber stations in detail. The size of terminal equipment, power consumption, extendability to further subscribers, and services and reliability are the main parameters of an appropriate comparison. An analysis of both realizations, giving emphasis to the switching and multiplexing, and the feasibility of analog optical transmission will be made. Alternative realizations and an estimation concerning subscriber stations for future service integrated broad band communications systems will be presented.     

A transport network layer based on optical network elements

An approach to the realization of a broadband, flexible, multiwavelength transport network employing an optical network layer. The design methodology for a network demonstrator is presented, and the transmission, switching, line, and management/supervisory subsystems and components are described     

Multiplexing Scheme of Long-Period Grating Sensors Based on a Modified Optical Frequency Domain Reflectometry

We propose a novel quasi-real-time sensing scheme by employing a modified optical frequency domain reflectometry technique to multiplex long-period grating (LPG) sensors of transmission mode. Different sensing signals are demodulated by different beat signals through presetting different values for the optical path differences between the measuring arms and a static reference arm. The amplitude of each beat signal is associated with the transmissivity of a sensing LPG. The present multiplexing scheme has the advantages of real-time, high speed, high sensitivity, large capacity, and high resolution over an intermediate length. A measurement of fiber bending curvature is demonstrated to verify good performances of the present LPG sensing system.