Optical sensor
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.
1. An optical sensor comprising:
an optical cavity defined by a dielectric body and responsive to one or more physical environmental conditions;
a waveguide having a terminal end spaced apart from the optical cavity such that light is optically coupled from the terminal end of the waveguide to the optical cavity; and
a collimator for collimating the light emitted from the waveguide;
a spacer extending between the dielectric body at a proximal end of the spacer and towards the terminal end of the waveguide;
the spacer arranged such that the distance between the terminal end of the waveguide and the optical cavity is sufficient such that, in use, the waveguide is maintained at a first temperature that would not damage the mechanical or optical properties of the waveguide, and the dielectric body is maintained at a second temperature, higher than the first temperature, that would be sufficient to damage the mechanical or optical properties of the waveguide; and
an interrogator coupled to the waveguide and arranged to detect changes in the properties of the optical cavity.
2. The optical sensor of claim 1 , wherein the collimator is a rod or GRIN lens.
3. The optical sensor of claim 1 , wherein the collimator comprises a lens attached to the terminal end of the waveguide by an attachment.
4. The optical sensor of claim 3 , wherein the attachment is a fusion bond between the terminal end of the waveguide and the lens.
5. The optical sensor of claim 3 , wherein the lens comprises a first surface including a curved portion surrounded by a planar portion.
6. The optical sensor of claim 5 , wherein the lens further comprises a planar second surface parallel with the planar portion of the first surface.
7. The optical sensor of claim 5 , wherein the curved portion is formed by micro-machining.
8. The optical sensor of claim 5 , wherein the curved portion is formed by etching.
9. The optical sensor of claim 1 , wherein the spacer is selected from the group consisting of sapphire, MgO, MgAlO, alumina and zirconia.
10. The optical sensor of claim 1 , wherein the spacer is bonded to a mount.
11. The optical sensor of claim 1 , wherein the bonding is an oxide seal.
12. The optical sensor of claim 1 , wherein the mount is formed from a material having thermal expansion properties substantially matched to that of the dielectric body.
13. An optical sensor comprising:
an optical cavity defined by a dielectric body and responsive to one or more physical environmental conditions;
a waveguide having a terminal end spaced apart from the optical cavity such that light is optically coupled from the terminal end of the waveguide to the optical cavity; and
a spacer extending between the dielectric body at a proximal end of the spacer and towards the terminal end of the waveguide,
wherein the spacer is configured so as to space the waveguide from the optical cavity at a distance sufficient such that, in use, the waveguide is maintained at a first temperature that would not damage the mechanical or optical properties of the waveguide, and the dielectric body is maintained at a second temperature, higher than the first temperature, that would be sufficient to damage the mechanical or optical properties of the waveguide.
14. The optical sensor of claim 13 , wherein the spacer is selected from the group consisting of sapphire, MgO, MgAlO, alumina and zirconia.
15. The optical sensor of claim 13 , wherein the spacer is bonded to a mount.
16. The optical sensor of claim 15 , wherein the bonding is an oxide seal.
17. The optical sensor of claim 15 , wherein the mount is formed from a material having thermal expansion properties substantially matched to that of the dielectric body.
18. The optical sensor according to claim 13 , wherein the optical cavity in the dielectric body is defined at one end by a membrane deflectable in response to changes in external pressure.
19. An optical sensor comprising:
an optical cavity defined by a dielectric body and responsive to one or more physical environmental conditions;
a waveguide having a terminal end spaced apart from the optical cavity such that light is optically coupled from the terminal end of the waveguide to the optical cavity,
a spacer extending between the dielectric body at a proximal end of the spacer and towards the terminal end of the waveguide;
the spacer arranged such that the distance between the terminal end of the waveguide and the optical cavity is sufficient such that, in use, the waveguide is maintained at a first temperature tat would not damage the mechanical or optical properties of the waveguide, and the dielectric body is maintained at a second temperature, higher than the first temperature, that would be sufficient to damage the mechanical or optical properties of the waveguide; and
wherein the optical cavity in the dielectric body is defined at one end by a membrane deflectable in response to changes in external pressure.