MXPA01005492A - Bragg grating pressure sensor - Google Patents

Abstract

A fiber grating pressure sensor includes an optical sensing element (20, 600) which includes an optical fiber (10) having a Bragg grating (12) impressed therein which is encased within and fused to at least a portion of a glass capillary tube (20) and/or a large diameter waveguide grating (600) having a core and a wide cladding and which has an outer transverse dimension of at least 0.3 mm. Light (14) is incident on the grating (12) and light (16) is reflected from the grating (12) at a reflection wavelength lambda 1. The sensing element (20, 600) may be used by itself as a sensor or located within a housing (48, 60, 90, 270, 300). When external pressure P increases, the grating (12) is compressed and the reflection wavelength lambda 1 changes.

Description

BRAGG GRID PRESSURE SENSOR CROSS REFERENCES TO RELATED REQUESTS The present is a continuation in part of the United States of America patent application serial No. 09 / 399,404, filed on September 20, 1999, which is a continuation in part of the United States patent application. United States of America serial No. 09 / 205,944, filed December 4, 1998. Likewise, the United States of America patent applications co-pending with serial number (Case No. CiDRA CC-0078B), entitled "Tube-Encases Fiber Grating", Serial No. (Case No. CiDRA CC-0128B), entitled "Strain-lsolated Bragg Grating Temperature Sensor", Serial No. (No. is case CiDRA CC-0129B), entitled "Compression-Tunned Bragg Grating and Laser", Serial No. (Case No. CiDRA CC-0146B), entitled "Pressure Isolated Bragg Grating Temperature Sensor", Serial No. (Case No. CiDRA CC-0014A) , entitled "Fiber Optic Bragg Grating Pressure Sensor", and serial number (Case No. CiDRA CC-0230), entitled "Large Diameter Optical W aveguide, Grating, and Laser ", all presented in a contemporary way with the present, and the serial No. (No. of case CiDRA cc-0130), entitled "Method and Apparatus for Forming A Tube-Encases Bragg Grating", presented on December 4, 1998, which have all the subject matter in question related to that described herein.

TECHNICAL FIELD This invention relates to fiber optic pressure sensors, and more particularly to a Bragg grid pressure sensor.

PREVIOUS TECHNIQUE Sensors for the measurement of various physical parameters such as pressure and temperature often rely on the transmission of voltage from an elastic structure (eg, a diagram, bellows, etc.) to a sensing element. In a pressure sensor, the detector element can be attached to the elastic structure with a suitable adhesive. It is also known that the detector element to the elastic structure can be a main source of error if the joint is not highly stable. In the case of sensors that measure parameters that change very slowly or statically, the long-term stability of the bond with the structure is extremely important. A major source of such long-term sensor instability is a phenomenon known as "stretching," that is, the change in the voltage of the sensing element without changing the load applied to the elastic structure, resulting in a current fluctuation. direct or a bypass error in the sensor signal. Certain types of fiber optic sensor to measure static and / or quasi-static parameters require a highly stable bond with very little stretching of the optical fiber towards the elastic structure. There are several techniques to join the optical fiber to the elastic structure. There are several techniques for joining the fiber to the structure to minimize stretching, such as adhesives, joints, epoxy, cements and / or welds. However, said joining techniques may exhibit stretching and / or hysteresis with time and / or high temperatures. An example of a sensor based on optical fiber is that described in the patent application of the United States of America Serial No. 08 / 928,598 entitled "High Sensitivity Fiber Optic Pressure Sensor for Use in Harsh Environments" for Robert J. Marón , which is incorporated herein by reference in its entirety. In that case, an optical fiber is attached to a compressible bellows at a location along the fiber and to a rigid structure at a second location along the fiber with a Bragg grid embedded within the fiber between those two locations of fiber union and with the grid that is in tension. As the neck is compressed due to an external pressure change, the tension on the fiber grid is reduced, which changes the wavelength of the light reflected by the grid. If the union of the fiber to the structure is stable, the fiber can move (or stretch) in relation to the structure to which it is attached and the aforementioned measurement inaccuracies are presented. Another example, a fiber optic Bragg grid pressure sensor where the fiber is secured in tension to a glass bubble by a UV cement described in Xu, MG, Beiger, H, Dakein, JP, "Fiber Grating Pressure Sensor However, as described above, said bonding techniques may exhibit stretching and / or hysteresis with time and / or high temperatures. temperatures, can be difficult or expensive to manufacture BRIEF DESCRIPTION OF THE INVENTION Objects of the present invention include providing a fiber optic pressure sensor with a minimum stretch In accordance with the present invention a sensor, comprising an optical sensing element having at least one pressure reflective element positioned thereon as along an axis length of the sensing element, the pressure reflecting element having a pressure reflecting wavelength, the sensing element being axially tensioned due to a change in external pressure, the axial tension causing a change in the pressure reflex wavelength, and the change in the pressure reflex wavelength which is indicative of a change in pressure, and at least a portion of the sensing element having a transverse cross section that is contiguous and is made substantially of the same material and having an external transverse dimension of at least 0 3 mm According to the present invention, the The detector element comprises an optical fiber, having the reflecting element embedded therein, and a tube, having an optical fiber, and the reflective element introduced therein along a longitudinal axis of the tube, the tube being fused by at least a portion of the fiber In accordance with the present invention, the sensing element comprises a large diameter optical waveguide having an outer coating and an internal core placed therein, and an outer waveguide dimension of at least 0 3 mm According to the present invention the reflective element is a Bragg grating. In accordance with the present invention the sensing element has a canine bone shape. In accordance with the present invention the sensing element comprises a canine bone shape and comprises an outer tube fused to at least a portion of the large sections of the canine bone shape on opposite axial sides of the reflex element. The present invention provides a fiber grating placed in an optical sensing element that includes an optical fiber fused to at least a portion of a vitreous capillary tube ("fi ber / grating inserted in tube") and / or a grating. Large diameter waveguides having an optical core and a wide coating, which is elastically formable based on the applied pressure The present invention substantially eliminates stretching and other bonding problems of the optical fiber The sensing element may be made of a vitreous material, such as, silica or other glasses. Also, the invention provides detection with very low hysteresis. The present invention allows forces to be applied axially against the end faces of the detector element thus allowing the high sensitivity of the sensor. The present invention provides also an accounting of the sensor when it is used in compression, also, one or more rejill Thus, fiber laceres or a plurality of fibers can be placed on the element. The gratings or laceres can be "introduced" into the tube by having the tube fused to the fiber over the grid area and / or on opposite axial sides of the area of the fiber. grid adjacent to or a predetermined distance from the grid The gratings or laces may be fused within the pipe or partially within or towards the outer surface of the pipe Also, one or more wave