MXPA01005330A - Tube-encased fiber grating - Google Patents

Abstract

A tube-encased fiber grating includes an optical fiber (10) having at least one Bragg grating (12) impressed therein which is embedded within a glass capillary tube (20). Light (14) is incident on the grating (12) and light (16) is reflected at a reflection wavelength&lgr;1. The shape of the tube (20) may be other geometries (e.g., a"dogbone"shape) and/or more than one concentric tube may be used or more than one grating or pair of gratings may be used. The fiber (10) may be doped at least between a pair of gratings (150, 152), encased in the tube (20) to form a tube-encased compression-tuned fiber laser or the grating (12) or gratings (150, 152) may be constructed as a tunable DFB fiber laser encased in the tube (20). Also, the tube (20) may have an inner region (22) which is tapered away from the fiber (10) to provide strain relief for the fiber (10), or the tube (20) may have tapered (or fluted) sections (27) which have an outer geometry that decreases down to the fiber (10) and provides added fiber pull strength. Also, the tube encased grating (12) exhibits lower mode coupling from the fiber core to the cladding modes due to the increased diameter of the cladding where the tube (20) is fused to the fiber (10) where the grating is located (12).

Description

FIBER GRILLE INSERTED IN TUBE CROSS REFERENCES TO RELATED REQUESTS This is a continuation in part of the United States of America patent application, Serial No. 09 / 399,495 filed September 20, 1999, entitled "Tube Encased Fiber Grating" which is a continuation in p- art of 09 / 205,943 presented on December 4, 1998. Likewise, the co-pending United States of America patent applications Serial No. (case number CiDRA No. CC-0036B), entitled "Bragg Grating Pressure Sensor", serial number (case number CiDRA No. CC-0128B) , titled, "Strain-lsolated Bfagg Grating Temperaiure Senor", and serial number (number of case CiDRA No. CC-0146B), entitled "Pressure-lsolated Gras Grating Temperature Sensor", were all presented in a contemporary form to the present, contain matter in question related to that described here.

TECHNICAL FIELD This invention relates to fiber grids, and more particularly to a fiber grid inserted into a tube.

Prior Art Optical fibers are known in the art that Bragg gratings embedded in the fiber can be used to deviate parameters such as temperature and tension, such as those described in the United States of America patent No. 4, 806, 012, entitled "Distributed, Spatially Resolving Optical Fiber Strain Gauge," for eltz et al, and United States Palette No. 4,996, 419, entitled "Distributed Multiplexed Optical Fiber Bragg Grating Sensor Arrangement" , for Morey, which are incorporated herein by reference to the extent necessary to understand the present invention. It is also known that the fiber grids can be used in compression to act as a selectable filter or a selectable laser beam, as described in U.S. Patent No. 5,469,520, entitled "Compression Tuned Fiber Laser" for Morey. , et al and U.S. Pat. No. 5,691,999, entitled "Compression Tuned Fiber Laser" for Ball et al. , respectively, which are incorporated herein by reference to the extent necessary to understand the present invention. However, when a fiber fiber by itself is compressed, the fiber is deformed. One technique used to avoid deforrpation of the fiber is to use sliding splints around the fiber and grid and place the splints in a mechanical structure, guiding, aligning and confining the fibers and the fiber. This technique is described in the aforementioned US Pat. Nos. 5,469, 520 and 5,691, 999. However, it would be desirable to obtain a configuration that allows a fiber grid to be compressed without deformation and without sliding ferrules and without requiring said mechanical structure. It is also known that the Bragg gratings in the optical fibers can create an undesirable coupling between the core and the coating modes of a fiber. ? Greater overlap of the mode field between the two modes, the greater the coupling. Such coupling creates undesirable optical losses in the fiber.

BRIEF DESCRIPTION OF THE INVENTION The objects of the present invention include the provision of a fiber configuration that allows the grid to be used in compression without requiring sliding ferrules or a mechanical support structure and / or which is suitable for reducing the core for the coating coupling. According to the present invention, a fiber optic reflective element introduced into a tube comprises an optical fiber having at least one reflective element embedded therein; and a tube, having the optical fiber and the reflective element inserted therein along a length of a longitudinal axis of the tube, the tube that is fused to at least a portion of the fiber.

According to the present invention, the tube is made of a vitreous material. Also according to the present invention, the tube is fused to the optical fiber where the reflecting element is located. Also according to the present invention tube 5 is fused to the optical fiber on opposite axial sides of the reflective element. The present invention provides a fiber grid embedded and fused to at least a portion of a capillary tube and a method for making the same. The tube can be made of a vitreous material to introduce a fiberglass. The grid inserted allows the grid to be compressed without deformation of the fiber. Likewise, it allows the fiber to be isolated from the deformation from the deformations in any part of the fiber. The invention can also be used in numerous applications where fiber grating compression can be used, for example, parameter detection or wavelength selection. Also, the invention exhibits less mode coupling from the fiber core for the coating modes due to the effective increased diameter of the coating when the tube is melted to the fiber where the grid is located. The grid can be embedded (or printed) in the fiber before or after the fiber is introduced into the tube. To cause the fiber to be introduced and fused to the tube, the tube can be heated and collapsed around the fiber. 5 ^^^^^^^ i ^ t ^^^^^^ g ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Also, one or more gratings, fiber lasers, or a plurality of fibers can be introduced into the tube. The grid (s) or laser (s) are "inserted" into the tube by having the tube fused to the fiber over the grid area and / or at opposite axial ends of the grid area adjacent to the grid. a predetermined distance from the grid. The reflector (s) or eJ or the laser (s) may be fused within the tube or partially inside or on the outer surface of the tube. The foregoing and other objects, features and advantages of the present invention will become apparent in light of the following detailed description of the illustrative embodiments thereof.

