Self-protected Ethernet passive optical networks using coarse wavelength division multiplexed transmission

Proposed and experimentally demonstrated is a novel self-protected architecture for Ethernet passive optical networks. The protection of the traffic transported between the central office and customer terminals against feeder fibre cable breaks is carried out by switching and overlaying the disrupted transmission channels onto a separate Ethernet passive optical network using waveband separation.     

Frequency division multiplexed optical networks using heterodynedetection

The optical heterodyne process is described. Because the best attainable system gain (transmitter power divided by receiver sensitivity) is only about 50 dB for lightwave systems, as compared with values approaching 100 dB at radio frequencies, it is extremely important in building an optical network (such as a local area network, or LAN) to minimize excess tap losses. It is shown that a star coupler provides a nearly ideal means for interconnecting a multiterminal network. Three areas in which problems unique to optical systems have been discovered are discussed. Theses are transmitters for coherent optical systems, optical frequency determination and control, and polarization control and optical receivers. Experimental progress is briefly discussed     

波分复用无源光网络

介绍波分复用无源光网络（ＷＤＭＰＯＮ）的结构相对传统的ＰＯＮ结构的优越性,同时分析了两种最新ＷＤＭＰＯＮ结构中采用的两项技术：光源共享和频谱分割的原理和技术细节,最后指出ＷＤＭＰＰＯＮ是宽带接入网的最佳选择,文中ＷＤＭＰＯＮ优缺点的讨论,对电信运营者考虑 入网应采取何种结构,具有重要的参考价值。     

Repeater using two wavelengths for passive optical star networks connection

A repeater for the 32 Mbit/s star-configured optical local area network (SOLARnet) has been developed. This repeater permits a tree-type interconnection of SOLARnets at layer 1 and enlarges the network scale. Wavelength-division multiplexing (WDM) is used to overcome self-collision (collision of the packet header with its packet).     

Energy-efficient dynamic wavelength and bandwidth allocation algorithm with delay constraint for time and wavelength division multiplexed passive optical networks

Based on offline scheduling and node modular design,an energy-efficient dynamic wavelength and bandwidth allocation algorithm with the delay constraint (EE-DWBA-DC) was proposed.Optical line terminal (OLT) and optical network units (ONU) were considered to save energy.Under the constraint of packet delay,the number of active wavelengths could be reduced as much as possible and the length of polling cycle was increased.At the same time,the uplink and downlink transmission time of OLT and ONU were concentrated to reduce the state conversion times and extend its low-power duration.In addition,the high energy consumption voids of channels were attempted to be minimized.The simulation results verify that the proposed algorithm can reduce the energy consumption of OLT and ONU and the total energy consumption of the whole network under the premise of guaranteeing packet delay constraints.     

Mesh waveguide optical star coupler

A new multimode optical star coupler with a mesh waveguide configuration is proposed to reduce the device length by stimulating light mixing in a short waveguide. A 4×4 optical star coupler has been fabricated and its branching variation of 2.8 dB is realised with the device length as short as 14.5 mm.     

A novel design of orthogonal frequency division multiplexing-based passive optical networks

Orthogonal frequency division multiplex (OFDM) has been successfully used in wireless communications, and now people begin to see it as an excellent candidate technique in optical access networks. In this article, we first make comparison between OFDM-based passive optical network (PON) and traditional PONs, and then review some previous work of OFDM PON. After that we introduce our physical layer scheme. In addition, network architecture, medium access control (MAC) protocol, and three dynamic bandwidth allocation schedules that optimized for OFDM communication are recommended. At last, computer simulation results are given to demonstrate the performance of the three schedules.     

Gain transient control for wavelength division multiplexed access networks using semiconductor optical amplifiers

Gain transients can severely hamper the upstream network performance in wavelength division multiplexed (WDM) access networks featuring erbium doped fiber amplifiers (EDFAs) or Raman amplification. We experimentally demonstrate for the first time using 10 Gb/s fiber transmission bit error rate measurements how a near-saturated semiconductor optical amplifier (SOA) can be used to control these gain transients. An SOA is shown to reduce the penalty of transients originating in an EDFA from 2.3 dB to 0.2 dB for 10 Gb/s transmission over standard single mode fiber using a 2³¹–1 PRBS pattern. The results suggest that a single SOA integrated within a WDM receiver at the metro node could offer a convenient all-optical solution for upstream transient control in WDM access networks.     