guides and / or the grid / fiber introduced into the pipe may be axially fused In addition, the invention can be used as an individual sensor (single point) or as a plurality of multiplexed distributed sensors (multiple point). Also, the invention can be a direct-feed design or a design without direct supply The element detector can have alternative geometries, for example, a canine bone shape, which provides enhanced strength for sensitivity of the displacement of the wavelength and is easily scalable for the desired sensitivity The invention can be used in adverse environments (high temperature and / or pressure), such as oil wells and / or gas, engines, combustion chambers, etc. For example , the invention can be a fully glass sensor capable of operating at high pressures (>15 kpsi) and high temperatures (> 150 ° C) The invention will work equally well in other applications independent of the type of environment The above and other objects, features and advantages of the present invention will become apparent in the light of the following description detailed illustrative modalities of it BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of a fiber grating sensor inserted into a tube, according to the present invention; Fig. 2 is a side view of an alternative embodiment of a grating sensor inserted into a tube, according to the present invention; Figure 3 is a side view of an alternative embodiment of a fiber grating sensor inserted in a tube, according to the present invention; Figure 4 is a side view of an alternative embodiment of a fiber grating sensor inserted in a tube, according to the present invention. Figure 5 is a side view of an alternative embodiment of a fiber grating sensor inserted into a tube, according to the present invention. Figure 6 is a side view of an alternative embodiment of a fiber grid sensor inserted in a tube, according to the present invention. Figure 7 is a side view of an alternative embodiment of a fiber grating sensor inserted in a tube, according to the present invention. Figure 8 is a side view of an alternative embodiment of a fiber grating sensor inserted in a tube, according to the present invention. Figure 9 is a side view of a fiber grating sensor inserted in a tube, mounted to a wall of a housing, according to the present invention. Figure 10 is a side view of a fiber grating sensor inserted in suspended tube within a housing, in accordance with the present invention. Figure 11 is a side view of an alternative embodiment of a fiber grating sensor inserted into a tube having two gratings in a fiber inserted into a tube, according to the present invention. Figure 12 is a side view of an alternative embodiment of a fiber grating sensor inserted into a tube having a double capillary tube, according to the present invention; Figure 13 is a side view of an alternative embodiment of a grating sensor; of fiber introduced into a tube having a collapsed capillary tube and fused to the fiber on opposite sides of a grid, according to the present invention. Figure 14 is a side view of an alternative embodiment of a fiber grating sensor inserted in the tube of Figure 13, according to the present invention. Fig. 15 is a side view of an alternative embodiment of a fiber grating inserted into a tube having an axially long projecting section, according to the present invention. Figure 16 is a side view of an alternative embodiment of a fiber grating sensor inserted into a tube having a diaphragm, according to the present invention. Figure 17 is a side view of an alternative embodiment of a fiber grating sensor inserted into a tube having an axially long protruding section as a portion that is not collapsed on the fiber, according to the present invention. Fig. 18 is a side view of an alternate embodiment of a fiber grating sensor inserted into a tube having a circular housing cross section according to the present invention. Fig. 19 is a side view of an alternate embodiment of a fiberglass sensor inserted into a tube having a piston having a hollow section held under pressure, in accordance with the present invention. Fig. 20 is a side view of a alternative of Figure 19, in accordance with the present invention Figure 21 is a block diagram of a plurality of fiber-grid sensors introduced into a tube connected in series, according to the present invention. Figure 22 is a side view of A fiber grating sensor inserted into a tube having two separate optical fibers inserted into a common tube, according to the present invention. Figure 23 is an end view of the embodiment of Figure 21., according to the present invention Figure 24 is an end view of a fiber grating sensor inserted into a tube having two separate optical fibers inserted into a common tube, according to the present invention. Figure 25 is a side view of a fiber grating introduced into a tube where the tube is collapsed on the fiber only over the length of the grid, according to the present invention. Figure 26 is a side view of an alternative embodiment of a fiber grating sensor inserted in the fiber. tube, according to the present invention Figure 27 is a fiber grating sensor introduced into a tube with a portion mounted within the constrained region of a housing and a portion of a tube located outside the pressurized region, in accordance with the present invention. Figure 28 is an alternative embodiment of a fiber grating sensor inserted into a tube having a temperature grid isolated from the pressure, according to the present invention. Fig. 29 is an alternative embodiment of a fiber grid sensor inserted into a tube having a temperature grid exposed to pressure, according to the present invention. Fig. 30 is a side view of an alternate embodiment of a fiber grating sensor inserted into a tube having a selectable distributed fiber feedback fiber (DFB) laser in a tube, according to the present invention. Figure 31 is a side view of a large diameter optical waveguide having a grid placed therein, in accordance with the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Referring to Figure 1, a Bragg fiber grating pressure sensor comprises a known optical guide 10, for example, a standard single-mode telecommunication fiber optic that has a patterned Bragg grid (or embedded or printed) in Figure 10. Fiber 10 has an outer diameter of about 125 microns and comprises silica glass (SiO2) having the appropriate dopants, as is known, to allow light 14 to propagate at length of the fiber 10 The Bragg12 grating, as it is known, is a periodic or non-periodic variation in the effective refractive index and / or the effective optical absorption coefficient of an optical waveguide, similar to that described in the US patent. United States of America No. 4,725,110 and 4,807,950, entitled "Method for Impressing Gratings Within Fiber Optics", for Glenn et al, and the United States patent No. 5,388,173, entitled "Method and Apparatus for Forming Apepodic Gratings m Optical Flbers," for Glenn, which are incorporated by reference to the extent necessary for the understanding of the present invention. However, any selectable wavelength grid or reflective element embedded, etched, and printed or otherwise formed in the fiber can be used if desired. As used herein, the term "grid" represents any of said reflective elements. In addition, the reflective element (or grid) 12 can used in the reflection / transmission of light Other materials and dimensions for the optical fiber or the waveguide 10 can be used if desired For example, the fiber 10 can be made of any glass, silica, phosphate glass or other glass or made of glass and plastic or plastic, or other materials used to make optical fibers For high temperature applications, fiber optic made from u In addition, the fiber 10 can have an external diameter of 80 microns or other dimensions. In addition, instead of an optical fiber, any optical waveguide, such as a multi-mode, birefringent, biasing, polarizing, multi-core, or multiple-coat waveguide, or a smooth waveguide, can be used. or flat (where the waveguide is rectangular in shape), or other waveguides As used herein the term "fiber" includes the waveguides described above. Light 14 is incident on the grid 12 which reflects a portion thereof as indicated by a line 16 having a determined wavelength band of the light centered at a reflection wavelength? 