Fiber-optic switch arrays for optical subscriber transmissionsystems

Optical array devices play an important role in subscriber transmission systems because they can efficiently accommodate the large number of optical channels required. The use of two single-mode fiber-optic switch arrays in subscriber transmission systems is discussed. The first is a 16-element micromechanical switch array which is electrostatically driven and is used to separate abnormal subscriber units that transmit disturbing light signals. The second is a 16-element switch array which interconnects a pair of probe fibers and any one of 16-channel subscriber-line fibers to execute fault testing     

Loop Test System: A New Maintenance Feature for the Distributed Integrated Digital Network

The introduction of the digital Class 5 switch offers unique solutions to the requirements of growth and demands for improved service. For example, remote subscriber switches (RSS's) and subscriber carrier terminals (SCT's) can now be located near subscribers and digitally connected to the Class 5 switch via T1 repeatered lines or radio links. The result is shorter subscriber loops, improved transmission, and deferment or elimination of feeder plant additions. Traditionally, interposing electronics between the subscriber loops and the Class 5 switch resulted in isolating these loops from the office loop testing facilities. Remote testing of RSS and SCT assigned loops is an important step toward minimizing maintenance costs. Loop testing is accomplished in TRW Vidar's ITS5 switching system by locating loop test equipment in the remote RSS and SCT cabinets. This equipment is available to the test operator for real-time testing, and to the switch for automatic line testing. Some of the requirements that the loop test equipment must meet are: low cost, no adjustments, low power consumption, small size, operation in a harsh environment, and centralized testing capability from a test console. The data returned to the office must be in a quantitative form to allow further processing by the console. It must also be compatible with the direct distance dialing (DDD) network to allow transmission not only to the Class 5 switch serving the RSS and SCT, but also to distant service centers. This paper describes a newly developed system that meets the above objectives.     

Providing Multiple-Channel Communication Using the Experimental Digital Switch

This report describes the functional characteristics of a circuit-switched network which is capable of providing data communication paths as well as voice channels. In the system described, the circuit switch may be shared in order to provide multiple independently switched paths through the network. Unlike a conventional circuit switch, this sharing permits only a fraction of the switching capacity to be consumed which is proportional to the allocated bandwidth of the path. Additional economy is gained by providing multiple communication paths over the single communication resource between the subscriber and the switching machine. The fraction of the communication resource which is used by the subscriber is proportional to the total bandwidth of the channels which have been allocated. This allocation is performed dynamically, in response to subscriber requests. Algorithms are presented which perform this allocation efficiently. The resulting network provides a communication vehicle which provides both data and voice services in an integrated fashion.     

A phased array optical scanning (PHAROS) device used as a 1-to-9way switch

An optical switch is demonstrated which uses a phased array of 30 closely spaced, individually addressed electrooptic AlGaAs-GaAs waveguides to focus and steer a light beam under electronic control in a planar output waveguide. A small and potentially very high speed 1-to-9 way optical switch, (with -15 dB of crosstalk) was made by placing an array of nine output waveguides at different positions in a focal plane 1 mm from the end of the electrooptic array     

论用户数据中心在交换网中的重要性

传统的本地交换网中的用户数据是在各个本地网端局中分散管理的,这样的模式已经成为交换技术向软交换甚至更先进的交换技术发展的主要瓶颈.而伴随软交换技术引进的用户数据中心网元,集中了本地网全网的用户数据,通过灵活的协议接口实现与传统交换机、NGN交换机互通,利用自身多元化的业务数据制作能力,克服了传统交换网实现全网网络智能化所遇到的各种阻碍和弊端,已经成为现代固网交换发展的必要网元.文中从用户数据中心引入的必要性入手,阐述了用户数据中心在整个交换网络中的重要性.     

