Systems and methods for traceable cables

A traceable cable includes at least one data transmission element, a jacket at least partially surrounding the at least one data transmission element, and a tracing optical fiber incorporated with and extending along at least a portion of a length of the cable. The tracing optical fiber includes a core having a first index of refraction and a cladding having a second index of refraction. The traceable cable also includes at least one launch point provided through at least a portion of the jacket for optically accessing the tracing optical fiber. The launch point includes an optical medium accessible from an exterior of the jacket and in contact with the tracing optical fiber, wherein the optical medium is substantially index-matched to the core of the tracing optical fiber. Related systems and methods are also disclosed.

BACKGROUND

This disclosure generally relates to cables and cable assemblies, such as telecommunication patch cords, that are traceable due to the addition of a tracing optical fiber that emits light for visualization purposes. More particularly, this disclosure relates to systems and methods of providing tracer light to the tracing optical fiber(s) of the cables or cable assemblies.

Computer networks continue to increase in size and complexity. Businesses and individuals rely on these networks to store, transmit, and receive critical data at high speeds. Even with the expansion of wireless technology, wired connections remain critical to the operation of computer networks, including enterprise data centers. Portions of these wired computer networks are regularly subject to removal, replacement, upgrade, or other moves and changes. To ensure the continued proper operation of each network, the maze of cables connecting the individual components must be precisely understood and properly connected between specific ports.

In many cases, a data center's cables, often called patch cords, are required to bridge several meters across the data center. The cables may begin in one equipment rack, run through the floor or other conduit, and terminate at a component in a second equipment rack.

As a result, there is a need for an improved system that allows a select cable to be quickly and easily traceable for the purpose of identifying the path and/or approximate terminal end of a given cable that is being replaced, relocated, or tested. Particularly, there is a need for a system that is able to effectively couple light from an external source into the cable to facilitate tracing.

SUMMARY

The present disclosure includes various embodiments of traceable cables. According to one embodiment, a traceable cable includes at least one data transmission element, a jacket at least partially surrounding the at least one data transmission element, and a tracing optical fiber incorporated with and extending along at least a portion of a length of the traceable cable. The tracing optical fiber includes a core having a first index of refraction and a cladding with a second index of refraction. At least one launch point is provided through at least a portion of the jacket for optically accessing the tracing optical fiber. The launch point comprises an optical medium accessible from an exterior of the jacket and in contact with the tracing optical fiber, wherein the optical medium is substantially index-matched to the core of the tracing optical fiber.

The present disclosure also includes systems having traceable cables. One embodiment of a system includes a traceable cable and a launch tool. The traceable cable includes at least one data transmission element, a jacket at least partially surrounding the at least one data transmission element, and a tracing optical fiber incorporated with and extending along at least a portion of a length of the traceable cable. The traceable cable also comprises at least one launch point provided through at least a portion of the jacket for optically accessing the tracing optical fiber. The launch point comprises an optical medium accessible from an exterior of the jacket and in contact with the tracing optical fiber, wherein the optical medium is substantially index-matched to the core of the tracing optical fiber. The launch tool includes a light source and a delivery waveguide, with the light source being configured to couple light into a terminal end of the delivery waveguide. The delivery waveguide has an opposite terminal end for delivering the light from the light source to one of the launch points.

The present disclosure further includes methods of forming a traceable cable. One example method involves providing a cable that has at least one data transmission element, a jacket at least partially surrounding the at least one data transmission element, and a tracing optical fiber embedded with the jacket and extending along a length of the cable. The tracing optical fiber has a core and a cladding, wherein the core has an endface. The method further involves sliding a sleeve over the cable, the sleeve having at least one aperture therethrough. The aperture of the sleeve is aligned to be centered over the tracing optical fiber, and the sleeve is affixed to the cable. A portion of the jacket that is located within the aperture of the sleeve is removed. The removed portion of the jacket is then replaced with a clear material, the clear material being index-matched with the core of the tracing optical fiber.

Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art. It is to be understood that the foregoing general description, the following detailed description, and the accompanying drawings are merely exemplary and intended to provide an overview or framework to understand the nature and character of the claims.

DETAILED DESCRIPTION

Various embodiments will be further clarified by examples in the description below. In general, the description relates to systems, and subsystems thereof, for tracing cables and cable assemblies containing at least one tracing optical fiber. The description also relates to methods of forming and using the systems and subsystems described herein. More particularly, this disclosure provides various embodiments of devices for providing light into an optical fiber, for example a tracing optical fiber within a traceable cable.

A problem that occurs in data centers or similar network locations is congestion and clutter caused by large quantities of cables.FIG. 1shows an example of congestion in an equipment rack16. Network operators frequently desire to change connections to accommodate moves, adds, and changes in the network. However, such congestion makes it difficult to trace a particular cable from the source to the receiver, which may be required to perform the moves, adds, and changes in the network.

This disclosure provides various embodiments, components and subcomponents of a tracing system that allows for tracing operations performed on cables to be quickly and easily conducted by a single technician, resulting in a possible reduction of labor costs, down time, and errors. The tracing system makes the process of performing a trace or otherwise identifying a cable in a congested environment simple and fast for a technician. As a result, the technician can reliably identify the one cable in question (which may be a telecommunication patch cord) from amongst many other cables (which may also be telecommunication patch cords). In some cases, the service technician may be able to reliably identify the cable in question along its length once tracing capability at one end of the cable has been activated. The tracing system may also have the advantage of being an optically-activated tracing system using only passive tracing elements within the cable (although active tracing elements, such as light emitting diodes or the like, may still be provided on the cable assembly in addition to the passive tracing elements, if desired). As will be described in greater detail below, the act of tracing involves tracing a cable based upon an optical signal or stimulus, for example, a visible spot of light that is provided by a source external to the cables themselves. The source external to the cables may alternatively provide non-visible light for tracing purposes, with the tracing system including components to detect such non-visible light, as will be described in further detail below.

An example tracing system18is schematically illustrated inFIG. 2. The tracing system18includes a traceable cable20(hereinafter “cable20”) extending between two locations, such as two equipment racks16in a data center, telecommunications room, or the like. The cable20may, for example, operably connect a port on a server in one of the equipment racks16with a port on a server in another of the equipment racks16.

The tracing system18also includes a launch tool22configured to connect to the cable20and provide tracer light from a light source24. The tracer light may provide illumination at discrete points along the cable20. Such discrete points are represented by element26inFIG. 2and will be referred to herein as emission points26or tracer locations26. In alternative embodiments, the cable20may be configured to provide more continuous emission along its length, or illumination only at or near ends of the cable20.

The tracing system18may further comprise a controller28and an observation tool30. The controller28in the embodiment shown is a remote control unit configured to communicate with the launch tool22. A technician may, for example, use the controller28to send operational commands to the launch tool22to control operation of the light source24. The observation tool30in the embodiment shown comprises a pair of glasses configured to enhance visibility of the tracer light emitted at the emission points26. This may be achieved by enhancing visibility of the wavelength of the tracer light and/or by dampening other visible wavelengths. In embodiments where the tracer light has a non-visible wavelength, the observation tool30may include sensors configured to detect such light and electronics configured to display a representation of such light to a technician.

FIG. 3illustrates one embodiment of the cable20in slightly more detail. The cable20in this embodiment is part of a cable assembly that includes a connector32installed on an end of the cable20. Although not shown, it should be understood that a similar or different connector may be present on an opposite end of the cable20to allow the cable assembly to act as a telecommunications patch cord between different components of a network. Additionally, it should be understood that the connector32may vary widely depending on the nature of the cable20(e.g., the quantity and type of signals transmitted) and the components being connected. The distance between the connectors32on opposite ends of the cable20may define a length L for the cable20. The length L may be at least about 1 meter or even several tens of meters, such as thirty meters or more, depending on the intended use of the cable20.

