RETRACTABLE REEL FOR HANDLING OPTICAL FIBER
A cassette for optical fiber includes one or more optical sensors. The cassette has a spool for handling optical fiber. An adjustable shaft is disposed such that the spool is configured to rotate about the adjustable shaft. The adjustable shaft is configured to handle spools having different diameters. A spool controller is coupled to the adjustable shaft and configured to rotate the adjustable shaft to perform one or more of extract and retract the optical fiber. One or more bushings are disposed proximate the spool and are configured to prevent the optical fiber from jumping off the spool.
This application relates generally to techniques for structural health monitoring. The application also relates to components, devices, systems, and methods pertaining to such techniques.
BACKGROUNDFiber optic (FO) sensors can be used for detecting parameters such as strain, temperature, pressure, current, voltage, chemical composition, and vibration. FO sensors are attractive components because they are thin, lightweight, sensitive, robust to harsh environments, and immune to electromagnetic interference (EMI) and electrostatic discharge. FO sensors can be arranged to simultaneously measure multiple parameters distributed in space with high sensitivity in multiplexed configurations over long optical fiber cables. One example of how this can be achieved is through fiber Bragg grating (FBG) sensors. A FBG sensor is formed by a periodic modulation of the refractive index along a finite length (typically a few mm) of the core of an optical fiber. This pattern reflects a wavelength, called the Bragg wavelength, determined by the periodicity of the refractive index profile. The Bragg wavelength is sensitive to external stimulus (strain and/or temperature, etc.) that changes the periodicity of the grating and/or the index of refraction of the fiber. Thus, FBG sensors rely on the detection of small wavelength changes in response to stimuli of interest. In some implementations, FO sensors can be attached to structures and operated to detect parameters, e.g., strain, temperature, vibration, related to the health of the structures.
SUMMARYEmbodiments described herein involve a cassette for optical fiber comprising one or more optical sensors. The cassette comprises a spool for handling optical fiber. An adjustable shaft is disposed such that the spool is configured to rotate about the adjustable shaft. The adjustable shaft is configured to handle spools having different diameters. A spool controller is coupled to the adjustable shaft and configured to rotate the adjustable shaft to perform one or more of extract and retract the optical fiber. One or more bushings are disposed proximate the spool and are configured to prevent the optical fiber from jumping off the spool.
Embodiments involve an apparatus, comprising a cassette for optical fiber comprising one or more optical sensors. The cassette comprises a spool for handling optical fiber. A shaft is disposed such that the spool is configured to rotate about the shaft. A spool controller is coupled to the adjustable shaft and is configured to rotate the adjustable shaft to perform one or more of extract and retract the optical fiber. One or more adjustable bushings are disposed proximate the spool and are configured to prevent the optical fiber from jumping off the spool. The one or more adjustable bushings are configured to adjust to accommodate spools of different diameters;
Throughout the specification reference is made to the appended drawings wherein:
The figures are not necessarily to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.
DETAILED DESCRIPTIONSome embodiments disclosed herein involve apparatuses for attaching FO sensors to structures. Fiber optic sensors can be deployed on various types of structures, e.g., bridges, roadways, railways, and electrical devices such as transformers, to monitor the structural health of the structures. The disclosed embodiments can facilitate mounting FO sensors to the structures in such a way that strain from the structures is transmitted to the sensors. The approaches discussed herein provide for attachment of FO sensors that is flexible enough to attach the FO sensors to a variety of different substrates, e.g. concrete, metal, and wood. Repeatability of the attachment is desired so that at least some or most of the FO sensors have the same pre-strain once attached. The disclosed attachment approaches can be simple and rapid to perform to facilitate the deployment of multiple FO sensors on a structure. Installing optical fibers on structures involves extensive fiber handling during the install. Optical fibers are fragile, and breaks and/or tangles cost time, which is detrimental e.g. because roads must be shut down to service a structure. According to various configurations, the sensors may be fiber Bragg grating (FBG) strain sensors, Fabry Perot sensors, and/or other interferometric optical sensors. In some cases, the sensors may include one or more of electrical and/or resistive sensors, mechanical sensors, and/or other types of strain gages. In some cases, a combination of different types of sensors may be used.
