Nobuo Tomita

Maintenance method using 1650-nm wavelength band for optical fiber cable networks

This paper proposes a maintenance method for optical fiber cable networks that uses 1650-nm wavelength band light. We determined the maintenance wavelength of 1650-nm after considering the maintenance system requirements and the future trends in optical transmission systems. We improved the conventional maintenance system by adding appropriate system components including a narrow wavelength light source and a fiber-grating filter for the 1650-nm wavelength band. We designed the system and undertook manufacturing trials. The characteristics of our proposed maintenance method indicate good practical performance levels.

Design and Performance of Novel Optical Fiber Distribution and Management System With Testing Functions in Central Office

This paper describes the design and performance of a novel central office optical fiber distribution and management system for optical access networks. We clarify the requirements for an optical fiber distribution and management system with a testing function. We propose integrated distribution modules (IDMs) and high-count indoor cables for high-capacity cable termination and cross connection, a management system using identification tags for easy administration and reference with respect to the distribution facilities, and a new optical fiber line testing system using an optical testing module with a 1650 nm optical time-domain reflectometer for in-service testing. We evaluated the prototype system. The prototype IDM could accommodate 4000 fibers and the insertion loss of the communication lines and the system dynamic range of testing system met our requirements for use in an optical access network including a 7 km outside cable and an eight-branch optical splitter. We compared the cost and testing time required for the conventional and proposed systems. We found that the proposed distribution system can reduce the distribution cost by 40% and connection work time by 12% compared with the conventional system. We also found that the testing system can reduce the system cost by 63% compared with the conventional testing system and required testing time is 73% less than testing time by hand, thus reducing the operations, administration, and maintenance costs.

Optical Fiber Line Testing System Employing 1.65μm Test Light Bypass Module for In-Service Monitoring of ADM Ring Networks

This paper describes a novel optical fiber line testing system operating at 1.65μm using test light bypass modules. We show a new testing configuration for add/drop multiplexer (ADM) ring networks. The test light bypass modules were installed in individual customer buildings so the test light can bypass the ADMs. We evaluated the bit-error performance with a 2.48832Gbit/s ADM ring network using a prototype test light bypass module. We confirmed that this testing system can monitor the optical fiber cables of an ADM ring network, and that it causes no degradation in transmission quality. We show the operating area provided by the system dynamic range expressed in terms of fiber length and customer building number. The prototype system could monitor an ADM ring network linking five buildings with a 5km loop. We also performed an in-service monitoring field trial in a 2.6km ring network with three ADM nodes. This testing system enables us to reduce the operating, administration, and maintenance cost and improves the transmission quality of ADM ring networks.

Accurate Sensing of Optical Connector Loss using OTDR and Neural Networks

This paper proposes a novel method for sensing optical connector losses with superimposed Fresnel relfections using OTDR and neural networks which reduces the sensing distance between connectors to one fourth that of the conventional method.