BRIEF DESCRJPCJÓfl D-E THE DÍB JJOS Figure 1 is a Jaw view of a fiber grating inserted in a tube, according to the present invention. Figure 2 is a side view of a fiber grating inserted into a tube having an alternative geometry for the tube, according to the present invention. Figure 3 is a side view of a fiber grating inserted into a tube having an alternative geometry for the tube, according to the present invention. Figure 4 is a side view of a fiber grating inserted into a tube having an alternative geometry for the tube, 25 according to the present invention.

Fig. 5 is a side view of a glass grating inserted in glass having more than one tube around the grid according to the present invention. Figure 6 is a side view of an inserted pound screen where the tube is fused over the opposite axial ends of the grid area, according to the present invention. Fig. 7 is a side view of a fiber grating inserted into a tube where the tube is fused on opposite axial ends of the grid area according to the present invention. Figure 8 is a side view of more than one grid on a fiber inserted into a tube, according to the present invention. Figure 9 is a side view of two fiber grids on separate optical fibers inserted into a common tube, according to the present invention. Figure 10 is an end view of the embodiment of Figure 9, according to the present invention. Figure 11 is an end view of two fiber grids on separate optical fibers inserted into a common tube and separated by a distance, according to the present invention. Figure 12 is a side view of a fiber grating inserted in a tube where the tube is fused onto the fiber only in the length of the reel-in accordance with the present invention.

Figure 13 is a diagram showing a process for introducing a fiber into a glass tube, according to the present invention. Fig. 14 is a side view of a DFB laser of selectable fiber 5 inserted into a tube, according to the invention. Figure 15 is a graph of an optical transmission profile of a grid in a standard optical fiber showing the coupling of the coating mode, according to the present invention. Figure 16 is a graph of the optical transmission profile of a fiber grating inserted into a tube showing the coupling of the reduced coating mode, according to the present invention. 15 BEST WAY TO CARRY OUT THE INVENTION Referring to FIG. 1, a fiber Bragg grating inserted into a tube comprises a known waveguide or waveguide 10, for example, a simple standard telecommunication optical fiber, having a Printed Bragg 12 mesh 1.0 embedded or printed) on the fiber 10. Figure 10 has an external diameter of approximately 125 microns and comprises silica glass (SiO2) which has the appropriate impurifiers, as it is known, to allow cμxe and light 14 spreads to the Jargo of fiber 10, i_a rejiJia 12 is similar to that described in U.S. Patent Nos. 4,725,110 and 4,807,950, entitled "Method for Impressing Gratings Within Fiber Optics," for Glenn et al; and the patent of the United States of Nerieamérica No. 5,388,173, entitled "Method and Apparatus for Forming Aperiodic Gratings in Optical Fibers", for Glenn, which are incorporated by reference to the extent necessary to understand the present invention. However, any suitable Jongilud wave grating or reflective element embedded, etched, printed or otherwise formed in the fiber 28 may be used if desired. As used herein, the term "grids" means any of the reflective elements. In addition, the reflective element (or grids) 12 can be used in the reflection and / or transmission of light. Other materials and dimensions of the optical fiber or waveguide 10 may be used if desired. For example, the optical fiber 10 can be made of any glass, for example, silica, phosphate glass or other glass or made of glass and plastic, or only plastic. For high temperature applications, optical fiber made of a vitreous material is desirable. Likewise, the fiber 10 can have an external diameter of 80 microns or other diameters. In addition, instead of an optical fiber, any optical waveguide can be used, such as a multiple-mode waveguide, birefrin, people, bias-keeping, polarization, multiple-core, or multiple-coating optics, or a flat or smooth waveguide (where the waveguide is rectangular in shape) or other wave guides. As used herein, the term "fibers" includes the waveguides described above. The light 14 is incident on the reflection 12 which reflects a portion thereof as indicated by the line 16 having a predetermined wavelength band of light centered on the reflection wavelength β, and passing the lengths wavelengths of the incident light 14 (within a predetermined wavelength range), as indicated by line 18. The fiber 10 with the 12th refji in it is introduced deniro and fused to at least a portion of a cylindrical vitreous capillary tube 20 having an outer diameter d1 of about 3mm and a length L1 of about 10mm. The grid 12 has a length Lg of about 5mm. Alternatively, the length L1 of the tube 