1, and passing the remaining wavelengths of the incident light 14 (within a predetermined wavelength range), as indicated by a line 18. The fiber 10 with the grid 12 therein is inserted into and fused to at least a portion of an elastically definable pressure sensing element. ormable 10 as a cylindrical vitreous capillary tube referred to herein as a tube The tube 20 may have an outer diameter d1 of about 2mm and a length L1 of about 12mm The grid 12 has a length Lg of about 5mm Alternatively, the length L1 of the tube 20 can be substantially the same length as the length Lg of the grid 12, as by the use of a larger grid, or a shorter tube. Other dimensions and lengths of the tube 20 and the grid 12 can be used. fiber 10 and grid 12 do not need to fuse in the center of tube 20 but can be fused anywhere in tube 20 Also, tube 20 does not need to fuse to fiber 10 over the full length L1 of tube 20 tube 20 is made of a vitreous material, such as a natural or synthetic quartz, fused silica, silica (S? O2), from Pyrex® by Corning (borosilicate), or Corning Vycor® (approximately 95% silica and 5% other components such as boron oxide), or other glasses The tube 20 must be made of a material so that the tube 20 (or the inner diameter surface of a hole in the tube 20), can be fused to (i.e., create a molecular bond with or fuse with) the outer surface (or coating) of the optical fiber 10 so that the interface surface between the internal diameter of the tube 20 and external diameter of the fiber 20 is substantially eliminated (i.e., the inner diameter of the tube 20 can not be distinguished and forms part of the coating of the fiber 10) For the best coupling of the thermal expansion of the tube 20 to the fiber 10 on a large temperature scale, the coefficient of thermal expansion (CTE) of the material of the tube 20 must substantially couple the CTE of the material of the fiber 10 In general, a lower melting temperature of the vitreous material, higher the CTE, for example, a fused silica tube and optical fiber Therefore, for a silica fiber (which has a high melting temperature and a low CTE), a tube made of other vitreous material, such as Pyrex® or Vycor® (having a lower melting temperature and higher CTE) results in a decoupling of thermal expansion between the tube 20 and the fiber 10 with the temperature. However, it is not required for the present invention that the CTE of the fiber 10 couple the CTE of the tube 20 (described in greater detail below). Instead of the tube 20 being made of a vitreous material, other elastically deformable materials can be used on condition that the tube 20 can be fused to the fiber 10. For example, for an optical fiber made of plastic, a tube made of of plastic material. The axial ends of the tube 20 where the fiber 10 exits the tube 20 may have an internal region 22 that is tapered inwardly (or widened) away from the tube 10 to provide tension release of the fiber 10 or for other reasons. In that case, an area 19 between the tube 20 and the fiber 10 can be filled with a tension release filler material, for example polyimide, silicone, or other materials. Also, the tube 20 may have tapered (or bevelled or angled) outer corners or edges 24 to provide a seat for the tube 20 to engage with another part (described below) and / or to adjust the angles of force on the tube 20. or for other reasons. The angle of the beveled corners 24 is fixed to achieve the desired fusion. The tube 20 may have side cross-sectional shapes other than the circular one, such as square, rectangular, elliptical, shell-like or other, and may have side view (or transverse) shapes other than rectangular, such as as circular, square, elliptical, shell-shaped or others. Also, the outer rings or sleeves 29 may be located around the outer diameter of the inner tapered region 22 of the tube 20 to help prevent cracking of the fiber 10 at the junction of the tube 20 and the fiber 10 due to the Poisson effect (described hereinafter) or other force effects when the axial force is applied to the tube 20. The sleeves 29 are made of a hard and rigid material such as a metal. Alternatively, instead of having the internal tapered region 22, the axial ends of the tube where the fiber 10 exits the tube 20 may have an outer tapered section (or fluted, conical, or joining), shown as the dotted lines 27, the which has an external geometry that decreases toward the fiber 10 (described below with Figure 12). In that case, the rings 22 may not be necessary. It has been found that using the striated sections 27 provides improved attraction resistance in and near the interface between the fiber 10 and the tube 20, for example 8.88 kg / m or more, when the fiber 10 is pulled as along its longitudinal axis. When the fiber 10 leaves the tube 20, the fiber 10 can have an external 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 has a thickness of about 25 microns. Other thicknesses and diverting materials for the diverter layer 21 can be used. If the tapered axial region 22 is used and is large enough, the diverter layer 21 can be inserted into the region 22 to provide a transition from the discovered fiber to an offset fiber., if the region has an external taper 27 of the diverter 21 it would start where the fiber of the tube exits 20 If the diverter starts after the fiber exit point, the fiber 10 can be coated with an additional diverter layer (not shown) covering any fiber discovered outside the fused region and overlaps with the diverter 21 and may also overlap with part of the region 27 or the end of the tube 20 The glass grating introduced in glass 20 may be used by itself or as a component in a Greater configuration for measuring the pressure For example, the glass grid tube 20 of the embodiment shown in FIG. 1 can be used directly as a pressure sensor (also described below with FIGS. 9, 10). In this case, the diameter, length and material of tube 20 determine whether the reflection wavelength of grid 12? 1 will move up or down and determine the amount of displacement of the wavelength Likewise, the material properties of the tube 20 such as the Poisson's ratio (the ratio between the change in length to the change of the bar, due to an external force) and the Young's modulus (ie, the axial compression capacity of the bar as a function of the length of the bar) help to determine the displacement of the wavelength. In particular, if the tube 20 is placed in an environment with a pressure P, there will be forces of armpit pressure 26 and forces of radial pressure 28. The pressure P can be fluid pressure (when a fluid is a liquid a gas or a combination thereof). Depending on the Poisson's ratio and Young's modulus (or the axial compressive capacity) and other properties of the tube material 20, the tube 20 can be compressed or elongated axially as the pressure increases. For the tube 20 made of glass or metallic materials (and other materials with low Poisson ratios), as the pressure increases, L1 will decrease, that is, it will be compressed axially (independent of the length L1 and the diameter d1 of the tube 20) , for a uniform axial pressure field around the tube 20, which causes the reflex wavelength? 1 of the grid 12 to decrease. Conversely, if the axial pressure 26 is a predetermined amount less than the radial pressure 28 , the tube 20 can be stretched or lengthened axially causing L1 to increase which also causes the reflection wavelength? 1 of the grid 12 to increase also. The amount of the axial length change for a given pressure P (or force per area unit) is also determined by the axial compressibility of the tube 20. In particular, the more axially compressible the material of the tube 20, the greater the length L1 of the tube 20 will change for a a given initial length (? L1 / L1). Also, as the temperature changes, the length of the tube 20 changes based on a known coefficient of thermal expansion (CTE or a). Typical approximate values of Poisson's ratio, Young's modulus and Thermal Expansion Coefficient (CTE) for certain vitreous materials for tube 20 are provided in Table 1 below.

