Fiber-optic Subscriber Research Articles

MPO-type single-mode multi-fiber connector: Low-loss and high-return-loss intermateability of APC-MPO connectors

The electrical communication laboratory of NTT started the research of MT (Mechanically Transferable) connector in early 1980s. The initial goal was to realize a multi-fiber connector which can repeat low loss, stable, reliable and low-cost connections of subscriber optical fiber cable networks for more than 20 years period in the field. We review the multi-fiber alignment design with two guide pins, and following several technical improvements toward the final MT connector used in the commercial telecommunication networks. And then, we review development histories to reach to the low-loss, high-return-loss and reliable APC-MPO (Angled Physical Contact Multi-fiber Push On) connectors introduced in NTT COs and in Verizon’s FTTH (Fiber To The Home) networks. In the latter half, we propose the low-loss intermateability design for connectors made by different suppliers in order to enable mass introductions into large scale systems. In addition we also describe an accurate connector loss presumption method for different lots’ ferrules based on the MT ferrule dimension data before assembling the connectors. We believe with a wide intermateability of APC-MPO connector will increase its use in the fields. The APC-MPO connector manufactured based on the proposed design had low insertion losses of less than 0.25 dB at the same level of simplex connectors and the higher level of return losses higher than 65 dB.

A reconfiguration method for fiber optic subscriber loops

AbstractA fiber optic subscriber loop provides many services that require high quality for a large number of subscribers. This means that it is necessary to establish a highly reliable, economical subscriber network.A method for high‐reliability network construction has been proposed. In this method, the amount of equipment is reduced by utilizing a fiber access module (FAM), which allows fiber lines between the adjacent loops to be connected in the optical subscriber loop. to realize the function of the FAM inexpensively, manual cross‐connection is indispensable. However, the restoration time in the event of cable failure is quite long for manual crossconnection.This paper proposes a reconfiguration method, the selected node reconfiguration method (SRM), which has a shorter restoration time than the conventional method, assuming a manual cross‐connection FAM. to further shorten the restoration time, a cross‐connection method is proposed in which several fibers are switched at the same time. the efficiency of this method and the functional structure of the FAM will be shown.

Wavelength division multiplexed CATV distribution service overlay on two-fibre passive optical dialogue star networks

The 1.3 μm/1.55 μm wavelength division integration of 5.18Mbit/s dialogue services and analogue BK450MHz CATV distribution service in fibre optic subscriber access systems (fibre-in-the-loop) is considered. The mutual interference of the services is investigated. Based on a two-fibre passive optical star network the optimum concept is derived from theoretical and experimental data.

Advanced technology for fiber optic subscriber systems

Key issues in handling optical frequencies for broadband communication services and constructing optical frequency-division multiplexing (OFDM) systems are discussed. The configuration of OFDM transmission systems, their use of multichannel frequency stabilization, multiplexer/demultiplexer, tunable filters, and common amplification systems, and the effects of optical-fiber nonlinearities of OFDM systems are described. The applicability of OFDM to various kinds of telecommunication networks, such as high-capacity end-to-end transmission, information distribution, multinode networks and subscriber systems of both transfer and access networks is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Fiber optic subscriber systems

The introduction of fiber subscriber systems is assessed from the viewpoints of incentives for the network operator, merits for the users, and the expansion of the social infrastructure. The design of point-to-multipoint transmission system, which will be applied to fiber-to-the-home and fiber-to-the-floor systems, are presented. It is shown that the penetration of these systems depends on new service demand, especially for FTTH. Service development and system development are both essential. >

Subscriber optical fiber cable transfer splicing system using mechanically transferable connectors

An optical fiber cable transfer splicing system is developed for use in removing or changing optical fiber cables. The system enables rapid transfer from existing optical fiber cables to newly installed ones. The transfer is carried out synchronously using two mechanically transferable connectors which terminate the optical fiber cables at two different points, such as manholes. Before the transfer splicing, the system identifies a fiber ribbon in order to avoid mistransfer. A transfer time of less than 30 ms was achieved. The fiber ribbon was identified with a loss, from an identification light source to an identification point, of 35.5 dB. With this system, cable transfer can be faultlessly carried out with only a slight interruption to working transmission systems and circuit quality degradation is suppressed. >

Intermodulation distortion in 48 TV channel FM-FDM optical transmission

The effect of dispersive fibers on multichannel FM video transmission characteristics is experimentally investigated. A directly modulated 1.5 mu m distributed feedback laser diode (DFB-LD) and a LiNbO/sub 3/ external modulator with a continuous-wave (CW) 1.55 mu m DFB-LD are used as optical signal sources. When the 1.3 mu m single-mode fiber (SMF) is used, directly modulated DFB-LDs suffer from second-and third-order intermodulation distortion (IMD). The external modulator realizes good transmission characteristics irrespective of the fiber's dispersion value. This means that external modulators can realize multichannel FM television signal transmission systems that use the standard 1.3 mu m SMF already installed in fiber optic subscriber loops.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Passive fibre-loop architecture providing both switched and broadcast transport

We report the experimental demonstration of a new passive fibre-optic subscriber loop architecture. The architecture provides each of 16 subscribers with a dedicated, two-way broadband channel for switched services, as well as with an array of broadcast video channels. The dedicated channels are provided via 16-channel dense wavelength-division multiplexing (WDM), and the broadcast channels are transported over the same loop fibre via FM subcarrier multiplexing. A number of potential advantages of this hybrid (switched/broadcast) approach are foreseen.

