Fiber-optic digital video distribution system for usinghigh-definition television signals using laser-diode optical switch

A fiber-optic high-definition television (HDTV) distribution system is discussed, which economically distributes HDTV signals to customers at a bit rate of about 100 Mb/s. The subscriber network is formed in a star topology to facilitate bidirectional connection. The distribution system uses digital video transmission at 1.3 μm wavelength using single-mode fiber. The video channel selection is made by an optical video selector. The optical selector consists of laser diode optical switch modules, which have a gain in the `ON' state and two-input, two-output 3 dB couplers. The authors describe the bit error rate characteristics of a signal-mode fiber digital distribution system using a four-input, one-output optical selector     

Design and performance of a fiber-optic video distribution systemusing BPSK microwave subcarriers

The design and performance of a fiber-optic video distribution system using bi-phase shift keyed (BPSK) microwave subcarriers to provide each subscriber with 20 107 Mb/s digitized video channels and one voice/data channel at 2.048 Mb/s are described. The combined microwave subcarriers are used to intensity-modulate a 1.3 μm single-mode laser, one dedicated to each subscriber. The penalty in system sensitivity resulting from the use of more than one subcarrier is calculated. The design and implementation of subcarrier generation, BPSK modulation, multiplexing/demultiplexing, and subscriber receivers are described. An experiment procedure to obtain an optimum laser driver level is also described. A bit error rate of 10^-9 or less is achieved at a received optical power of -12 dB (1 mW) for all channels for each subscriber     

Digital optical CATV system using hubbed distribution architecture

A hubbed distribution architecture based on a bus-star configuration, three-level single single-mode fiber transmission using M-TPC line code, and high-speed IC technology is proposed. The architecture is cost-effective and compact. It is well suited to metropolitan area CATV systems and would allow a gradual transition to a broadband ISDN (integrated-services digital network) subscriber loop in the future. The proposed architecture is applied to a digital optical CATV system prototype. The equipment making up this system consists of a transmitter, hubs including video selectors, and subscriber unit. Two video channels are selected for each subscriber from eight video channels at hub stations. The transmission speed is 900 Mb/s, three-level for the trunk line and 200 Mb/s, three-level for each subscriber loop. Very compact and low-cost equipment is realized by using recently developed high-speed ICs. Experimental results show that the system satisfies requirements and that its commercial application is feasible     

Fiber Optic Transport Systems for Present and Future Local Networks

This paper describes fiber optic transport systems for present and future local networks. The present most important fiber optic system in a local network emerges as a broad-band video distribution system, because large-scale system introduction might be attained only for distributed video services. The system architecture and system parameters are presented. As for future integrated services, a highspeed digital transmission system and local network architecture are very important. The network architecture should be constructed to meet the demands for increased flexibility, capacity, reliability, and economy. Considering expected future demands and technologies, a new fiber optic local network architecture is proposed. The architecture's main features are the use of transmission processing nodes and a multilane-ring structure in subscriber transfer networks in combination with star-shaped subscriber access lines.     

Call-by-Call Activation Technique for Fiber-Optic Subscriber Transmission Units

A call-by-call activation technique for fiber-optic subscriber systems has been developed to reduce electric power consumed in transmission units installed on subscriber premises. The major part of the transmission unit is supplied power call-by-call. The technique has been applied for a fiber-optic subscriber system in the INS Model System (NTT project) for which the PFM technique is used to transmit a frequency division multiplexed signal containing video, audio, and digital signals bidirectionally. This paper describes the control procedure and hardware implementation for this call-by-call activation. Discussion is made on methods of achieving optical carrier sensing. A unique technique is proposed which enables rapid and accurate indication of frame synchronization together with no considerable bit error occurrence for the digital signal just after activation. Experimental results which reveal validity of control procedure, carrier sensing, and frame synchronization methods are also shown together with the effect of power saving and assessment of build-up time required for activation.     

Deployment of ATM subscriber line systems

A B-ISDN introductory scenario is described from the viewpoint of service, and a virtual-path (VP)-based access network architecture based on this scenario is discussed. In the access network each VP is dedicated to one service, such as a leased circuit, switched circuit, or video distribution. The concept and functions of a subscriber line terminal (SLT) to realize this capability are introduced. Asynchronous transfer mode (ATM) subscriber line system deployment and the main SLT functions are discussed     

Fiber-optic subscriber loop systems for integrated services--The strategy for introducing fibers into the subscriber network

Two approaches to fiber-optic subscriber loop system development in Japan are described. In the first. Approach I, NTT aims at introducing inexpensive fiber-optic subscriber loop systems using conventional LED's, multimode fiber, and analog transmission techniques in the near future. In the second, Approach II, fiber-optic subscriber loop systems will be made highly functional by evolving from analog to digital transmission. This paper presents system fabrication examples for each approach and the results obtained in the tests.     