TABLE 1 The grid 12 may be printed in Figure 12 before or after the capillary tube 20 is introduced around the fiber 10 and the grid 12. If the grid 12 is printed in Figure 10 after the tube 20 is introduced around of 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 (case No. Cidra CC) -0130), entitled "Method and Apparatus For Forming A Tube-Engaging Bragg Grating", filed December 4, 1998. To introduce the fiber 10 into the tube 20, the tube 20 can be heated, collapsed and fused to the grid 12, by means of a laser beam, filament, flame, etc., as described in co-pending United States patent application, serial No. (Case No. Cidra CC-0078B), entitled " Tube-Encases Fiber Grating ", presented in a contemporary way with the pre sentence, which is incorporated into it by reference. Other techniques may be used to fuse tube 20 to fiber 10, as described in U.S. Patent No. 5,745,626, entitled "Method For An Encapsulation of An Optical Fiber," for Duck et al., and / or U.S. Patent No. 4,915,467, entitled "Method of Making Fiber Coupler Having Comprehensive Precision Connection Wells," for Berkey, which are incorporated herein by reference to the extent necessary to understand the invention and other techniques Alternatively, other techniques can be employed to fuse the fiber 10 to the tube 20, such as, for example, using a high temperature glass soldering iron, for example, silica solder (powder or solid), so that the fiber 20, the tube 20 and the welder are all fused together, or using laser / fusion welding or other fusion techniques. Also, the fiber may be fused within the tube or partially within or on the external surface of the tube (described below with Figure 24). For some of the embodiments described herein, the grid 12 can be introduced into the tube 20 having an initial pre-tension on the grid (compression or tension) or without pre-stressing. For example, if the Pyrex® glass or other 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 the tube 20 Alternatively the fiber grid 12 can be introduced into the tube 20 under tension by placing the grid in tension during the process of heating and melting the tube. In that case, when the tube 20 is compressed, the tension on the grid 12 is reduced. Also, the fiber grid 12 can be introduced into the tube 20 resulting in no tension or understanding on the grid 12 when external forces are not applied to the tube 20 The fluted sections 27 where the fiber 10 joins tube 20 can be formed in various ways, such as described in co-pending patent application of the aforementioned United States of America, Serial No. (Case No. Cydra CC-0078B) For example, tube 20 can be heated and the tube 20 and / or fiber 10 pulled on one end to form the fluted sections 27 Alternatively, the fluted ends 27 can be formed using other vitreous forming techniques, such as etching, polishing, milling, etc. Other techniques can be used to Also, the inner region 22 can be created through numerous techniques, such as described in the above co-pending United States patent application (Case No. CiDRA CC-0078B) For example, without collapsing the tube 20 to the fiber 10 in the regions 22 or to create a region 22 that is greater than the internal diameter of the tube 20, the tube 20 can be heated in the desired region to be expanded and internal pressure is applied to the tube 20 Referring to Figure 2 in an alternative embodiment, it has been found that the increased sensitivity can be achieved by varying the geometry of the capillary tube. In particular, the tube 20 may have a "canine bone" shape having a narrow central section 30 and longer external sections 32 (or pistons). The narrow section 30 has an outer diameter of approximately 2mm and a length L2 of approximately 9 25mm The long sections 32 have an external diameter d3 of approximately 4mm and a length L3 of approximately 6 35mm Other lengths L2, L3 of sections 30, 32 may be used, while avoiding deformation For example, the length L3 it can be more than 6 36 mm (for example greater than 25 4mm in length) or it can be much smaller than 6 36mm in length The ratio of cross-sectional areas (pd2) of the car The axial ends of the tube 20 and the narrow portion 30 provide a diagonal force gain area of 4 Also, the sections 32 of the tube 20 may have the internal tapered regions 22 or the outer tapered sections 27 at the ends of the tube 20, as shown in FIG. described above. In addition, sections 32 may have tapered (or beveled) outer corners 24, as described above. An internal transition region 33 of the long sections 32 may have a sharp or angled vertical edge or may be curved as indicated by dashed lines 39. A curved geometry 39 has lower stressors than a sharp edge or corner and thus reduces the probability of rupture. Also, 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 an individual side canine bone, where instead of having the two longer sections 32, it may be only the long section 32 on one side of the narrow section 30 and the other side may have a straight edge. 31 which may have bevelled corners 24 as described above. In that case, the canine bone has the shape of a "T" on its side. Said single-sided canine bone form is also referred to herein as a "canine bone" form. Instead of a canine bone geometry, other geometries that provide improved tension sensitivity or force angle adjustment on the tube 20 or provide other desirable characteristics can also be used. It has been found that such dimensions change between the dimension d3 of the long section 32 and the dimension d2 of the narrow section 30 provides an increased force to the sensitivity of wavelength offset of the grid (or gain or scale factor) by The amplification of the tension Likewise, the dimensions provided in the present for the canine bone are easily scalable to provide the desired amount of sensitivity. Instead of a canine bone geometry, other geometries that improve the sensitivity or adjust the angles of force on the Tube 20 can be used if desired The increased sensitivity of the canine bone geometry is provided by the voltage amplification caused by the difference between the dimensions d3 and d2 To optimize the sensitivity of the canine bone geometry the longer sections 32 must isolate from the opposing axial forces 35 over the transition region int erna 33 and the narrow section 30 must be insulated from the radial forces 37. This can be achieved by abutting the canine bone with a cylinder, membrane, walls, or other interface, as described hereinafter. Radial forces on the narrow section 30 they are subtracted from the displacements caused by the axial forces, due to the Poisson effect, thus causing the sensor's decreased sensitivity. The canine bone geometry can be formed by etching, grinding or polishing the central section of the capillary tube 20 to obtain the narrow diameter d2 Used the chemical etching (for example, with hydrofluoric acid or other chemical engravers) laser engraving, or laser-enhanced chemical etching are some techniques that reduce the diameter external without applying direct contact force as required by grinding and polishing Other techniques can be employed to obtain the narrow diameter region 30 After the canine bone (or other geometry) is formed in tube 20, the surface of the tube 20 can be buffed to remove surface impurities, improve strength or for other reasons. Referring to Figure 3, alternatively, the canine bone geometry can be formed using multiple pieces such as a center piece 40, similar to the grid introduced in glass 20 of figure 1, surrounded by two ends 42 (analogous to the long sections 32 in figure 2) The end pieces 42 can slide on the fiber 10 and be pressed against the center piece 40 The center piece 40 can be seated or lowered into two end pieces 42 (as shown in Fig. 3) or placed flat against the end pieces 42 Referring to Figure 4, a way to use the canine bone geometry as a sensor 48 is to encircle the canine bone by an external cylinder or outer tube 50. The cylinder 50 prevents the pressure T from exerting direct radial forces 37 on the medial narrow section. and that it exerts opposite axial forces 35 on the long sections 32 The cylinder 50 the material and the properties can exert other forces (axial and / or radial) on the device that should be evaluated and selected for the desired application The cylinder 50 can be made of the same material as that of section 32, for example, a glass or other material, for example, a metal If section 32 and cylinder 50 are made of a vitreous material, the cylinder 50 can be fused to the sections 32, similar to the way that the tube 20 is fused to the fiber 10 Alternatively, the cylinder 50 can be etched