FIG. 4is a cross section of the cable20to further represent one possible embodiment. As shown inFIG. 4, the cable20includes a data transmission element34and a jacket36surrounding the data transmission element34. Although only one data transmission element is shown in this embodiment, there may be more than one data transmission element in other embodiments. In general, the data transmission element34is a structure capable of carrying a data signal from one end of the cable20to the other end of the cable20. For example, the data transmission element34may be configured to transmit an electrical signal using a copper wire or other electrically conductive material. Alternatively, the data transmission element34may be configured to transmit an optical signal by conducting electromagnetic waves to carry data from one location to another. The data transmission element34shown inFIG. 4is of the latter type (i.e., an optical transmission element) having a core38and a cladding40. There may be strength members (e.g., aramid yarns) or other elements located within the cable20between the data transmission element34and the jacket36.

In alternative embodiments, the cable20may be more appropriately referred to as a conduit, without having any data transmission elements. Instead of transmitting a data signal, these cables may transmit fluids such as air or liquid. These cables may be appropriate for use in a medical setting such as IV lines or oxygen tubing.

Still referring toFIG. 4, the cable20further includes at least one tracer element, which is shown in the form of a tracing optical fiber42(also referred to as a “tracer optical fiber42”) configured to transmit and emit tracer light for visualization purposes. The tracing optical fiber42may be incorporated as part of the cable20in several configurations. In the embodiment shown inFIG. 4, the tracing optical fiber42is embedded within a portion of the jacket36. In other embodiments, the tracing optical fiber42may be adjacent to the data transmission element34, inside a conduit defined by the jacket36. In yet other embodiments, the tracing optical fiber42may be provided on, mounted to, or otherwise attached to an outside of the jacket36.

The tracing optical fiber42includes a core44having a first index of refraction, and a cladding46at least partially surrounding the core44. The cladding46has a second index of refraction different and lower than the first index of refraction. The tracing optical fiber42may be configured to emit light at ends of the tracing optical fiber42and/or along the length of the tracing optical fiber42in a continuous or periodic manner. The tracing optical fiber42may, for example, include features or otherwise be configured to scatter light at discrete locations along the length of the tracing optical fiber42. Such periodic scattering of light may form the emission points26(FIG. 3) of the cable20, alone or in combination with features on the jacket36, such as openings/windows (not shown) in the jacket36or portions of reduced material thickness between the tracing optical fiber42and an outer surface of the jacket36. The term “side-emitting optical fiber” may be used to refer to the tracing optical fiber42in embodiments where light is scattered along the length of the tracing optical fiber42in a periodic or continuous manner.

As mentioned above, the tracer light emitted by the tracing optical fiber42may be provided by the launch tool22(FIG. 2). An example of the launch tool22is schematically shown inFIG. 5. The launch tool22may have a number of elements stored in a housing48, including the light source24(e.g., a red or green laser), an electrical power source50(e.g., batteries), and control circuitry52to control the light source24and power usage. A receiver54or other wireless communication components, such as a combination transmitter/receiver, may be also be included in or on the housing48to receive commands from the controller28(FIG. 3) and optionally transmit information back to the controller. Furthermore, a speaker56may be included to allow for the generation of audible signals. Audible signals may make recovery of the launch tool22easier in a crowded data center environment. The housing48may also include an on-off switch58and be designed approximately the size of a standard flashlight or smaller. The housing48should be sufficiently durable to protect the launch tool22, even in the event of a drop onto a hard surface.

In one embodiment, the light source24may be a semiconductor laser emitting green light at a wavelength between 510-540 nm. Alternatively, other colors/wavelengths may be emitted, such as red light from approximately 620 to 650 nm. In other embodiments, non-laser light sources may be used, such as light emitting diodes (LEDs). Determining the light source24may involve consideration, evaluation, and testing of several factors, including visibility, cost, eye safety, peak power, power consumption, size, and commercial availability.