Design of a Switched Broad-Band Communications Network for Interactive Services

The congestion in broad-band communications networks resulting from the increased demand for interactive services is considered. It is shown that services such as a video library could not be provided to the majority of subscribers in a conventional CATV network. A design is developed for a space division multiplex broad-band network which can be expanded at minimum cost to meet an increasing demand for interactive services. The network contains two signal distribution networks: a cablecast system similar to the Rediffusion system, and a switched communication network providing point-to-point circuits for both one-way and two-way services. All broad-band signals are transmitted to the subscribers in the 1- to 10-MHz spectrum, permitting the use of twisted pair video cables and a minimum number of cable amplifiers. The broad-band cable network (BCN) is organized around 15 local switching exchanges and one central exchange. Multipoint switches in local exchanges under wired-logic circuit control connect individual subscriber communication lines to any channel. Crosspoint matrix switching groups in the local and central exchanges connect communication circuits in the broad-band communication network under programmed computer control. This network is accessed via links terminating on one channel of the multiposition switches. Per-subscriber costs are estimated to be 190 dollars for a cablecast system serving 3800 subscribers. Additional expenditures per subscriber of 40 dollars for fixed costs and 40 dollars for variable costs would provide interactive services. The range of interactive services provided would be extremely flexible, including both one-way video library service and point-to-point two-way communications.     

Implementation of a broadband integrated services hybrid network

The issues involved in the design of a broadband integrated services digital network (B-ISDN), that utilizes optical fibers in the subscriber loop, are considered. A hybrid scheme that provides integrated access to ISDN and broadband services by delivering voice/data signals in a digital format while using an analog format for full-motion video services to subscribers is proposed. The discussion covers planning for a B-ISDN, the system concept, implementation, the loop fiber network, subscriber equipment, and cost comparison and analysis     

Shared access packet transmission systems for compressed digitalvideo

The problem of designing shared access packet-transport-based transmission systems for compressed video signals is studied. The feasibility of using conventional link-level and transport-level protocol services to transmit compressed video is examined by focusing on two practically important scenarios for compressed video transmission: (1) multipoint-to-multipoint video transmission using a 200 Mb/s implicit token passing (ITP) fiber-optic local area network (LAN); and (2) point-to-multipoint broadcast video distribution using a 90 Mb/s packet time-division multiplexing (packet-TDM) direct-broadcast satellite channel. To evaluate the performance of such shared-access broadband packet video systems accurate simulation models were developed that were driven by realistic `broadcast quality' compressed video sources for the ITP-LAN and packet-TDM systems. The models were used to determine design tradeoffs between channel throughput, video quality (measured by clipping probability), and the transport-level and media-access-level protocol features and parameters implemented in the packet video network interface unit     

Crosstalk in a fibre access network demonstrator carryingtelevision and interactive digital services

An optical access network is being constructed as part of the RACE programme to demonstrate the feasibility of providing both interactive broadband and television distribution services over a single, shared fibre to a residential subscriber. The interactive and distributive services will be transmitted in the 1.3 μm and 1.5 μm optical windows, respectively, of the fibre. To prevent crosstalk between the two services a wavelength division demultiplexer which gives adequate isolation between the two optical carriers must be provided at the subscriber receiver. Performance deterioration due to mutual crosstalk is calculated and measurement results presented. Theory and measurement show that the deterioration of the interactive signal caused by the distributive signal sets the most demanding isolation requirement. For an interactive signal penalty of 0.5 dB the isolation has to be 40 dB, which is at the limit of the performance achieved by commercially available wavelength division demultiplexers     

The fiber-optic subscriber network in Japan

Nippon Telegraph and Telephone Corporation (NTT) has two primary aims regarding the installation of optical fiber cables for subscriber networks as the access network: to provide high-speed broadband services, and to provide narrowband services through optical fiber cables with subscriber-line multiplex technology. Thus, NTT is preparing an infrastructure to support the forthcoming B-ISDN subscriber networks. NTT has been developing technologies for implementing the full-scale construction of fiber-optic subscriber networks. The present article describes the deployment methodology for these networks, their current status, and plans for their future development     

Acoustooptic tunable filters in narrowband WDM networks: systemissues and network applications

The system issues and network applications of acoustooptic tunable filters (AOTFs) are discussed. AOTFs are thought to be attractive system components in dense wavelength-division multiplexed (WDM) networks because of their broad continuous electronic wavelength tunability and narrow filter bandwidth. Their unique multiwavelength filtering capability adds a greater dimension of flexibility to network design. The characteristics of the AOTF are reviewed from a system viewpoint and the performance and capabilities of bulk-devices, integrated-optic devices, and fiber-based devices are discussed and compared. Three network applications using the acoustooptic tunable filters are described. The first application is as wavelength-tunable receivers or taps for local users in a subscriber loop distribution network. The second is as multiwavelength tunable receivers in a broadcast local-area cross-connect for packet communication with very-high-throughput data rate. The third is as wavelength-selective space-division switch fabric for routing and cross-connect between central offices. Future prospects and various issues for future research are also discussed     

Parametric methodology for analyzing implementation strategies ofresidential broadband networks: the incremental cost of integratedaccess

