Phase modulator, phase modulator assembly, and photosensor

• US 8,319,958 B2
• Filed: 01/09/2009
• Issued: 11/27/2012
• Est. Priority Date: 01/10/2008
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation), Toshiba Industrial Products Manufacturing Corporation (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation), Toshiba Industrial Products Manufacturing Corporation (Toshiba Corporation)
• Inventors: Takahashi, Masao, Hamaguchi, Masahiro, Kuwabara, Tsuyoshi, Umemura, Tokihiro, Sasaki, Kinichi, Miyabe, Takashi
• Primary Examiner(s): NGUYEN, TU T
• Application Number:
  US12/812,320
• Publication Number:
  US 20100315621A1
• Time in Patent Office: 1,418 Days
• Field of Search: None
• US Class Current: 356/73.1
• CPC Class Codes: G01C 19/721 Details
• CPC Class Codes: G01D 5/344 using polarisation G01D5/35303 takes precedence
• CPC Class Codes: G01D 5/35351 using other means to detect the measured quantity
• CPC Class Codes: G01D 5/3538 using a particular type of fiber, e.g. fibre with several cores, PANDA fiber, fiber with an elliptic core or the like
• CPC Class Codes: G02B 6/024 with polarisation maintaining properties
• CPC Class Codes: G02B 6/274 based on light guide birefringence, e.g. due to coupling between light guides G02B6/105, G02B6/024 take precedence; mechanically induced birefringence G02F1/0134
• CPC Class Codes: G02F 1/0134 in optical waveguides
• CPC Class Codes: G02F 2203/15 involving resonance effects, e.g. resonantly enhanced interaction
• CPC Class Codes: G02F 2203/50 Phase-only modulation

Abstract

The present invention provides a photosensor that uses a phase modulation technique for optical detection and conducts a highly accurate measurement. The photosensor uses a phase change difference of light propagated through a polarization preserving fiber with respect to tensile stress and employs proper polarization preserving fibers for a phase modulator 10, light-transmitting polarization preserving fiber 23, and coil-shaped polarization preserving fiber 30, to achieve a highly accurate measurement.

Claims

1. A phase modulator comprising a cylindrical or columnar actuator whose body has a characteristic of inducing mechanical vibration and a polarization preserving fiber having two light propagation axes that are orthogonal to each other, the fiber being wound around the actuator in such a manner to receive mechanical stress caused by the mechanical vibration in directions each of about 45 degrees with respect to the two light propagation axes.

2. The phase modulator as set forth in claim 1, wherein:

the actuator is a piezoelectric element; and

the polarization preserving fiber is wound around the piezoelectric element in such a manner that the light propagation axes of the polarization preserving fiber each form an angle of about 45 degrees with respect to a diametrical direction of the piezoelectric element.

3. A phase modulator assembly comprising the phase modulator of claim 1 and a vibration-proof material.

6. The phase modulator as set forth in any one of claims 1 to 5, wherein the polarization preserving fiber is a panda-type fiber.

7. The phase modulator as set forth in claim 6, wherein the polarization preserving fiber is a panda-type fiber of about 80 μ

m in clad diameter.

8. The phase modulator as set forth in any one of claims 1 to 5, wherein the polarization preserving fiber is covered with a clad material that is hard in a side pressure direction.

9. The phase modulator as set forth in claim 8, wherein the clad material of the polarization preserving fiber is ultraviolet curing resin.

10. The phase modulator as set forth in claim 8, wherein the clad material of the polarization preserving fiber is a metal film.

11. The phase modulator as set forth in claim 1 or 4, wherein the actuator is a ceramic element.

4. A phase modulator comprising a cylindrical or columnar actuator whose body has a characteristic of inducing mechanical vibration and a polarization preserving fiber having two light propagation axes that are orthogonal to each other, the fiber being wound around the actuator in such a manner to receive mechanical stress isotropically with respect to the two light propagation axes.

5. A phase modulator comprising a cylindrical or columnar actuator whose body has a characteristic of inducing mechanical vibration and a polarization preserving fiber having two light propagation axes that are orthogonal to each other, the fiber being wound around the actuator at a predetermined twist rate.

12. A photosensor comprising a photo-sensing unit to measure a measuring physical quantity, a signal processing unit to calculate a specified physical quantity according to a light signal from the photo-sensing unit, and an optical fiber to optically connect the photo-sensing unit and signal processing unit to each other, the optical fiber being a polarization preserving fiber having two light propagation axes each of which propagates light,

the polarization preserving fiber being one that demonstrates a small change in a propagation constant difference between the two light propagation axes with respect to tensile stress.

13. The photosensor as set forth in claim 12, wherein the polarization preserving fiber to optically connect the photo-sensing unit and signal processing unit to each other is a bow-tie fiber.

14. The photosensor as set forth in claim 13, wherein the polarization preserving fiber to optically connect the photo-sensing unit and signal processing unit to each other is a bow-tie fiber of about 80 μ

m in clad diameter.

15. The photosensor as set forth in claim 12, wherein the polarization preserving fiber to optically connect the photo-sensing unit and signal processing unit to each other is an elliptic core fiber.

16. The photosensor as set forth in claim 15, wherein the polarization preserving fiber to optically connect the photo-sensing unit and signal processing unit to each other is an elliptic core fiber of about 80 μ

m in clad diameter.

17. The photosensor as set forth in any one of claims 12 to 16, wherein the cladding of the polarization preserving fiber to optically connect the photo-sensing unit and signal processing unit to each other is surrounded with a resilient material.

18. The photosensor as set forth in claim 17, wherein the protective tube has a side face provided with holes at predetermined intervals.

19. The photosensor as set forth in any one of claims 12 to 16, wherein the polarization preserving fiber to optically connect the photo-sensing unit and signal processing unit to each other is inserted in a protective tube to prevent external tensile stress from being applied to the fiber, the inside of the protective tube being structured not to cause a resonance due to vibration or sound.

20. The photosensor as set forth in claim 19, wherein a sound absorbing material is filled between the polarization preserving fiber and the protective tube.

21. The photosensor as set forth in claim 20, wherein the protective tube has a side face provided with holes at predetermined intervals.

22. A photosensor including a photo-sensing unit to measure a measuring physical quantity, a signal processing unit to calculate a specified physical quantity according to a light signal from the photo-sensing unit, and an optical fiber to optically connect the photo-sensing unit and signal processing unit to each other, the photosensor comprising:

other than a phase modulator, a coil-shaped optical element formed of a polarization preserving fiber that demonstrates a small change in a propagation constant difference between two light propagation axes of the fiber with respect to tensile stress.

23. The photosensor as set forth in claim 22, wherein the polarization preserving fiber is a bow-tie fiber.

24. The photosensor as set forth in claim 22, wherein the polarization preserving fiber is an elliptic core fiber.