Optical fiber based polymer core sensor
View Patent ↗An optical fiber based polymer core sensor includes an optical fiber having a core and an end having a cured polymer core affixed to the core of the optical fiber. The cured polymer core extends outward from the end of the optical fiber and has a diameter approximately equal to the core of the optical fiber. Note the cured polymer core can be substantially cylindrical, tapered or geometrically shaped. The optical fiber based polymer core sensor can be used to measure a temperature, measure a strain, measure a distance, measure a refractive index, detect or measure an analyte, detect a toxin, detect a biological agent, monitor a chemical process, or a combination thereof.
1. A method for fabricating an optical fiber based polymer core sensor comprising the steps of:
providing an optical fiber having a core;
aligning a flat reflective object with the core of the optical fiber to provide a gap between the core and the flat reflective object;
depositing a light-curable polymer within the gap;
transmitting a light through the core such that the light-curable polymer forms a cured polymer core connecting the core to the reflective object, wherein the cured polymer core has a diameter approximately equal to the core; and
removing the reflective object such that the cured polymer core remains affixed to the optical fiber.
2. The method as recited in claim 1 , further comprising the steps, prior to depositing the light-curable polymer, of:
transmitting a white light through the optical fiber;
measuring the gap using the optical fiber and the reflective object as a white light Fabry-Perot interferometric distance sensor; and
adjusting the gap to provide a specified distance between the optical fiber and the reflective object.
3. The method as recited in claim 1 , further comprising the steps of:
removing any uncured light-curable polymer; and
packaging the cured polymer core and a portion of the first optical fiber.
4. The method as recited in claim 3 , wherein the cured polymer core and the optical fiber are packaged within a capillary tube.
5. The method as recited in claim 1 , further comprising the step of modifying a shape of the cured polymer core.
6. The method as recited in claim 5 , wherein:
the shape of the cured polymer core is substantially cylindrical; and
the modified shape of the cured polymer core is tapered or geometrically shaped.
7. The method as recited in claim 1 , further comprising the step of controlling a length of the cured polymer core by measuring and adjusting the gap between the optical fiber and the reflective object.
8. The method as recited in claim 1 , wherein:
the flat reflective object comprises a second optical fiber or a mirror; or
the light-curable polymer comprises a UV-curable polymer and the light comprises a UV light.
9. The method as recited in claim 1 , wherein:
the light is generated using a light-emitting-diode (LED) or other light source attached to the optical fiber that is suitable for curing the light-curable polymer; and
the light-curable polymer comprises a light-curable optical epoxy.
10. The method as recited in claim 1 , wherein the light-curable polymer is selected or modified to adjust a sensitivity or a range of the refractive index sensor.
11. The method as recited in claim 1 , wherein the cured polymer core has a higher reflective index than the light-curable polymer and acts as a waveguide to confine the light inside the cured polymer core.
12. The method as recited in claim 1 , wherein a refractive index of the optical fiber is different that a refractive index of the cured polymer core.
13. The method as recited in claim 1 , wherein the cured polymer core serves as a Fabry-Perot cavity that introduces a phase shift to a light propagating through the cured polymer core from the first optical fiber.
14. The method as recited in claim 1 , wherein the optical fiber based polymer core sensor has a reflectance spectrum of
I
(
λ
)
=
I
1
(
r
)
+
∑
j
I
1
(
2
j
)
+
∑
j
I
1
(
r
)
I
1
(
2
j
)
cos
(
2
β
j
L
)
+
∑
i
≠
j
I
1
(
2
i
)
I
1
(
2
j
)
cos
[
2
(
β
j
-
β
i
)
L
]
.
15. The method as recited in claim 1 , wherein the optical fiber based polymer core sensor is used to measure a temperature, measure a strain, measure a distance, measure a refractive index, detect or measure an analyte, detect a toxin, detect a biological agent, monitor a chemical process, or a combination thereof.
16. The method as recited in claim 1 , wherein the optical fiber based polymer core sensor is used to measure a temperature change as defined by
Δ
T
=
Δ
(
O
P
D
)
O
P
D
(
α
+
ξ
)
.
17. A method for fabricating an optical fiber based polymer core sensor comprising the steps of:
providing an optical fiber having a core;
aligning a flat reflective object with the core of the optical fiber to provide a gap between the core and the flat reflective object;
transmitting a white light through the optical fiber;
measuring the gap using the optical fiber and the reflective object as a white light Fabry-Perot interferometric distance sensor;
adjusting the gap to provide a specified distance between the optical fiber and the reflective object;
depositing a light-curable polymer within the gap;
transmitting a light through the core such that the light-curable polymer forms a cured polymer core connecting the core to the reflective object, wherein the cured polymer core has a diameter approximately equal to the core;
removing the reflective object such that the cured polymer core remains affixed to the optical fiber;
removing any uncured light-curable polymer; and
packaging the cured polymer core and a portion of the first optical fiber.
18. An optical fiber based polymer core sensor comprising:
an optical fiber having a core and an end; and
a cured polymer core affixed to the core of the optical fiber and extending outward from the end of the optical fiber wherein the cured polymer core has a diameter approximately equal to the core of the optical fiber, wherein the cured polymer core is fabricated in accordance with the method of claim 1 .
19. The optical fiber based polymer core sensor as recited in claim 18 , wherein the cured polymer core and a portion of the optical fiber are disposed within a package.
20. The optical fiber based polymer core sensor as recited in claim 18 , wherein the cured polymer core is substantially cylindrical, tapered or geometrically shaped.
21. The optical fiber based polymer core sensor as recited in claim 18 , wherein the light-curable polymer is selected or modified to adjust a sensitivity or a range of the optical fiber based polymer core sensor.
22. The optical fiber based polymer core sensor as recited in claim 18 , wherein a refractive index of the optical fiber is different that a refractive index of the cured polymer core.
23. The optical fiber based polymer core sensor as recited in claim 18 , wherein the cured polymer core serves as a Fabry-Perot cavity that introduces a phase shift to a light propagating through the cured polymer core from the optical fiber.
24. The optical fiber based polymer core sensor as recited in claim 18 , wherein the optical fiber based polymer core sensor has a reflectance spectrum of
I
(
λ
)
=
I
1
(
r
)
+
∑
j
I
1
(
2
j
)
+
∑
j
I
1
(
r
)
I
1
(
2
j
)
cos
(
2
β
j
L
)
+
∑
i
≠
j
I
1
(
2
i
)
I
1
(
2
j
)
cos
[
2
(
β
j
-
β
i
)
L
]
.
25. The optical fiber based polymer core sensor as recited in claim 18 , wherein the refractive index sensor is used to measure a temperature, measure a strain, measure a distance, measure a refractive index, detect or measure an analyte, detect a toxin, detect a biological agent, monitor a chemical process, or a combination thereof.
26. The optical fiber based polymer core sensor as recited in claim 18 , wherein the optical fiber based polymer core sensor is used to measure a temperature change as defined by
Δ
T
=
Δ
(
O
P
D
)
O
P
D
(
α
+
ξ
)
.