We developed a compact, 16-channel integrated optical subscriber module for one-fiber bi-directional optical access systems. They can support more subscribers in a limited mounting space. For ultimate compactness, we created 8-channel integrated super-compact optical modules, 4-channel integrated limiting amplifiers, and 4-channel integrated LD drivers for Fast Ethernet. We introduce a new simulation method to analyze the electrical crosstalk that degrades sensitivity of the optical module. A new IC architecture is applied to reduce electrical crosstalk. We manufactured the optical subscriber module with these optical modules and ICs. Experiments confirm that the module offers a sensitivity of -27.3 dBm under 16-channel 125 Mbit/s simultaneous operation.

Optical connectors for printed circuit board interfaces are required for the implementation of high-density multi-fiber connection. We have developed a fiber physical contact (FPC) connector to meet this requirement. The FPC connector has to ensure reliability when bare fibers are used. Moreover, the FPC connector must employ an established coupling mechanism and provide higher density connection. To meet these requirements, we developed a 16-fiber FPC connector that utilizes the MU connector coupling mechanism and a shutter. We connect the 16 fibers in the housing of the duplex MU connector. We developed compact shutters that open only when they come into contact with each other. Moreover, the developed FPC connector enables us to clamp the fibers to a plug without adhesive. This structure can greatly boost the production yield. We confirmed that the developed FPC connector has an easy connection operation and good optical performance, and we verified that the shutters open properly.

We propose and demonstrate a new type of field installable optical connector that enables us to realize physical contact connection without polishing the fiber endface by using a sharpened fiber endface and the compression force of buckled fiber. We confirmed that all the assembled connectors achieved physical contact connection without the fiber endface being polished, and provided good optical performance with a low insertion loss of 0.08 dB and a high return loss of over 49 dB.

We have developed a fiber physical contact (FPC) connector for the high-density connection of optical fibers. This connector individually aligns multiple bare fibers in micro-holes without ferrules and realizes physical contact by using the buckling force of the fibers themselves. The fiber endfaces must be tapered to allow the fibers to be inserted into the micro-holes. The endfaces must also be polished so that they realize physical contact (PC) with excellent optical performance. For each process, we examined the required shape and processing condition of the fiber endface for the FPC connector. As regards tapering, we determined the processing condition for achieving a target tapering angle and developed a non-breaking process with the optical fibers bent. In terms of polishing, we revealed that it is important for the fiber endface angle error to be less than 0.7 degrees if we are to achieve excellent optical performance. These results allowed us to fabricate an FPC connector that exhibited excellent levels of optical performance.

We describe a physical-contact (PC) multicore fiber (MCF) connector with good optical characteristics. To achieve stable physical-contact connection, we clarify the relationship between connector-end deformation and compression force with spherical polished ferrule end structures using finite element analysis and actual measurements. On the basis of the obtained relationship, we demonstrate a design approach that shows the physical-contact condition of all the cores of a multicore fiber with a simplex connector. In addition, we clarify the design criteria for low-loss connection by employing a rotational angle alignment structure, and devise an SC-type rotational MCF connector with high alignment accuracy. Based on our designs for PC and low-loss connection, we demonstrate an MCF connector with PC connection that provides a sufficiently high return loss exceeding 50dB and a sufficiently low connection loss of below 0.2dB for all the cores of a 7-core single-mode MCF.

We have developed a novel method of numerical synthesis of optical waveguides, which consists of the endless loop of the random sampling of waveguide parameters, numerical analysis and the judgment of calculated result. This loop is repeated until some objective solutions satisfying required characteristics are discovered. When the structural condition is almost unknown and there is no clue to search it, this method is useful for discovering new-type waveguides, and this concept is applicable to any other devices. We applied this method to the search of new waveguide structures having multilayer claddings, and obtained many types of low loss single mode waveguides, including ARROW-type waveguides, waveguide-type polarizers and a very narrow band wavelength filter.