Abstract: An objective of the present invention is to provide an optical fiber sensor which has a simple configuration to enable sensitively measuring a refractive index of a measurement medium in a wide range of refractive indexes. An optical fiber sensor according to the present invention includes; an optical fiber having a core in which a short-period gratings are formed and a cladding, the optical fiber being made so that transmission loss occurs due to cladding-propagation-mode leakage at its cladding portion where the short-period gratings are formed; a light source from which light having a wavelength range of the cladding propagation mode is emitted; and a light receiving unit for receiving transmission or reflection light having passed through the cladding at the position where the short-period gratings are formed.

Abstract: An optical fiber sensor measuring refractive index of a medium with high sensitivity in a wide range. The optical fiber sensor includes an optical fiber causing a transmission loss due to leakage in the clad propagation mode from a portion of a core and a clad where a Bragg grating is provided, a light source permitting light in a wavelength band in the clad propagation mode to enter the optical fiber, and a light-receiving section receiving the transmitted or reflected light transmitted through the core and the clad at the portion where the Bragg grating is provided. The refractive index of the medium to be measured in contact with the clad is measured according to total intensity of the light received by the light-receiving section. The Bragg grating is inclined at a predetermined angle of inclination to the vertical line vertical to the length direction of the optical fiber.

Abstract: An objective of the present invention is to provide an optical fiber sensor which has a simple configuration to enable sensitively measuring a refractive index of a measurement medium in a wide range of refractive indexes. An optical fiber sensor according to the present invention includes; an optical fiber having a core in which a short-period gratings are formed and a cladding, the optical fiber being made so that transmission loss occurs due to cladding-propagation-mode leakage at its cladding portion where the short-period gratings are formed; a light source from which light having a wavelength range of the cladding propagation mode is emitted; and a light receiving unit for receiving transmission or reflection light having passed through the cladding at the position where the short-period gratings are formed.

Abstract: An optical fiber sensor measuring refractive index of a medium with high sensitivity in a wide range. The optical fiber sensor includes an optical fiber causing a transmission loss due to leakage in the clad propagation mode from a portion of a core and a clad where a Bragg grating is provided, a light source permitting light in a wavelength band in the clad propagation mode to enter the optical fiber, and a light-receiving section receiving the transmitted or reflected light transmitted through the core and the clad at the portion where the Bragg grating is provided. The refractive index of the medium to be measured in contact with the clad is measured according to total intensity of the light received by the light-receiving section. The Bragg grating is inclined at a predetermined angle of inclination to the vertical line vertical to the length direction of the optical fiber.

Abstract: An optical fiber sensor that can detect a liquid level or detect a property of liquid with high reliability even under a frequently vibrational environment. The optical fiber sensor includes an optical fiber that includes a core having an area where a grating is formed and a clad, the optical fiber being disposed so that at least a part of the area with the grating is immersed in liquid, a light source for making light incident to the optical fiber so that a cladding mode light having a wavelength band is generated by the grating, and a light receiving unit for detecting the intensity of light which is incident from the light source to the optical fiber and transmitted through the grating.

Abstract: An optical fiber sensor that can detect a liquid level or detect a property of liquid with high reliability even under a frequently vibrational environment. The optical fiber sensor includes an optical fiber that includes a core having an area where a grating is formed and a clad, and is disposed so that at least a part of the area with the grating is immersed in liquid, a light source for making light incident to the optical fiber so that a cladding mode light having a wavelength band is occurred by the grating, and a light receiving unit for detecting the intensity of light which is incident from the light source to the optical fiber and transmitted through the grating.

Abstract: A tunable dispersion compensator in which a heater portion can be easily constructed to reduce cost. A tunable dispersion compensator includes: an optical fiber having a grating portion; a heating unit for heating the grating portion to apply a temperature distribution to the grating portion; and a control unit for controlling the temperature distribution applied by the heating unit to control the group delay time characteristic of the grating portion. The heating unit includes: a heater including a single conductor having electrical resistors and which extends in a longitudinal direction of the grating portion over at least the entire length of the grating portion; and wirings electrically connected with the heater in respective positions along the longitudinal direction. The control unit supplies a voltage to each of the wirings.

Abstract: A tunable dispersion compensator in which a heater portion can be easily constructed to reduce cost. A tunable dispersion compensator includes: an optical fiber having a grating portion; a heating unit for heating the grating portion to apply a temperature distribution to the grating portion; and a control unit for controlling the temperature distribution applied by the heating unit to control the group delay time characteristic of the grating portion. The heating unit includes: a heater including a single conductor having electrical resistors and which extends in a longitudinal direction of the grating portion over at least the entire length of the grating portion; and wirings electrically connected with the heater in respective positions along the longitudinal direction. The control unit supplies a voltage to each of the wirings.

Abstract: A polarization dispersion compensation apparatus includes a polarization controller, a polarization beam splitter, an optical delay circuit, and a polarization beam combiner. The polarization controller controls polarization of an optical signal so that the polarization axis of the input optical signal substantially coincides with the optical axis of an optical transmission line, and the polarization beam splitter section splits the optical signal into two polarized components perpendicular to each other. The optical delay circuit section causes a difference in delay between the two polarized components, and the polarization beam combiner section combines the two polarized components output from the optical delay circuit section.