The launch tool22may include a delivery waveguide60, sometimes referred to as an umbilical, that provides a path for tracer light to travel from the light source24to the tracing optical fiber42of the cable20. The delivery waveguide60may include optional optics to help couple light from the light source24into the delivery waveguide60and/or optics to help couple light from the delivery waveguide60into the tracing optical fiber42. The delivery waveguide60may be several meters in length so the housing48of the launch tool22can be placed on the ground while the end of the delivery waveguide60is coupled with the cable20several meters away.

Attachment features62may be provided at or near a terminal end64(FIG. 7) of the delivery waveguide60to secure the delivery waveguide60to the cable20and keep the terminal end64of the delivery waveguide60in a desired position for establishing and maintaining an optical connection with the tracing optical fiber42. The attachment features62may, for example, include a clasping structure that holds the terminal end64of the delivery waveguide60in a precise spot along the cable20and at a correct angle so that tracer light can couple into the tracing optical fiber42. The attachment features62may provide a secure connection so that the delivery waveguide60remains in optical communication with the tracing optical fiber42after the technician has stepped away (e.g., in search of the far end of the cable20). In some embodiments, the attachment features62may form one portion of a two-part optical connector, as will be discussed further below.

The tracing optical fiber42receives light from the delivery waveguide60through a launch point66(seeFIG. 2) to form an optical junction or connection between the launch tool22and the cable20. Where emission points26are used, sufficient brightness along the full length of the tracing optical fiber42may be desired with the least amount of power for the light source24. Therefore, the coupling efficiency of the optical junction may be important in some embodiments.

The efficiency at which light is coupled from a source (e.g., the terminal end64of the delivery waveguide60) to a receiver (e.g., an endface68of the tracing optical fiber42) may be influenced by: (a) the acceptance half angle θ of the receiver (seeFIG. 6); (b) the étendue of the source; (c) the cross-sectional area of the receiver and (d) the distance between the source and the receiver.

The acceptance half angle θ defines the boundary of an acceptance cone70. For example, light approaching an endface68of the core44from an angle within the acceptance cone70will tend to couple into the core44. Light that approaches from a steeper angle outside of the acceptance cone70will tend to transmit through the side of the core44and therefore may not be captured and transmitted down the core. For a typical plastic optical fiber (POF) with a 0.5 numerical aperture, the acceptance half angle θ is about thirty degrees. For a glass core optical fiber with a polymer cladding and a numerical aperture of 0.39, the acceptance half angle θ is about 23 degrees.

The étendue for a source of light may be considered as a measure of the divergence of light as it leaves the source and the cross-sectional area of the source. The étendue may be calculated as the product of the acceptance solid angle (i.e., two times θ) of the source and the cross-sectional area of the source.

With this in mind, the delivery waveguide60is emitting light in the form of a cone that is spreading after the light leaves the delivery waveguide60. Therefore, it may be desirable for a longitudinal axis A of the delivery waveguide60to form as small of an angle of attack a (seeFIG. 7) with a longitudinal axis Z of the tracing optical fiber42as possible, and in any event should be less than the acceptance half angle θ of the tracing optical fiber42. Further, it may be desirable for the terminal end64of the delivery waveguide60to be positioned as close as possible to an endface68of the tracing optical fiber42to maintain as much overlap between the acceptance cone70of the tracing optical fiber42and the emission cone (not shown) of the delivery waveguide60. In some embodiments, the accuracy of placement along the longitudinal axis Z should be +/−70 microns. Described another way, the intersection of the longitudinal axis Z and the longitudinal axis A should closely correspond to the endface68of the tracing optical fiber42. The depth of the tracing optical fiber42relative to the outer diameter of the cable20should also be accurately maintained within about +/−25 microns.

