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.

An optical sensor having one or more sensing interference elements is disclosed. A first detector function generates a coarse optical path difference signal for example using a discrete Fourier transform of a detected interference spectrum, and a second detector function generates a refined optical path difference signal using the coarse optical path difference signal and for example a cross correlation of the interference spectrum with one or more sets of periodic transfer functions.

An optical sensor is described for distinguishing between liquids of different refractive index, through strength of interference caused by an optical cavity having an exposed optical boundary in contact with such liquids. The sensor may be used, for example, to distinguish between water and aviation fuel in an aircraft fuel tank.

An air pressure sensor based on a suspended-core fiber and a side-hole fiber is provided and includes a broadband light source, an optical fiber circulator, a sensing head and a spectrometer; the optical fiber circulator is connected with the broadband light source, the sensing head and the spectrometer; the sensing head includes a single mode fiber, a multimode fiber, the suspended-core fiber and the side-hole fiber; the single mode fiber is connected with the suspended-core fiber through the multimode fiber; and the multimode fiber is connected with the side-hole fiber through the suspended-core fiber. The sensor uses a fabrication method of fiber fusion, and the operation is simple; the sensor has advantages of small volume, compact structure and convenient use; the sensor has good stability without adhesive; additionally, parallel connection of double cavities could produce vernier effects, so the sensor has good contrast of interference spectrum and high sensitivity.

In some embodiments, apparatuses and methods are provided herein useful for sensing pressure. In some embodiments, miniature housings are manufactured at ends of optical fibers. In some embodiments, a diamond diaphragm is provided on a hollow housing that receives a fiber optic cable and is sealed to form a Fabry-Perot cavity. In some forms, a plurality of sensors may be manufactured in batch.

A system includes an optical pressure sensor. A controller is operatively connected to receive input from the optical pressure sensor. An output connection is operatively connected to communicate output data from the controller. The controller includes machine readable 5 instructions configured to cause the controller to receive data from an optical pressure sensor, detect an accumulation of contaminant on the optical pressure sensor, and initiate a corrective action through the output connection in response to detecting the accumulation of contaminant.

A pressure sensor includes a movable electrode formed in a movable region of a diaphragm, and a fixed electrode formed opposite to the movable electrode. A pressure receiving surface of the diaphragm is held in an inactive state. The inactive pressure receiving surface of the diaphragm is in a state in which molecules of gas to be measured are hard to absorb onto the pressure receiving surface. The pressure receiving surface of the diaphragm can be made inactive by predetermined surface treatment. A layer for making the pressure receiving surface of the diaphragm inactive is formed by the surface treatment, and the pressure receiving surface of the diaphragm is held inactive with the presence of the layer.

A miniature diaphragm-based fiber-optic tip FP pressure sensor, and fabrication method and application thereof. A miniature diaphragm-based fiber-optic tip FP pressure sensor includes an optical fiber, a hollow-core optical fiber, and a pressure sensing diaphragm, wherein the optical fiber and the hollow-core optical fiber have the same diameter, the two are spliced by arc welding; and the pressure sensing diaphragm is bonded to the endface of the hollow-core optical fiber by hydroxide catalysis bonding. The FP pressure sensor can not only realize the all-silica structure of a sensor, but also make the joint of each component free of organic polymer, and has extremely high long-term stability and thermal stability. Meanwhile, by means of a fabrication method of the miniature diaphragm-based fiber-optic tip FP pressure sensor, the application range and service life of the sensor are increased, and fabrication costs are reduced.

An example method for installing optical sensors for a fuel level measurement system includes mounting a plurality of fittings through a wall of a fuel tank, positioning a plurality of optical sensors within the plurality of fittings and a respective optical sensor includes a first pressure sensing end inserted through the fitting and internally into the fuel tank and a second end extending externally from the fuel tank, and mounting an optical fiber bundle external to the fuel tank. The optical fiber bundle has an optical fiber connected to each of the plurality of optical sensors for guiding light to each of the plurality of optical sensors.

A temperature-tolerant, shock and vibration resistant absolute pressure sensor may be constructed by joining a ruggedized lens assembly and optical fiber assembly to create a stable beam of collimated light. The lens may be captured by brazing or welding to high-strength spherical metal components. The light delivery assembly may be comprised of a metal jacketed optical fiber, ceramic ferrule, and metal alignment sleeves that are mechanically and/or chemically joined to one another using high temperature sealing glass preforms or brazing materials. The optical fiber assembly may be joined to the lens assembly securing the end face of the optical fiber in the operative focal position relative to the lens. The joined assembly results in a structure where no parts are subject to movement even at extreme temperatures or when subjected to severe shock and vibration. All the air-to-glass interfaces may have anti-reflection coatings to reduce optical losses, back reflection, and false signals. This rugged collimated beam assembly may be joined to a sensor assembly comprised of a diaphragm and window which comprise a Fabry-Perot interferometer. The external wetted surfaces of the diaphragm may be coated to reflect the radiant energy or with passive conductive and convective arrangements to keep the sensor cool and to minimize the long-term change in sensitivity of the diaphragm due to oxidation. The resulting sensors can be further enhanced by attaching the sensor to an absolute, hermetically sealed connector comprised of a lens assembly which is aligned and welded to the sensor transducer body. The resulting sensors can be further enhanced with windows for collecting UV energy and may use wide spectral band optical fibers to multiplex UV, visible, and IR energy from the sensing environment. These enhancements can be used to detect the presence of a flame and to make temperature measurements resulting in safety-certified optical sensors for use in many harsh industrial applications.