Abstract: A variable dispersion compensator includes an optical waveguide, a temperature controller. The optical waveguide has a chirped grating having a Bragg wavelength changing along the longitudinal direction of the grating. A temperature distribution T1(x) is applied to a central portion of the grating, defined as a region where a distance x from an end of the grating is a range of 20 % to 80 % of total length of the grating. Temperature distribution T2(x) and T3(x) are applied to end portions of the grating, defined as two regions extending from respective ends of the grating to the central region, respectively. At least one of T2(x) and T3(x) has a distance dependence different from that of the T1(x).

Abstract: In a polarization mode dispersion compensating apparatus for controlling polarization mode dispersion of an optical signal, a first optical monitor detects and outputs, based on an optical signal outputted from a first optical transmission line having a grating, a first detection signal indicating magnitude of waveform distortion of the first optical transmission line, and a second optical monitor detects and outputs, based on an optical signal output from a second optical transmission line having a grating, a second detection signal indicating magnitude of waveform distortion of the second optical transmission line. A calculator circuit calculates from the first and second detection signals an output signal. A controller controls a polarization controller based on the output signal from the calculator circuit.

Abstract: A polarization dispersion compensation apparatus of the present invention is provided with a polarization controller 4, a polarization beam splitter section 1, an optical delay circuit section 2 and a polarization beam combiner section 3. The polarization controller 4 controls polarization state of an optical signal so that the polarization axis of the inputted optical signal substantially coincides with the optical axis of an optical transmission line, and the polarization beam splitter section 1 splits, and outputs the optical signals of two polarized components perpendicular to each other from the optical signal outputted from the polarization controller 4. The optical delay circuit section 2 causes a difference in delay between the optical signals of the two polarized components outputted from the polarization beam splitter section 1, and the polarization beam combiner section 3 combines and outputs the optical signals of the two polarized components outputted from the optical delay circuit section 2.

Abstract: A method of manufacturing a grating in an optical waveguide that includes a core and a cladding covering the core. The method includes scanning a laser beam along an optical axis of the optical waveguide to modulate the refractive index of the core. The core is made of a material having a refractive index that is changeable upon irradiation by radiation. In addition, in scanning the core, the irradiation range of the laser beam is controlled and the core is scanned several times. Therefore, a predetermined distribution of irradiation is obtained in a direction of the optical axis of the grating.

Abstract: A variable dispersion compensator (1) includes an optical waveguide (8), a temperature controller (3, 5, 6, 7). The optical waveguide has a chirped grating (2) having Bragg wavelength changed along the longitudinal direction. Temperature distribution based on T1(x) is applied to a central portion defined as a region where a distance x from an end of the grating is a range of 20% to 80% of total length of the grating. Temperature distribution based on T2(x) and T3(x) are applied to both end portions defined as two regions extending from both ends of the grating to the central region, respectively. At least one of the T2(x) and T3(x) has distance dependence different from that of the T1(x).

Abstract: A temperature control device for controlling temperature variable devices disposed near a grating of a variable dispersion equalizer including an optical waveguide having the grating. The temperature variable devices control temperatures independently of each other. The temperature control device includes a controller for controlling the temperature variable units, and a storage device which stores temperature control patterns including combinations of control signals for the respective temperature variable units. The controller controls the temperature variable devices with a control signal of at least one of the temperature control patterns selected from the storage device.

Abstract: In a polarization mode dispersion compensating apparatus for controlling polarization mode dispersion of an optical signal, a first optical monitor detects and outputs, based on an optical signal outputted from a first optical transmission line having a grating, a first detection signal indicating magnitude of waveform distortion thereof, and a second optical monitor detects and outputs, based on an optical signal outputted from a second optical transmission line having a grating, a second detection signal indicating magnitude of waveform distortion thereof: A calculator circuit performs a predetermined calculation about the first and second detection signals, and outputs an output signal indicating a result of the calculation. A controller controls a polarization controller based on the output signal from the calculator circuit.

Abstract: An optical dispersion compensator comprises a heater unit for heating a fiber grating, a heater controller and a Peltier controller. The fiber grating heater unit includes heater elements formed in line on a quartz substrate and a fiber grating arranged on the heater elements. The fiber grating is secured on the quartz substrate using a cap. A step is formed in the quartz substrate to position the cap relative to the heater elements. The fiber grating is inserted into a groove in the cap to position the fiber grating relative to the heater elements.

Abstract: A variable dispersion compensator comprises a substrate, a fiber grating, and a plurality of heater elements. Main heater elements are arranged in a grating range of the fiber grating. A sub-heater element is arranged within the grating range of the fiber grating. Heat from the sub-heater element is used to correct a temperature distribution produced by the main heater elements in the fiber grating to achieve a linear temperature distribution.

Abstract: A waveguide grating device controlling Bragg wavelength after manufacture of the device includes an optical waveguide on a substrate. A variable stress is applied to a waveguide grating in part of the waveguide to bend at least the portion of the substrate including the waveguide grating, changing the Bragg wavelength.

Abstract: This invention provides a temperature control device for controlling a plurality of temperature variable devices disposed near a grating of a variable dispersion equalizer including an optical waveguide having the grating. The temperature variable devices are able to control the temperatures independently of each other. The temperature control device includes a controller for controlling the temperature variable units, and a storage device which stores a plurality of temperature control patterns includes combinations of control signals of the respective temperature variable units. The controller controls the temperature variable devices by a control signal of at least one of the temperature control patterns selected from the storage device.