Distributed optical passive star couplers

A technique is presented by which a single centralized passive star coupler in an optical star network is replaced by a distributed one. This is done by partitioning the star coupler into numerous pieces and placing them at the network nodes. Such a placement results in a great saving in the number of fibers required to build the star network. In addition to this saving, the problems associated with constructing a large single N*N star coupler are bypassed.<>     

A media-access protocol for time- and wavelength-divisionmultiplexed passive star networks

A media access protocol is presented for time- and wavelength-division multiplexed optical passive star networks. The protocol is based on a bus-mesh virtual topology. The network provides minimum latency and high throughput while requiring only a single fixed wavelength transmitter and receiver at each station. The use of nonagile, fixed wavelength devices, readily available with current technology, reduces costs, improves reliability and avoids tuning delays and limitations. The multihop access protocol operates effectively in an environment with lengthy propagation delays. The wavelength-division multiplexing system is required to support only a small, easily achievable number of wavelength channels     

Novel algorithm for time division multiple access in broadband ISDN passive optical networks

For shared access to a broadband communication network using the asynchronous transfer mode (ATM) a passive optical network (PON) has previously been proposed. A novel algorithm to evaluate the time division multiple access (TDMA) protocol which controls the traffic from the various subscribers towards the shared access equipment (upstream direction) is proposed. It uses counters to estimate the moment of a data packet arrival at the subscriber side. By this ‘look-ahead’ technique no extra upstream channels are needed to initiate the polling by the subscriber. The algorithm guarantees fair access for all subscribers and minimizes the necessary overhead. Both the maximum access delay and overhead may be readily calculated, and the obtained results were supported by numerical simulation. Applicability in the standard broadband network environment has been proved by hardware design simulation.     

Protocols for very high-speed optical fiber local area networks using a passive star topology

This paper deals with the problem of interconnection of many high-speed bursty traffic users via an optical passive star coupler. Each user can tune its laser over a range of wavelengths, thus resulting in a wavelength division multiplexed communication. The total number of wavelengths over which user tunability exists could be much smaller than the number of users. Therefore, some form of random access sharing and packet switching may be necessary. We propose several protocols that require each user to have a tunable receiver. The information on "where" and "when" to tune the laser is confined to a control (setup) channel that users tune to when in idle mode. An interconnection between two users lasting for the length of a data packet is set up on the control channel by the transmitting user who informs the receiving user where to tune in order to receive the data packet. No centralized control or coordination is required among the users. After analyzing each protocol, we present the throughput/ delay versus the offered traffic and the delay versus throughput in a sequence of plots. We show that in typical applications an average throughput of up to 0.95 can be achieved at a reasonable average delay using one of these protocols. In our benchmark examples we present an optical local area network (LAN) with a total throughput of 100- Gbit/s in which every user has access to a 1-Gbit/s data rate and the network can support over 1000 users. The protocols can be used in a) large LAN's that do not require a large capacity, b) small LAN's (1 kin) that require a large capacity and c) large LAN's (tens of kilometers) that require a rather large capacity.     

Optical design and performance of wavelength-division-multiplexed optical repeater for fiber-optic passive star networks connection

New optical repeaters that use a wavelength-division-multiplexing (WDM) technique to connect CSMA/CD-based fiber-optic passive star networks are discussed. Two types of optical filters that are essential for obviation of closed-loop formation in construction of such repeaters, have been designed and fabricated. Results of a field trial of the filters and optical modules using the filters show good agreement with design values. The repeaters were also found to operate reliably.     

Synchronization for passive optical networks

There is widespread interest in the passive optical network as a solution for a future fiber in the loop network. This paper addresses the problem of synchronization at the line termination of a passive optical network that uses high-speed time division multiple access. Synchronization is a critical function since each asynchronous transfer mode (ATM) cell arrives with unknown phase. An ASIC has been developed to perform this function at 622 Mb/s and is outlined here     

Partitioned optical passive star (POPS) multiprocessorinterconnection networks with distributed control

This paper presents a partitioned optical passive star (POPS) interconnection topology and a control methodology that, together, provide the high throughput and low latency required for tightly coupled multiprocessor interconnection applications. The POPS topology has constant and symmetric optical coupler fanout and only one coupler between any two nodes of the network. Distributed control is based on the state sequence routing paradigm which multiplexes the network between a small set of control states and defines control operations to be transformations of those states. These networks have highly scalable characteristics for optical power budget, resource count, and message latency. Optical power is uniformly distributed and the size of the system is not directly limited by the power budget. Resource complexity grows as O(n) for the couplers, O(n√n) for transceivers, and O[√nlog(n)] for control. We present analysis and simulation studies which demonstrate the ability of a POPS network to support large scale parallel processing (1024 nodes) using current device and coupler technology     

