Variable optical attenuator with a transmitting non-attenuating diffracting prism

Patent metadata

Field	Value
Publication number	US-9632253-B1
Application number	US-201615349369-A
Country	US
Kind code	B1
Filing date	Nov 11, 2016
Priority date	Nov 12, 2015
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

Abstract

A variable optical attenuator is provided. The variable optical attenuator includes an input optical fiber, an output optical fiber, a non-attenuating, transmission-type diffracting prism and a prism positioning system. The input optical fiber, the non-attenuating, transmission-type diffracting prism and the output optical fiber are optically arranged such that an optical path from the input core of the input optical fiber to the output core of the output optical fiber passes through the non-attenuating, transmission-type diffracting prism. The non-attenuating, transmission-type diffracting prism diffracts an optical signal propagating from the input optical fiber to the output optical fiber such that an input portion of the optical path is non-linear with an output portion of the optical path. The prism positioning system changes a pose of the non-attenuating, transmission-type diffracting prism within the optical path thereby attenuating the optical signal.

First claim

What is claimed is:

1. A variable optical attenuator comprising:
an input optical fiber comprising an input core;
an output optical fiber comprising an output core;
a non-attenuating, transmission-type diffracting prism; and
a prism positioning system; wherein
the input optical fiber, the non-attenuating, transmission-type diffracting prism and the output optical fiber are optically arranged such that an optical path from the input core of the input optical fiber to the output core of the output optical fiber passes through the non-attenuating, transmission-type diffracting prism;
the non-attenuating, transmission-type diffracting prism comprises an input face and an output face oriented at a non-zero angle relative to the input face;
the non-attenuating, transmission-type diffracting prism is configured to diffract an optical signal propagating from the input optical fiber to the output optical fiber such that an input portion of the optical path from the input core to the input face of the non-attenuating, transmission-type diffracting prism is non-linear with an output portion of the optical path from the output face of the non-attenuating, transmission-type diffracting prism to the output core; and
a pose of the non-attenuating, transmission-type diffracting prism is changeable within the optical path by the prism positioning system to vary the degree to which the output portion of the optical path is aligned with the output core of the output optical fiber.

2. The variable optical attenuator of claim 1 , wherein the prism positioning system is for moving the non-attenuating, transmission-type diffracting prism in a direction along which the non-attenuating, transmission-type diffracting prism moves into or out of the input portion of the optical path from the input core to the input face of the non-attenuating, transmission-type diffracting prism such that a thickness through which the optical signal passes between the input face and the output face of the non-attenuating, transmission-type diffracting prism changes.

3. The variable optical attenuator of claim 1 , wherein the prism positioning system is for moving the non-attenuating, transmission-type diffracting prism in a direction generally parallel to the input portion of the optical path from the input core to the input face of the non-attenuating, transmission-type diffracting prism such that a distance between the input face of the non-attenuating, transmission-type diffracting prism and the input core of the input optical fiber changes.

4. The variable optical attenuator of claim 3 , wherein the prism positioning system comprises a threaded shaft and a threaded block, wherein the non-attenuating, transmission-type diffracting prism is attached to the threaded block such that rotating of the threaded shaft moves the threaded block and the non-attenuating, transmission-type diffracting prism in the direction generally parallel to the input portion of the optical path from the input core to the input face of the non-attenuating, transmission-type diffracting prism.

5. The variable optical attenuator of claim 1 , wherein the prism positioning system is for moving the non-attenuating, transmission-type diffracting prism in a direction along which the non-attenuating, transmission-type diffracting prism moves into or out of the input portion of the optical path from the input core to the input face of the non-attenuating, transmission-type diffracting prism and in another direction generally parallel to the optical path from the input core to the input face of the non-attenuating, transmission-type diffracting prism.

6. The variable optical attenuator of claim 1 , wherein the prism positioning system is for rotating the non-attenuating, transmission-type diffracting prism about an axis to produce a roll of the non-attenuating, transmission-type diffracting prism.

7. The variable optical attenuator of claim 1 , wherein the prism positioning system is for rotating the non-attenuating, transmission-type diffracting prism about an axis to produce a pitch of the non-attenuating, transmission-type diffracting prism.

8. The variable optical attenuator of claim 1 , wherein the prism positioning system is for rotating the non-attenuating, transmission-type diffracting prism about an axis to produce a yaw of the non-attenuating, transmission-type diffracting prism.

9. The variable optical attenuator of claim 1 , further comprising an input reflector and an output reflector, wherein:
the input reflector is positioned between the input core of the input optical fiber and the input face of the non-attenuating, transmission-type diffracting prism for reflecting the optical signal propagating from the input core to the input face of the non-attenuating, transmission-type diffracting prism; and
the output reflector is positioned between the output face of the non-attenuating, transmission-type diffracting prism and the output core of the output optical fiber for reflecting the optical signal propagating from the output face of the non-attenuating, transmission-type diffracting prism to the output core of the output optical fiber.

10. The variable optical attenuator of claim 9 , further comprising an input fiber handling ferrule and an output fiber handling ferrule, wherein:
the input optical fiber is aligned within the input fiber handling ferrule;
the output optical fiber is aligned with the output optical fiber; and
the input fiber handling ferrule is oriented non-parallel to the output fiber handling ferrule.

11. The variable optical attenuator of claim 1 , wherein:
the variable optical attenuator further comprises an intensity-independent positioning feedback system comprising a feedback light source, a light source integrity photodetection zone, and a prism movement photodetection zone;
the feedback light source defines an optically diverging interrogation path;
the light source integrity photodetection zone and the prism movement photodetection zone are positioned in different portions of the optically diverging interrogation path;
the degree of optical obstruction in the prism movement photodetection zone varies with movement of the non-attenuating, transmission-type diffracting prism such that an intensity feedback signal from the prism movement photodetection zone is indicative of prism movement; and
the degree of optical obstruction in the light source integrity photodetection zone is independent of movement of the non-attenuating, transmission-type diffracting prism such that an intensity feedback signal from the light source integrity photodetection zone is indicative of an absolute intensity of the feedback light source.

12. The variable optical attenuator of claim 11 , wherein:
the variable optical attenuator further comprises a blocking element; and
optical obstruction in the prism movement photodetection zone is attributable to movement of the blocking element with the non-attenuating, transmission-type diffracting prism.

13. The variable optical attenuator of claim 12 , wherein the blocking element is attached to and extends from the non-attenuating, transmission-type diffracting prism.

14. The variable optical attenuator of claim 11 , wherein the light source integrity photodetection zone and a prism movement photodetection zone correspond to a pair of photodetectors.

15. The variable optical attenuator of claim 11 , wherein the light source integrity photodetection zone and the prism movement photodetection zone are positioned in a common detection plane of the optically diverging interrogation path.

16. A variable optica

Assignees

• Alliance Fiber Optics Prod Inc

Inventors

• Wang Xinzhong
• Huang Yu
• Li Yao

Classifications

• G02B6/4226

  Positioning means for moving the elements into alignment, e.g. alignment screws, deformation of the mount · CPC title

• G02B6/4286

  Optical modules with optical power monitoring · CPC title

• G02B6/266 Primary

  the optical element being an attenuator · CPC title

• G02B6/4225

  by a direct measurement of the degree of coupling, e.g. the amount of light power coupled to the fibre or the opto-electronic element · CPC title

• G02B6/34

  utilising prism or grating {(G02B6/293 takes precedence)} · CPC title