Each cable20may have one or more of the tracing optical fibers42spaced around the circumference of the jacket36. In some embodiments, the delivery waveguide60may attach to the cable20in a position around a longitudinal axis Z′ of the cable20that is adjacent to the tracing optical fiber42. In the illustrated example ofFIG. 7, the cable20is shown with the portion of the circumference of the cable20that contains the tracing optical fiber42facing upward. Therefore, the delivery waveguide60may be attached to the relative top of the cable20in the illustrated embodiment. Attachment may be provided with precision within +/−1 degree around the longitudinal axis Z′ of the cable20.

In the embodiment ofFIG. 7, the terminal end64of the delivery waveguide60may be provided with a notch72to provide an emission surface74. The notch72may extend from the terminal end64a short distance along the delivery waveguide60, and at an angle with respect to the longitudinal axis A. The notch72may produce an emission surface74that is oblique to the longitudinal axis A. Because the emission surface74should face the launch point66, the notch72renders the delivery waveguide60rotationally dependent. In other words, the rotational orientation of the delivery waveguide60around the longitudinal axis A becomes important to achieve the desired optical junction. To correspond to the illustrated orientation of the cable20, the delivery waveguide60may be rotated around the longitudinal axis A until the notch72faces downward.

The ability to orient or rotate the notch72with respect to the longitudinal axis A may be provided by one of several features. In one embodiment, the delivery waveguide60may be of sufficient length such that the delivery waveguide60itself can be twisted as one end relative to an opposite end. In another embodiment, the delivery waveguide60may be attached to the housing48of the launch tool22by a swivel connector (not shown) to provide for rotation around the longitudinal axis A. The magnitude of rotation about the longitudinal axis A may be influenced by the number of tracing optical fibers42present in the cable20. For example, if there are two tracing optical fibers42mounted in diametrically opposite locations around the longitudinal axis Z′ of the cable20, the delivery waveguide60may rotate +/−90 degrees. For three tracing optical fibers42, the rotational capability may be +/−60 degrees, and so on.

FIGS. 7 and 8show an embodiment of an optical junction. Generally speaking, optical junctions described herein facilitate coupling light from an external source (i.e., the launch tool22) to the tracing optical fiber42without requiring an end-to-end connection between the tracing optical fiber42and the external source. Instead, the cable20is provided with at least one launch point66through which tracer light is intended to reach the tracing optical fiber42. The launch point66may comprise a segment of the cable20where a portion of the jacket36has been removed, leaving behind the endface68of the tracing optical fiber42. The endface68may have been formed by cleaving the tracing optical fiber42. The launch point66may then comprise a transparent material76or optical medium, such as PVC, to fill in the void caused by the removal of the jacket36. The transparent material76should have the same or similar index of refraction, (i.e., be substantially index matched) as the core44of the tracing optical fiber42. Use of a transparent material76with a substantially similar index of refraction helps minimize the effects of the boundary formed between the endface68and the optical medium in the launch point66. A launch point66may be located proximate to each end of the cable20. Each launch point66may, for example, be less than one meter from an adjacent connector32(FIG. 3), less than 0.5 meters from the adjacent connector32, or even less than 0.1 meters from the adjacent connector32in some embodiments.

FIGS. 7 and 8illustrate an entrance surface78of the optical medium as having a cylindrical curvature to match the outer surface of the jacket36. The emission surface74of the delivery waveguide60, as a result of the shape of the notch72, may be provided with an opposite concave curvature to promote a close contact and efficient optical connection when the emission surface74is mated with the entrance surface78.

FIG. 9shows another embodiment where the exterior surface of the optical medium (i.e. transparent material76) is molded with a projection80that provides the entrance surface78. The projection80may allow the terminal end64of the delivery waveguide60to mate with the entrance surface78at the desired acceptance angle between the longitudinal axis A and the longitudinal axis Z without providing the terminal end64with the notch72, in which case the terminal end64would provide the emission surface74. Providing the emission surface74perpendicular to the longitudinal axis A may limit light loss that could otherwise occur when the emission surface74is at a shallow angle with respect to the longitudinal axis A.

