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     

Error correction performance in digital subscriber looptransmission systems

The author describes an error correction system for digital subscriber loop transmission systems which use time compression multiplexing (TCM). An interleaved block code is used to correct the burst errors due to impulse noise from analog telephone circuits. This interleaving method requires no extra hardware and contributes no additional delay. To evaluate the transmission performance of this error correction system, the bit error rate after decoding is derived on the basis of a burst error model for 200 kb/s digital subscriber transmission using the alternate mark inversion (AMI) line code. The experimental results for a 200 kb/s TCM system show that burst errors are substantially reduced     

Multiple wavelength bidirectional transmission for subscriber loop applications

A laboratory demonstration of two uniwavelength bidirectional transmission systems, one at 780 nm and another at 1300 nm, multiplexed on a standard single-mode fibre is described. Based on experimental results, a duplex-quadruplex system for the subscriber loop is possible, which again doubles the information carrying capacity of the fibre system.<>     

Flexible synchronous broad-band subscriber loop system: opticalshuttle bus

A flexible, synchronous, broadband subscriber loop system called the optical shuttle bus is discussed. The emphasis is on the proposed design architecture and performance of a 1.8-Gb/s prototype system. The optical shuttle bus is constructed of multigigabit/second intelligent optical shuttle nodes (OSNs). The software-defined OSNs allow the bus to be configured as a synchronous transmission network with any topology and provides flexible channel allocation by means of a drop/insert/cross-connect function. The OSN can be configured as a highly reliable network by virtue of its self-healing functions such as line switch, bypass, and loop back. The proposed bus architecture has been successfully applied in a 1.8-Gb/s prototype in which three OSNs are connected by one 10-km and two 5-dm single-mode fibers in a ring configuration. Very compact and inexpensive equipment is realized by using high-speed ICs. Experimental results show the proposed architecture to be a powerful one for the realization of synchronous broadband subscriber loop systems     

Performance evaluation of a fast computation algorithm for the DMTin high-speed subscriber loop

The discrete multitone (DMT) modulation is considered to be a viable transmission scheme for high-speed subscriber loop. In this paper, the fast algorithm for computing the equalizer settings derived in [1] is extended and applied for the DMT in high-speed subscriber loop. The channel pulse response is assumed to be given by the channel identification method, and then the equalizer filter settings are computed. In simulations, a fast algorithm for the symbol spaced equalizer in a colored noise channel is used. Simulation results performed in various CSA loops indicate that the fast algorithm yields the near-optimum settings for the DMT system     

Implementation of a TDM passive optical network for subscriber loopapplications

An experimental prototype system for subscriber loop applications that has been implemented using a passive optical network architecture is described. The system, known as MACNET, uses time-division multiplexing and transmission over a network of single-mode optical fibers and couplers to provide narrowband digital service access to 16 customers. Experience gained from developing the system is outlined. Future transmission options, including a fixed-bit-rate customer access approach to allow early network application of this technology, are described     

Lightwave subscriber loop systems toward broad-band ISDN

The state-of-the-art of lightwave subscriber loop systems is reviewed. An approach is described for deriving an architecture for subscriber loop systems that can accommodate technological trends in broadband ISDN such as asynchronous transfer mode (ATM) and synchronous digital networks. Key component technology is discussed, namely, optical fibers and cables, splicing and connectors, and switching     

Configuration and Characteristics of a Fiber-Optic Video Distribution System

A multiservice fiber-optic subscriber system using wavelength division multiplexing technology has been developed by Nippon Telegraph and Telephone Corporation to provide both 64 kbits/s and broad-band communication services on a single multimode fiber. The subscriber network is formed in a star topology to facilitate bidirectional connection. The system was put in service in March, 1985, as part of the information network system (INS) model system. This paper describes the configuration and characteristics of the video distribution system of this fiber-optic subscriber system. The distribution system uses analog baseband video transmission at a 0.89μm wavelength. The video channel selection is made by an FDM video tuner installed in a central office. The overall performance successfully met design objectives.     

Fiberguide systems in the subscriber loop

This paper presents an overview of the application of fiber optics in the subscriber loop plant. A review of the limitations of existing loop plant networks is given and the characteristics that fiber optics offer to overcome these limitations are examined. Possible network topologies for fiber optic loop systems are discussed and current designs, particularly those based on a centrally switched star configuration, are described. The component availability, system cost and other considerations are discussed. Finally, features of major current fiber optic loop system field trials and experiments are highlighted.     