for other dimensions of the longer sections 32 and the tube 20 by welding, welding, melting, adhesives or epoxies or other suitable joining techniques Cylinder 50 forms a hermetically sealed chamber (or cavity) 34 between cylinder 50 and the narrow section of tube 20 When pressure P is applied, as shown in FIG. indicated by the lines 26, the radial pressure 28 causes the cylinder 50 to flex radially within the chamber 34 and the axial pressure 26 acts on the outer axial end faces of the sections 32 and the cylinder 50, causing the sections 30, 32 and the cylinder 50 are compressed axially. The amount of axial compression and radial deflection of the parts 30, 32, 50 will depend on the properties and dimensions of their material. A canine bone 20 can be formed by one or more pieces as described Alternatively, the geometry of the outer cylinder 50 can be different from the straight cylinder, and it can have a geometry that changes the formability or elasticity of the outer cylinder 50 For example, the cylinder outer 50 may have a corrugated (or bellows) shape, as indicated by dotted lines 49 or an internal or external curvature preset as indicated by dotted lines 47, 51 respectively or other geometries Bellowing allows axial compatibility to increase as long as the pressure of resistance to the maximum radial rupture of the cylinder is not reduced. Referring to figure 26, alternatively, the outer tube 50 can be fused to the tube 20 away from the internal transition region 33 and / or near the axial ends 46 of the tube 20 In that case, there would be a space g2 of approximately 0 5mm between the diameter in cylinder 50 and the external diameter of the long sections 32 (or pistons) of the canine bone, the thickness T2 of the outer tube 50 is about 0.5 mm In addition, the length L2 of the short portion 30 of the canine bone is about 7 Omm and the length between where the tube 50 fuses to the pistons (2 * L3 + L2) is approximately 3 56cm and the diameters d2,3, of sections 30, 32 are approximately 1 Omm and 3 Omm respectively For those dimensions made of a vitreous material (fused silica and natural quartz) the sensor 48 provides a grid wavelength shift to a pressure sensitivity ratio of approximately 0 5 picometers / psi (or 2 0 psi / pm) and can be used as a sensor from 0 to 5000 psi for long-term operation It has been found that the structure of figure 26, with the dimensions described above can withstand an external pressure before rupture of more than 15 kpsi For a sensor operating range of 0 to 15,000 psi, which has a sensitivity of 0 3846 pm / psi (or 2 6 psi / pm), the pu dimensions They can be as follows wall thickness t1 of about 1 mm, diameter d2 of about 1.12 mm, outer diameter d9 of about 6 mm, length L2 of about 7.4 mm and length (2 * L3 + L2) of about 49 mm and a general length L1 of approximately 59 mm. For said 15 Kpsi sensor, it has been found that the rupture pressure is more than about 45 Kpsi. Other operating ranges can be used for the given dimensions. Alternatively, the pistons 32 may extend axially beyond the end of the outer tube 50 as indicated by the axially extending regions 44. In that case, the regions 44 may be axially symmetrical or not, depending on the application. For a 15 Kpsi individual end sensor, the length L20 of the section 44 can be approximately 20 mm. Also, there may be axially extended regions 36 (as will be described later with FIG. 8) at one or both axial ends. The length L21 of the axial extended sections 36 can be any desired length based on the design criteria, for example 12 mm. Other lengths can be used. Alternatively as previously described with the single-sided canine bone shape, the pistons 32 of the canine bone shape may have equal lengths or there may be only one piston 32 having the length of the two pistons (2 * L3) in one side of the tube / grid 30 and the end cap 46 on the other side, in the latter case, there would be more compression of the individual piston 32 due to the increased length. Also, if the sensor is not of a direct feed (ie, individual end) design, one end may be bent at an angle to reduce optical retroreflections, for example 12 degrees from the vertical as indicated by the dotted line59. Other angles can be used. Also, said configuration allows the sensitivity (or resolution) to be increased by changing the overall length L! (ie, the lengths L3 of the pistons 32 and the outer tube 50). In particular (for a given length of the pistons 32 and the tube 50), for a change L in the length L1 due to a change in pressure, a large portion L 'of the change L occurs through the length L2 of the small section 30 where the grid 12 is located (the rest that is through as the large pistons 32). Then, if the length of the pistons 32 and the tube 50 are increased, the tube 50 will comprise or flex more (ie, a L greater) for the same pressure change (because the amount of compression for a given force increases with length). This increased L is observed through the same length L2, thereby increasing the L / L 2 sensitivity (described below with Fig. 7). If desired, other values can be used for space g2 and thickness T2, lengths L1, L2, L3 and diameters d2, d3 depending on the design specification and the application. For example, there are several ways to increase the sensitivity (pm / psi), such as by decreasing the thickness of the wall T2 (while resisting the maximum external pressure required), increasing the space g2, increasing the overall length L1 between where the tube 50 is fused to the pistons 32 (for example, increases the length of the tube 50 and the length L3 of the piston), decreases the diameter d3 of the narrow section of the canine bone shape, or increases the diameter d3 of the large sections 32 (or pistons) of the canine bone shape In particular, for a sensitivity of about 0 6 picometers / psi the overall length L1 can be increased from about 3 56 cm to about 5 08 cm Similarly, in that case, the chamber 34 It would be a chamber of an I shape (or rotated H shape). In addition, there may be a flange 52 near where the outer tube 50 is fused to the outer tube 20 Referring to FIG. 5, an alternative embodiment of the present invention comprises a housing 60 having a pressure port 62 and an internal chamber 64 The pressure port 62 carries the pressure P1 inside the chamber 64 The fiber 10 passes through a front wall (or end cap) 66 of the housing 60 through a hermetically sealed direct feed 67 and exits through a rear wall (or end cap) 68 of the housing 60 through a sealed direct feed 69 A bellows 70 is located inside the chamber 64 and has one end of the bellows 70 connected to the wall of the rear housing 68 and the other end connected to a bellows plate 72. The tube 20 is located within a bellows 70 and is positioned between the rear housing wall 68 and the bellows plate 62 which is free to move axially. A portion 73 of the fiber 10 outside the bellows 70 may have a clearance to allow the fiber 10 to flex with the compression of the bellows 70 without placing the portion 73 of the fiber 10 under tension. The gap can be provided by a helical bending or wrapping or other tension release technique for the fiber 10. The plate 72 and the wall 68 apply axial forces against the grid / tube 20 within the bellows 70. Between the tube 20 and the bellows 70 is a bellows chamber 74. Pressure P2 in bellows chamber 74 can be 0 psi for an absolute sensor or atmospheric pressure, for example, 14.7 psi (1 atm), or other fixed pressures. If a delta-P pressure sensor is desired, a pressure port 76 may be provided to carry a second pressure P2 within the bellows chamber 74. The axial ends of the tube 20 may be depressed in the plate 72 and the wall 68 as shown in Fig. 5 or be level against the plate 72 and / or the wall 68. As the pressure P1 increases around the outside of the bellows 70, it causes the bellows 70 to shorten or compress (and plate 72). move to the right) which compresses the tube 20 and the grid 12 and causes the reflection length light? 1 from the grid 12 to be reduced. The spring constant of the bellows 70 is selected to be smaller relative to the spring constant of the tube 20, but large enough not to break under the applied pressure. This minimizes the error induced by the stretch by supplying the maximum amount of source pressure to tube 20 Tube 20 may also be formed in a canine bone geometry or other forms as described herein if desired Alternatively, if the pressure P2 is greater than P1 by a predetermined amount, the tube 20 (and the bellows 70) will expand axially and the reflection wavelength of the grid 12 would be increased. Referring to FIG. 6, another embodiment of the present invention comprises two grids inserted in a pushing / pulling arrangement. In particular, the configuration is substantially the same as that shown in FIG. 5 with a second grid 80 inserted in a second tube 82 similar to the first tube 20 having a second reflex wavelength? 