An example system includes a fuel tank, fittings mounted through a wall of the fuel tank, and optical sensors positioned within the fittings. A respective optical sensor includes a first pressure sensing end inserted through a fitting and internally into the fuel tank and a second end extending externally from the fuel tank. The system also includes an optical fiber bundle mounted external to the fuel tank, and having an optical fiber connected to each of the plurality of optical sensors for guiding light to each of the plurality of optical sensors.

An optical sensor (10) comprises an optical cavity defined by a dielectric body and responsive to one or more physical environmental conditions, and a waveguide (70) having a terminal end spaced apart from the optical cavity such that light is optically coupled from the terminal end of the waveguide (70) to the optical cavity. The waveguide (70) is arranged such that, in use, it is maintained at a first temperature that would not damage the optical coupling to the optical cavity when the dielectric body is maintained at a second temperature sufficient to damage the optical coupling to the optical cavity.

A method of assembling an optical sensor for measuring pressure and/or temperature is disclosed. The optical sensor is adapted for use in high temperature environments, such as gas turbines and other engines. The method comprises fabricating a sensor element formed of a pill having an enclosed cavity, bonding the pill to a front end of a spacer, bonding a lens to the back end of the spacer to form the optical assembly, aligning an optical fiber to the optical assembly, and fixing the fiber in position by fusing the fiber to the lens.

The disclosed technology may include systems, methods, and apparatus for optical measurements. A method is provided that includes receiving, by first and second Extrinsic Fabry-Perot Interferometer (EFPI) sensors, respective portions of interrogation light. The first EFPI sensor is responsive to a measurement stimulus and both the first EFPI sensor and the second EFPI sensor are responsive to a common mode stimulus. The method includes detecting a measurement signal and a first common-mode signal responsive to receiving altered interrogation light from the first EFPI sensor, the measurement signal corresponding to the measurement stimulus. The method includes detecting a second common mode signal responsive to receiving altered light from the second EFPI sensor. The method includes producing a measurement output signal, the measurement output signal representing a difference between the second common mode signal and a combination of the measurement signal and the first common-mode signal, and outputting the measurement output signal.

A Fabry-P?rot sensor assembly includes an optical element defining a Fabry-P?rot optical cavity therein. A ferrule is affixed to the optical element. The ferrule is configured to physically connect to an optic fiber, aligning the optic fiber optically with the cavity. The optical element includes a MgAl.sub.2O.sub.4 spinel or aluminum oxynitride Al.sub.23N.sub.27O.sub.5. A method of making an Fabry-P?rot optical cavity includes using a ceramic processing etching process to remove material from a first optical member to form the cavity therein, leaving a rim of the optical member surrounding the cavity peripherally. The method includes affixing a second optical member to the rim to enclose the cavity.

This invention describes the structure and function of an integrated multi-sensing systems in stacked configuration. Integrated systems described herein may be configured to form a microphone, pressure sensor, gas sensor or accelerometer. The method uses Fabry-Perot Interferometer in conjunction with light source and a photodetector integrated in stacked configuration. It also describes a configurable method for tuning the integrated system to specific resonance frequency using electrostatic actuators.

A sensor for measuring pressure, temperature or both may be provided. The sensor may include a diaphragm that may respond to a change in temperature or pressure, a base connected to the diaphragm, a cavity, and an optical fiber that may conduct light reflected off of a surface of the diaphragm. The diaphragm and base may be sapphire elements. An interrogator may be provided for detecting a deflection of the diaphragm.

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.

A sensor network having a series arrangement of fiber-coupled, reflective sensors is disclosed. In operation, a first light signal having multiple wavelength bands is launched in an upstream direction on a fiber bus. Each sensor includes a wavelength filter and an FP sensor that is sensitive to a parameter. Each wavelength filter (1) selectively passes a different one of the wavelength bands to its FP sensor and (2) reflects the remaining wavelength bands back into the fiber bus to continue upstream. The FP sensor imprints a signal based on the parameter onto its received light and reflects it as a second light signal. The collimator, wavelength filter, and FP sensor of each sensor are arranged such that each second light signal is returned to the fiber bus, which conveys them in a downstream direction to a processor that measures them and estimates the parameter at each sensor.

An optical system having an optical sensor with an ultra-short FP cavity, and a low-resolution optical interrogation system coupled to the optical sensor and operational to send light signals and receive light signals to and from the optical sensor is disclosed. The optical system may operate in a wavelength range including the visible and near-infrared range. Optical assemblies and methods of interrogating optical sensors are provided, as are numerous other aspects.