Fiber stretcher apparatus

1. An optical fiber device, comprising:

a linear actuator responsive to a control signal to cause a dimensional change along a straight line;

a fiber stretcher frame comprising at least one expandable slot that is engaged to the actuator so that the dimensional change along the straight line is across the expandable slot to change a width of the expandable slot, the fiber stretcher frame structured to amplify the dimensional change of the actuator to produce an amplified change in a circumference of an exterior surface of the fiber stretcher frame; and

a fiber loop wrapping around the exterior surface of the fiber stretcher frame that changes a length of the fiber loop with the amplified change in the circumference of the exterior surface of the fiber stretcher frame.

2. The device as in claim 1 , wherein:

the fiber stretcher frame is partially divided into a first frame part and a second frame part by the expandable slot, wherein the first frame part and the second frame part are integral to each other and are connected at a pivot point around which the first and second frame parts move relative to each other under an operation of the actuator.

3. The device as in claim 2 , comprising:

a first actuator anchor on the first frame part to hold a first end of the actuator;

a second actuator anchor on the second frame part to hold a second end of the actuator and spaced from the first actuator anchor to exert an initial load on the first and second frame parts to set an initial width of the expandable slot which produces an initial stretch on the fiber loop,

wherein the actuator is operable to expand or contract to increase or decrease the initial stretch on the fiber loop, respectively.

4. The device as in claim 3 , comprising:

a screw mounted to the first actuator anchor and engaged to press against the first end of the actuator, the screw being adjustable to change a position of the actuator relative to the first actuator anchor to change the initial stretch.

5. The device as in claim 3 , comprising:

at least one of the first and second actuator anchors is adjustable in position to change the initial width of the expandable slot and thus the initial stretch.

6. The device as in claim 1 , wherein:

the fiber stretcher frame includes a first frame part and a second frame part that are separated from each other by the expandable slot, and a resilient connector that connects the first frame part and the second frame part at a pivot point around which the first and second frame parts move relative to each other under an operation of the actuator.

7. The device as in claim 6 , comprising:

a first actuator anchor on the first frame part to hold a first end of the actuator;

a second actuator anchor on the second frame part to hold a second end of the actuator and spaced from the first actuator anchor to exert an initial load on the first and second frame parts to set an initial width of the expandable slot which produces an initial stretch on the fiber loop,

wherein the actuator is operable to expand or contract to increase or decrease the initial stretch on the fiber loop, respectively.

8. The device as in claim 7 , comprising:

a screw mounted to the first actuator anchor and engaged to press against the first end of the actuator, the screw being adjustable to change a position of the actuator relative to the first actuator anchor to change the initial stretch.

9. The device as in claim 6 , comprising:

at least one of the first and second actuator anchors is adjustable in position to change the initial width of the expandable slot and thus the initial stretch.

10. The device as in claim 1 , wherein:

the exterior surface of the fiber stretcher frame includes straight sections and curved sections, and

wherein the fiber loop is fixed to the exterior surface in a way that each fiber segment in the fiber loop located in a curved section is isolated from expansion and extraction of the stretcher frame and each fiber segment in the fiber loop located in a straight section expands and contracts with the stretcher frame.

11. The device as in claim 10 , wherein:

each fiber segment in the fiber loop located in a straight section is fixed at both ends of the straight section to isolate an adjacent fiber segment in the fiber loop located on an adjacent curved section from expansion and extraction of the stretcher frame.

12. The device as in claim 11 , wherein:

each fiber segment in the fiber loop located in a straight section is fixed at both ends of the straight section by an adhesive.

13. The device as in claim 1 , wherein:

the fiber stretcher frame comprises a second expandable slot located adjacent to the first expandable slot; and

the actuator engaged to the expandable slot is also engaged to two sides of the second expandable slot to control widths of both the expandable slot and the second expandable slot in response tot the control signal.

14. The device as in claim 1 , wherein:

the fiber stretcher frame comprises a second expandable slot; and

the device comprises a second linear actuator engaged to the second expandable slot to change a width of the second expandable slot as the second linear actuator exhibits a dimensional change along a straight line, the fiber stretcher frame structured to amplify the dimensional change of the second linear actuator to, collectively with the actuator engaged to the expandable slot, amplify a change in the circumference of the exterior surface of the fiber stretcher frame.

15. The device as in claim 1 , wherein:

the linear actuator is a piezo-electric actuator, an electro-strictive actuator, a magneto-strictive actuator, a magneto-mechanical actuator, or a linear motor actuator.

16. The device as in claim 1 , comprising:

an optical polarization beam splitter (PBS) having a first port, a second port and a third port, wherein light at a first optical polarization transmits through the PBS between the first port and the second port, and light at a second optical polarization orthogonal to the first optical polarization that enters at either of the second port and the third port is reflected to the other of the second port and the third port;

a first optical path having a first end optically coupled to the second port of the PBS to receive light from the second port and to direct light to the second port;

a Faraday reflector coupled to a second end of the first optical path to reflect light received from the first optical path back to the first optical path with a reflected optical polarization that is, at each location along the first optical path, orthogonal to an optical polarization of the light when traveling in the first optical path from the PBS towards the Faraday reflector prior to the reflection;

a second optical path having a first end optically coupled to the third port of the PBS to receive light from the second port and to direct light to the third port; and

a reflector coupled to a second end of the second optical path to reflect light received from the second optical path back to the second optical path with a reflected optical polarization that is the same as an optical polarization of the light at the third port when entering the second optical path,

wherein the fiber loop wrapped around the fiber stretcher frame is connected as part of the first optical path between the Faraday reflector and the PBS to produce a variable optical delay in light in the first optical path as the control signal applied to the actuator changes.