2 The tube introduced in grid 82 is placed between the plate 62 and the front wall 66 of the housing 60 With this design, at the applied pressure P1 of "zero", the tension develops through the second grid 80 by the spring force of the bellows 70, while the first grid 12 is left without tension (or at a lower tension) As the pressure P1 increases, the bellows 70 is compressed, releasing the tension on the second grid 80 and applying more compression to the first grid 12 Other push-pull tension conditions and configurations on the grids 12, 80 may be used Alternatively, if the pressure P2 is greater than the pressure P1 by a predetermined amount, the tube 20 (and the bellows 70) would expand axially and the reflection wavelength of the grid 12 would increase. In this configuration, the pressure is determined by measuring the difference between the reflection lengths? 1,? 2 of the two grids 12 , 80 since the grid wavelengths? 1,? 1 move in opposite directions as the pressure changes. Therefore, the force required to obtain a given wavelength shift (??) is half that of a Individual grid transducer or, alternatively for a given force, the wavelength shift is twice that of an individual grid transducer Also, the two grid wavelengths? 1,? 2 move in the same direction as the temperature changes. Therefore, through measurement and displacement of the average value of the two reflection lengths? 1,? 2 the temperature can be determined, which allows the compensation to be executed Also, if there is stretching, the maximum stretch error can be determined. In particular, the average reflex wavelength between the two grids can remain identical in case there is no stretching for a certain temperature and pressure. Referring to the figure 7, another embodiment of the present invention, comprises a cylindrically shaped housing 90 comprising an outer cylindrical wall (or outer tube) 98, two end caps 95 and two end cylinders (or pistons) 92 each connected to one end of a of the end caps 95 The tube (with the grid 12 inserted therein) is placed against the other ends of and between the two pistons Other shapes of cross section and / or side view section may be used for the housing 90 and the elements 98, 95, 92 if desired. The end caps 95 may be separate pieces or part of u adjacent to the pistons 92 and / or the external cylinder 98 The pressure P (26,28) is applied to the outer walls 98, 95 of the housing 90 The pistons 92 have holes 94 having diameter dd, which passes the fiber 10 The end caps 95 of the housing 90 can having tapered regions 96 to provide tension release as described above Also, end caps 95 have direct supplies 106 where the fiber 10 comes out and can be hermetically sealed direct feeds Any hermetic direct feed of known optical fiber can be used for direct feeds 106, such as plating the fiber 10 with a metal and welding the fiber to the direct supply 106 Between the tube 20 and feeding them 106, the fiber 10 can have the outer protective diverter layer 21 described as hitherto to protect the outer surface of the fiber 10 from any damage., a region 88 between the fiber 10 and the internal dimension of the orifice 94 can be filled with a liquid or solid material, for example silicone gel, which further protects the fiber 10 and / or is thermally conductive to allow a temperature grid 250 (described above) quickly detect changes in the temperature of the pressure grid 12 or for other uses Between the internal dimension of the walls 98 and the external dimension of the tube 20 and the pistons 92, there is an internal I-shaped bed ( Also, there may be hollow regions 99 in the pistons 92 to allow some clearance or duty cycle 101 in the fiber 10 between the tube 20 and the end 106 of the housing 90 to accommodate the thermal expansion to the pistons 92 or for other reasons Pistons 92, outer cylinder walls 98, end caps 95 and tube 20 can be made of the same or different materials. In addition, pistons 92 can be of length different or there may be only one piston having the length of the two pistons 92 on one side of the tube 20 and the end cap 95 on the other side In the latter case, there would be more compression of the individual piston 92 due to its increased length An example of some possible dimensions for the housing 90 are as follows 3 dimensions can be used The tube 20 has the external diameter d2 of approximately 2mm and a length L1 of approximately 12 5mm, the stompings 92 each have external diameters d5 of approximately 19 1mm, the length L5 of each of the pistons is about 6 25cm, the diameter of the holes 94 in the pistons 92 is about 1mm, the overall length L4 of the housing 90 is about 12 7cm, the thickness t1 of the outer walls 98 is approximately 1.0mm and the space g1 between the internal dimension of the outer walls 98 and the external dimensions of the pistons 92 is approximately 1 .52mm. The walls 98 must be made of a material and thickness capable of resisting the external pressure P applied to the housing 90. The dimensions, materials and properties of the material (for example the Poisson's ratio, Young's modulus, the coefficient of thermal expansion and other known properties), the walls 98 and the pistons 92 are selected so that the desired tension is supplied to the capillary tube 20 at a specific pressure P (or external force per unit area). The resolution and the range to detect pressure P are scalable when controlling these parameters). For example, if the overall length L4 is increased, the sensitivity? L / L will be increased. In particular, as the pressure increases, the axial length L4 of the housing 90 decreases by an amount? L due to compression and / or deflection of the outer walls 98, A predetermined portion of the total axial length change? L 'is observed in the tube 20 due to the compression of the tube 20. The compression of the tube 20 reduces the Bragg reflex wavelength of the grid 12 by a predetermined amount that provides a wave displacement indicative of the pressure T. If the pistons 92 have a spring constant greater than that of the vitreous tube 20 the tube 20 will be compressed more than the pistons 92 for a given force. Also, for a given external force, a predetermined amount of the force is lowered through the outer walls 98, and the remainder is observed by the tube 20. The housing 90 can be made of a material having a high resistance, a low Poisson ratio and a low Young's modulus, such as titanium (Ti). For example, when the walls 98, the pistons 92 and the end caps 95 are all made of titanium having the dimensions described above, for an external force of 2200 Ibf, 2000 lbf are lowered through (or used to compress / flex) the outer walls and 299 Ibs are lowered through the tube 20. The cylinder walls act similar to a diaphragm or bellows that comprise or flex due to the increased external pressure. Other metals and metal alloys can be used for some or all of the parts 92, 98, 95 of housing 90 such as stainless steel, titanium, nickel-based alloys, such as Inconel®, Ni monic® (registered trademarks of I nco Alloys I International, I nc.) Containing various levels of nickel, carbon, chromium, iron, molybdenum and titanium (for example I nconel 625) and can. use other metals or metal alloys of high strength or corrosion resistant or high temperature or heat resistant, or other materials that have sufficient strength to compress the tube 20. Other materials having other properties can be used if desired depending on the application. Typical approximate values for Poisson's ratio, Young's modulus and thermal expansion coefficient (CTE) for titanium are given in Table 2 below. TABLE 2 Material CTE Module Ratio Poisson Youna Titanium (Ti) 0.3 15.5 kpsi 10.5 x 10_6 <; ° C Alternatively, one or more of the parts 92, 95, 98 of the housing 90 can be made of a vitreous material. In that case, one more of the vitreous materials and properties shown in Table 1 so far can be used. Other materials may be employed for the housing 90 if desired, depending on the application and the design requirements. The tube 20 can have the shape of canine bone described above with Figures 2, 3. Also, the sensor housing 90 can be divided transversely into two halves which are assembled as indicated at the junction points 104. Alternatively, the housing 90 It can be divided longitudinally. In addition, a separator or disc 97 may be provided to