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To realize low-loss low-crosstalk long- length polarization-maintaining fibers, this paper examines the "PANDA fibers" having a circular stress-applying part which has a high design accuracy and ease of fabrication. Stress-applied type polarization-maintaining optical fibers generally have two orthogonal polarized modes, and their coupling causes crosstalk which makes the transmission of polarized mode through a long-length of fibers difficult. To suppress this modes coupling, it is important (a) to make the modal birefringence larger, and (b) to reduce the deterioration of the symmetry of the stress applied. This paper examines the circular stress-applying type PANDA fiber and compares it with two other types of PANDA fiber having the typical shapes of the stress-applying part. As a result, (1) the structure parameters of the stress-applying part which gives the maximum modal birefringence and a low loss, and (2) the mode-coupling parameter, with the stress-applying part deviated, which can evaluate the cross- talk characteristics, have been obtained. Based on the results of these theoretical analyses, the symmetry in the stress-applying part is improved by using a large pre- form, and the increase of the modal birefringence by increasing the outer diameter of the fiber is carried out. The circular stress-applying type PANDA fiber having a crosstalk as low as -42 dB in 1 km has been realized. [ABSTRACT FROM AUTHOR]

An all-fiber optical Kerr shutter consisting of a short single-mode fiber and a highly birefringent fiber which serves not only as a polarizer but also as a wavelength filter to reject pump light is successfully realized. By utilizing the Kerr shutter, optical sampling is demonstrated. Time-varying signal light from a laser diode at λ=0.84 μm is sampled into a train of pulses through the Kerr shutter which is driven by an intense light pulse at λ=1.064 μm. The applications to high-speed signal processing and the generation of picosecond optical pulse are promising because of the fiber’s fast response of optical Kerr effect. [ABSTRACT FROM AUTHOR]