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.

The present invention is a temperature sensor for cryogenic systems using a fiber optic interrogation system that is capable of a large number of temperature readings across the cryogenic environment at high resolutions. The invention also includes a method of using such a system to measure temperatures in a cryogenic environment and a method of making such a system.

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.

An optical processing structure of an optical fiber, includes: an optical fiber that includes a core, a cladding, and a coating, the coating being partially removed; and a thermally conductive protective material made of a silicone-based thermally conductive compound and provided around the cladding in a coating removed region of the optical fiber. Further, the thermally conductive protective material contains a filler having a refractive index higher than a refractive index of the cladding, and the filler is present in a region where evanescent light seeping out of the cladding is present when cladding mode light propagating in the cladding is totally reflected.

Optical sensors having one or more soluble coatings thereon are used to detect the presence of a degrading fluid. In a generalized embodiment, the fiber optic sensor includes a fiber optic cable having two strain sensor positioned therein. A soluble layer is positioned over one of the strain sensor. Due to the presence of the soluble layer, the covered strain sensor optically responds differently than the other strain sensor to changes in pressure, strain and temperature. In the presence of a degrading fluid, the soluble layer degrades and ultimately dissolves, thereby changing the optical response of the previously covered strain sensor. When the soluble layer is dissolved, the strain induced by the soluble layer relaxes, thus causing a wavelength shift in the signal of the grating. By monitoring the wavelength shifts of both strain sensors, the fiber optic sensor acts as a detector for the presence of the degrading fluid.

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 sensing cable includes a first optical fiber, a second optical fiber that extends along the first optical fiber and that is spaced from the first optical fiber, and a transmitting material that includes an intervention portion present between the first optical fiber and the second optical fiber, the transmitting material being configured to transmit light from the first optical fiber to the second optical fiber through the intervention portion.

Optical sensors having one or more soluble coatings thereon are used to detect the presence of a degrading fluid. In a generalized embodiment, the fiber optic sensor includes a fiber optic cable having two strain sensor positioned therein. A soluble layer is positioned over one of the strain sensor. Due to the presence of the soluble layer, the covered strain sensor optically responds differently than the other strain sensor to changes in pressure, strain and temperature. In the presence of a degrading fluid, the soluble layer degrades and ultimately dissolves, thereby changing the optical response of the previously covered strain sensor. When the soluble layer is dissolved, the strain induced by the soluble layer relaxes, thus causing a wavelength shift in the signal of the grating. By monitoring the wavelength shifts of both strain sensors, the fiber optic sensor acts as a detector for the presence of the degrading fluid.

Disclosed are various embodiments for high diffraction efficiency phase gratings. An organized set of nanoparticles are embedded within a polymer composite. The polymer composite is then etched to generate one or more trenches in the polymer composite that correspond to the organized set of nanoparticles.