A monolithic telephone subscriber loop interface circuit

An integrated circuit that interfaces a subscriber loop with the digital telephone exchange has been produced with conventional high-voltage IC technology. The monolithic SLIC controls DC loop current, converts signal transmission from two-wire to four-wire, and suppresses longitudinal induction. Bias control circuitry automatically reduces standby power when subscriber equipment is detected on-hook. High-voltage circuit techniques maintain performance when the supply voltage exceeds the n-p-n transistor BV/SUB CE0/, and circuit partitioning with two discrete transistors yields manageable junction temperature and an economical 102/spl times/112 mil die size.     

A long reach digital subscriber loop transceiver

An echo-cancelling duplex transmission system is described for the digital subscriber loop which uses a 4-level zero redundancy line code (2B1Q) to give very long reach in the presence of crosstalk. Novel digital signal processing algorithms are used to simplify the analogue line interface circuitry. All the digital signal processing, along with sophisticated maintenance and interfacing circuitry, can be contained on a single LSI circuit. Measured performance results are presented.     

Performance study of high-speed asymmetric digital subscriber linestechnology

Computer simulation results are presented for the loop range coverage of an asymmetric digital subscriber lines (ADSL) system that uses the quadrature amplitude modulation (QAM) signaling scheme, ADSL performance is evaluated in the presence of background additive white Gaussian noise (AWGN), and crosstalk noise from existing services in the local telephone loop plant. It is shown that coverage of the extreme carrier serving area (CSA) is possible at transmission rates that are well above the existing T1 rate     

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     

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.     

Profile detection in multiuser digital subscriber line systems

Multiuser transmission methods for digital subscriber line (DSL) systems have become of interest with the potential for increased data rate and loop reach. These methods often assume that the set of crosstalk interferers, called the crosstalk profile, and their associated channel responses are known. For DSL systems, the interferers are often uncoordinated, so that in a dynamic environment where DSL transmitters can energize and deenergize, the crosstalk profile cannot be transmitted to the user of interest. While the crosstalk channel estimation problem in a dynamic environment can be intractable for general transmission systems, channel and crosstalk analysis can make use of the specific DSL environment. Namely, the physical channels in a DSL system do not change rapidly, and hence estimates of the crosstalk channel can be saved for future reference. For this reason, we introduce the concept of a channel profile. We develop several algorithms to detect the crosstalk profile and investigate the asymptotic behavior of the new algorithms. Simulations show that for typical crosstalk interference scenarios, the observation time to determine the correct crosstalk profile at probability of error less than 10^-3 can be less than 2 ms     

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     

OEIC technology and its application to subscriber loops

Recent progress in GaAs- and InP-based optoelectronic integrated circuits (OEICs) for use in optical fiber transmission systems is reviewed. OEIC technology and system demonstrations for short-haul and high-speed transmission are described, and the problems arising in practical applications are discussed. Approaches to resolution of these problems are presented, and future OEIC applications, especially with regard to subscriber loops, are predicted     

High bit rate digital subscriber lines: a review of HDSL progress

The author gives an overview of progress made in the evolution of technology to provide DS1 rate telephone access in a restricted segment of the loop plant without intermediate repeaters, loop conditioning, or pair selection in assignment. This technology is called the high bit rate digital subscriber line (HDSL). Discussed are background information on electronics in the loop plant and characterization of the tranmission environment in the relevant frequency band. The progress of HDSL study project of the American National Standards Institute (ANSI) is outlined. Analytical and theoretical studies to determine the limits on the transmission capabilities of the loop plant, motivated by the need to determine the feasibility limits of HDSLs, are reviewed. Also discussed is progress in technical work on suitable transmission formats. The possibility of an asymmetrical digital subscriber line (ADSL), transmitting at the DS1 rate from the central office to a remote distribution point, through the entire nonloaded loop plant is discussed     

Digital subscriber line technology facilitates a gracefultransition from copper to fiber

The loop environment and the techniques that historically have been used for providing transmission treatment are reviewed. The digital subscriber line (DSL), which applies adaptive filtering to yield significant performance and administrative advantages, is introduced. How this technology will evolve to complement the emerging fiber-based network, providing timely, ubiquitous wire pair transmission capabilities at basic rate, primary rate, and above is examined     

Photonic highway: broad-band ring subscriber loops using opticalsignal processing

The introduction of optical signal processing technology into transmission systems and basic experiments with optical drop/insert using bistable laser diodes are discussed. With broadband integrated services digital network (B-ISDN) architecture and technology now under study, optical signal processing (OSP) is being considered to increase network capacity and flexibility. B-ISDN will require over 40 Gb/s in the feeder loop that connects the central office and remote terminals having drop/insert function. Remote terminals will process large amounts of high-speed data. An OSP-based broadband subscriber loop photonic highway that uses a ring architecture linking photonic access nodes (PANs) that directly process optical signals is proposed. Each PAN has an optical drop/insert function and can synchronize optical frame signals using a proposed optical sampling memory. Optical drop/insert experiments confirmed the feasibility of the proposed method