An output coupler can be used to couple multiple channels of light from a semiconductor waveguide to an optical fiber for wavelength division multiplexing. To couple light of a wide bandwidth (e.g., equal to or greater than 100 nm), two symmetrical gratings on two sides of a Fabry Perot cavity is used. The two symmetrical gratings are optimized to both reflect light for a Fabry Perot resonator and couple light out of the semiconductor waveguide.

A fiber optic cable includes a plurality of optical fibers and an optical sensor. The optical sensor includes a first optical coupler and a first mirror. The first optical coupler is coupled to a first of the optical fibers and to a second of the optical fibers at a first sensor takeout location. The first mirror is coupled to the first of the optical fibers at a second sensor takeout location. The first sensor takeout location is longitudinally offset from the second sensor takeout location.

A passive microscopic Fabry-Pérot Interferometer (FPI) sensor includes a three-dimensional microscopic optical structure formed on a cleaved tip of the optical fighter using a two-photon polymerization process on a photosensitive polymer by a three-dimensional micromachining device. The three-dimensional microscopic optical structure having a hinged optical layer pivotally connected to a distal portion of a suspended structure. A reflective layer is deposited on a mirror surface of the hinged optical layer while in an open position. The hinged optical layer is subsequently positioned in the closed position to align the mirror surface to at least partially reflect a light signal back through the optical fiber.

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.

Embodiments relate to an optical sensor for sensing hydrogen gas, which includes an optical fiber through which light moves; a ferrule formed at one end of the optical fiber to surround the optical fiber; and a sensor module configured to form an interference wave according to a Fabry-Perot interferometer with respect to light that moves through the optical fiber, wherein the sensor module includes a sensing material that expands and contracts by reacting with hydrogen gas, and spectrum periodicity of the interference wave changes according to a volume change of the sensing material, and a hydrogen gas detection system including the optical sensor.

A tunable optical filter for a detector is presented including a plate having a top side and a bottom side. The plate has material properties making it transparent to a range of optical frequencies. A transparent metasurface is proximate the top side of the plate. The transparent metasurface is configured to have a transmissive pass band and a stop band. An undercarriage support structure is proximate the bottom side of the plate. The undercarriage support is responsive to photothermal heating. The undercarriage support is configured to deform from the photothermal heating caused by an undesired signal thereby shifting the stop band in frequency toward the undesired signal to block reception of the undesired signal by the detector.

A tunable optical filter for a detector is presented including a plate having a top side and a bottom side. The plate has material properties making it transparent to a range of optical frequencies. A transparent metasurface is proximate the top side of the plate. The transparent metasurface is configured to have a transmissive pass band and a stop band. An undercarriage support structure is proximate the bottom side of the plate. The undercarriage support is responsive to photothermal heating. The undercarriage support is configured to deform from the photothermal heating caused by an undesired signal thereby shifting the stop band in frequency toward the undesired signal to block reception of the undesired signal by the detector.

Optical system comprising two optical fibres which are configured to define between them a Fabry-Perot cavity, and a connecting element bonded to each of the two optical fibres, the connecting element defining a through-passage, at least one of the two optical fibres comprising an end portion arranged in the through-passage and bonded to the connecting element, the two optical fibres extending along an axis and being separated from one another by a distance Le parallel to the axis, 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 parallel to the axis.

Disclosed is an adjustable optical filter device. The device comprises a first glass thin film provided with a first mirror and a second glass thin film provided with a second mirror. The peripheries of the surfaces of the first glass thin film and the second glass thin film that have a mirror are bonded to each other by means of a bond to form a cavity between the mirrors. The first glass thin film or the second glass thin film is provided with a driving unit for controlling the relative displacement of the first glass thin film and/or the second glass thin film. The tunable optical filter device has better optical filtering performance than existing filter devices, has the performance of small size and lower driving voltage, and can be applied to devices having a limited size, such as miniature spectrometers, small or even mini hyperspectral cameras or mobile phones.

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.