20 can be substantially the same length than the length Lg of the grid 12, such as by using a larger grid or a shorter tube. Other dimensions or lengths of the tube 20 and the grid 12 can be used. Likewise. The fiber 10 and the grid 12 do not need to merge into the center of the tube, although it can be fused anywhere in the 20 tube. itself, the tube 20 does not need to be fused to the fiber over the entire length L1 of the tube 20. The tube 20 is made of a vitreous material, such as a natural or synthetic quartz, fused silica, silica (SiO2), Pyrß-x ® from Corning (borosilicate), or Vycor® from Corning (approximately 95% silica and 5% of other components such as boron oxide), or other glasses The tube must be made of a material such that tube 20 (or the inner diameter surface of a hole in tube 20) can be fused to (ie create a molecular bond with or fuse together with) the outer surface (or coating) of the optical figure 10 so that the interface surface between the inner diameter of the tube 20 and the external diameter of the fiber 10 is substantially eliminated (ie, the internal diameter of the tube 20 can not be distinguished from the coating of the fiber 10). For the best thermal expansion coupling of tube 20 a the fiber 10 over a large temperature range, the coefficient of thermal expansion (CTE) of the material of the tube 20 must be substantially coupled to the CTE of the material of Figure 10, for example, the fused silica tube and the optical fiber. In general, at a lower melting temperature of the vitreous material, higher eJ CT ?. By Therefore, for a silica fiber (having a high melting temperature and a low CTE), a tube made of another vitreous material, such as Pyrex® and Vycor® (which has a lower melting temperature and a higher CTE) it results in a decoupling of the thermal expansion between the tube 20 and the fiber 10 with the temperature. However, it is not required in the present invention that eJ CT? of the fiber 10 attach to the CTE of the tube 20 (as described below). Instead of the tube 20 being made of vitreous material, other materials provided so that the tube 20 can be used can be used. melt to fiber 10. For example, for an optical fiber made of plastic, a tube made of plastic material can be used. The axial ends of the tube 20 where the fiber 10 exits the tube 20 may have an internal region 22 which is tapering towards 5 in (or widened) away from the fiber 10 to provide the deformation release for the fiber 10 or for other reasons In that case, an area 28 between the tube 20 and the fiber 10 can be filled with a deformation-releasing filler material, for example polyimide, silicone or other materials. Likewise, the tube 20 may have been tapered (or chamfered or angled) at the corners or outer edges 24 to provide a seat for the tube 20 to mate with another part (not shown) and Vol to adjust the force angles in the tube 20 or for other reasons. The angle of the beveled corners 24 is fixed to achieve the desired function. £ 1 tube 20 may have cross-sectional shapes other than circular, such as square, rectangular, elliptical, shell-shaped or other shapes and may have shapes in side view section other than rectangular, such as circular, square, elliptical, in shell shape or other shapes. Alternatively, instead of having the internal tapered region 22, one or both axial ends of the tube 22 where the figure 10 exits the tube 20 may have an outer tapered section (or fluted, conical or joining), shown as dotted lines 27 , which has an external geometry that decreases downward in the fiber 10 (described in more detail below in Figure 12) r It has been It has been found that using striated sections 27 provides improved tensile strength at and near the interface where the fiber 10 exits the tube 20, for example, 8.88 kilograms / meter or more, when the fiber 10 is pulled to the back of the tube. its long axisJ. When the fiber 10 leaves the tube 20, the fiber 10 may have an outer protective diverter layer 21 to protect the outer surface of the fiber 10 from damage. The diverter 21 can be made of polyimide, silicone, Teflon®, (polytetrafluoroethylene), carbon, gold and / or nickel, and have a thickness of approximately 25 microns. Other thicknesses and deviating materials can be used for the diverter layer 21. If the tapered region 22 is used and is large enough, the diverter layer 21 can be inserted into the region 272 to provide a transition from the discovered fiber to a deflected fiber. Alternatively, if the axial end has an external taper 27, the diverter 21 would start where the fiber leaves the tapered portion 27 of the tube 20. If the diverter 21 starts after the fiber exit point, the exposed exposed portion of the fiber 10 can be coated with a layer additional deflector (not shown) which covers any fiber discovered outside the tube 20 and may also overlap with the diverter 21 and / or the tapered region 27 or other geometrically shaped axial end of the tube 20.

