Masatoshi Shimizu

Frame-Loss-Free Optical Line Switching System for In-Service Optical Network

Fiber-to-the-home (FTTH) has now reached the stage where it is providing real-time broadband services. Since even a temporary suspension of broadcasting and telephone services cannot be permitted, it has become important to improve the reliability of FTTH network operation. We have developed an advanced optical line switching system that diverts transmission signals from an in-service line to a spare line without interrupting communication. This system is realized by equalizing the transmission times of the signals sent through dualized lines composed of an in-service line and a spare line. The transmission times are equalized by employing two techniques in the dualized lines. One is a technique that uses a free space optics system to tune the optical line length continuously. The other is a technique for measuring a wide range of time differences between signals transmitted through the dualized lines. Since the dualized lines have a Mach-Zehnder interference structure, the differences can be detected with high accuracy by employing dual-light interferometry. We applied this switching system to a gigabit Ethernet passive optical network (GE-PON) during transmission and succeeded in switching in-service lines without inducing any frame loss.

Identification system for optical fiber transmission operation lines with local-light injection and detection coupling system

An identification system using a local-light injection and detection coupling system is developed. The relation of bending fiber radius to both local-light injection and detection coupling efficiencies is shown. This system can be used for distances of up to 21 km at a bending radius R=7 mm. Also, the line number in the fiber ribbon, can be confirmed and transfer splicing loss can be estimated using this identification system. >

A new high-density fiber organizer for optical-fiber cable joints

A new slack fiber organizer structure composed of individual box-shaped plastic sheets is presented. It is capable of accommodating 800 fiber splices with the same size as the existing metallic cable joints. The conditions to accommodate reinforced mass-splices and slack fibers into the organizer are clarified by considering optical loss increase and reliability evaluation for bent fiber ribbons, and also a computer-aided dimension simulation. The new organizer with 800 fiber splices experimentally exhibits good transmission characteristics with an average slack fiber accommodation loss of 0.04 dB and a good workability of 1.2 min/ribbon.

Optical fiber switching system in optical cable network operation

This paper describes the basic concept of a future optical cable network operation system for optical subscriber loops. The problem of existing subscriber networks and the functions required of the integrated operation systems are clarified. In addition, for the optical fiber switching system in the integrated operation system, the system configuration and experimental studies are presented on switching functions. As the results, good performance has been confirmed for the development system.

Design and performance of optical transfer splicing system using multifiber connectors

The transfer splicing of optical fiber cables is performed at night using released circuits; this involves time-consuming manual work. To achieve highly efficient optical cable transfer splicings, development of low-loss transfer components is expected to speed up transfer operations. This in turn reduces interruption time and identification of cable fibers and also controls synchronization of each function and details required. This paper proposes an efficient system for the optical transfer splicing of the existing cables to the new ones. This system uses single-mode multifiber connectors. The design method and related details of rapid transfer, fiber identification and synchronous transfer control are described. The transfer splicing characteristics of this newer, more efficient system are evaluated and it is verified experimentally that satisfactory results are possible.

Optical fiber local‐light injection and detection coupling system for identification of fiber transmission operation lines

The development of optical fiber cable transfer splicing systems is being advanced to increase the speed of connection of in-use circuits to new ones, an operation that has been necessary in cable joints, branches, etc. In the construction of these systems, the conservation of the action-objectives of the in-use fiber between two different points must be confirmed and, therefore, the fiber identification techniques play the most important role. In this paper, considering the identification of in-use fibers, the conditions of bent fiber light injection and detection and their coupling systems are discussed. As to the bent fiber light injection, the relations among the ray angle of incidence which results in the injected optical signal to propagate as a core mode, the bending radius, the thickness deviations of the UV coat and the refractive index of the matching material are investigated. The bent-injection coupling efficiency in relation to the axial displacement between the identifying fiber and the injected one also is investigated. It is found that large coupling efficiencies can be achieved if the incident light beam spot-size is reduced and the light-source wavelength is increased. As to the condition of the bent fiber light detection system, the detection efficiency in regard to the source wavelength when the detected optical signal inside the core corresponds to the injected light is discussed. It is shown that large detection efficiency can be achieved if the optical source-wavelength is increased and the bending radius is kept below 6 mm.

Study of rotary mechanical optical fiber switch

A novel mechanical optical fiber switch by rotation has been proposed; the dynamic and switching characteristics have been studied. The structure, operational principle and analysis of the mechanical property, e.g., switching torque, have been evaluated. To characterize dynamic motion, the rotational transfer response time of switching and the transfer function were investigated. It was theoretically and experimentally confirmed that the optical switch has an internal feedback mechanism. The connection loss between multimode fibers caused by deviations of the rods, balls, and optical fibers has also been theoretically and experimentally investigated. In the test optical switch, the switching connection loss was 0.68 dB and the rotational transfer response time in 1 × 6 switching was 134 ms. These experimental results agree with the theoretical results.