Optical fiber that provides an indication that breakage is imminent, and method of manufacturing such as fiber

Abstract

An optical fiber includes an integrated detector in the form of phosphors that emit light of a characteristic frequency or wavelength in response to leakage, through the fiber cladding, of light having an interrogation wavelength 1. Stimulation of phosphor emission by the interrogation light is indicative of aging or wear on the layers surrounding the cladding, and therefore can be used to assess the risk of imminent breakage of the fiber.

Claims

1. An optical fiber having a core, at least one cladding layer, and at least one buffer layer, comprising: a built-in damage or wear detector in the form of phosphors that emit light of a characteristic emission wavelength 2 in response to leakage of light from the core through the at least one cladding layer, said light leaking from the core having an interrogation wavelength 1 and/or a characteristic pattern or signature, wherein stimulation of phosphor emission by the light of interrogation wavelength 1 and/or a characteristic pattern or signature is indicative of aging or wear on layers surrounding the at least one cladding layer, and therefore of the risk of imminent breakage of the fiber, wherein the phosphors are incorporated into a material of said at least one buffer layer.

2. An optical fiber as claimed in claim 1, wherein characteristic emission wavelength 2 is a visible wavelength, enabling detection of the presence of excess leakage radiation by an operator without the need for detection electronics.

3. An optical fiber as claimed in claim 1, wherein characteristic emission wavelength 2 is detectable by a sensor and detection electronics.

4. An optical fiber as claimed in claim 1, wherein said phosphor includes multiple different phosphors having different characteristic emission wavelengths.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic illustration of an optical fiber having a damage-detecting, breakage-predicting phosphor layer in accordance with the principles of a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(2) As shown in FIG. 1, an optical fiber includes a core, a cladding, and a buffer layer. The core, cladding, and buffer layer may be conventional optical fiber layers, and are well known to those skilled in the art. The core is arranged to carry laser energy that propagates though the core from a laser source at one end of the fiber to a target at a second end of the fiber as a result of internal reflection at the interface between the core and cladding. Although just a single cladding and buffer layer are illustrated, either or both of the cladding and buffer may be made up of multiple layers.

(3) As the optical fiber ages, the layers surrounding the core will degrade or deteriorate. For example, damage to the cladding and buffer layers may occur through a process of carbonization. During a single use, this is not a problem but, over time, the damage will accumulate and cause significant weakening of the fiber, and eventually result in fiber breakage.

(4) In the preferred embodiment illustrated in FIG. 1, a damage or wear detector in the form of a phosphor coating is added between the cladding and buffer layer. The phosphor coating emits light of wavelength 2 in response to stimulus from light of wavelength 1 that has leaked through the damaged cladding. The light of wavelength 1 may be injected into the fiber as an interrogation beam, or may part of or include an aiming beam. In addition, the light of wavelength 1 may be included in the therapeutic laser beam, take the form of a modulated reference or aiming beam of the type disclosed in U.S. Provisional Patent Appl. Ser. No. 62/011,747, and/or have a characteristic signature or pattern as disclosed in PCT Publication No. 2013/012986 and U.S. Patent Publication No. 2013/0218147.

(5) As the coatings or layers surrounding the fiber deteriorate, leakage of light increases, providing an indication of the condition of the coatings or layers, and therefore of the rink of imminent breakage. When light of wavelength 1 is present in the leakage, the phosphors in the phosphor coating are stimulated and emit light of wavelength 2. The resulting light emission from the phosphor coating is visible or detectable to provide a warning that breakage is imminent, and therefore of the need to replace the fiber before any damage occurs.

(6) As illustrated in FIG. 1, at least a portion of the light 2 emitted by the phosphor coating will travel along the fiber for detection or viewing at the input end of the fiber. Alternatively, light emitted to the exterior of the fiber may be viewed through a scope or introducer, or detected by a sensor positioned on an exterior of or outside the fiber. For example, when viewed through a scope, the light emitted by the phosphor may appear as a glow or aura surrounding the fiber and having a color corresponding to wavelength 2. When the glow is seen during testing of the fiber prior to reuse, the operator will have an indication that breakage is imminent.

(7) In order to distinguish phosphor emissions from the primary laser light, the phosphor emissions of wavelength 2 should be distinguishable from the stimulating emission having wavelength 1. As noted above, the light of wavelength 1 may be included in a dedicated interrogation or test beam, an aiming beam, a modulated reference or aiming beam, a feedback signal having a characteristic signature or pattern, or any other light injected or coupled into the fiber. The wavelength 2 of the phosphor emissions may be those of a single color of visible light, or multiple colors emitted by a multiple phosphors having different excitation frequencies or wavelengths.

(8) Those skilled in the art will appreciate that the sensitivity of the phosphor detector may be varied not only by the amount and type of phosphor or phosphors, but also by numerical aperture launch of the interrogation or aiming beam having wavelength 1.

(9) Although depicted as a single coating layer between the cladding and a buffer layer, it will be appreciated that the wear or damage detector in the form of the phosphor coating alternatively take the form of multiple coatings, of one or more coatings between multiple cladding and/or buffer layers, or of phosphors incorporated directly into the cladding and/or buffer layers of the optical fiber.

(10) In addition to providing an optical fiber with a built-in damage or wear detection detector, the preferred embodiments of the present invention include a method of making such an optical fiber. The method modifies conventional fiber manufacturing methods by adding the step of applying a phosphor coating to the cladding or to a buffer layer of the optical fiber, and/or the steps of incorporating phosphors into a buffer layers or layers surrounding the fiber cladding, the applied or incorporated phosphors emitting light of a characteristic frequency in response to leakage, through the fiber cladding, of light from an interrogation beam.

(11) Still further, the preferred embodiments of the invention include a method of assessing or detecting damage to coatings of an optical fiber, and therefore of predicting the risk of imminent breakage. The damage assessment of detection method of this embodiment includes a first step of introducing light having wavelength 1, and/or a characteristic pattern or signature, into an optical fiber with a built-in damage or wear detector, as described above, and a second step of detecting damage to the fiber by detecting emissions of wavelength 2 that result from stimulation of the phosphors by the light of wavelength 1 if excess leakage of the light of wavelength 1 has occurred.

(12) The second step of the damage or wear detection method of the preferred embodiment may be carried out by visual observation, by sensing light of wavelength 2 using a sensor and corresponding electronics, or by both visual observation and use of a sensor and electronics. In the case of visual observation, when light with characteristics of the stimulated emission from the phosphors appears in the field of view of the operator, for example as a ring surrounding the fiber or aiming beam, then the operator will have a clear indication that breakage is imminent. If enough phosphor is used so as to ensure visibility to an observer, it is possible to eliminate detection electronics, although electronics may still be used as a supplement to visual operation.

(13) On the other hand, if the phosphor emissions are to be detected solely by a sensor or electronics rather than by visual observation, then the emissions may be in a non-visible part of the spectrum, and the amount and location of the phosphors may be adjusted accordingly. In general, the phosphors may be applied incorporated over the entire length of the fiber, or anywhere that is subject to degradation and potential breakage.

(14) Having thus described a preferred embodiment of the invention in connection with the accompanying drawing, it will be appreciated that the invention is not to be limited to the specific embodiments or variations disclosed.