Fiber-optic local area networks (LANs) with Fiber Distributed Digital Interface (FDDI) protocol have come into use as backbones connecting other small LANs. This paper describes the current status of LANs, reviews a number of issues that stand in the way of further development and look at the future of LANs. Demands for wide-area networks (WANs) connecting LANs and multimedia LANs including voice and image capability has been extremely strong, spurring progress in geographical expansion and throughput increase, now over 100Mbit/s. The logical choice of transmission medium for next-generation systems is single-mode optical fiber, not only for backbone LANs but also, eventually, for floor LANs.

By optimizing the structure of erbium-doped fibers, high efficiency such as a gain coefficient of 6.3dB/mW, or a slope efficiency of 92.6% have been realized with very flat wavelength dependence. Though the optimized structure has high NA, the splice loss with standard fibers can be lowered by the additional arc technique. The carbon coated fiber with a fatigue parameter over 150 guarantees the reliability, even when wounded on a small coil. In-line isolators and WDM couplers have been also developed. An amplifier module has been assembled, resulting in an output power more than +16dBm owing to the high performance of each component.

This report will present an expression for the mechanical behavior of a drum-wound dual coated fiber and an analytical expression for the microbending loss in single mode dual coated fibers. These analytical expressions are then compared with experimental drumwinding microbending loss results to determine their validity.

This paper proposes a surveillance system concept, which includes the analysis of fiber fault factors and monitored items, the architecture for diagnosing fiber degradation and the system configuration. Fiber faults are classified into two types. One is fiber failure caused by fiber axial tensile strain and the other is fiber loss increase caused by fiber bending and the absorption of hydrogen molecules. It was found that there is an urgent need for fiber axial strain monitoring, sensitive loss monitoring operating at longer wavelengths and water sensing, in order to detect the origin and early indications of these faults before the service is affected. Moreover, an algorithm for predicting and diagnosing fiber faults based on the detected results was investigated and systematized.

We report on Brillouin optical-fiber time domain reflectometry (BOTDR) for distributed temperature or strain measurement along a single-mode optical fiber. BOTDR uses Brillouin scattering in optical fibers, whose Brillouin frequency shift increases in proportion to temperature or strain induced in the fiber. This method requires access to only one end of a fiber, as with conventional optical time domain reflectometry (OTDR) which uses Rayleigh scattering in optical fibers. In BOTDR, a coherent optical detection method is used as a backscattered light detection technique. This technique can achieve both high sensitivity and high frequency resolution and easily separate a weak Brillouin line from a strong Rayleigh scattering peak and Fresnel reflected light. Experimental results show the potential for measuring temperature and strain distribution with respective accuracies of 3 or 0.006%, and a spatial resolution of 100m in an 11.57km long fiber.

Single-mode fibers with intentionally induced periodical residual strains (IIPRS) along the fiber length are proposed for the suppression of the stimulated Brillouin scattering (SBS). A change of the residual strain along a fiber will change the Brillouin frequency shift, resulting in a broadening of the Brillouin gain profile. Such an increase of the line-width of the gain profile will cause a decrease of the gain coefficient which will raise the threshold power of the stimulated Brillouin scattering in optical fibers. Two types of the IIPRS fibers were fabricated. The residual strain of one IIPRS fiber is modified rectangularly while that of the other is changed triangularly. The measured spectra of the SBS are compared with that of a fiber with a constant strain. Using a novel mathematical model presented in this report, the possible improvements of the threshold powers for these two IIPRS fibers over the constant-strain fiber can be assessed through the SBS spectra. Finally, the achieved improvements are confirmed with the experimental results. The estimated improvement of the threshold for the IIPRS fiber with the rectangular profile is 2.9dB while the measured is 2.4dB. In case of the IIPRS fiber with a triangular profile, the improvement of the threshold is 5.4dB by estimation and is 5.1dB by experiment. While the limit of the threshold improvement for rectangular IIPRS fibers is 3dB, the threshold improvement for triangular IIPRS fibers is limited only by the allowable deviation of the tension applied during the drawing of fibers. It is estimated that a 5dB improvement is not difficult to realize.

To construct a Fiber-To-The-Home network, high count optical fiber cables are needed. The requirements for these cables are small diameter, light weight, and high capacity. We studied the cable structures for ribbon fiber, which are useful for quick splicing. We calculated the diameter of three types of cables: a slotted rod cable, a loose tube cable and a newly developed U-groove cable. When the same ribbons are cabled with the same clearance, the cross sectional area of the U-groove cablet is about 27% less than that of the other two cables. No problems with the manufactured 1500-fiber U-groove unit cable are detected by the conventional cable testing.

Recently, making good use of the advantages of optical fibers such as wide bandwidth and low loss, it has been investigated to apply optical fiber link to microcellular mobile communication systems. This system allows complex equipment to be located at microcell control station, and can simplify the equipment of microcell base stations compared with the conventional systems. In this paper, we analyze the performance of optical fiber link for microcellular mobile communication systems, taking radio link fading and optical link nonlinear distortions into consideration. From the calculated results, it is disclosed that the effect of both items does not generate the significant excess CNR degradation, and the correct CNR can be approximately calculated by using CNR of non-faded case. And it is also disclosed that the degradation of CNR due to optical link nonlinearity is slightly improved by taking adjacent channel signal fade into consideration.

Optical fiber transmission systems have advanced rapidly with the advent of highly advanced electronic and optical devices. This paper introduces several IC technologies required for ultra-high-speed optical transmission and overviews current IC technologies used for the existing and developing optical fiber trunk transmission systems. Future trends in device technologies are also discussed.

This letter proposes a non-metallic optical fiber cable which contains fiber ribbons inserted into slots, with a high impact resistant sheath which affords protection against shotgun pellets. The protective performance of the materials is investigated experimentally. Based on the results, non-metallic 100-fiber cable with a high impact resistant sheath was manufactured and its performance was evaluated. It is confirmed that this cable has excellent transmission, mechanical and antiballistic characteristics.

Optical fiber cable systems are being developed in many countries for subscriber loops as the infrastructure to realize B-ISDN (Broadband Integrated Services Digital Network). The present systems are DLC (Digital Loop Carrier) systems which provide leased lines, POTS (Plain Old Telephone Services), and N-ISDN (Narrowband ISDN) services. Before FTTH (Fiber To The Home) networks can be implemented, their construction cost must be lowered to the level of the current metallic network. The FTTH network must also be easy to operate and maintain. In this paper, we describe optical fiber cables, splicing, and testing technologies used in the NTT cable networks, and introduce the technologies being developed to construct FTTH networks.

We study the most appropriate network architecture for constructing FTTH (Fiber To The Home) networks. We conclude that the Single Star network is the most advantageous for supporting the various services required by subscribers who use broadband signal such as B-ISDN (Broadband-Integrated Services Digital Network). We also study high fiber count cable and low-loss connector which are needed for this network and clarify their requirements. We also show the cable structure, connector structure and connection loss reduction method, which satisfy these requirements. We describe a 4,000-fiber cable with a new structure, a 1,000-fiber one-touch connector, a 40-fiber unit connector and TEC-fiber (Thermally-diffused Expanded Core fiber) which reduces connection loss.

This paper describes the impact of EDFAs on AM/FM FDM subcarrier multiplexing (SCM) all-fiber video distribution (AFVD) systems. As AM/FM hybrid system using EDFAs which can simultaneously distribute 11 AM-TV channels and 50 FM-TV channels is proposed and discussed. 4-stage amplifier-branch transmission experiments are introduced. The construction and performance of a newly designed 50 channel FM tuner are also presented.