Abstract: The present invention relates to an interleaver and others with a transmission spectrum excellent in isolation between signal channels and flat near each channel wavelength. The interleaver is provided with an input port for receiving a signal of multiple channels, and first and second output ports for outputting signals of first and second channel groups, respectively, separated from the signal of multiple channels. Each of transmission spectra of output light from the first output port and output light from the second output port has such flatness that a difference between a maximum transmittance and a minimum transmittance in a wavelength range of ±0.06 nm centered about each signal channel wavelength falls within 0.4 dB, preferably within 0.2 dB, and crosstalk between adjacent signal channels is controlled to −20 dB or less, preferably to −30 dB or less.

Abstract: In this diffraction grating device manufacturing method, refractive-index-change-inducing light of a wavelength that induces a change in refractive index is irradiated onto an optical waveguide, thus forming a diffraction grating through refractive index modulation along the longitudinal direction of the optical waveguide. At this time, the position of irradiation of the refractive-index-change-inducing light onto the optical waveguide is swung in a direction perpendicular to the longitudinal direction of the optical waveguide.

Abstract: An optical communication system comprises an optical circulator and an optical component. The optical circulator has first, second, and third ends, outputs from the second end light fed into the first end, and outputs from the third end light fed into the second end. The optical component includes an optical waveguide type diffraction grating device connected to the second end of the optical circulator and provided with a plurality of refractive index modulation forming areas, disposed along the longitudinal direction of an optical fiber, for Bragg-reflecting a predetermined wavelength of guided wave. A predetermined region including the boundary position between two refractive index modulation forming areas adjacent each other in the optical waveguide type diffraction grating device is heated by a thin film heater, so as to adjust the optical path length thereof.

Abstract: In a diffraction grating device (1), index modulations are formed along the longitudinal direction of an optical fiber (10) serving as an optical waveguide. The optical fiber (10) has a core region (11), an inner cladding region (12), and an outer cladding region (13) sequentially from the optical axis center. Index modulations are formed in both the core region (11) and the inner cladding region (12) of the optical fiber (10) in each of a plurality of regions A1 to AN (N is an integer; N≧2) separated from each other along the longitudinal direction of the optical fiber (10). In the diffraction grating device (1), regions An (n=1 to N) in which index modulations are formed in both the core region (11) and the inner cladding region (12) and regions Bn (n=1 to N−1) in which no index modulations are formed alternately exist along the longitudinal direction.

Abstract: This invention relates to a diffraction grating device having a refractive index modulation formed in an optical waveguide region in a predetermined region in the longitudinal direction of the optical waveguide. In the diffraction grating device, a refractive index modulation is formed in the core region in a predetermined region in the longitudinal direction of the optical waveguide. In this diffraction grating device, the optical period of the refractive index modulation is substantially constant, the phase of the refractive index modulation is inverted at a phase inversion portion, and the number of phase inversion portions is one or two. In this diffraction grating device, the absolute value of a parameter R (equation (22a)) is smaller than 0.25. According to this invention, a diffraction grating device capable of shortening the region where the refractive index modulation is formed and flattening the reflectance characteristic in the reflection wavelength band is provided.

Abstract: Raman amplification pumping light output from a pumping light source unit is supplied to a Raman amplification optical fiber through an optical circulator. The remaining Raman amplification pumping light is detected by a light-receiving element through an optical circulator and bandpass filter. Signal light that has reached a Raman amplifier propagates through the Raman amplification optical fiber while being Raman-amplified. A control section controls the power or spectral shape of Raman amplification pumping light output from each of N pumping light sources included in the pumping light source unit on the basis of the power of the remaining Raman amplification pumping light, which is detected by the light-receiving element. Hence, a Raman amplifier capable of easily controlling gain spectrum flattening in the signal light wavelength band can be obtained.

Abstract: This invention relates to a diffraction grating device having a refractive index modulation formed in an optical waveguide region in a predetermined region in the longitudinal direction of the optical waveguide. In the diffraction grating device, a refractive index modulation is formed in the core region in a predetermined region in the longitudinal direction of the optical waveguide. In this diffraction grating device, the optical period of the refractive index modulation is substantially constant, the phase of the refractive index modulation is inverted at a phase inversion portion, and the number of phase inversion portions is one or two. In this diffraction grating device, the absolute value of a parameter R (equation (22a)) is smaller than 0.25. According to this invention, a diffraction grating device capable of shortening the region where the refractive index modulation is formed and flattening the reflectance characteristic in the reflection wavelength band is provided.