FIG. 10shows yet another embodiment of the launch point66created without cleaving or otherwise cutting through the tracing optical fiber42. As shown, only the jacket46is removed from adjacent to the tracing optical fiber42. The cladding46and any additional layers on the tracing optical fiber42are removed, exposing a portion of the core44. In this embodiment, tracer light can enter the core44completely from a peripheral surface rather than from an endface of the tracing optical fiber42. This embodiment may require an abrupt and precise demarcation between the exposed core portion and the remainder of the tracing optical fiber42that retains the cladding46used to keep light trapped within the core44. Without the precise demarcation, light injected into the peripheral surface of the core44may tend to come right back out again, instead of being propagated along the length of the tracing optical fiber42.

FIG. 11shows a spacer82that may be used as the transparent index matched material, i.e. the optical medium in the embodiment ofFIG. 10. The spacer82may be placed down onto the exposed surface of the core44to provide an optical pathway for tracer light from the delivery waveguide60to the periphery of the core44. The spacer82may provide an optical abutment surface84for the delivery waveguide60. In one embodiment, the optical abutment surface84is the floor of a blind hole86provided in the spacer82. By providing the blind hole86at the appropriate angle, the emission surface74of the delivery waveguide60may be kept perpendicular to the waveguide axis A similar to the embodiment ofFIG. 9. The spacer82may be pre-formed with a mating surface88having a curvature corresponding with the curvature of the core44of the tracing optical fiber42. An index matched optical adhesive can be used between the spacer82and the core44to couple light from the spacer82through the interface into the core44of the tracing optical fiber42.

Minimizing or eliminating air gaps between the delivery waveguide60and the launch point66can help avoid light loss due to high reflectance. One possible way to provide good optical mating may be to have an optically transparent, mechanically compliant material at the end of the delivery waveguide60that is pre-formed to match the contours of the launch point66but is also ductile to conform when the delivery waveguide60is brought into contact with the launch point66.

To help maintain a relative alignment within the optical junction, a two-part optical connector may be provided with a first portion associated with the cable20and a second portion (e.g., the attachment features62) associated with the delivery waveguide60. As shown inFIG. 12, the first connector portion may take the form of a low-profile sleeve90. A goal of the low-profile sleeve90is to keep the total diameter as small as possible around the sleeve90to avoid snagging or taking up too much space in a confined area within an equipment rack16. In one embodiment, the outer diameter of the sleeve90may be about 2 mm or less. By comparison, the outer diameter of the jacket36itself may be about 1.5 mm in such an embodiment.

The sleeve90may be installed around the cable20, particularly around the jacket36, and include an aperture92configured to be aligned with the launch point66. For example, the sleeve90may be adhered to an exterior surface of the jacket36. One or more alignment features may be provided on the sleeve90to assist with the desired positioning of the delivery waveguide60relative to the launch point66. In the illustrated example, a v-notch94is shown that extends in the direction of the longitudinal axis Z to assist with axial alignment so that the longitudinal axis Z′ of the cable20lines up with the longitudinal axis A of the delivery waveguide60. The v-notch94may have a trough axis T that is parallel to the longitudinal axis Z of the tracing optical fiber42. In other embodiments, the depth of the v-notch94may vary such that the trough axis T intersects the longitudinal axis Z of the tracing optical fiber42. A sloped embodiment of the v-notch94may help provide a desired angle of attack a for the delivery waveguide60toward the tracing optical fiber42.

The sleeve90illustrated inFIG. 12also includes a groove96configured such that when the sleeve90is installed on the cable20, the groove96extends along the circumferential direction of the cable20around the longitudinal axis Z′. The groove96may serve as an alignment feature to help facilitate proper positioning of the delivery waveguide60along the longitudinal axis Z′ of the cable20.