Fiber sensors are manufactured and delivered as multiple sensors on a single fiber strand wound on a compact spool which must be gradually unspooled in a controlled manner. Additionally, sag between attachment points can cause fibers to be susceptible to wind currents and animal or human interference that causes the fiber to break. Embodiments described herein involve a cassette which simplifies fiber handling during fiber sensor deployment. For example, the cassette described herein may be used to minimize the possibility of breaks and tangles and minimize sag in the installed fibers.
Available retractable spools are generally large size, large diameter spools designed for long lengths of jacketed and/or armored fiber. They may have manual or powered retraction mechanisms. Retraction mechanisms based on a spring can generally only handle up to 100 feet, and FBG sensing strands can be much longer (e.g., 200 feet). Fiber optic storage spools for telecommunication applications also have a relatively large size and do not feature a built-in retracting mechanism.
For example, the cassette 110 may include one more bushings 150, 152, 154 that help to prevent the optical fiber 120 from jumping off the spool 130. The bushings 150, 152, 154 may be configured to press up against the outside edge of the spool 130 and move along the spool 130 as the spool 130 rotates. The bushings 150, 152, 154 may be configured to move along the spool by one or more of a sliding motion and a rolling motion. For example, the bushings 150, 152, 154 may slide along the spool as it rotates e.g. using a flexible plastic or roll along the spool 130 as with a plastic and/or a rubber bushing.
A shaft 160 may be disposed such that the spool 130 is configured to rotate about the shaft. The shaft 160 and/or bushings 150, 152, 154 and/or exit port 175 may be adjustable to accommodate optical fiber spools or different sizes, for example. Having an adjustable shaft position may allow for the optical fiber to maintain a substantially horizontal line between where the fiber exits the spool 165 and where the fiber exits the cassette.
According to various configurations, the shaft 210 may be adjustable into two or more distinct shaft positions 242, 244 along the shaft adjustment mechanism 240 as shown in
According to various embodiments described herein, the shaft may have a flexible clamping mechanism to accommodate different spool keyways.
In some embodiments, the cassette 110 may feature a guide feed 170 located where the optical fiber 120 exits the cassette 110. The guide feed 170 may be configured to move back and forth parallel to the axis of the spool 130 as the optical fiber 120 retracts. This guide feed 170 prevents the retracted optical fiber 120 from bunching up on one end of the spool 130 as the optical fiber 120 retracts. The guide feed 170 may be especially useful when large lengths of optical fiber 120 need to be retracted, such as in the case of a reloadable spool, for example. The guide feed 170 may feature a large bend radius that prevents the optical fiber 120 from undergoing a sharp bend at the exit of the cassette 110. The bend radius may be in a range of about 3 mm to about 10 mm, for example.
A more detailed view of a guide feed is shown in
Some embodiments may feature a fiber optic rotary joint as shown in
Some embodiments may include a drag adjustment mechanism and/or braking mechanism that allows the line tension to be adjusted during extraction and/or to lock the spool so that no additional fiber may be extracted. This could be adjusted using a knob, set screw, and/or handle, for example.
According to various embodiments described herein, the cassette may be configured to be handheld, attached to a human body, attached to a structure, and/or free standing as shown in
Specifically,
The first housing portion 710 and/or the second housing portion 712 may have an spool controller attachment 790 for retracting and/or extracting the optical fiber 795. The spool controller may include one or more of a crank, a knob, a handle, a magnetic mechanism, and/or a powered mechanism such as a motor, for example and/or other type of system. A brake mechanism 780 may be disposed proximate the attachment point 790. The cassette 700 may have one or more attachment points 770 configured to allow for attachment of the housing to a structure, for example. While the example shown in
Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range.
