An apparatus for producing strain in an optical fibre proportional to dynamic pressure fluctuation in the surrounding substance. The apparatus includes a diaphragm having a first face that, in use, is exposed to dynamic pressure fluctuations in the substance, and a second, opposite face, the diaphragm being adapted to flex in response to dynamic pressure fluctuations applied to it. One or more optical fibres are mounted on either the first or the second face of the diaphragm, whereby strain is produced in the fibre when the diaphragm flexes.

An optomechanical pressure-measurement system measures pressure in the range of 10.sup.−6 Pa-10.sup.−2 Pa by measuring various properties of a vibrational mode of an ultra-thin membrane member. With independent measurements of the thickness and density of the membrane, in addition to the measured vibration mode properties, the system can operate as a primary pressure sensor. The membrane member is mounted on a vibration-isolated mount and is excited by a drive force. A laser beam impinges on the excited membrane, and an optical phase detector detects the amplitude of the oscillations, as well as parameters of the laser beam affected by the membrane vibration. In one embodiment, a mechanical damping is computed based on the amplitude or frequency shift (depending on the pressure range), and the pressure based on the ring-down time of the membrane vibration mode.

There is provided a MOMS sensor comprising a fiber interface comprising a fiber passthrough for one or more optical fibers, a cavity comprising an element hermetically encapsulated within the cavity, wherein the element is movably anchored by SiN arms, which are movable with respect to walls of the cavity, wherein the SiN arms comprise anchor portions at first ends of the SiN arms, which are connected to the element, and at second ends of the SiN arms, which are connected to the walls of the cavity, and the fiber interface is configured to receive the fibers through the fiber passthrough into positions for communications of light between the element and the fibers. In this way a robust structure that supports sensitivity of the sensor is provided.

An apparatus for producing strain in an optical fibre proportional to dynamic pressure fluctuation in the surrounding substance. The apparatus includes a diaphragm having a first face that, in use, is exposed to dynamic pressure fluctuations in the substance, and a second, opposite face, the diaphragm being adapted to flex in response to dynamic pressure fluctuations applied to it. One or more optical fibres are mounted on either the first or the second face of the diaphragm, whereby strain is produced in the fibre when the diaphragm flexes.

There is provided a MOMS sensor comprising a fiber interface comprising a fiber passthrough for one or more optical fibers, a cavity comprising an element hermetically encapsulated within the cavity, wherein the element is movably anchored by SiN arms, which are movable with respect to walls of the cavity, wherein the SiN arms comprise anchor portions at first ends of the SiN arms, which are connected to the element, and at second ends of the SiN arms, which are connected to the walls of the cavity, and the fiber interface is configured to receive the fibers through the fiber passthrough into positions for communications of light between the element and the fibers. In this way a robust structure that supports sensitivity of the sensor is provided.