A long-term in-situ observation device for the deep sea bottom supported engineering geological environment is provided, including: a sediment acoustic probe, a sediment pore water pressure probe, a three-dimensional resistivity probe, a water observation instrument, a long-term observation power supply system, a probe hydraulic penetration system, a general control and data storage transmission system, an acoustic releaser, an underwater acoustic communication apparatus, and an instrument platform. The observations include the engineering properties, physical properties, mechanical properties, and biochemical properties of a seawater-seabed interface-sediment. The engineering properties and the physical and mechanical indexes of seafloor sediments are comprehensively determined by three-dimensional measurement of seafloor resistivity and acoustic wave measurements. The physical and biochemical properties of seawater are expected to be acquired by sensors. The observation probe penetrates into the sediments following the hydraulic method.

An optical sensor includes a tube-shaped base formed from a metal, an optical fiber member received inside the base, and a sensor head formed from monocrystalline alumina and bonded to the base to be optically connected with the optical fiber member. The sensor head is provided with a first cavity including a first reflection surface configured to reflect a part of light introduced through the optical fiber member and a second reflection surface provided facing the first reflection surface and configured to reflect a part of the light reflected by the first reflection surface. A first interference light produced by an interference between the light reflected by the first reflection surface and the light reflected by the second reflection surface is output from the first cavity.

An optical sensor includes a tube-shaped base formed from a metal, an optical fiber member received inside the base, and a sensor head formed from monocrystalline alumina and bonded to the base to be optically connected with the optical fiber member. The sensor head is provided with a first cavity including a first reflection surface configured to reflect a part of light introduced through the optical fiber member and a second reflection surface provided facing the first reflection surface and configured to reflect a part of the light reflected by the first reflection surface. A first interference light produced by an interference between the light reflected by the first reflection surface and the light reflected by the second reflection surface is output from the first cavity.

An optical fiber sensing system, method and apparatus for simultaneously measuring temperature, strain, and pressure are provided and belong to the field of optical fiber sensors. A distributed optical fiber temperature sensor is configured to monitor the temperature, and transmit the monitored temperature to a fiber grating strain and pressure sensor; the fiber grating strain and pressure sensor performs self temperature compensation based on received temperature; and the fiber grating strain and pressure sensor monitors the strain and the pressure. The distributed optical fiber temperature sensor is used to replace a temperature compensation function of the fiber grating strain sensor, and sense temperature distribution of each point along a route. Further, the fiber grating strain and pressure sensor is simplified inside, temperature demodulation is no longer required and speed of obtaining values of the strain and the pressure has been accelerated.

A pressure transducer and a fabrication method thereof are provided. The pressure transducer includes a light-emitting element, an interference light-filtering structure and a light-sensing element stacked on top of each other. The light-emitting element is configured to emit incident light onto the interference light-filtering structure. The interference light-filtering structure is configured to change its thickness in accordance with the pressure exerted on the pressure transducer and generate emergent light corresponding to the pressure. The light-sensing element is configured to detect the emergent light and generate an electrical signal corresponding to the emergent light.

A pressure transducer and a fabrication method thereof are provided. The pressure transducer includes a light-emitting element, an interference light-filtering structure and a light-sensing element stacked on top of each other. The light-emitting element is configured to emit incident light onto the interference light-filtering structure. The interference light-filtering structure is configured to change its thickness in accordance with the pressure exerted on the pressure transducer and generate emergent light corresponding to the pressure. The light-sensing element is configured to detect the emergent light and generate an electrical signal corresponding to the emergent light.

A system for determining pH of a fluid and a method to determine the pH of a fluid contacting a sensor, the method having the steps of: providing the sensor to an environment such that the sensor is in contact with the fluid, wherein the sensor features a fiber extending between a first end and a second end along a longitudinal axis, wherein the fiber further features a medial portion positioned between the first and second ends, wherein the sensor further features a pH sensitive coating on the medial portion of the fiber, and wherein the pH sensitive material features a metal oxide including but not limited to SiO.sub.2, TiO.sub.2, ZrO.sub.2, Ta.sub.2O.sub.5, A.sub.2O.sub.3, and combinations thereof; interrogating the sensor with an optical signal; collecting a modified optical signal after the sensor has been interrogated; and determining the pH of the fluid contacting the pH sensor using the modified optical signal.

An optical device for an optical sensor comprises a gain element of a semiconductor laser, a wavelength selective feedback element, and a sensing element. At least part of the wavelength selective feedback element and the sensing element are arranged in a common sensor package. The gain element is arranged to generate and amplify an optical signal. The gain element and the wavelength selective feedback element form at least part of an external cavity of the semiconductor laser, thereby providing a feedback mechanism to sustain a laser oscillation depending on the optical signal. The wavelength selective feedback element is arranged to couple out a fraction of the optical signal and direct said fraction of the optical signal towards the sensing element to probe a physical property of the sensing element.

The present invention discloses a residual pressure measurement system for a MEMS pressure sensor with an F-P cavity and method thereof, the measurement system includes a low-coherence light source, a 3 dB coupler, a MEMS pressure sensor, an air pressure chamber, a thermostat, a pressure control system, a cavity length demodulator, an acquisition card and a computer. The measurement method comprises: performing cavity length measurement by using the reflecting light by the pressure control system at two temperatures, respectively, so as to calibrate the MEMS pressure sensor and establish a relationship between the absolute phase of a monochromatic frequency and the external pressure; performing linear fitting to the two measurement data to obtain all the external pressure when the cavity length of two measurement data are equal to each other, and substituting the theoretical equation for calculation to obtain the residual pressure under the flat condition of the diaphragm.

The present invention discloses a residual pressure measurement system for a MEMS pressure sensor with an F-P cavity and method thereof, the measurement system includes a low-coherence light source, a 3 dB coupler, a MEMS pressure sensor, an air pressure chamber, a thermostat, a pressure control system, a cavity length demodulator, an acquisition card and a computer. The measurement method comprises: performing cavity length measurement by using the reflecting light by the pressure control system at two temperatures, respectively, so as to calibrate the MEMS pressure sensor and establish a relationship between the absolute phase of a monochromatic frequency and the external pressure; performing linear fitting to the two measurement data to obtain all the external pressure when the cavity length of two measurement data are equal to each other, and substituting the theoretical equation for calculation to obtain the residual pressure under the flat condition of the diaphragm.