To introduce and melt the fiber 10 into the tube 20, the tube 20 can be heated, collapsed and melted around the reeds (or grid area) as described below. The Bragg grid 12 can be printed on the fiber 10 before or 5 after the capillary tube 20 is introduced around the fiber 10 and the grid 12. For any of the embodiments shown herein, the fiber 10 and / or the grid 12 can be fused to the tube 20 with an initial pre-formation on the fiber 10 and / or the grid 12 (compression or voltage) or without pre-tension. For example, if Pyrex® or another glass having a higher coefficient of thermal expansion than that of the fiber 10 is used for the tube 20, when the tube 20 is heated and fused to the fiber and then cooled, the grid 12 is placed in compression by tube 20. Alternatively, the fiber grid 12 can be introduced into the tube 20 under tension by placing the grid in tension during the heating of the tube and the melting process. Likewise, the fiber grid 12 can be introduced into the tube 20 resulting in no tension or compression = ore the grid 12. 20 If the grid 12 is printed on the fiber 10 after the tube is introduced around the grid 12, the grid 12 can be engraved through the tube 20 within the fiber 10 as described in the co-pending United States patent application, serial number (document number Citron No .

CC-0130), entitled "Method and Apparatus For Forming A Tube- - * a **, * ~ t- * - "'* • < MteA - * ^ - * - * - *» iiiii? IIGIG? I iiiftiiii iiiniipiifiiiiiriiffi g ^ A ^ Encased Bragg Grating ", presented on December 4 1998 and incorporated herein by reference. If the grid 12 is printed on the fiber 10 before the tube 20 is introduced around the grid 12, the melting temperature 5 of the capillary tube 20 must be smaller enough to allow the pollen tube 20 to become smooth and casts the fiber optic 10 without significantly "whitening" (or annealing or weakening) the reflective capacity of the grid 12 below the desired level, which may occur when a grid is exposed to high temperatures. The capillary tubing made of Pyrex® or an equivalent glass that has a softening temperature below that of a quartz fiber and is therefore suitable for this purpose. If Pyrex® or another glass having a higher coefficient of thermal expansion (CTE) than that of fiber 10 is used for pipe 20, when the The tube 20 is heated and melted to the fiber and then cooled, the screw 12 is placed in compression by the Jubo 20. Alternatively, the fiber plug 12 can be introduced into the tube 20 under tension by placing the grid at during the process of heating and melting the tube. Also, the fiber grid can be introduced into the tube 20 resulting in there being no tension or compression on the grid 12. With reference to Figure 2, the capillary tube 20 can have a variable geometry, depending on the application. For example, tube 20 may have a "canine bone" shape that has a narrow central section 30 and more external sections large 32. The narrow section 30 has an outer diameter of two of approximately 2mm and a length of L2 of approximately 9.25mm. The large sections 32 have an external diameter d3 of approximately 4mm and a length of L3 of approximately 6.35mm. Other lengths L2, L3 of sections 30, 32 may be used. For example, the length 13 may be much greater than 6.36mm (for example, greater than 25.4mm in length) or may be much smaller than 6.36mm in length. The aliernativas dimensions can be: d2 = 1 mm, d3 = 3mm, L3 = 4mm, L2 = 7.37 mm. You can use other dimensions if desired, depending on the application. The canine bone shape can be used to provide increased force to the wavelength displacement sensitivity of the grid when used in a compression or force sensor application based on compression or to hold the tube 20 in a tension configuration , as described in the co-pending United States patent application, serial number (case number CiDRA No. CC-0036B), entitled "Fiber Grating Pressure Sensor", or a selectable grid in? iase compression and laser application as described in the United States of America patent application co-pending serial number (case number CiDRA No. CC-0129B), entitled "Compression Tuned Fiber Grating and .Laser", presented in a manner joint with the present or that can be used for other applications. Likewise, the dimensions of the canine bone are my.*? *. *? A ** »i- * mm ***.".,. ,, .., ...?. M, ...,, .Jto. i > ? tíJ .., ... ** & * .. , .. ~ ~ ^ ,. ..M ^.,, "_ ^ Fe .... J ...,,,, ^ ^^^ ¿. easily scalable to provide the desired amount of sensitivity. An internal transition region 33 of the long sections 32 can be an edge here or can be curved as indicated by dotted lines 34. A curved geometry 34 has fewer stress risers than a sharp edge or corner and therefore reduces the probability of rupture. Likewise, the sections 32 of the tube 20 can have the inwardly tapered regions 22 or the external fluted sections 27 at the ends of the tube 20, as described hereinabove. In addition, the sections 32 may have the external (or bevelled) tapered corners 24 as described hereinabove. Likewise, the canine bone geometry is not required to be symmetrical, for example, the lengths L3 of the two sections 32 may be different if desired. Alternatively, the canine bone may be a single-sided canine bone, where instead of having the two longer sections 32, it may be only a long section 32 on one side of the narrow section 30 and the other side may have a straight edge. 37 which may have beveled corners 24 as described above. -In that case, the canine bone has the shape of a "T" on its side. Just as a single-sided canine bone should also be referred to herein as a "canine bone" form. Instead of a canine bone geometry, other geometries that provide sensitivities of Improved formation or adjustment of force angles on the tube 20 or provide other desirable characteristics. Referring to Figure 3, an alternative geometry for the capillary tube 20 may have other geometries that extend axially. In particular, the left side of the tube 20 can have an axial extended section 36 which can have the grooved section 27 at the end. Likewise, the right side of the tube 20 may have an axial extended section 51 (which may have the ridged section 27 at the end) that is, larger than the other axial end 36. In addition, the fiber 10 in one or both axial extended sections 36, 51 may have grids 52, 50, respectively. Some example dimensions for tube 20 of Figure 3 are as follows and other dimensions may be used. In particular, L6 is approximately 26.7 mm, .L7 is approximately 1 1 .66mm, L8 is approximately 12.7mm, L9 is approximately 2.29mm, and d7 is approximately 0.813mm and d2, d3 and