An engineering framework for estimating the investment cost of two implementation strategies intended to provide broadband (video services) access to residential customers in new construction areas is described. One strategy is the deployment of a single (digital and fiber) integrated network, and the other is the codeployment of dual, separate networks (one for narrowband and the others for TV distribution). The methodology derives the investment per subscriber as a function of network element's costs and demographical, topological, and service penetration parameters. The methodology is applied to TELEFONICA's network. The incremental cost of the integrated network (compared with dual networks codeployment) is estimated to be around $700 per customer. The results highlight the importance of broadband services that would not be fully provided by conventional cable TV distribution networks     

High-Speed and Broad-Band Communication Systems in Japan

This paper presents the current state of each high-speed and broad-band system and the development of the high-speed and broad-band network (HBN) in Japan. System configuration of a video conference system, a video transmission system, a high-speed digital circuit system, and so on, are introduced. Fundamental technologies to realize HBN, 1) switching technologies to handle broad bit-rate class transmission, 2) high-capacity transmission and high-speed digital terminal technology, 3) economical fiber optic subscriber loop technology, and 4) high-performance video codec technology, are discussed. Based on the above discussion, configuration of HBN is proposed.     

浅谈交互式电视

通过简要介绍数字交互系统的参考模型,交互式电视的种类、特点和实现方法,以及交互式电视的业务类型,说明交互式电视的基本特征;针对交互电视网系统结构,说明各部分的主要作用;最后介绍交互式电视的视频服务器技术、用户接入网技术、用户接口技术等几个关键技术,其中包括视频服务器中采用的数字压缩技术、视频流传输技术和数据库技术。     

BER Analysis of Equalized OFDM Systems in Nakagami, <Emphasis Type="Italic">m</Emphasis> < 1 Fading

The orthogonal frequency division multiplexing (OFDM) transmission scheme is currently experiencing increased popularity due to advances in very large scale integration technology. It is used for a variety of broadband systems such as asymmetric digital subscriber lines, very-high-speed digital subscriber lines, digital video, and audio broadcasting, and wide local area network standards such as IEEE 802.11a, IEEE 802.11 g, and ETSI Hiperlan/2. However, propagation impairments can cause severe degradation in bit error rates (BER) for coherent detection. We derive a semi-analytical method to evaluate BER of a quadrature phase shift keying (QPSK)-OFDM system in Nakagami, m < 1 fading and additive noise where pilot-assisted linear channel estimation and channel equalization are used. This allows modeling of more severe fading environments than can be depicted by a Rayleigh distribution. Numerical simulations are used to validate the proposed methods. The techniques developed can be applied to other channel estimation techniques, modulation schemes and the performance evaluation of equalized single carrier narrowband systems.     

Technology and system issues for the WDM-based fiber looparchitecture

A fiber-optic subscriber loop architecture employing multichannel wavelength-division multiplexing (WDM) techniques is discussed. The architecture, which is called the passive photonic loop (PPL), eliminates the need for outside-plant multiplexing and routing electronics while maintaining complete compatibility with broadband ISDN. An experimental demonstration of the PPL employing 32-channel WDM and a combination of distributed-feedback (DFB) laser and light emitting diode (LED) transmitters is described. A family of alternative PPL implementations is identified. Tradeoffs between these alternatives are explored, and related hardware issues such as wavelength alignment and WDM-component temperature sensitivity are discussed. An economic analysis comparing the PPL with the use of dedicated fiber between the central office and customer premises is presented. The analysis predicts that the PPL can achieve a cost advantage for at least 80 to 90% of the subscribers served in today's network, given DFB-laser and dense-WDM-component cost reductions of approximately one order of magnitude from today's unit-quantity prices     

一种新型光开关交换器

探讨了光偏振现象和旋光现象的特点 ,进而利用偏振和旋光现象提出一种新型光开关交换器。这种交换器具有结构简单、与输入光的偏振态无关、不会产生相位差、插入损耗和信道串扰小、响应速度快、器件体积小等优点 ,同时可以使用此器件和光波分复用 /解复用器相结合 ,方便地实现任意波长的上下路。对 2× 2开关交换器的性能进行了分析 ,结果表明它的插入损耗和信道串话都很小。     

FBG应变传感系统在巷道涌水模型试验中的研究

针对传统的电类应变传感器防水性能差、测量精度低和不能满足巷道涌水模型试验的需要等问题,基于模型相似材料研制了一种新型光纤光栅(FBG)应变传感器。采用波分复用(WDM)技术和Fabry-Perot(F-P)腔解调技术组成FBG应变传感网络,并编写了具有实时显示和自动预警功能的系统软件。将该系统用在巷道涌水模型试验中,在巷道周围布置了14个FBG应变传感器,对巷道推进过程以及模型加载和巷道扩挖过程中围岩应变进行实时监测。试验结果表明,设计的FBG应变监测系统测量精度高,防水性能强,并且提前4 206 s成功捕获了巷道涌水前兆信息,为预测煤矿矿等涌水事故提供了一种新的有效手段。