Abstract: The present invention relates to a method and an apparatus for measuring the temperature of optical fibers during fusion splicing or thermal processing, said method comprising: a) measuring, using an interferometric method, a change in an optical path length in an optical fiber due to temperature dependent properties of the optical fiber during fusion splicing or thermal processing; and b) determining the temperature of the optical fiber based on the measured changes in the optical path length.

Abstract: A method of forming a longitudinal solid body within at least one longitudinal hole formed in an optical fiber, comprising the steps of placing a first end and a portion of the optical fiber in a heating chamber; keeping a second end of said optical fiber outside of the heating chamber; forcing a molten material into the longitudinal hole of the fiber from the first end; and thereupon longitudinally extracting the optical fiber from the heating chamber at a controlled rate. Preferably, the fiber is extracted while molten material is being urged into the fiber.

Abstract: The invention relates to a method and a device for controlling the refractive index in the core of an optical fiber. According to the invention, an optical fiber is provided with a longitudinal electrode running along the core of the fiber. An electric current is passed through the electrode to induce ohmic heating thereof, causing thermal expansion and consequently a compressing force upon the core of the fiber. This compression of the core leads to induced changes in the refractive index in the direction of the compressing force, and hence induces or alters birefringence in the core.

Abstract: PROBLEM TO BE SOLVED: To provide a polarization control element which may be easily produced and miniaturized and has high reliability. SOLUTION: A core region 11 is a region of a circular shape in cross section disposed at the center of an optical fiber 10 and has a refractive index n1. A clad region 12 is a region disposed around this core region 11 and has a refractive index n2 smaller than the refractive index n1 of the core region 11. A pair of conductive parts 13a and 13b are respectively symmetrical with each other with respect to the optical axis center and are disposed within the clad region 12 over a specified range in a longitudinal direction. When current is passed to a pair of the conductive parts 13a and 13b, respectively, a stress is generated therein and a strain is generated in the core region 11 and the clad region 12. The propagation light propagated in the optical fiber 10 is controlled in the polarization state according to this strain.

Abstract: A method of forming a longitudinal solid body within at least one longitudinal hole formed in an optical fiber, comprising the steps of placing a first end and a portion of the optical fiber in a heating chamber; keeping a second end of said optical fiber outside of the heating chamber; forcing a molten material into the longitudinal hole of the fiber from the first end; and thereupon longitudinally extracting the optical fiber from the heating chamber at a controlled rate. Preferably, the fiber is extracted while molten material is being urged into the fiber.

Abstract: In an optical fiber or other light guiding body is utilized that the diffusion properties of fluorine, which reduces the refractive index, are strongly changed, if also a doping with phosphorous is made, to change the refractive index and hereby the light guiding properties. In for example a single mode fiber (1) thus locally an additional waveguide core (9) can be created parallel to the already existing waveguide core (3), by providing in parallel to the ordinary core (3) an activatable region (5) having substantially the sane dimensions as the existing core and having suitable dopings of fluorine and phosphorous. This can be utilized to produce an optical filter element If the optical fiber is D-fiber, a sensor element can be produced. Furthermore, for suitable concentrations of these dopants and of germanium an existing waveguide core can be erased by a heating operation.

Abstract: In order to produce a periodically varying refractive index in an optical material such as optical fiber, the concentration of a refractive index varying material, for example, fluorine, is periodically varied. A mobile substance is first diffused into the optical material. A portion of this mobile substance is periodically activated by application of periodically varying radiation supplied to the optical material having the mobile substance diffused therein. Molecular hydrogen may be used as such a mobile substance. After activation of the mobile substance, inactivated mobile substance is diffused out of the optical material, this diffusion step being accelerated by application of heat. Subsequently, the optical element is heated to a predetermined level to further react the mobile substance whit a component of the optical material which may then be diffused out of the optical material to produce a periodically varying optical property such as refractive index.