The various embodiments described above may be implemented using circuitry and/or software modules that interact to provide particular results. One of skill in the computing arts can readily implement such described functionality, either at a modular level or as a whole, using knowledge generally known in the art. For example, the flowcharts illustrated herein may be used to create computer-readable instructions/code for execution by a processor. Such instructions may be stored on a computer-readable medium and transferred to the processor for execution as is known in the art.
The foregoing description of the example embodiments have been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the inventive concepts to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. Any or all features of the disclosed embodiments can be applied individually or in any combination, not meant to be limiting but purely illustrative. It is intended that the scope be limited by the claims appended herein and not with the detailed description.
Claims
1. An apparatus, comprising:
- a cassette for optical fiber comprising one or more optical sensors, the cassette comprising: a spool for handling optical fiber; an adjustable shaft disposed such that the spool is configured to rotate with the adjustable shaft, the adjustable shaft configured to handle spools having different diameters; a spool controller coupled to the adjustable shaft and configured to rotate the adjustable shaft to perform one or more of extract and retract the optical fiber; and one or more bushings proximate the spool configured to prevent the optical fiber from jumping off the spool; wherein the bushings are adjustable to accommodate different spool types.
2. The apparatus of claim 1, wherein the one or more optical sensors comprise one or more fiber Bragg grating (FBG) sensors.
3. The apparatus of claim 1, wherein the one or more bushings are configured to move along the spool as the spool rotates.
4. The apparatus of claim 3, wherein the one or more bushings are configured to move along the spool by one or more of a sliding motion and a rolling motion.
5. The apparatus of claim 1, wherein the spool controller comprises a crank.
6. The apparatus of claim 1, further comprising a guide feed disposed proximate a fiber exit location of the cassette.
7. The apparatus of claim 6, wherein the guide feed comprises a bend radius in a range of about 3 mm to about 10 mm.
8. The apparatus of claim 1, further comprising a fiber optic rotary joint configured to maintain alignment between at least two optical fibers as one of the optical fibers rotates.
9. The apparatus of claim 1, further comprising a drag adjustment mechanism configured to adjust a tension needed to extract the optical fiber.
10. The apparatus of claim 1, further comprising an enclosure configured to isolate the optical fiber from an environment until the optical fiber is extracted.
11. The apparatus of claim 10, further comprising a lid at least partially covering the enclosure that is configured to be removed to insert spools of optical fiber.
12. The apparatus of claim 1, wherein the adjustable shaft comprises a flexible clamping mechanism configured to accommodate different spool keyways.
13. The apparatus of claim 1, wherein the adjustable shaft is configured to have an adjustable position relative to the spool to accommodate different spool diameters such that a fiber exit location is along a horizontal tangent line to the spool.
14. (canceled)
15. The apparatus of claim 1, wherein the cassette comprises a handle.
16. The apparatus of claim 1, wherein the cassette comprises at least one hole configured to accommodate a carabiner.
17. An apparatus, comprising:
- a cassette for optical fiber comprising one or more optical sensors, the cassette comprising: a spool for handling optical fiber; a shaft disposed such that the spool is configured to rotate with the shaft; a spool controller coupled to the shaft and configured to rotate the shaft to perform one or more of extract and retract the optical fiber; and one or more adjustable bushings in contact with the spool and configured to prevent the optical fiber from jumping off the spool, the one or more adjustable bushings configured to adjust to accommodate spools of different diameters.
18. The apparatus of claim 17, wherein the one or more optical sensors comprise one or more fiber Bragg grating (FBG) sensors.
19. The apparatus of claim 17, wherein the one or more bushings are configured to move along the spool as the spool rotates.
20. The apparatus of claim 19, wherein the one or more bushings are configured to move along the spool by one or more of a sliding motion and a rolling motion.
Type: Application
Filed: Apr 20, 2021
Publication Date: Oct 20, 2022
Inventors: Jacob N. Chamoun (Somerville, MA), Qiushu Chen (San Jose, CA), Peter Kiesel (Palo Alto, CA), Mark R. Teepe (Menlo Park, CA), Kyle Arakaki (Mountain View, CA)
Application Number: 17/235,138