A resin composition includes a base resin containing a urethane (meth)acrylate oligomer, a monomer, and a photopolymerization initiator, and surface-modified inorganic oxide particles having an ultraviolet curable functional group, wherein the content of the surface-modified inorganic oxide particles is 1% by mass or more and 60% by mass or less based on the total amount of the resin composition and the amount of surface modification on the surface-modified inorganic oxide particles is 0.15 mg/m.sup.2 or more.

An optical fiber includes a core region having a relative refractive index profile .sub.1 with a maximum relative refractive index .sub.1max in a range from 0.20% to 0.50%, and a surrounding cladding region that includes a triangular trench cladding region and an outer cladding region, and a relative refractive index .sub.3 with a minimum relative refractive index .sub.3min greater than 0.60% and less than 0.00%, and a trench volume greater than 30% m.sup.2. The outer cladding region has a relative refractive index .sub.4 in a range from 0.01% to 0.06% and a chlorine concentration greater than 1500 ppm. The optical fiber has a mode field diameter at 1310 nm of greater than 9.0 microns, a cable cutoff wavelength of less than 1260 nm, a zero dispersion wavelength between 1300 nm and 1324 nm, and low macrobend loss.

In a multicore optical fiber sensor, an absorptive material integrated into the cladding, or into a waveguide core not used for sensing, may facilitate sensing. The absorptive material is absorptive to light in a wavelength band in which the fiber sensor is configured to operate. Coating such a fiber sensor with a material whose refractive index is smaller than that of the cladding may be done with reduced signal mixing.

The invention relates to a securing method, comprising the following Steps: providing an optical waveguide made of a material with a first melting temperature, wherein a sensor region of the optical waveguide has at least one integrated temperature sensor element; providing a capillary made of a material with a second melting temperature, in such a way that the capillary surrounds at least regions of the sensor region of the optical waveguide, and that a securing region of the capillary is arranged at a distance from the sensor region, wherein the second melting temperature is lower than the first melting temperature, wherein the temperature sensor element is arranged in an end region of the optical waveguide, and the end region is inserted into the capillary; securing the securing region of the capillary to the optical waveguide, involving a heating of the securing region of the capillary to a heating temperature that is equal to or higher than the second melting temperature; and heating the free end of the capillary to a heating temperature that is equal to or higher than the second melting temperature. A temperature sensor comprising an optical waveguide with at least one integrated temperature sensor element can be obtained with the method. A securing device comprises an Insertion region for the capillary, a detector and a heating region. The securing device can be used for carrying out the method.

An optical component includes: a first fiber having a first end and a second end; a second fiber having a third end and a fourth end; a third fiber having a fifth end and a sixth end; a first coating layer that covers the cladding of the second fiber and has a higher refractive index than that of the cladding of the second fiber; and a first high refractive index layer that covers part of an outer peripheral surface and an end face of the second fiber. The first high refractive index layer has a higher refractive index than that of the cladding of the second fiber. The outer diameter of the cladding of the first fiber is smaller than that of the cladding of the second fiber. The outer diameter of the cladding of the third fiber is smaller than that of the cladding of the second fiber.

A fiber optic cable assembly includes an elongate housing, a signal fiber placed inside the housing and extending longitudinally, and a plurality of sensing fibers placed inside the housing and extending longitudinally. The plurality of sensing fibers is placed around the signal fiber. Each of the plurality of sensing fibers carries a respective laser signal of a distinct frequency. The signal fiber carries one or more evanescent coupling signals responsive to the laser signals in the plurality of sensing fibers.

A fiber optic cable assembly includes an elongate housing, a signal fiber placed inside the housing and extending longitudinally, and a plurality of sensing fibers placed inside the housing and extending longitudinally. The plurality of sensing fibers is placed around the signal fiber. Each of the plurality of sensing fibers carries a respective laser signal of a distinct frequency. The signal fiber carries one or more evanescent coupling signals responsive to the laser signals in the plurality of sensing fibers.

Described herein are systems, methods, and articles of manufacture for a coated fiber modified by actinic radiation to increase back-scattering, which experiences very little back-scattering decay at a temperature and time of exposure that is sufficient to noticeably degrade the coating and/or noticeably degrade the optical fiber due to outgassing of hydrogen from the coating. In one embodiment, an optical fiber comprises a fiber length, a coating having a treated coating weight, wherein the treated coating weight is at least 25% less of an original coating weight prior to an annealing treatment, and an optical back-scatter along the fiber length greater than a Rayleigh back-scattering over the fiber length, wherein the optical back-scatter does not decrease along the fiber length by more than 3 dB after exposure to annealing treatment. A further embodiment relates to a method comprising receiving an optical fiber at an inlet of at least one heat source, the optical fiber including a coating having an original coating weight and an optical back-scatter along a fiber length and applying an annealing treatment to the optical fiber by the least one heat source at a predetermined temperature T.sub.a during a predetermined time t.sub.a, wherein the original coating weight is reduced by at least 25% to a treated coating weight during the annealing treatment, wherein the optical back-scatter does not decrease along the fiber length by more than 3 dB after the annealing treatment.

An optical fiber for use in distributed vibration sensing has perturbations along its length. The perturbations may be applied externally to a mode field diameter of the optical fiber. Alternatively, the perturbations may be applied through the use of fusion splicing of fiber lengths that form the optical fiber.

A fiber optic cable assembly includes an elongate housing, a signal fiber placed inside the housing and extending longitudinally, and a plurality of sensing fibers placed inside the housing and extending longitudinally. The plurality of sensing fibers is placed around the signal fiber. Each of the plurality of sensing fibers carries a respective laser signal of a distinct frequency. The signal fiber carries one or more evanescent coupling signals responsive to the laser signals in the plurality of sensing fibers.