Refractory anchoring devices include a main body and a mounting feature for mounting to a thermal vessel. The main body has the shape of two end-to-end Y's forming a central segment, branch segments extending from ends of the central segment, and extension segments extending from the branch segments, to collectively form four unenclosed cell openings that are semi-hexagonally shaped. Some embodiments include reinforcement segments extending into respective cell openings, voids extending through respective adjacent branch and extension segments, an underbody gap under the central segment, a single stud-welding stud for the mounting feature, and/or a collar-and-stud connection between the anchor main body and a stud-welding stud of the mounting feature. Refractory anchoring systems and methods include an array of the refractory anchoring devices arranged and mounted so that the unenclosed semi-hexagonal cell openings of adjacent anchoring devices cooperatively form substantially hexagonal cells.

An optical filter comprising a first lens, and first and second optical elements. The first lens has an optical axis, configured to focus beams propagating parallel to the optical axis at a focal point. The first optical element has a first semi-reflective surface, the first semi-reflective surface being curved and having a first radius of curvature around a first centre of curvature on the optical axis. The second optical element has a second semi-reflective surface. The first radius of curvature is between 1 and 10,000 times the distance between the first semi reflective surface and the focal point along the optical axis. The first and second semi-reflective surfaces are arranged to form a resonator. The first lens and the first and second semi-reflective surfaces are arranged along the optical axis such that light is transmittable along an optical path through the lens and the resonator. The optical filter further comprises one or more expansion elements located outside of the optical path, and arranged such that expansion of the expansion elements causes relative movement of the first and second semi-reflective surfaces.

An etalon-based mid-infrared probe can be configured for spectroscopic tissue discrimination, such as between non-normal (e.g., cancerous) and normal (e.g., healthy) tissue. A broadband light source can be applied to the etalon to generate fringes at spectroscopic wavelengths of interest, which can be delivered to a tissue specimen via a fiber loop probe. A response signal can be spectral dispersed across a parallel array of detector pixels, such as using a diffraction grating, and signal processed for performing the tissue classification. A learning model can be trained, using full IR spectral data, for applying a reduced set of wavelengths for performing the spectroscopic tissue analysis and classification.

Optical system (20) comprising two optical fibres (3, 5) which are configured to define between them a Fabry-Perot cavity, and a connecting element (7) bonded to each of the two optical fibres (3, 5), the connecting element (7) defining a through-passage, at least one of the two optical fibres (3, 5) comprising an end portion (22, 23) arranged in the through-passage and bonded to the connecting element (7), the two optical fibres (3, 5) extending along an axis (A) and being separated from one another by a distance Lc parallel to the axis (A), one of the optical fibres being bonded to the connecting element at a first bonding zone, and the other optical fibre being bonded to the connecting element at a second bonding zone separated from the first bonding zone by distance L1 parallel to the axis (A), wherein the two optical fibres (3, 5) have a first thermal expansion coefficient, and the connecting element (7) has a second thermal expansion coefficient, so that the first thermal expansion coefficient is equal to the product of the second thermal expansion coefficient multiplied by the term (1−Lc/L1) to within a margin of 10.sup.−6.

A fiber optic temperature sensor, a sensing head structure, and a manufacturing method are provided. The fiber optic temperature sensor includes a broad spectrum light source, a first fiber optic coupler, a spectrometer, a first sensing interferometer, and a second sensing interferometer. The first sensing interferometer and the second sensing interferometer have opposite temperature responses. A first free spectral range corresponding to the first sensing interferometer is close to but not equal to a second free spectral range corresponding to the second sensing interferometer. In the fiber optic temperature sensor, two sensing interferometers both sensitive to temperature are used, and the two sensing interferometers have opposite temperature responses, thereby achieving an enhanced vernier effect, and improving the sensitivity of temperature measurement.

A reflective structure includes an input/output port and an optical splitter coupled to the input/output port. The optical splitter has a first branch and a second branch. The reflective structure also includes a first resonant cavity optically coupled to the first branch of the optical splitter. The first resonant cavity comprises a first set of reflectors and a first waveguide region disposed between the first set of reflectors. The reflective structure further includes a second resonant cavity optically coupled to the second branch of the optical splitter. The second resonant cavity comprises a second set of reflectors and a second waveguide region disposed between the second set of reflectors.

Disclosed are a Fabry-Perot sensor and a method for manufacturing the same. A Fabry-Perot sensor including: a base part; a cavity formed between the base part and a pressure-sensitive film, and enclosed by the base part and the pressure-sensitive film; the pressure-sensitive film, fixed to the base part, wherein the pressure-sensitive film has one or more localised areas, each localised area has a doping substance doped into a base material of the pressure-sensitive film to produce stress, no localised area penetrates the entire thickness of the pressure-sensitive film, and under the effect of stress, the pressure-sensitive film has a corrugated structure; an optic fibre used for conducting a light signal, one end part of the optic fibre being fixed to an optic fibre mounting part of the base part, and the optic fibre mounting part being located at an end part of the base part opposite the cavity.

A passive microscopic Fabry-Pérot Interferometer (FPI) sensor includes an optical fiber a three-dimensional microscopic optical structure formed on a cleaved tip of an optical fighter that reflects a light signal back through the optical fiber. The reflected light is altered by refractive index changes in the three-dimensional structure that is subject to at least one of: (i) thermal radiation; and (ii) volatile organic compounds.

One illustrative device disclosed herein includes a layer of semiconductor material and a first Bragg reflector structure positioned in the layer of semiconductor material, wherein the first Bragg reflector structure comprises a plurality of dielectric elements and a first internal area defined by an innermost of the first plurality of dielectric elements. In this example, the device also includes an optical component positioned above the layer of semiconductor material, wherein at least a portion of the optical component is positioned within a vertical projection of the first internal area.

A passive microscopic Fabry-Pérot Interferometer (FPI) pressure sensor includes an optical fiber and a three-dimensional microscopic optical enclosure. The three-dimensional microscopic optical enclosure includes tubular side walls having lateral pleated corrugations and attached to a cleaved tip of the optical fiber to receive a light signal. An optically reflecting end wall is distally engaged to the tubular side walls to enclose a trapped quantity of gas that longitudinally positions the optically reflecting end wall in relation to ambient air pressure, changing a distance traveled by a light signal reflected back through the optical fiber.