Abstract: A no polarization dependent waveguide type optical circuit can resolve polarization dependency completely and can reduce reflected return light. An intermediate portion of the two connecting waveguide are formed with S-shaped waveguides of the same shape consisted of respectively two curved waveguides or two curved waveguides and straight waveguides connecting the curved waveguides. One polarization mode converter is provided in a groove formed across the S-shaped waveguide, and a perpendicular line to an incident surface of light of the polarization mode converter and the S-shaped waveguide forms an angle greater than 0°.

Abstract: A guided-wave circuit module includes a guided-wave circuit chip having an input waveguide part and an output waveguide part at the ends thereof, a guided-wave circuit part having a predetermined function and positioned between the input waveguide part and the output waveguide part; and a holder for supporting the guided-wave circuit chip, wherein the guided-wave circuit part of the guided-wave circuit chip does not come in contact with the chip holder; at least part of the input and output waveguide parts of the guided-wave circuit chip is fixed to the holder with a fixing agent; and the packaged chip does not have a warp which leads to deterioration of characteristics. A fixing agent having a high hardness is applied to the periphery of the endfaces of the input and output waveguide parts of the guided-wave circuit module and to the periphery of the fiber endfaces of the optical fiber array connected to the module.

Abstract: A waveguide-type optical matrix switch including as its switching element a Mach-Zehnder interferometer which includes two directional couplers and an optical phase shifter. The two directional couplers are arranged by placing two optical waveguides in close proximity at two positions on a substrate, and have an identical coupling ratio. The optical phase shifter is disposed over at least one of the two optical waveguides between the directional couplers. The two optical waveguides have an effective optical path length difference of half a wavelength of a light signal between the two directional couplers, and are intersected in the optical switch element. The waveguide-type optical matrix switch is little affected by fabrication errors in the coupling ratio of the directional couplers, and superior in the extinction ratio.

Abstract: A method for adjusting a characteristic of a guided-wave optical circuit which includes one or more waveguides formed by a substrate, a cladding layer formed on the substrate, and a core portion having one or more cores embedded in the cladding layer. The method is carried out by producing a reversible thermal hysteresis phenomenon, after the clading layer and core portion have been formed. The thermal hysteresis phenomenon is produced in a thermal hysteresis produced region preselected so as to include at least a portion of the cladding layer and/or the core portion, thereby adjusting a refractive index difference between the cladding layer and the core portion.