一种实现CSFB的方法研究

探讨了一种电路域回落(CSFB)的实现方法,该方法可以避免对现网已经部署的访问移动交换中心服务器(VMSC)、网关移动交换中心(GMSC)升级改造,易于在现网部署。在本CSFB解决方案中,由归属用户服务器(HSS)执行呼叫重试功能,从组网来看,只需要增加一个Proxy移动交换中心(MSC)服务器,对现网已经部署的VMSC、GMSC没有改造要求。     

A Digital Telephone with Extensions

A digital telephone concept is described where each subscriber set sends and receives digital signals (8-bit PCM). Duplex, simultaneous operation of extensions on a single pair of wires is made possible by time division multiplex (TDM) techniques. A successful feasibility demonstrator of the concept that operates at 512 kbits/s is also described. It has a digital switch at one end and digital telephones at the other, with up to three extensions talking at one time. The telephones feature a separate digital signaling channel, automatic loop-back testing, and low-power transducers.     

A high capacity metropolitan area network using lightwavetransmission and time multiplexed switching

The technical feasibility of a lightwave communication system capable of providing service to thousands of subscribers within cities or large suburban areas is examined. Each subscriber in this system has available upon demand an aggregate bit rate of up to 100 Mb/s. The aggregate bit rate of the entire network is on the order of 5 Tb/s. The network topology is that of a star-on-star wherein each subscriber line terminates on one of a multitude of remote concentrators. Each high-speed link from a remote concentrator to a centrally located time-multiplexing photonic switch consists of a single-mode fiber carrying several wavelength-division multiplexed (WDM) channels. Each channel operates in a time-division multiplexed (TDM) mode at a data rate of 2 Gb/s and is powered by a multimode laser. No regeneration is required at the central switch, and at the remote concentrators, each channel is terminated by a direct-detection receiver. The approach achieves high throughput by reusing the same channels, that collectively occupy a tiny fraction of the optical band, among all interconnecting links and, with the exception of large-dimensional switch arrays, employs readily available technology     

Low crosstalk 4 × 4 TiLiNbO3optical switch with permanently attached polarization maintaining fiber array

Several low crosstalk 4 × 4 crossbar optical switch arrays have been fabricated for use atlambda = 1.3 mum. Each array consists of 16 independently functioning directional coupler switches. We describe the typical device performance characteristics. The average insertion loss is 5.2 dB. Crosstalk levels routinely measured < -35 dB. The voltage required to operate the device is ≈ 13 V. The inputs to one of the device arrays were permanently attached to four laser transmitters using lensed polarization maintaining fiber at the laser end and an array of polarization maintaining fibers at the device end.     

Timing Jitter Effects on Digital Subscriber Loop Echo Cancellers: Part II--Considerations for Squaring Loop Timing Recovery

The performance of an adaptive echo canceller at the looptimed subscriber end of a digital subscriber loop has been shown to be sensitive to jitter arising from the timing recovery subsystem. We evaluate this degradation for the common timing recovery subsystem consisting of a prefilter, a squarer, and a second-order phase-locked loop. The evaluation shows the influence of equalization, prefilter shape, and phaselocked loop parameters. A narrow-band accurately tuned prefilter, line equalizer, and a narrow-band phase-locked loop are found to be necessary for adequate performance in a 144 kbit/s bipolar-coded digital subscriber loop system employing echo cancellation.     

A closed-form analysis of fading envelope correlation across a wideband basestation array

This letter proposes a simple analytical model to accurately quantify the degree of fading envelope correlation among the received signals at the antenna elements of an adaptive array operating in a frequency-selective environment. The adaptive array is assumed to be at an elevated base station with scattering being confined to a local region around the subscriber station. This corresponds to the so-called "local scattering" or "macrocell" assumption and it results in most of the received energy at the base station array being concentrated within a given beamwidth. Our formulation provides closed-form, finite sum expressions for the covariance and correlation coefficients as a function of spatial and frequency separation.     