assist in the assembly, alignment and / or fixation of the pretension on the tube 20. Other assembly techniques may be used if desired. Also, the axial end faces of the tube 20 and / or the seats on the pistons 92 can be plated with a material that reduces stresses or improves the coupling of the tube 20 with the seating surface on the pistons 92. To make a delta sensor -P, a pressure port 102 can be provided through one or both pistons 92 to transmit a second pressure P2 inside the internal I chamber 100. The configuration of figure 7 does not require bellows and therefore it is probably easier and cheap in its manufacture than a design based on bellows. It also has a robust construction capable of withstanding adverse environments. Referring to Figure 8, alternatively, to help reduce the stress on the fiber 10 at the interface between the fiber 10 and the tube 20, the tube 20 may have the sections 36 extending axially along the length of the tube. fiber 10 and attached to the fiber 10 in an axially outward location where the pressure (or force) is applied to the large sections 32 by the pistons 92 (or other end pieces as heretofore described herein) . The axial length of the sections is fixed depending on the application, as has been described so far with figure 26. Also, sections 36 need not be axially symmetrical and do not need to be at both axial ends of tube 20. Sections 32 can having the internal tapered regions 22, on the outer fluted sections 27 where the fiber interfaces within the tube 20 as described above. Alternatively, they may be an alternating section 39 as part of the sections 36. In that case, the region 22 may be in or near the stepped section 39 as indicated by the dashed lines 38. The regions 106 may be air or filled with an adhesive or filler. Also, the tube 20 may have a straight constant cross section as described heretofore and as indicated by dotted lines 107 instead of a canine bone shape. In addition, the orifice 94 through the pistons 92 can have a larger diameter as indicated by dotted lines 109 for all or a portion of the length of the hole 94. Referring to Figure 12, more than one concentric tube can merge to form tube 20 of the present invention. For example, a small internal capillary tube 180 having a diameter d4 of about 0.5mm can be placed inside a larger external capillary tube 182, which has a diameter d 1 described above, and the two tubes 180, 182 are fused together. One or both ends of the small tube 180 can be contracted and fused to Figure 10 to form the scored sections 27. Other values for the diameters d 1, d4, of the inner and outer tubes 180, 182 can be used if desired. Also, more than two concentric capillary tubes can be used. The material of the tubes can be identical to minimize the decoupling of thermal expansion on the temperature. Also, the shape of the outer tube 182 can 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 fusing two separate tubes 188, 190 on the inner tube 180 on opposite axial sides of the grid 12, as indicated by dotted lines 186.

Referring to Figures 13 and 14, alternatively, the tube 20 may be fused to the fiber 10 at opposite axial ends of the grid 12 adjacent to or a predetermined distance L10 from the grid 12, where L10 may be any desired length or edge of the grid (L10 = zero). In particular, the regions 200 of the tube 20 are fused to the fiber 10 and a central region 210 of the tube around the grid 12 does not fuse to the grid 10. The region 202 around the grid 12 can contain natural air or be evacuated (or be at another pressure) or can be filled partially or fully with an adhesive, for example, epoxy or other filler, for example, a polymer or silicone, or other material. The internal diameter d of the tube 20 is about 0.1 to 10 microns greater than the diameter of the optical figure 10, for example, 125.1 to 136 microns. Other diameters may be used, however, to help prevent deformation of the fiber when the tube 20 is compressed axially, the diameter d6 should be as close as possible to the outer diameter of the fiber 10 to limit the amount of radial movement of the fiber. grid 10 and fiber 10 between the melting points. Also, the distance L10 need not be symmetrical around both sides of the grid 12. Referring to Figure 14, alternatively, the same result can be achieved by merging two separate tubes 210, 212 on opposite sides of the grid 12 and then merging a outer tube 214 through tubes 210, 212. Alternatively, tubes 210, 212 may extend beyond the ends of outer tube 214 as indicated by dotted lines 216. Alternatively, tube 20 may be one piece individual with an indicative shape of the tubes 212, 214. Referring to the figures, 7, 8, 15, 17, 19, the reflection wavelength of the grid 12 changes with the temperature (?? /? T), as you know. Also, the tension of the grid 12 can change with the temperature due to a thermal decoupling between the tube 20 and the fiber 10. Also, the forces on the tube 20 can change with the temperature due to the expansion or contraction of the housing 90 with temperature. In that case, a separate temperature grid 250 can be used to measure the temperature in order to correct for the displacements induced by the temperature of the reflection wavelength? 1 of the pressure grid 12. The temperature grid 250 has a length Reflection wavelength that is different from the reflection wavelength of the pressure grid 12, which changes with the change in temperature and does not change due to a change in pressure P. This is achieved by locating the temperature grid 250 in thermal proximity to the grating the pressure 12, outside the region stressed by pressure of the tube 20 and otherwise isolated from the pressure being measured. In particular, the temperature grid 250 can be located in Figure 10 between the tube and the direct feed 106. Referring to Figure 8, alternatively, the temperature grid 250 can be located on the portion of fiber 10 that is introduced or fused in the axially protruding section 120, 36, 251 of the vitreous tube 20 outside the region that is comprised by the pistons 92. Alternatively, the temperature grid 250 may be in a separate optical fiber (not shown) located near or in the sensor housing 90 and may be optimally coupled to the fiber 10 or separated from the fiber 10. Alternatively, the temperature grid 250 may be a temperature sensor isolated from the voltage in a separate tube (not shown), as shown in FIG. describes in the co-pending United States patent application, serial No. (case number CiDRA CC-0128B), entitled "Strain-lsolated Fiber Grating Tem Perature Sensor ", presented in a contemporary way with the present. Likewise, for any of the embodiments shown herein, the temperature grid 250 can be introduced into the tube 20 having an initial pre-tension on the grid (compression or tension) or without pre-tension. Referring to Fig. 28, alternatively, the temperature grid 250 in the extended section 251 can be introduced into a second external tube 400 to form a pressure-isolated temperature sensor as described in the patent application of US Pat. United States of America co-pending, serial No. (case number CiDRA CC-0146B), entitled "Pressure-lsolated Fiber G rating Temperature Sensor", which is incorporated herein by reference. In particular, the second tube 400 is fused to the section 251 and the outer diameter of an end cap tube 402. The tube 402 can be made of the same tube material 20. Figure 10 is fed and fused to the end tube 402 of similarly to the fiber 10 which is fused to the tube 20. A sealed chamber 406 exits between the section 251, the end tube 402 and the outer tube 400. Likewise, figure 10 has some hue 404 to allow the camera 406 expand. As the external pressure changes, the outer tube 400 is compressed or flexed, the end cap 402 and / or the section 251 move toward the otrei and the figure 10 flexes in the chamber 406. However, the section 251 in grid 250 it is not exposed to pressure change. Therefore, the reflection wavelength of the temperature grid 250 does not change due to the change in pressure. In addition, the outer tube 50 and the second outer tube 400 may be a tube that is fused to the inner tubes 20, 402. Other embodiments and configurations for the pressure isolated temperature sensor may be used such as those described for the request of above-mentioned patent (case number Ci DRA CC-0146B), likewise, for a non-direct feed sensor instead of the fiber 10 which is fed directly to the chamber 406 of the end cap 402, the fiber 10 can finish within section 251 to the left of temperature grid 250. In addition, instead of end cap 402, tube 400 can be collapsed on itself to form chamber 406.