the other dimensions of the canine bone are as described above herein. The long axis 51 may be made through the methods described herein. for making the canine bone or other shapes for the tube 20, or it can be made by fusing from the section 51 to the section 32 (before or after the fiber 10 is introduced into the tube 20) in a puncture 53 or it can also be made . Alternatively, the tube 20 shown in Figure 3 with the section 51 can be formed using two tubes, one inner tube with length L6 that slides through a hole ^ ¡= ^^ gjg ^ 58 in canine bone sections 30, 32 and fused to sections 30, 32 similar to that described so far with figure 5. It should be understood that the dimensions, geometries and 5 materials described for any of The modalities herein, are for illustrative purposes only and as such, others may be employed other dimensions, geometries, or materials if desired, depending on the application, size, performance, manufacturing or design requirements, or other faciers, in view of 10 the teachings in the present. Referring to Figure 4, the long axial axis 51 may be fused to the fiber 10 near where the grid 50 is placed and not fused onto the fiber 10 in the region 90 near the end of the section 51. In that case, region 90 may be filled with an epoxy or other filler described herein. The internal diameter d6 of the tube 20 in section 90 is about 0.01 to 10 microns larger than the diameter of the optical fiber 10, for example, 125.01 to 135 microns. It can be used if other diameters and dimensions are desired. When the fiber 10 leaves the extended region 51, the fiber 10 can have the outer protective diverter layer 21 to protect the outer surface of the fiber 10 from damage, as described hereinabove. Referring to Figure 5, more than one concentric tube can be fused to form tube 20 of the inododucide grid in tube of the present invention. For example, an internal capillary tube small 180 having an outer diameter d4 of about 5.5mm, can be located within an outer capillary tube plus Jargo 182 having the diameter d 1 hitherto present, and the two tubes 180, 182 are fused together. One or both ends of the small tube 180 can be contracted around the fiber 10 to form the fluted sections 27. Other values for the diameters d 1, d4, of the inner and outer tubes 180, 182 can be used if desired, likewise , more than two concentric capillary tubes can be used. The material of the tubes can be the same for reduce to the minimum the decoupling of the thermal expansion with the temperature. Likewise, the shape of the outer tube 182 may have a canine bone shape as indicated by dotted lines 184 or other shapes as described heretofore. Alternatively, the canine bone shape can be created by melting two separate tubes 188, 190 on the inner tube 180 on opposite axial sides in the grid 12, as indicated by dotted lines 186. Referring to FIGS. 6 and 7, alternatively, the tube may be fused to the fiber 10 in opposite axial ends of the reji 12 adjacent to or at a predetermined distance L10 of the key 12 where L10, can be any desired length or on the edge of the grid 12 (L10 = zero). In particular, the regions 200 of the tube 20 are fused to the fiber 10 and a section 202 of the tube around the grid 12 that is not fused with the fiber 10. region 2Q2 around the grid 12 may contain ambient air or to be evacuated (or to be at another pressure) or it may be filled partially or completely with an adhesive, for example, epoxy, or other filler material, for example, a polymer or silicone or other material. As described now in the present invention, the internal diameter d6 of the tube 20 is about 0.01 to 10 microns larger than the diameter of the optical fiber 10, for example 125.01 to 135 microns. Other diameters can be used; however, to help avoid deformation of the fiber when the tube 20 is compressed axially, the diameter d6 should be as close as possible to the external diameter of the fiber 10. Also, the distance L10 need not be symmetrical about the sides of the grid. Referring to Figure 7, alternatively the same result can be joined by joining the two separate tubes 210, 212, on opposite sides of the grid 12 and then melting an outer tube 214 through the tubes 210, 212. Alternatively, the tubes 210, 212 may extend beyond the ends of the outer tube 214 as indicated by dotted lines 216. Alternatively, the tube 20 may be a single piece with a shape indicative of the tubes 212, 214. Referring to Figure 8, for any of the embodiments described herein, instead of a single grid inserted within the tube 20, two or more grids 150, 152 can be embedded in the fiber 10 that is inserted in the tube 20. The grids 150, 152 can have the same wavelength of reflection and / or profiles or different wavelength and / or profiles. The grids 105, 152 can be used individually in a known Fabry Perot arrangement. In addition, one or more fiber lasers such as those described in U.S. Patent No. 5,513,913, entitled "Active Multipoint Fiber Laser 5 Sensor", U.S. Patent No. 5, 564,, 832 , entitled "Birefringent Active Fiber Laser Sensor", or US Pat. No. 5,666,372, "Compression Tuned Fiber Laser" may be embedded within fiber 10 in tube 20, which are incorporated herein by reference to the extent necessary to understand the present invention. In that case, the louvers 150,152 form an optical cavity and the fiber 10 at least between the louvers 150, 152 (and may also include the louvers 150, 152 and / or the fiber exterior of the louvers, if desired) would be doped with a dopant of rare earth, for example, erbium and / or ytterbium, etc. Referring to Fig. 14, another type of selectable fiber laser that can be used is the distributed distributed feed fiber (DFB), as described in V.C. Lauridsen, et al, "Design of DFB Fiber Lasers", 0 Electronic Letters, October 15, 1998, Vol.34, No. 21, pp 2028-2030; P Varming, et al, "Erbium Doped Fiber DGB Laser Permanent ITU 2 Phase-Shift Induced by UV Post-Processing", IOOC'95, Tech. Digest, Vol. 5, PD1-3, 1995; U.S. Patent No. 5,771,251"Optical Fiber Distributed 5 Feedback Laser", for Kringlebotn et al; or the patent of the States United States No, 5, 51 1, 083, "Polarized Fiber Laser Source", for D'Amato et al. In that case, the grid 12 is recorded in a fiber impurified with rare earth and configured to have a phase shift of X / 2 (where? Is the wavelength 5 of the laser action) at a predetermined location 180 near the center of the grid 12 which provides a well-defined resonance condition that can be continuously selected in a single longitudinal mode operation without variation as is known. Alternatively, instead of a single grid, the two grid 