17. The device as in claim 1 , comprising:

a first optical path comprising a first end and a second end that includes a reflector to direct light received from the first end back to the first end;

a second optical path comprising a first end and a second end that includes a reflector to direct light received from the first end back to the first end; and

an optical coupler that couples the first and second optical paths to each other at the first end of the first optical path and the first end of the second optical path to split an input beam into a first beam into the first optical path and a second beam into the second optical path and to mix reflections of the first beam and the second beam to cause optical interference,

wherein the fiber loop wrapped around the fiber stretcher frame is connected as part of the first optical path between the first end and the second end to produce a variable optical delay in light in the first optical path as the control signal applied to the actuator changes.

18. The device as in claim 17 , comprising:

a light source to produce a probe beam;

an optical probe head coupled to receive the probe beam and to transmit a first part of the probe beam into a sample to collect reflected light from the sample as a sampling beam and to reflect a second part of the probe beam away from the sample to produce a reference beam to mix and co-propagate with the sampling beam as a returned probe beam,

wherein optical probe head and the optical coupler are in communication to direct the returned probe beam as the input beam to the optical coupler; and

an optical detector coupled to receive an interference signal produced by interference of light from the first and second optical paths at the optical coupler.

19. The device as in claim 18 , comprising:

an optical circulator having a first port, a second port and a third port to receive the probe beam from the light source at the first port and to direct the received probe beam to the second port to which the optical probe head is coupled, and to direct the returned probe beam from the optical probe head to the third port to which the optical coupler is coupled to receive the returned probe beam.

20. An optical fiber device, comprising:

an inner circular frame;

a plurality of exterior arc frames separate from one another and arranged to surround the inner circular frame to form an outer circle concentric with the inner circular frame;

a plurality of connectors respectively connecting the plurality of exterior arc frames to an outer surface of the inner circular frame, one connector per exterior arc frame, wherein each connector holds each exterior arc frame to the inner circular frame as an integral structure;

a plurality of linear actuators arranged in a circle concentric with and engaged to the inner circular frame, each linear actuator oriented to expand or contract along a straight line in a radial direction of the inner circular frame and two linear actuators being engaged to one exterior arc frame symmetrically on two sides of a respective connector for the exterior arc frame to expand and contract to change a radial position of the exterior arc frame relative to the inner circular frame; and

a fiber loop wrapping around the exterior surfaces of the exterior arc frames forming the outer circle under an initial stretch condition so that the fiber loop changes a length when the linear actuators expand and contract to change the circumference of the outer circle.

21. The device as in claim 20 , comprising:

a plurality of screws mounted to the inner circular frame and engaged to press the linear actuators, respectively, along the radial direction against respective exterior arc frames, each screw being adjustable to change a position of a respective linear actuator to change the initial stretch on the fiber loop.

22. The device as in claim 20 , wherein:

each linear actuator is a piezo-electric actuator, an electro-strictive actuator, a magneto-strictive actuator, a magneto-mechanical actuator, or a linear motor actuator.

23. The device as in claim 20 , comprising:

an optical polarization beam splitter (PBS) having a first port, a second port and a third port, wherein light at a first optical polarization transmits through the PBS between the first port and the second port, and light at a second optical polarization orthogonal to the first optical polarization that enters at either of the second port and the third port is reflected to the other of the second port and the third port;

a first optical path having a first end optically coupled to the second port of the PBS to receive light from the second port and to direct light to the second port;

a Faraday reflector coupled to a second end of the first optical path to reflect light received from the first optical path back to the first optical path with a reflected optical polarization that is, at each location along the first optical path, orthogonal to an optical polarization of the light when traveling in the first optical path from the PBS towards the Faraday reflector prior to the reflection;

a second optical path having a first end optically coupled to the third port of the PBS to receive light from the second port and to direct light to the third port; and

a reflector coupled to a second end of the second optical path to reflect light received from the second optical path back to the second optical path with a reflected optical polarization that is the same as an optical polarization of the light at the third port when entering the second optical path,

wherein the fiber loop wrapping around the exterior surfaces of the exterior arc frames is connected as part of the first optical path between the Faraday reflector and the PBS to produce a variable optical delay in light in the first optical path as the control signal applied to the actuator changes.

24. The device as in claim 20 , comprising:

a first optical path comprising a first end and a second end that includes a reflector to direct light received from the first end back to the first end;

a second optical path comprising a first end and a second end that includes a reflector to direct light received from the first end back to the first end; and

an optical coupler that couples the first and second optical paths to each other at the first end of the first optical path and the first end of the second optical path to split an input beam into a first beam into the first optical path and a second beam into the second optical path and to mix reflections of the first beam and the second beam to cause optical interference,

wherein the fiber loop wrapping around the exterior surfaces of the exterior arc frames is connected as part of the first optical path between the first end and the second end to produce a variable optical delay in light in the first optical path as the control signal applied to the actuator changes.

25. The device as in claim 24 , comprising:

a light source to produce a probe beam;

an optical probe head coupled to receive the probe beam and to transmit a first part of the probe beam into a sample to collect reflected light from the sample as a sampling beam and to reflect a second part of the probe beam away from the sample to produce a reference beam to mix and co-propagate with the sampling beam as a returned probe beam,

wherein optical probe head and the optical coupler are in communication to direct the returned probe beam as the input beam to the optical coupler; and

an optical detector coupled to receive an interference signal produced by interference of light from the first and second optical paths at the optical coupler.