Abstract: The present invention provides a method for determining a condition of aging for an optical waveguide grating. In this method, the aged deterioration curve of the optical waveguide grating is set as a form of C·t−&agr;, where t represents time, and &agr; and C represent parameters. Then, the condition of the aging is determined based on the aged deterioration curve.

Abstract: A semiconductor laser module has a semiconductor light-emitting device and an optical fiber provided with a diffraction grating. The diffraction grating is a chirped grating having a refractive index with a period continuously changing along the optical axis direction (light-guiding direction) of optical fiber, whereas the amplitude of refractive index of the chirped grating changes so as to draw an envelope (apodization curve) along the light-guiding direction. The period of refractive index of chirped grating becomes the shortest on the side closer to the semiconductor light-emitting device and successively expands along the propagating direction of laser light (light-guiding direction). Consequently, the reflection spectrum characteristic of diffraction grating mildly changes with a single peak in a region having a width not narrower than the half width of reflection spectrum, whereby a plurality of peaks are restrained from occurring in the reflection spectrum characteristic.

Abstract: The present invention relates to an optical filter having a long-period grating which couples, in signal light propagating through a core region, core mode light having a predetermined wavelength to cladding mode light, thereby attenuating the core mode light; and a method of making the same. In particular, in the filter area provided with the long-period grating, the intervals of individual parts exhibiting its average refractive index is constant along the advancing direction of the signal light, whereas values of maximum points and minimum points of a refractive index modulation function defining the refractive index vary along the advancing direction of the signal light.

Abstract: The present invention relates to an optical I/O module and light-reflecting device comprising a structure excellent in expandability having a high degree of freedom in designing. The optical I/O module according to the present invention comprises a directional coupler having, at least, input and output ports for constituting a part of a transmission line and an intermediate port for constituting a branch; and a light-reflecting device, optically connected to the intermediate port, for transmitting therethrough a specific wavelength. This structure can realize various configurations which allow a specific wavelength to be dropped from the transmission line and to be added to the transmission line, without influencing the configuration of the transmission line.

Abstract: The wavelength-variable light source comprises a semiconductor light-emitting device 11; a first light waveguide 31 optically coupled to the semiconductor light-emitting device; a plurality of second light waveguides 32, disposed in parallel to each other, in which light-waveguide-type diffraction gratings 21 having wavelengths different from each other are respectively disposed; a first optical switch 12 formed such that the first light waveguide can oppose the second light waveguides; and a condenser 13 which collects output optical powers from a plurality of second light waveguides into one beam. The semiconductor light-emitting device 11, first light waveguide 31, second light waveguides 32, and light-waveguide-type diffraction gratings 21 form a resonator 40, which oscillates light having a wavelength reflected by the light-waveguide-type diffraction gratings 21.

Abstract: A diffraction grating portion (12) is formed in an optical fiber (10), having a diameter of 125 .mu.m and serving to transmit light, along its optical axis. The optical fiber is concentrically surrounded by a lower coating portion (14) having an outer diameter of 300 .mu.m and consisting of a silicone resin. The lower coating portion is concentrically surrounded by a coating portion (16) having an outer diameter of 900 .mu.m and consisting of a liquid crystal polymer, e.g., polyester amide. The coating portion is further surrounded by an outermost coating portion (18) having an outer diameter of 1 mm and consisting of a UV curing resin colored for identification. Both the optical fiber (10) and the lower coating portion (14) have positive thermal expansion coefficients. In contrast to this, the coating portion (16) consisting of the liquid crystal polymer has a negative thermal expansion coefficient.

Abstract: A semiconductor laser module in which: the distance between a semiconductor laser chip and a diffraction grating can be shortened; the light output spectrum is stabilized; and the output characteristic does not fluctuate due to the external condition. In the semiconductor laser module, a diffraction grating structure is constituted in an optical fiber by at least two diffraction gratings for reflecting light with different wavelengths respectively. The diffraction grating structure is formed in a place corresponding to the inside of the package or the inside of the coupling means.

Abstract: An array type light emitting element module having a plurality of light emitting elements, a plurality of optical fibers (2) being placed in a one-to-one correspondence with the light emitting elements (1) so as to receive light emitted therefrom on one end face, and diffraction gratings (2a) each having a specific diffraction wavelength which are formed in the optical fibers near the incident ends of the optical fibers (2).

Abstract: This invention provides an optical waveguide having diffraction gratings with sufficiently high reflectivity, a waveguide member for obtaining the optical waveguide, and a production process thereof. An optical waveguide in which desired diffraction gratings are formed in a core and in a cladding at a predetermined portion by using a waveguide member in which germanium dioxide is added in the core and in the cladding and irradiating the predetermined portion of the waveguide member with interference fringes of ultraviolet light. By this, the optical waveguide according to the present invention reflects guided light throughout the entire mode field region, thus having a high reflectivity.

Abstract: The pulse laser light source apparatus in the OTDR apparatus of present invention comprises an optical waveguide which receives and guides the light emitted from the first light-emitting end face, wherein the optical waveguide comprises a reflecting area which selectively reflects a part of light emitted from a light-emitting end face of a semiconductor light-emitting device, a core of the reflecting area comprises a first diffraction grating which is disposed in a first area and whose refractive index periodically changes along an optical-axis direction, the first diffraction grating selectively reflects, of the light emitted from the light-emitting end face of the semiconductor light-emitting device, a part of the light within a first wavelength range. And the diffraction grating is one of denvices which constitute a laser resonator.

Abstract: This invention provides an optical waveguide having diffraction gratings with sufficiently high reflectivity, a waveguide member for obtaining the optical waveguide, and a production process thereof. An optical waveguide in which desired diffraction gratings are formed in a core and in a cladding at a predetermined portion by using a waveguide member in which germanium dioxide is added in the core and in the cladding and irradiating the predetermined portion of the waveguide member with interference fringes of ultraviolet light. By this, the optical waveguide according to the present invention reflects guided light throughout the entire mode field region, thus having a high reflectivity.