Shuichi Ohara

Low excess losses in a Y-branching plastic optical waveguide formed through injection molding

We have demonstrated low excess losses (1.9 dB at 660-nm wavelength) in a Y-branching plastic optical waveguide (POWG) that was fabricated using an injection-molding method. The waveguide had an amorphous vinyl polymer as the core and transparent polyolefin as the cladding. We then studied a method for isolating the excess loss in the Y-branching POWG, and with that method we estimated the lower limit of the loss to be 1.41 dB at 660 nm. The sample had a heat-resistant plastic optical fiber (POF) with a core composed of crosslinked poly (methyl methacrylate) (PMMA) copolymer, and a cladding composed of poly (tetrafluoroethylene-co-hexafluoropropylene). The POWG has sufficient reliability for ordinary uses below 100 °C. A model for a bidirectional wavelength-division multiplexing opticalcommunication system with the developed Y-branching POWG and the POF was also demonstrated.

A humidity sensor using ionic copolymer and its application to a humidity-temperature sensor module

Abstract A humidity-temperature sensor module with a frequency output signal was fabricated by integrating a humidity sensor, temperature sensor and measuring circuit on a ceramic substrate. The humidity sensor had a copolymer of ionic and non-ionic monomers as its humidity-sensitive material, and a chip thermistor served as the temperature sensor. The measuring circuit was an astable multivibrator, and the humidity and temperature sensors were used as circuit elements to determine the oscillation frequency. Operation of the humidity-sensing circuit was evaluated on the basis of an analysis of the frequency dependence of the humidity sensor impedance. In the derivation of the humidity-oscillation frequency characteristics from the impedance data, a model that expresses the humidity sensor impedance by the bulk resistance of the humidity-sensitive material gave relatively good agreement with expe The fabricated module offers superior long-term stability. Changes in humidity-oscillation frequency and temperature-oscillation frequency characteristics were less than ±3% r.h. and ±0.1 °C, respectively, after more than two years in an open laboratory atmosphere.