Precise Incident Power Density Pattern Measurement through Antenna Pattern Deconvolution

Future cellular and fixed wireless loops (FWL) systems employing highlydirective base stations antennas (5 to 8 degrees beamwidth) and moderatelydirective subscribers' antennas (15 to 25 degrees beamwidth) offer very largecapacity due to reduced interference. An important property of the environmentof such systems is the interference caused by scattering of the signal froma subscriber transmitter into directions other than the direct line of sightbetween the subscriber and the base station. In particular, for multibeam basestation applications scattering could arrive at the base station in thedirection being used by a different beam, resulting in interference that isdifficult to reduce by normal nulling techniques. Thus interference can behighly dependent on the incident power density pattern (IPDP) caused byscattering of the signal radiated from the subscriber. We discuss herein theuse of a uniformly illuminated array accompanied by electric fielddeconvolution to measure the crucial IPDP with the same performance as a lowsidelobe array of the same size. The mathematical correction technique usesdeconvolution of the measured complex electric field pattern with that of theantenna in free space by means of the Fourier Series and limiting the rangeof Fourier coefficients to those that are not negligible in the free spacepattern. Application of the technique to an experimental uniform array witha 2.5 degree azimuthal beamwidth shows the practicality of the deconvolutionwith real antennas in real environments. The improved resolution and accuracyprovided by Taylor weighting versus unweighted deconvolution when trying tomeasure weak scattered components in the presence of a nearby strong specularcomponent is demonstrated. The IPDP was measured from many sites surroundinga suburban base station. A plot of the cumulative distribution of the ratioof the widely scattered power to that within a prescribed beamwidth summarizesthe result of using the deconvolution technique on this experimental data.     

国外光集成／光电集成技术的发展

ＰＩＣ／ＯＥＩＣ是实现长距离大容量光通信网、光用户网、光交换等关键器件。本文主要介绍了最近两年国外半导体材料技术、工艺技术的进展以及ＰＩＣ／ＯＥＩＣ器件的研制状况。     

Subscriber Line Equipment for an Elastic Carrier Switching System

This is the third of three papers [l], [2] dealing with an elastic carrier-concentrator system. The functioning of the subscriber line equipment is described herein. The system serves 256 telephone subscriber lines by digital concentration switching and transmission of multiplexed message channels over a singleT1transmission line. The concentration switching function is nonblocking. Message channels are the individual communication links between terminals and are created on demand at the request of active subscriber lines. They are not merely inactive without service requests; they do not exist unless service is requested. The created message channels serve for their normal communication function and, in addition, carry for each line the ancillary functions of dialing, ringing, and pay-station coin disposal. Message channels are coded by delta modulation, which permits flexible digital concentration and provides a smooth tradeoff of channel quality versus the instantaneous traffic load. Each of two complementary subscriber line interface units, one per line at each end, provides the delta-modulation encoding and decoding functions for the analog voice-band signal input and output and, by overriding the delta codec, provides the desired signaling functions of dialing, ringing, etc. The line interface units provide the major equipment interface between the subscriber line and the digitalT1line. An integral test facility permits remote loop-back of any selected subscriber line unit via a test channel to the office terminals and at the same time connects the subscriber loop to an auxiliary programmed test facility which may transmit pertinent loop-test results to the office terminal.     

Broadcast digital subscriber lines

The adoption of asymmetrical digital subscriber lines (ADSL) technology in conjunction with the broadcast digital subscriber lines (BDSL) proposed in this paper could provide a cost effective solution for the introduction of digital video services in the near term. BDSL provides the same digital broadcast video programs to all subscribers through existing twisted pair telephone loops. In this paper, the basics of telephone loop-based digital subscriber lines are first discussed. Then the potential of BDSL is explored in the twisted pair loop plant near end crosstalk (NEXT), far end crosstalk (FEXT), and white noise environment. The capability of BDSL is examined with different serving areas and transmit power levels. The possibility of using orthogonal quadrature amplitude modulation (QAM) to implement a zero guard-band BDSL system is studied. Computer BDSL performance simulations are then presented. The combination of high-bit-rate digital subscriber lines (HDSL), ADSL, and BDSL can provide telephone subscribers many digital broadband services     

