Sensor device having an integrated beam splitter

Patent metadata

Field	Value
Publication number	US-11047885-B2
Application number	US-201916253755-A
Country	US
Kind code	B2
Filing date	Jan 22, 2019
Priority date	Jul 22, 2016
Publication date	Jun 29, 2021
Grant date	Jun 29, 2021

Abstract

The optical interferometric sensor device comprises an integrated beam splitter having a first facet and a second facet with optical ports arranged therein. On the beam splitter, the beam splitting junctions as well as the optoelectronics-side ports and the sensing-side port are arranged with a mutual displacement along the direction of the first facet. This displacement reduces undesired interference effects caused by stray light. Also, a quarter-wave retarder is provided in a recess of the beam splitter with layers of soft adhesive adjacent to it in order to reduce stress.

First claim

The invention claimed is:

1. An optical sensor device comprising:
a light source,
a first fiber, wherein light from said light source is coupled into said first fiber,
an integrated-optics beam splitter having an optoelectronics-side entry port, a first and a second optoelectronics-side exit port and a sensing-side port, wherein light entering said optoelectronics-side entry port is coupled at least partially into said sensing-side port and light entering said sensing-side port is split at least partially into said first and second optoelectronics-side exit ports, and wherein said first fiber is positioned to send light into said optoelectronics-side entry port,
a sensing element whose birefringence changes as a function of a measurand, wherein light from said sensing-side port is coupled into said sensing element, is reflected and is coupled back into said sensing-side port,
at least a second fiber and a third fiber, wherein light from said first and said second optoelectronics-side exit ports is fed into said second and third fibers, respectively,
light detectors for measuring light exiting from said second and third fibers,
wherein said beam splitter comprises
a) a plurality of waveguide sections and splitting junctions, and
b) a first and a second facet on opposite sides of said integrated-optics beam splitter, wherein said optoelectronics-side entry port and said optoelectronics-side exit ports are arranged at said first facet and said sensing-side port is arranged at said second facet,
wherein, in a direction Y parallel to said first facet, said sensing-side port is offset, by a non-zero minimum port-port-offset, in respect to said optoelectronics-side entry port and said first and second optoelectronics-side exit ports,
wherein in said direction Y, said sensing-side port is offset, by a non-zero minimum junction-port-offset, in respect to any junction that the light from said optoelectronics-side entry port passes on its way to said sensing-side port.

2. The sensor device of claim 1 , wherein said integrated-optics beam splitter has, in a direction perpendicular to said first facet, a length of L, and wherein said minimum port-port offset is at least L/20.

3. The sensor device of claim 1 , wherein said minimum port-port-offset is at least 250 μm.

4. The sensor device of claim 1 , wherein, in said direction Y, said first and second optoelectronics-side exit ports are offset, by a non-zero minimum junction-port-offset, in respect to any junction that the light from said sensing-side port passes on its way to any of said optoelectronics-side entry or exit ports.

5. The sensor device of claim 4 , wherein said minimum junction-port-offset is at least D/20, in particular at least D/10, with D being the farthest distance of any of said junctions to any of said facets.

6. The sensor device of claim 4 , wherein said minimum junction-port-offset is at least 125 μm.

7. The sensor device of claim 1 , wherein said waveguide sections are birefringent and introduce a phase shift of 90°+n·180°, with n being zero or a positive integer, between two polarization modes of light passing from said optoelectronics-side entry port to said sensing-side port and, with swapped polarizations, back to one of said optoelectronics-side exit ports.

8. The sensor device of claim 1 , comprising:
a quarter-wave retarder arranged between at least one of said fibers and sensing-side port,
wherein said beam splitter comprises a recess or slit, wherein said quarter-wave retarder is arranged in said recess or a width of said slit, respectively, is larger than a width of said quarter-wave retarder.

9. The sensor device of claim 8 , wherein an input side and/or an output side of said quarter-wave retarder is bordering a transparent adhesive layer of a thickness of at least 5 μm and a Young's modulus of said adhesive layer is at least smaller by a factor of 10 than a Young's modulus of said quarter-wave retarder.

10. The sensor device of claim 9 , wherein said adhesive layer is a silicone, an acrylate, a urethane acrylate, or an adhesive layer with a glass transition temperature below −40° C.

11. The sensor device of claim 1 , comprising at least a first and a second polarizer arranged between said fibers and said optoelectronics-side entry port and said optoelectronics-side exit ports.

12. The sensor device of claim 8 , wherein said quarter-wave retarder is arranged in the recess between at least one of said polarizers and said integrated-optics beam splitter.

13. The sensor device of claim 11 , wherein said polarizers have a first side having stronger anisotropic absorption than a second side, and wherein said polarizers are arranged with said first side facing said integrated-optics beam splitter.

14. The sensor device of claim 11 , further comprising first and a second birefingent fibers arranged between said second and said third fibers and said integrated-optics beam splitter, wherein said birefingent fibers are arranged with principal axes under 45° in respect to a polarization direction of said polarizers, and wherein a birefringent group delay of said birefringent fibers is larger than a coherence length of the light source.

15. The sensor device of claim 1 , wherein said sensing element comprises a magneto-optic component or an electro-optic component, and said sensor device is adapted to measure a current or voltage.

16. The sensor device of claim 1 , wherein said integrated-optics beam splitter comprises a first junction and a second junction, wherein said first junction splits light from said sensing-side port between said optoelectronics-side entry port and said second junction, and wherein said second junction splits light from said first junction between said first optoelectronics-side exit port and said second optoelectronics-side exit port.

17. The sensor device of claim 16 , wherein, along said direction Y,
said first junction is arranged between said optoelectronics-side entry port and said first optoelectronics-side exit port and/or
said second junction is arranged between said first and said second optoelectronics-side exit ports.

18. The sensor device of claim 8 , wherein said quarter-wave retarder is arranged between said first fiber and said first junction.

19. The sensor device of claim 1 , wherein said beam splitter comprises a first junction, a second junction and a third junction, wherein said first junction splits light from said sensing-side port between said second and third junctions, and wherein said second junction splits light from said first junction between said second optoelectronics-side exit port and a third optoelectronics-side exit port, and wherein said third junction splits light from said first junction between said optoelectronics-side entry port and said first optoelectronics-side exit port.

20. The sensor device of claim 1 , wherein an M×N integrated-optics splitter with integers M=1, 2, . . . and N=5, 6, 7, . . . is used and provides at least two, in particular at least four, optoelectronics-side exit ports for being connected to two separate sensor electronics units which generate at least two redundant signals indicative of the measurand.

21. Use of the sensor device of claim 1 for determining a temperature at said quarter-wave retarder or for correcting said measurand by measuring a difference between normalized signals from said light detectors, wherein said difference is measured in the absence of a phase shift in said sensing element or is derived from low-pass filtered

Assignees

• Abb Power Grids Switzerland Ag

Inventors

• Bohnert Klaus
• Frank Andreas
• Lin Yang
• Gu Xun
• Müeller Georg

Classifications

• G01R15/246 Primary

  based on the Faraday, i.e. linear magneto-optic, effect · CPC title

• G01R19/32

  Compensating for temperature change · CPC title