150, 152 can be placed close enough to form a cavity that has a length of (N + 1) ?, where N is an integer (including 0) and grid 150, 154 is a fiber impurified with rare earth . Referring to Figures 9 and 10, alternatively, two or more fibers 10,250, once one having at least one grid 12,252 therein, respectively, can be introduced into the tube 20. In that case, the hole in the tube 20 before heating and melting the tube 20 It would be large enough to accommodate both fibers and may be different from the circular shape, for example square, triangular, etc. Also, the hole for the tube 20 does not need to be centered along the center line of the tube 20. Referring to Figure 11, alternatively, instead of the 10,250 fibers touching each other, as shown in the figure 10, the fibers 10,250 can be separated in the tube 20 through ^^ g ^^ g ^^^ «^^^^^^^ and ^^^^^ J ^^^^ J ^^^^^^^^^ > | ^^^^^^^^^^^^^ ^^? í * * j ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ a predetermined distance. The distance can be any desired distance between the fibers 10,250 and have any orientation within the external diameter of the tube 20. Likewise, for any of the embodiments shown herein, as has been previously neglected, part or all of the optical fiber and / or the grid may be fused within, partially within or on the outer surface of the tube 20, as indicated by the fibers 5-00, 502, 504 respectively. Referring to figure 12, alternatively, the The tube 20 can be melted onto the fiber 10 only when the grid 12 is placed. In that case, if the tube 20 is larger than the grid 12, the internal tapered or flared regions 22 described heretofore may exist and the areas 28 between the tube 20 and the fiber 10 may be filled with a filling material, how has it described so far in the present. Referring to Figure 13, a technique and configuration for melting the tube 20 around the fiber 10 is as follows. The tube 20 is slid over the fiber 10 to a location where the lens 12 exists or will exist. The upper end of the tube 20 is connected to the lower end of a rigid support, alignment and vacuum tube 350 having a gear 351 attached thereto. The upper end of the tube 35D is connected to the upper end of a vacuum connector 352 having a rotary vacuum seal 354. The other vacuum connector end 352 is connected to one end 5 of a flexible vacuum tube 356. The other end of empty tube 356^ ¿Am ». . .. ,. * t. . ^^ ,. ^ ~., ^ a _ a ^^ -] * tm -, -. ^ > .- "is connected to a vacuum pump 358. The vacuum pump 358 creates a vacuum inside the tube 20 to create a collapsing force on the tube 20 sufficient to cause the tube 20 to collapse on the stem 10 when heated . The tube 20 is held in place and sealed by an epoxy seal 360 to maintain a vacuum in the rigid tube 350. The lower end 361 of the tube 20 can be connected or sealed by the external deviator layer 21 (FIG. 4) of the fiber 10, by epoxy or by other means to allow vacuum to exist in tube 20. Other sealants can be used. The connector 352 is attached to a rotary motor 362 which is connected to a gear 366 which is interspersed with the gear 351 attached to the vacuum tube 350. When the motor 362 rotates, it rotates the gear 366 which rotates the other gear 351, Jo which causes the lubricant 15 350, the tube 20 and the fiber 10 to rotate about the longitudinal axis of the fiber 10 and the tube 20 as indicated by the arrow 367. The tube 20 and the fiber 10 are rotated to provide heating uniform circumferential of the tube 20 and the fiber 10. The connector 352 is also attached to a movable member 368 20 of a vertical transfer stage 370 having a helical gear 362 that is attached to a second motor 371. The gear 372 is interspersed with and moves vertically with the member 368, the connector 352 and the motor 362 up and down along the transfer stage 370 as indicated by the arrows Thesis: «rip # ?! ÍBH -'iJtiar-it t - * Ar i ¡M -i mW m ^^« .. ^ MT., J ^ & ^^. ^ J i. "..., .. J. - ^^. ^^ m ^ 374. Other configurations and hardware may be used to rotate and transfer the tube 20. A stationary heating source 380, such as a CO2 laser, for example, the LC-50 laser from DeMaria Electro Optic 5 Systems, provides a predetermined amount of heat to a localized area 382 of the tube 20 (which performs a laser welding) and is configured to allow the tube 20 to move vertically through the heating area 332. The laser 380 provides a laser 384, which has a diameter of 3mm with about 30 to 40 watts of power in tube 20 at a wavelength of about 10.6 microns. Other powers, beam sizes and shapes can be used provided that the appropriate amount of heat is applied to the tube 20. Also, instead of illuminating the tube 20 on only one side, the tube 20 can can be illuminated in multiple locations around the circumference of the tube 20 or completely around the tube 20. In this case, flat or cylindrical mirrors (not shown) can be used to divide and / or reflect the beam 384 simultaneously to the desired regions around the the circumference of the tube 20. 20 Other heating devices and / or heating techniques may be used if desired, such as an oxyacetylene torch (e.g., a propane / oxygen or oxygen / hydrogen sepel), a filament heater of tuxethane (or molybdenum), another type of laser, small furnace (for example, wire of filament inside an isolated shelter) or any other heating technique that provides sufficient heat to collapse tube 20 on fiber 10. Also, if heat source 380 applies heat uniformly around the circumference of fiber 10 and tube 20, tube 20 and fiber 10 5 may not need to be turned to the longitudinal axis of the fiber 10 during heating. Instead of a vacuum other techniques can be used to create a collapse force on the tube 20. For example, create an external pressure on the tube 20, while maintaining the internal tube pressure under external pressure. The external pressure can be exerted by mechanical or hydraulic means or others. Alternatively, if the internal diameter d6 (FIG. 4.6) of the tube 20 is very close to the external diameter of the fiber, for example, approximately one larger diameter (approximately 126 microns of internal diameter), the tube 20 can be collapsed on the fiber 10 under its own surface tension without the need for a vacuum or other collapse force. Alternatively, an intermediate or filler material having a composition similar to that of fiber 10 and tube 20, such As a fine glass powder or solder (eg, silica powder), it can be used between the fiber 10 and the tube 20 and which is fused to the tube 20 and the fiber 10 to facilitate the melting process. In that case, the tube 20 may not collapse as much as (or at all) the fiber 10.