阵元切换时间对单通道阵列测向性能的影响

单通道阵列采用单个通道贯续接入各阵元进行采样,与常规阵列相比,单通道阵列减少了硬件成本以及通道幅相特性不一致问题对估计性能的影响,但现有研究均未考虑单通道阵列的阵元切换时间对系统性能的影响。为填补这一空白,首先参照常规阵列,明确了单通道阵列中窄带信号的带宽限制及其与单通道阵列阵元切换时间的关系;再以单通道阵列MUSIC算法为例,同时考虑信号带宽与单通道阵列阵元切换时间对单通道阵列协方差阵特性的影响,从理论上推导了单通道阵列MUSIC算法关于扩展相对带宽的一阶估计误差。最后对单通道阵列MUSIC算法与单通道阵列空间FFT算法在不同阵元切换时间下进行仿真,对两种算法测向误差与阵元切换时间的关系进行分析,验证了理论推导结果的正确性。      

Switching System Software Design for ISDN

The ISDN offers various services through multipurpose digital subscriber lines. The switching program for the ISDN should be so designed as to realize the control of various voice and nonvoice services and provide for developing service enhancement. To attain the goal, the ISDN services are classified hierarchically and each category is allocated to appropriate network nodes for implementation. As a result, the local switching program provides an out-slot subscriber line signaling capability and call connection with appropriate compatibility checking including a check for access capability to communications processing nodes. The switching program modules specific to analog services and those specific to digital services are separated to allow the use of the existing program file and to afford easy program design and maintenance. Remote-controlled switching is a suitable means for an economical introduction of the ISDN services to low traffic density areas. Special routing and reliability arrangements as well as the program structure for a remote-controlled switch are discussed.     

Performance evaluation of a multichannel transceiver system forADSL and VHDSL services

The authors study the performance of a multichannel modulation method for asymmetric digital subscriber lines (ADSLs) and very high-speed digital subscriber lines (VHDSLs). In the ADSL case, over all unloaded North American subscriber lines in the test set, a unidirectional 1.536 Mb/s data rate service from the end office to the customer premises is possible on a single twisted pair at an error rate of 10^-7 with at least a 6 dB margin used coded multichannel modulation with sufficient transmit power. In the VHDSL case, data rates in excess of 100 Mb/s can be transmitted reliably, at an error rate of 10^-7, using uncoded multichannel modulation on a single twisted pair over a distance ⩽150 ft with a sufficiently high sampling rate (≈24 MHz) and transmit power. It is shown that a cost-effective multichannel transceiver design suggested for high-speed digital subscriber line (HDSL) service will also work well for ADSL and VHDSL services with only minimal modifications     

Microcell design principles

The ways in which microcell systems can help cellular operators face a number of challenges to achieve continued growth, including the need for increased system capacity, enhanced coverage, lower network cost per subscriber, improved performance, delivery of innovative value-added services, and well-planned equipment and service migration strategies, are discussed. It is argued that microcells must work with conventional cellular systems with lower equipment costs per subscriber, and should require only minimal preinstallation RF design and engineering. Keys to cost-effective microcell deployment are high-performance RF component and digital signal processing technology, efficient radio resource management, optimized distributed network design, and effective switch and network integration     

10 /spl Omega/ 370 V high voltage switches for line circuit application

The authors describe the integration of 8 high-voltage switches together with their low-voltage polygate CMOS control logic in an 18-pin package, the HVX chip. This custom IC is intended to be used as a switching cross-point between the subscriber line and circuit equipment in digital telephony. The high-voltage DMOS is processed in a dielectrically isolated substrate, and allows the switches to have both terminals floating with respect to the low-voltage circuitry. A novel control circuit guarantees that the switch status will be defined under all circumstances.