Residential Fiber Optic Subscriber Loops: Information Pipeline or Technology Pipedream?

Fiber optic systems are now being considered for the "last mile" of the telecommunications network, the distribution portion of the subscriber loop. Early promoters have emphasized the enormous potential of fiber as an information pipeline. They view fiber as the key to revolutionizing the way in which we receive and interact with data in the developing information society. The investment of both technical and economic resources required to develop and deploy fiber optic systems for residential subscriber loops, however, will demand real economic returns. This will dictate new approaches to both the technology and the business strategies that strive to bring the system costs in line with the value of the information being carried. These approaches must also recognize the competitive service environment that is developing in the area of local distribution. This paper considers some of the major issues currently affecting the development of subscriber loop applications for fiber optics and their impact on technical and market requirements.

Optical Fiber Facilities for Subscriber Loops

This paper gives an overview of the introduction and subsequent development of optical fiber cable and its application to subscriber networks enabling economical broad-band services, such as video and high-speed digital data transmissions. This paper also outlines NTT's developments on subscriber optical fiber cable technology-in particular, the five-fiber ribbon cable structure, mass-fusion splicing machine, and multifiber connector-in its ongoing endeavors to establish economical and flexible subscriber optical fiber networks which provide optical fibers to each subscriber.

Optical Fiber Cable Installation Techniques

When installing junction optical fiber cable, which essentially must be longer than conventional metallic-conductor cable to effectively reduce splice loss, the applied tensile load must be within tolerable limits to prevent an increase in loss and a decrease in lifetime. It has recently become possible to meet this requirement through the development of a new cable installation system which makes use of a modified cable pulling truck and a new intermediate cable pulling machine. Furthermore, this new installation system, capable of achieving a 1.0-1.5 km installation length for all types of cable accommodations, has already been put into practice. In addition, this paper presents three new cable installation techniques for facilitating subscriber optical fiber cable installations under various environmental conditions: a tension-controlled pulling technique, a cable pulling eye attachment technique, and a cost-effective damage-free cable installation technique in older buildings.

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.

Determination of installation cable size and the ratio of common fibers to total fibers in subscriber optical fiber cable network

AbstractTo construct an efficient subscriber optical fiber cable network, a highly economical and versatile distribution method is needed. This paper clarifies a technique in which by determining the installation cable size of feeder system and the ratio of common fibers to total fibers, a balance between the service requirement and cost is obtained.First, gamma distribution, practically used for metal cables, is applied to the demand forecast error distribution and the relation between the number of fibers and the ratio of common fibers to total fibers, which is required to obtain the desired equipment reliability, is clarified. Next, the relation between the cross‐connecting probability is determined and utilizing the ratio of common fibers, the cost function of optical cable system is derived. Here, both the cable installation cost and cross‐connection cost are considered. These two factors are combined and a design method of installation cable size and the ratio of common fibers to total fibers is clarified. This method ensures the desired equipment reliability and is the most economical one. Using this method and assuming all the various costs, it is clarified that for high cross‐connection cost, a cable having a large number of fibers should be installed and the cable network construction having comparatively low ratio of common fibers to total fibers is desirable. When the cross‐connection cost is less, the installation cable having a smaller number of fibers and a higher ratio of common fibers to total fibers is desirable. Moreover, with these results in mind, an economical subscriber optical fiber cable network construction is proposed.

Design of plant expansion in subscriber optical fiber cable network

AbstractThis paper considers the low‐cost trends of optical fiber cables and the measures for coping with the widely scattered demands thatare regarded as special features in the initial stage of the formation of a subscriber optical fiber cable network. A method for economical construction of an optical cable network is discussed. First, the low‐cost trends of the optical fiber cables are dynamically grasped and a method is clarified for designing installation intervals and the sizes of the cables which will make the present annual expense worth a minimum by using dynamic programming. Next, for cable construction systems connecting the local office and the plural distribution areas, three systems, the fiber‐reduction system, fiber‐nonreduction system, and independent cable system, are considered and the applicable domains of these systems are clarified from the economical viewpoint with the installation cable size and distribution area as parameters. Moreover, a method is obtained for simultaneous design of the cable construction system which will minimize the total cost, and the distribution area size is shown for a given installation cable size. It is clarified from these results that it is more economical to use a shorter installation interval in the initial stage of the formation of the subscriber optical cable network than the present subscriber cable network using the symmetrical pair cables. Also, it is desirable to set a wide distribution area consolidating two to four present fixed distribution areas.

A Field Trial of Fiber Optic Subscriber Loop Systems Utilizing Wavelength-Division Multiplexers

Future subscriber loops will provide various services including broad-band video. Fiber optic technology is the key for introducing these services. The Electrical Communication Laboratories (ECL) of Nippon Telegraph and Telephone Public Corporation (NTT) have been promoting research and development on basic technology of fiber optic subscriber loops, and studying the ways to use fiber optic subscriber loops for new services. As one of the programs, a field trial of fiber optic subscriber loops was planned and conducted in the Yokosuka area from April 1980 until May 1981. This paper first describes fiber optic transmission technologies for subscriber loops. Then, the system configuration and experimental results of the Yokosuka field trial are presented.