To melt the tube 20 to the fiber 10, the tube 20 is heated and fused from the beginning (towards the vacuum source) using the heater 380. For a given section, the tube 20 is heated to a predetermined temperature for example from about 1800 ° C for a quartz tube or fused silica) until the tube 20 is soft enough to collapse under the collapsing forces and melt into tube 20, after the tube 20 is moved to the next section to be heated and melted. This heating technique avoids causing bubbles in the tube / fiber interface. For example, the transition stage moves the tube 20 vertically at a speed of approximately 0.06mm / sec and the tube 20 is rotated at a speed of approximately 100rpm. Other transfer and rotation speeds may be used if desired. The longitudinal axis of the tube 20 and the fiber 10 are oriented vertically during heating to minimize gravitational effects and optimize axial symmetry; however, if desired, other orientations may be used. Also, instead of moving the tube 20 and the fiber 10, the heating fiber 56 can move vertically or the heating source 380 and the fiber / tube can move. Other techniques can be used to collapse and melt the tube to the fiber 10, as described in U.S. Pat. No. 5,745,626, entitled "Method For And Encapsulation of An Optical Fiber", for Ouck. et al. , and / or the palenle of U.S. Pat. Nos. 4,915,467, entitled "Method or Making Fiber Coupler UAving Integral Precision Connection Wells," for Berkey, which are incorporated herein by reference to the extent necessary to understand the present invention or other techniques. Alternatively, other techniques can be employed to melt the fiber 10 to the tube 20, such as using a high temperature glass solder, for example silica solder (powder or solid), such as fiber 10, tube 20 and solder which are fused together or using laser welding / fusion or other fusion techniques. Likewise, the fiber may be melted within the tube or partially within or on the end surface of the tube (previously described with Figure 11). Instead of sliding the capillary tube 20 over and along the fiber 10 to the desired location, the tube 20 can be longitudinally divided into two or more pieces and assembled together at the desired location of the grid 12 to be flushed to the fiber 10. The fluted sections 27 (Figure 1) can be formed in various ways, such as by heating the tube 20 and removing the tube 20 and / or the fiber 10. Alternatively, the fluted ends 27 of the tube 20 can be formed using other techniques of formation of glass such as grinding, polishing or etching the axial ends of the capillary tube 20. Using chemical recording (for example, with hydrofluoric acid or other chemical etchants), laser etching or laser-enhanced chemical etching are some techniques that reduce the external diameter without applying direct contact force as required by grinding and polishing. Other techniques can be used to obtain the fluted ends 27. Sections 27 can be made before, during or after the heating and melting of the tube 20 to the fiber 10. Likewise, the internal tapered region 22 can be created through numerous techniques. For example, without melting the tube 20 to the fiber 10 in the regions 22 or to create a region 22 that is larger than the internal diameter of the tube 20, the tube 20 can be heated in the desired region to expand and the applied internal pressure to the tube 20. The canine bone geometry described above can be formed by etching, grinding or polishing the central section of the capillary tube 20 to obtain the narrow diameter d2 and / or the beveled corners 24, as described heretofore with respect to The fluted sections 27. Other technique can be used to obtain the narrow diameter region 30 and the corners 24. After the canine bone (or other geometry) is formed in the tube 20, the surface of the tube 20 can be polished to the fire to remove surface impurities, to improve resistance or for other reasons. In addition, for any of the embodiments shown herein, instead of the fiber 10 passing through the tube 20, the fiber may be single end, ie only one end of the fiber 10 saLe of the tube 20. In that case, one end of the fiber would be at the exit point of the fiber 10 from the tube 20 or before the exit point. Also, the term "tube" as used herein may also represent a block of material having the properties described herein. Referring to FIGS. 15, 16, it has been found that the present invention also reduces the coupling between core and coating modes typically caused by a fiber grating, due to the increased extreme cross-sectional area between the core and the coating. the fiber 10. Thus, a grid 12 recorded in the core of the optical fiber 10 exhibits lower loss of optical transmission and exhibits a lighter optical profile than a conventional fiber grid due to the larger coating region that dissipates the modes of Coated coating, thereby reducing core coupling to coating modes. In general, the greater the difference in cross-sectional area between the core and the coating, the less the field overlap of mode and the lower the coupling to the coating modes. When the tube 20 is fused to the fiber at least where the grid 12 is located, the tube 20 becomes part of the coating of the fiber 10, as described above. Accordingly, said increase in coating thickness reduces the core to the coating coupling typically caused by the grid 12. The thickness of the tube 20 can be fixed to optimize this effect. Figure 15 shows an optical transmission profile for a standard grid in an optical fiber that It has a core diameter of 9 microns and an external diameter of 125 microns. Said grid exhibits the coupling to the coating modes as indicated by the peaks 100. Figure 16 shows an optical transmission profile for a grid introduced in tube 5 described herein having a core diameter of 9 microns and a tube with external diameter of 3mm 20 which exhibits a very reduced coupling towards the coating modes as indicated by the lack of a peak on the profile. Other diameters of the fiber core and the tube 20 may be used if desired. so that the optical coupling to the coating modes is reduced to the desired levels. It should be understood that, unless otherwise stated herein, any of the features, qualities, alternatives or modifications described with respect to A particular embodiment herein may be applied, used or incorporated with any other modality described herein. Likewise, the drawings herein are not drawn to scale. Although the invention has been described and illustrated with respect to the illustrative embodiments thereof, the foregoing and various Other additions and omissions may be made herein and to the same without departing from the spirit and scope of the invention.

