A simple length measuring method for single mode fiber coiled around a drum using Sagnac effect, is proposed. Phase difference variation caused by rotating the coil is measured, and fiber length can be derived by processing the measured results. Typically, a length measurement accuracy of 1% is obtained.

Recently, information display equipment such as a navigation system has often come to be installed in a vehicle, and a variety of useful information has been offered to the driver by voice and images while driving. The necessity of improving safety when the driver receives such information has come to be stressed. As one of the means of solving this problem, we can develop a system that presents the driving and road conditions information such as a lane changing car to the driver by using a warning sound. The purpose of our study is to clarify the effectiveness of an auditory display that uses spatial sounds on such a system. An experiment for measuring the driver's reaction time and eye movements to LED lighting during actual driving has been carried out to investigate whether the spatial sound can quicken the driver's operation and decrease human error. We evaluated the effectiveness by two measures, average reaction time and the number of largely delayed reactions. We considered that the average reaction time corresponds to the quickness of the driver's operation, and the number of largely delayed reactions corresponds to the probability of human error. As a result of the experiment, the use of directional sound clearly showed better performance than the use of monaural sound and no sound in the number of largely delayed reactions. Moreover, we analyzed the factors involved in delay of the reaction by the results of eye movement measurements. Consequently, it has been found that directional sound can decrease the number of the largely delayed reactions, which lead to an accident during actual driving.

In an optical fiber gyroscope consisting of sensing fiber coil, an optical phase modulator and an electronic switching circuit for Sagnac phase shift detection, a ratio of the second and the fourth harmonics in the detected output signal is used to control the modulation index. Experimental results show improved operation with stabilized scale factor.