A reservation-based multicast protocol for WDM optical star networks

In this paper, we present a reservation-based medium access control (MAC) protocol with multicast support for wavelength-division multiplexing networks. Our system is based on the single-hop, passive optical star architecture. Of the available wavelengths (channels), one channel is designated as a control channel, and the remaining channels are used for data transmission. Each node is equipped with a pair of fixed transceiver to access the control channel, and a fixed transmitter and a tunable receiver to access data channels. For easy implementation of the protocol in hardware and for precisely computing the protocol's processing overhead, we give a register-transfer model of the protocol. We simulate the protocol to study its throughput behavior, and present its analytic model. For a node to be able to send data packets in successive data slots with no time gap between them, in spite of the situation that the protocol's execution time may be longer than data transmission time, we propose the idea of multiple MAC units at each node. Unicast throughput of our protocol reaches the theoretically possible maximum throughput for MAC protocols with distributed control, and the multicast throughput is at least as good as, and even better than, those delivered by existing MAC protocols with distributed control.     

Novel schemes for local area network emulation in passive optical networks with RF subcarrier multiplexed customer traffic

This paper proposes two novel optical layer schemes for intercommunication between customers in a passive optical network (PON). The proposed schemes use radio frequency (RF) subcarrier multiplexed transmission for intercommunication between customers in conjunction with upstream access to the central office (CO) at baseband. One scheme employs a narrowband fiber Bragg grating (FBG) placed close to the star coupler in the feeder fiber of the PON, while the other uses an additional short-length distribution fiber from the star coupler to each customer unit for the redirection of customer traffic. In both schemes, only one optical transmitter is required at each optical network unit (ONU) for the transmission of customer traffic and upstream access traffic. Moreover, downstream bandwidth is not consumed by customer traffic unlike in previously reported techniques. The authors experimentally verify the feasibility of both schemes with 1.25 Gb/s upstream baseband transmission to the CO and 155 Mb/s customer data transmission on the RF carrier. The experimental results obtained from both schemes are compared, and the power budgets are calculated to analyze the scalability of each scheme. Further, the proposed schemes were discussed in terms of upgradability of the transmission bit rates for the upstream access traffic, bandwidth requirements at the customer premises, dispersion tolerance, and stability issues for the practical implementations of the network.     

Optimal WDM schedules for optical star networks

We consider single-hop wavelength-division multiplexed networks in which the transmitters take a nonzero amount of time, called tuning latency, to tune from one wavelength to another. For such networks, we show that, under certain conditions on the traffic matrix, there exist polynomial-time algorithms that produce the optimal schedule. Further, the tuning latency is masked in the length of the optimal schedule. Using Chernoff-Hoeffding bounds, we show that the condition on the traffic matrix is satisfied with high probability when the wavelength reuse factor is large, i.e., the number of nodes is large compared to the number of wavelengths. Simulation results show the dramatic improvement in the performance of the network using our algorithm as compared with other heuristics     

一种PON系统光缆监测新方案

无源光网络(PON)是一种点到多点的光接入技术,采用传统的光时域反射仪(OTDR)技术对PON的各分支光路进行监测出现了技术瓶颈.针对这一问题,文章分析了现有几种解决方案的不足之处,在此基础上,提出了一种以光供能方式驱动光开关测试的新方案,并详细描述了该方案的实现过程.     

可实现多点测量的波分复用光纤氢气传感系统

随着实际应用的发展,核电站、飞行器发动机、气体燃料等领域均提出了进行大数量点数氢气监测的要求,但目前已有的光纤氢气传感系统仅能实现单点测量。为解决上述问题,将波分复用技术和光纤氢气传感技术相结合,设计了一种可实现多点测量的波分复用光纤氢气传感系统,阐述了该系统的基本原理、光路结构和技术优势,并从理论上分析了进行多点氢气监测的可行性。根据理论分析的结果,基于已有器材搭建了一套4通道的波分复用光纤氢气传感系统,同时设计了一套实验装置并利用该装置对传感系统进行了验证实验。通过对光纤链路各节点传输光光谱和传感头反射信号光功率的测试,验证了所提出的新型氢气传感系统不仅可以实现多点测量,而且各测点具有较好的独立性和性能,一小时内测量稳定性优于1%,测量范围达到了0～4%,基本误差优于2%。理论分析和实验结果对于研究大数量点数氢气测量技术及系统极具参考意义。