Claims (38)

1. A fiber optic device introduced into a tube, comprising: an optical fiber, having at least one reflective element embedded therein; and a tube, having the optical fiber and the reflective element inserted therein along a longitudinal axis of the tube, the tube that is fused to at least a portion of the fiber.

2. The apparatus according to claim 1, characterized in that the tube is made of a vitreous material.

3. The apparatus according to claim 1, characterized in that the tube is fused to the optical fiber where the reflecting element is located.

The apparatus according to claim 1, characterized in that the tube is fused to the optical fiber on opposite axial sides of the reflective element.

5. The apparatus according to claim 1, characterized in that the optical fiber is made of a vitreous material.

The apparatus according to claim 1, characterized in that the tube has at least one external tapered axial section.

7. The apparatus according to claim 1, characterized in that the tube has at least one axially extended end.

8. The apparatus according to claim 1, characterized in that the tube has at least one internal axial section.

The apparatus according to claim 1, characterized in that at least a portion of the lubricant has a cylindrical shape.

10. The apparatus according to claim 1, characterized in that the shape of the tube comprises a canine bone shape. eleven .

The apparatus according to claim 1, characterized in that the fiber has at least one pair of reflective elements introduced into the tube and the fiber is impurified with a rare earth impurifier at least between the pair of elements to form the laser. fiber.

12, The apparatus according to claim 1, characterized in that the fiber laser acts at a laser-acting wavelength that changes as the force on the lubricant changes.

The apparatus according to claim 1, characterized in that at least a portion of the fiber is doped with a rare earth dope where the reflective element is located and the reflective element is configured to form a fiber laser DFB.

14. The apparatus according to claim 13, characterized in that the fiber laser DFB acts at a wavelength of laser action that changes as the force changes on the laser. tube.

15. The apparatus according to claim 1, characterized in that the tube is cast in the fiber where the reflective element is located and the tube has an external diameter in a manner 5 that the optical coupling in the coating modes is less than the optical coupling in the coating modes that exist when the tube is not fused to the fiber where the reflective element is located.

16. The apparatus according to claim 1, characterized in that the tube is fused to the fiber where the reflective element is located and the tube has an outer diameter so that the optical coupling to the coating modes is substantially eliminated.

17. A method of introducing an optical reflective element 15 into a tube, comprising: a) obtaining an optical fiber having a predetermined grid location where the reflecting element is to be embedded therein; b) place a tube around the fiber at the 20-point location; c) heating the tube until the tube is melted to at least a portion of the fiber so that the predetermined grid location is introduced into the tube; and d) embedding a fiber reflecting element in said grid location.

18. The method according to claim 17, characterized in that in step (d) it is executed between steps (a) and (b).

19. The method according to claim 17, which further comprises exerting a collapse force on the tube during the heating step.

The method according to claim 17, characterized in that a longitudinal axis of the tube and the fiber is oriented vertically.

21. The method according to claim 17, characterized in that the heating step is carried out by means of a laser.

22. The method according to claim 17, characterized in that the tube is melted to the optical fiber where it is 15 locates the reflective element.

The method according to claim 17, characterized in that the tube is fused to the optical fiber on opposite axial sides of the reflective element.

The method according to claim 17, characterized in that the embedding stage comprises embedding at least a part of the reflective element in a corresponding number of grid locations in the fiber, and the fiber is contaminated with a ground dopant rare at least between the pair of elements to form a fiber laser. 25

25. An optical reflective element introduced into a tube, made by a process, comprising the steps of: a) obtaining an optical fiber having a predetermined grid location where the reflecting element is to be embedded therein; b) placing a tube around the fiber in the grid location; c) heating the tube until the tube is melted to at least a portion of the fiber so that the predetermined grid location is introduced into the tube; and d) embedding a reflective element in the fiber at said grid location.

26. The process product according to claim 25, characterized in that step (d) is executed between steps (a) and (b).

27. The process product according to claim 25, further comprising exerting a collapsing force on the tube during the heating step.

28. The process product according to claim 25, characterized in that a longitudinal axis of the tube and the fiber is oriented vertically.

29. The process product according to claim 25, characterized in that the heating step is executed by means of a laser.

30. The process product according to claim 25, characterized in that the tube and the fiber are rotated about a longitudinal axis of the fiber and the tube during the heating step

31. The process product according to claim 25, characterized in that the iubo is fused to the optical fiber where the reflective element is located.

32. The process product according to claim 25, characterized in that the tube is fused to the optic fiber on opposite axial sides of the reflecting element.

33. A method for introducing a fiber optic reflective element into a tube, comprising. a) obtaining an optical fiber, which has at least one reflective element embedded therein; b) place the tube around the fiber at least where the reflective element is located; and c) heating the tube to a predetermined temperature until the tube melts at least a portion of the fiber, so that the reflective element is introduced into the tube.

34. The method according to claim 33, further comprising exerting a collapsing force on the tube during the heating step.

35. The method according to claim 33, characterized in that a longitudinal axis of the tube and the fiber is oriented vertically.

36. The method according to claim 33, characterized in that the heating step is performed by a laser.

37. The method according to claim 33, characterized in that the tube is fused to the optical fiber where the reflecting element is located.

38. The method according to claim 33, characterized in that the tube is fused to the optical fiber on opposite axial sides of the reflecting element.