The second connector portion (e.g., the attachment features62) may take the form of a clasping element attached to the delivery waveguide60for clasping onto the first connector portion (e.g., the sleeve90). The clasping element may have mating features configured to engage the alignment features of the first connector portion to facilitate angular orientation around the longitudinal axis Z′ of the cable20and proper alignment along the cable20. The clasping element may lock the terminal end64of the delivery waveguide60in position for the duration of the tracing process and then be able to be removed. In one example, the bottom of the sleeve90may include a recess98where a resilient dimple from the second connector portion could be placed to allow the clasp to be held securely in place in the alignment features.

The second connector portion can be made in many different ways. One embodiment employs a strap attached to the top of the delivery waveguide60, which would encircle both the delivery waveguide60and the cable20. Once in place, the strap could be fastened tightly.

An example of a process for forming the launch point66within the cable20may include inserting the sleeve90onto each end of the cable20, and then sliding the sleeve90to a predetermined distance from each end of the cable20. At some point the sleeve90may be angularly aligned around the longitudinal axis Z′ of the cable20so that the aperture92in the sleeve90is centered over the tracing optical fiber42. Once aligned, the sleeve90may be affixed in place by adhesive or other means. The jacket36and tracing optical fiber42inside the launch point66may be cut away and removed using optional reference features in the sleeve90to guide the location of the cut. The cut-away or removed portion of the jacket36can be refilled or replaced with the clear, index-matched transparent material76or spacer82. The exterior surface of the optical medium may then be molded or otherwise processed to provide the desired entrance surface78for mating with the delivery waveguide60.

The above-described method is particularly suited for embodiments where the tracing optical fiber42comprises a plastic optical fiber (i.e., the core44comprises plastic). If the tracing optical fiber42comprises a glass core44and polymer cladding46, formation of the launch point66may further require pulling the tracing optical fiber42out of the jacket36after a portion of the jacket36has been removed. The endface68of the tracing optical fiber42may be further processed by removing any cladding46or coating on a portion of the core44to expose that portion. Creating this small region of exposed core may increase the efficiency at which light is accepted into the core44and transmitted down the tracing optical fiber42.

In another embodiment, the core44of the tracing optical fiber42may remain intact as shown inFIG. 10. A laser or other means may be used to ablate the jacket36and any outer layer along an underlying segment of the tracing optical fiber42, such as a protective coating and the cladding46. As a result, the core44does not have to be cut, and only a portion of the circumference of the tracing optical fiber42may be affected. This embodiment may require an abrupt and precise demarcation between the exposed core portion and the remainder of the tracing optical fiber42that retains the cladding46which keeps light trapped in the core44. Without the precise demarcation, light injected into the peripheral surface of the core44may tend to come right back out again, instead of being propagated along the length of the tracing optical fiber42.

Instead of filling a void in the jacket36with a liquid transparent material that is subsequently cured, the pre-formed spacer82may be inserted to form the launch point66. The spacer82may be placed down onto the exposed peripheral surface of the core44to provide an optical pathway for tracer light from the delivery waveguide60to the core44. An index-matched optical adhesive can be applied between the spacer82and the core44to couple light from the spacer82, through the interface, and into the core44.

Persons skilled in optical communications will appreciate additional variations and modifications of the devices and methods already described. Additionally, where a method claim below does not explicitly recite a step mentioned in the description above, it should not be assumed that the step is required by the claim. Furthermore, where a method claim below does not actually recite an order to be followed by its steps or an order is otherwise not required based on the claim language, it is not intended that any particular order be inferred.

The above examples are in no way intended to limit the scope of the present invention. It will be understood by those skilled in the art that while the present disclosure has been discussed above with reference to examples of embodiments, various additions, modifications and changes can be made thereto without departing from the spirit and scope of the invention as set forth in the claims.