Sensors for measuring pressure and temperature
A Fabry-Pérot sensor assembly includes an optical element defining a Fabry-Pérot 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 MgAl2O4 spinel or aluminum oxynitride Al 23 N 27 O 5 . A method of making an Fabry-Pérot 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.
1 . A Fabry-Perot sensor assembly comprising:
an optical element comprising:
a first end opposite a second end relative to a longitudinal axis of the Fabry-Perot sensor assembly;
a first optical member at the first end;
a second optical member at the second end, wherein the second optical member comprises a diaphragm, and wherein the diaphragm deflects more than the first optical member to pressure changes external to the optical element;
a reflective coating connected to the diaphragm and facing the first optical member;
an optical cavity between the first end and the second end; and
a ring-shaped mirror attached to a surface of the first optical member and facing the second optical member, wherein the ring-shaped mirror does not interfere with light propagation at an end of a bore that interfaces with the first optical member and contains an optical fiber; and
a sensor ferrule affixed to the first end of the optical element and defines the bore for receiving the optical fiber that extends along the longitudinal axis to the optical element, wherein the sensor ferrule is configured to physically connect to the optical fiber, optically aligning and spacing the optical fiber with the optical cavity, wherein the optical element includes MgA1 2 O 4 spinel or aluminum oxynitride A1 23 N 27 O 5 .
2 . The assembly as recited in claim 1 , further comprising the optical fiber affixed within the sensor ferrule optically aligned with the optical cavity along the longitudinal axis.
3 . The assembly as recited in claim 2 , further comprising an interrogator optically connected to the optical fiber, wherein the interrogator is configured to illuminate the cavity through the optical fiber, to receive reflected spectrum from the cavity, and to measure temperature and/or pressure of the cavity based on the reflected spectrum.
4 . The assembly as recited in claim 1 , wherein an optical path passes from the bore, through the first optical member, through the optical cavity, reflects off of the second optical member and passes back through the optical cavity and through the first optical member into the bore and back into the fiber.
5 . The assembly as recited in claim 1 , wherein at least one of the first and second optical members is MgA1 2 O 4 spinel.
6 . The assembly as recited in claim 1 , wherein at least one of the first and second optical members is aluminum oxynitride A1 23 N 27 O 5 .
7 . The assembly as recited in claim 1 , wherein the optical cavity recesses axially into the second optical member, forming a cavity rim that extends circumferentially around the optical cavity relative to the longitudinal axis, and wherein the diaphragm is connected to the cavity rim.
8 . The assembly as recited in claim 1 , wherein the optical cavity recesses axially into the first optical member, forming a cavity rim that extends circumferentially around the optical cavity relative to the longitudinal axis, and wherein the first optical member is connected to the cavity rim.
9 . The assembly as recited in claim 1 , further comprising anti-reflective coating on at least one surface of the optical element.
10 . The assembly as recited in claim 1 , further comprising a cavity ring between the first and second optical members and connected to both the first and second optical members, wherein the optical cavity is bounded by the cavity ring and the first and second optical members.
11 . A method of making a Fabry-Perot optical element comprising:
forming a first optical member comprising MgAl 2 O 4 spinel or aluminum oxynitride Al 23 N 27 O 5 ;
forming a second optical member comprising a diaphragm, and comprising MgAl 2 O 4 spinel or aluminum oxynitride Al 23 N 27 O 5 ;
creating a reflective coating on a first side of the second optical member, wherein the first side of the second optical member is formed by the diaphragm;
connecting a ring-shaped mirror on a first side of the first optical member, wherein the first side of the first optical member faces the first side of the second optical member, wherein the ring-shaped mirror does not interfere with light propagation at an end of a bore that interfaces with the first optical member and contains an optical fiber; and
connecting the first optical member to the second optical member such that the first optical member forms a first end of the optical element and the diaphragm of the second optical member forms a second end of the optical element, wherein the reflective coating of the second optical member faces the first optical member, and wherein an optical cavity is formed between the first end and the second end.
12 . The method of claim 11 , further comprising:
joining a sensor ferrule to the first end of the optical element wherein the sensor ferrule is configured to physically connect to the optical fiber and optically align an end of the optical fiber to the optical cavity, and wherein the sensor ferrule may include MgAl 2 O 4 .
13 . The method of claim 11 , further comprising:
forming part of the first optical member through a ceramic etching process.
14 . The method of claim 11 , further comprising:
forming part of the second optical member through a ceramic etching process.
15 . A Fabry-Perot sensor assembly comprising:
an optical element comprising:
a first end opposite a second end relative to a longitudinal axis of the Fabry-Perot sensor assembly;
a first optical member at the first end, further comprising:
a first side;
a second optical member at the second end, wherein the second optical member comprises a diaphragm, and wherein the diaphragm deflects more than the first optical member to pressure changes external to the optical element;
a reflective coating connected to the diaphragm and facing the first side of the first optical member and adjacent to the diaphragm;
a ring-shaped mirror connected to the first side of the first optical member and facing the reflective coating, wherein the ring-shaped mirror does not interfere with light propagation at an end of a bore that interfaces with the first optical member and contains the optical fiber; and
an optical cavity between the first optical member and the second optical member; and
a sensor ferrule affixed to the first end of the optical element, wherein the sensor ferrule is configured to physically connect to the optical fiber, optically aligning and spacing the optical fiber with the optical cavity, and wherein the optical element includes MgA1 2 O 4 spinel or aluminum oxynitride A1 23 N 27 O 5 .