Currently, most regional Bell operating companies (RBOCs) favor centralized powering as the predominant method for powering fiber-in-the-loop (FITL) systems. This is because centralized power systems can provide indefinite power backup, as well as consolidation of power equipment and batteries. The capabilities of such a power system are dependent on several parameters including supply cable gauge, load requirements, and equipment location. This paper examines two centralized powering architectures and determines the impact of these parameters on the installed first cost of the power system. The paper also provides a review of the anticipated narrowband FITL power requirements and specifications.

The purpose of this paper is to review the issues associated with powering of fiber optic systems in feeder and distribution plant. Powering of existing feeder plant, fiber to the curb (FTTC) and fiber to the home (FTTH) systems are discussed. Recommendations for powering fiber in the loop (FITL) topologies in the NYNEX region are made at the conclusion of this paper. Recommendations made are those that can be deployed now using existing systems.

Exciting possibilities exist for those developing countries taking major steps in revamping their telecommunications infrastructure. Unlike more developed countries that are tethered to supporting old standards for equipment, developing countries can standardize on new technologies providing substantial cost and feature advantages over equipment supporting old standards. This paper investigates variable power costs of FITL systems from an energy cost perspective and then from a peak power cost perspective. These cost perspectives are then related to telephones to show how improvements in telephone efficiency affect life cycle costs. Finally, these cost improvements are related to the networks of developing countries to show the overall system cost savings. For the sake of power calculations U.S. standards for telephone equipment are used, because they are familiar and much supporting cost analysis exists. Standards drafted by CCITT are similar to U.S. standards.

CATV systems traditionally use a tree and branch architecture to bring up to 550 MHz of analog bandwidth to every home in a franchise area. This changed slightly with the advent of AM fiber optic equipment, as fiber optics were used in an overlay fashion to reduce coaxial amplifier cascades and improve subscriber quality and reliability. Within the last year, fiber has economically replaced coaxial trunking. The resulting fiber to the serving area architecture combines fiber and coaxial stars for a network that looks much like the carrier serving area architectures used by telephone companies.

With the growing deployment of fiber in the loop (FITL) systems, switched video services are becoming a reality. A digital TV supertrunk was developed by BroadBand Technologies for the Fiber Loop Access (FLX^TM) 1100 system. This paper presents an overview of this supertrunk.

Passive optical networking is being considered for the provision of digital services in the local loop. In the UK, TPON is under investigation for the delivery of telephony and other narrowband services. This paper describes a carrier based system which is being considered as a short term overlay to TPON. Both broadband and narrowband services may be supported, representing an evolutionary path to the provision of integrated services for the information intensive customer.

The fiber-to-the-home (FTTH) feature of the SLC^R Series 5 Loop carrier system shifts the channel unit that terminates the copper wire pair to the customer's premises from the remote terminal of the system to the mutliservices distant terminal that is connected to the remote terminal by a fiber umbilical and is located in close proximity of the customer premises. This configuration transforms the traditional metallic-distribution carrier system to a fiber-distribution one, in which the metallic portion of the CO/network interface facility is limited to the extremely short drop between the distant terminal and the network interface. No new channel units are developed for this specific application, and the distant terminal accommodates the existing SLC Series 5 channel units. The Series 5 POTS channel units, that have been designed for a metallic-distribution system, can serve distribution wire pairs long enough to have a dc resistance of up to 1500 ohms in some cases, 900 ohms in others. The loss plan of these units takes into account the transmission loss introduced by the expected wire pair length, and therefore they implement a 0 or 1 dB loss between the CO and their tip- ring interface. This loss plan results in `too loud' complaints from customers served by short drops that are the norm when service is provided by the FTTH feature. The designers of the FTTH feature were faced with the challenge of modifying the loss plan in order to improve the loss grade of service without changing the channel unit circuitry. Ours was a two-step effort: First, determine what the modified loss plan should be. Second, design its implementation outside the channel unit in a cost-effective way. This paper describes the grade-of-service study that yielded the loss plan that was implemented; namely, build up the loss of each POTS channel unit to 4 dB. It then discusses the implementation of this plan, that uses digital signal processing rather than a look-up table, to introduce the loss digitally. We chose this approach for its flexibility and low manufacturing cost. Tests have shown that this implementation meets all the transmission requirements while improving the grade of service.

While it is clear that the development of the laser and low loss optical fiber has had an unmistakable impact on the field of telecommunications, the deployment of optical fiber in the subscriber (local) loop is an especially challenging task. It requires development of low cost equipment that will initially be used at low bit rates (< few tens of Mb/s) due to the fact that basic telephone service does not require more than 64 kb/s per subscriber. Transmission of TV data, in either analog or digital form, will make more efficient use of the fiber bandwidth and generate additional revenues. But as seen from the perspective of the telephony industry, basic telephone services are the principal source of revenue and economic justification for the installation of subscriber loop fiber systems. For large scale deployment in the subscriber loop, the fiber optic system must provide basic telephone services with equal or better performance at a cost that is competitive with that of existing copper pair technology. In this paper we examine a number of possible fiber-to-the-home (FTTH) and fiber-to-the-curb (FTTC) architectures, and present an architecture for urban areas that is best classified as fiber-to-the-building (FTTB). We examine the costs and performance characteristics of the various networks. We show how demographic information can be used to optimize the capacity of the remote terminals. It is shown that for the demography of Spain (where in urban areas the majority of the population resides in apartment buildings with 10 or more dwellings) a remote terminal with a variable subscriber capacity presents a cost savings over remote terminals with a fixed number of subscriber channels.

As a result of the new architectures used in fiber optic CATV networks, status monitoring is now much easier to implement than in conventional tree and branch coaxial networks. Status monitoring as an aid to improved network operation is more valuable than ever because there is a genuine drive to improve CATV system performance and reliability. At the same time status monitoring systems are becoming more sophisticated providing system engineers with new tools to improve network operations.

Short wavelength transmission of narrowband services over single-mode fiber optimized for long wavelengths can provide both economic advantages and added flexibility for applications where the addition of broadband services are contemplated. In particular, high production volumes of 780 nm compact disc lasers drive their cost significantly below long wavelength devices. Transmission will occur below the fiber cutoff wavelength, and bimodal or trimodal propagation results. Adjustments to loss budget methodolf the CO/network interface facility is limited to the extremely short drop between the distant terminal and the network interface. No new channel units are developed for this specific application, and the distant terminal accommodates the existing SLC Series 5 channel units. The Series 5 POTS channel units, that have been designed for a metallic-distribution system, can serve distribution wire pairs long enough to have a dc resistance of up to 1500 ohms in some cases, 900 ohms in others. The loss plan of thks is proposed.

Economic wideband, linear fiber optic transmitters and receivers pave the way for broadband to the home. The diamond network architecture (DNA) delivers 1 GHz bandwidth. This provides standard video, HDTV, and switched two-way broadband digital services to the home. An economic model is presented using the DNA that considers the impact of digital TV, HDTV, and the evolution of switched voice and data services on a CATV system.

Regulatory restrictions effectively limit Telco participation in CATV to transport service. The use of fiber optics for CATV transport is now economically viable. Having a large embedded fiber network and extensive experience, NYNEX investigated the opportunity of providing a CATV transport service. While pursuing the development of a tariffed service based on AM transmission we encountered technical and operational obstacles as well as a reluctance by the CATV industry to use Telco transport.

The Telesector Resources Group is currently in the process of detailing the life cycle cost benefits of deploying fiber based distribution systems over copper based systems. Although many of the benefits would appear to be easily identifiable most are not as obviously quantifiable at this point in time as one might expect. Hopefully, this paper provides some insight into some of the difficulties of providing full and complete life cycle cost analyses.

Subcarrier multiplexing using low loss and wide band analog fiber optic links for mobile communication systems is a useful approach to simplifying base stations and the small zone approach. A system design based on the relationships among the noise and nonlinear distortion generated by an optical fiber system, the input dynamic range, and the C/I characteristic is discussed.

A new multiplexing and transmission method for optical video signals using appropriate combinations of bidirectional amplifiers, medium-density WDM and space switching techniques has been proposed. The optical selector composed of a WDM filter and switch on one chip silica based waveguide, that is able to receive both AM-FDM and FM-FDM signals, is compact and cost-effective.

Future networks are expected to handle a wide variety of traffic categories including voice, low-speed data, high-speed data, band-compressed video for teleconference, and full-motion video for video signal transmission. It is hoped that ATM technology can provide integrally wide varieties of network services including LAN. The prototype design of our ATM switching system using the Banyan network with input buffers has been completed and some evaluation of the system has been performed. Furthermore, the characteristics of the Banyan network with a sorting network and a large ATM switching system has been simulated to implement a cross-connect system. The performance of the ATM switching system was estimated by computer simulations.

Advances in data communications infrastructure, display technology, and man-machine interfaces have changed business applications and the requirements of public network data transport. These changes have created opportunities for a new generation of public broadband services to more efficiently extend high speed communications capabilities beyond the customer premises. This paper provides a view of the technology and market evolution of these public broadband data communications services, and suggests early customer networked applications that justify the deployment of a public switched broadband network infrastructure.

The recent push to provide fiber in the local loop has spawned several innovative system architectures and a need for components with which to build these systems. This paper describes the development of a noninvasive coupler for use in a single-mode fiber bus application. Performance requirements, practical aspects of coupling to a bent fiber, and the relationship between reading from and writing to single-mode fiber are discussed. Practical limitations imposed by the electro-optic components and the fiber are reviewed.

As fiber is becoming more prevalent in subscriber loop applications, telephony passive optical networks (TPON) and broadband passive optical networks (BPON) have been proposed using 1 X N trees. In the past, these 1 X N trees have been formed using standard 1 X 2 couplers that are spliced together. The resulting tree had fairly high excess loss due to the splicing together of couplers, a large package size (typically 152 mm X 108 mm X 12.7 mm), and a higher probability of failure, with N-1 possible failure points for each 1 X N tree. Aster has produced a single fused, UnitaryTM fiber optic coupler that exhibits a typical excess loss of less than 0.3 dB, a dramatic decrease in size (69 mm X 3 mm cylindrical tube), and improved reliability, with only one possible failure point per tree. The UnitaryTM coupler is available in any configuration, from 1 X 3 to 1 X 7. We report on the optical performance of these devices, typical excess losses, maximum insertion losses, typical uniformities and discuss their manufacturability. Preliminary results of environmental testing are discussed.

A high performance HDWDM multiplexer capable of combining 32 channels spaced 1 nm apart onto a monomode fiber is reported. A microlens array is utilized to give a channel bandwidth of 0.7 nm. The wavelength range is 1.5285 micrometers to 1.5595 micrometers , within the erbium fiber amplification range. The mean insertion loss over 32 channels is 6.7 dB, and the polarization sensitivity is less than 0.7 dB. A design for a more compact and lower loss device is also presented.

Passive optical networks (PON) potentially may require optical splitting ratios ranging from 1x2 to 1x32, the maximum spilt recommended by Beilcore SR 1681. In anticipation of this, Corning has developed a monoilthic 1x16 single-mode splitter that offers significant performance advantages for PON using the same integrated-optics in glass technology that currently produces 1x2, 1x4 and 1x8 devices. This paper will review the performance characteristics of lxN planar spiltters, including the new Ix 16. Additionally, preliminary results will be shown for developmental 2xN devices.