Referring to Figure 29, alternatively, the temperature display 250 may be located in an isolated area without pressure, such as in the wide region 32 of the canine bone geometry. In that case, both grids 12, 250 are subjected to pressure and temperature variations where the pressure displacement sensitivities at the wavelength for the grids 12, 250 are different. Therefore, the pressure and temperature can be determined analytically. Alternatively, if the change of the wavelength with the temperature is the same (or predictable) for both grids 12, 250 and the change in wavelength with the pressure is different for the two grids 12, 250, then you can get analytically a measurement of the pressure compensated by temperature, for example, subtracting the two wavelengths. Alternatively, a temperature grid 450 may be located in the region where the outer tube 50 is fused to the inner tube 20 or a temperature grid 452 may be located in the axial extended section 251. In those locations, the temperature grid 450, 452 would exhibit a lower sensitivity to pressure changes than the temperature grid 250, which can increase the compensation accuracy by temperature. Alternatively, instead of using a fiber grid to measure the temperature of the pressure grid 12, any other technique for determining the temperature of the pressure grid 12, for example, electronics, thermocouple, optics, etc. can be used. Referring again to Figure 7, housing 90 may be designed to minimize changes in compression of tube 10 with temperature. In particular, if the walls 98 and the pistons 92 are made of the same material, for example, titanium and the tube is made of a different material, for example, glass, which has a lower CTE, as the temperature increases, the pistons 92 will increase in length as well as the outer walls 98, except on the region 86 between the ends of the pistons 92 (where a CTE coupling will be presented). As a result, the force on the tube 20 decreases as the temperature increases. Alternatively, a section 230 on one or both pistons 92 can be made of a material having a CTE that compensates for the further expansion of the section 86 to maintain a substantially constant force on the tube 20 with the temperature. Alternatively, the outer walls 98 may be made of a material having a CTE to maintain a substantially constant force on the tube 20 at the temperature or otherwise compensate a predetermined amount of force change with the temperature. Referring to Figure 15, an alternative geometry for the capillary tube 20 may have an axial end 251 that is greater than the other axial end. In that case, the temperature compensation grid 250 may be located in the fiber 10 at the large axial end 251. Some example dimensions for tube 20 of Figure 15 are as follows, although other dimensions may be used. In particular, L6 is approximately 2.66cm, L7 is approximately 1.16cm, L8 is approximately 1.27cm, L9 is approximately 0.22cm, and d7 is approximately 0.08cm. The large axial end 251 can be made by fusing the section 251 to the section 32 (before or after the fiber 10 is introduced into the tube 20) at a point 253 or it can be done through other methods described below herein to make the canine or other bone shape for the tube 20. Alternatively, the tube 20 shown in Fig. 15 with the section 251 can be formed using two tubes, an inner tube with the length L6 slid through the sections in the form of canine bone 30, 32 as indicated by dotted lines 258 and fused to section 3032, similarly to that described with FIG. 12. Referring to FIG. 17, the long axial end 251 can be collapsed and fused to FIG. 10 where the temperature grid 250 is located and not collapsed on the fiber 10 in FIG. a region 290 near the end of section 251. In that case, region 290 may be filled with an epoxy or other filler. The internal diameter d6 of the tube 20 in the section 290 is approximately 125 to 135 microns and the diameter d8 of the orifice 34 is approximately 1mm (1000 microns) as described above. Other diameters and dimensions can be used if desired. When the fiber 10 leaves the extended region 251, the fiber 10 may have the outer protective diverter layer 21 to protect the outer surface of the fiber 10 from damage, as described above. Referring to Figs. 19, one or both pistons 92 may have a hollow section 310 which is brought towards the external pressure P through the holes 31 1 in the end cap 95. The roe section 310 has external walls 312 and internal walls 314. Said configuration can be used to help increase sensitivity or for other reasons. The length and thickness of the walls 312, 314 will determine the amount of increased sensitivity that exists. For example, as the pressure P increases, the walls 312, 314 will be placed in tension and the piston 92 will be lengthened. Alternatively, the inner wall 314 may be a pipe that may have a different material than the rest of the piston 92 and that is attached to the pistons 92 at a point 318. Likewise, the wall 314 may have a protrusion 316 to allow clearance in fiber 10. Alternatively, inner wall 314 is removed if desired. In that case, the fiber 10 would be exposed to the pressure P. Figure 10 may have the outer protective diverter coating 21 as described above. Referring to Figure 20, the end cap 95 may have holes 31 1 or support beams 320 to stabilize the wall and / or to provide a stable exit point for the fiber 10. Referring to Figure 16, in an embodiment Alternatively, a housing 270 has a diaphragm 274 which is connected to one end of the tube 20. At another end of the tube 20 is connected to a rigid rear wall 278. The rigid walls 280 connect the rear wall 254 and the diaphragm 274. Within the housing 274 is a chamber (or cavity) 272. Chamber 272 can be evacuated, be at atmospheric pressure or be brought to a second pressure P2, for differential pressure measurement (or delta P). As the pressure P 1 increases, the diaphragm 274 flexes within the chamber 272, as indicated by the dotted lines 277, which compresses the tube 20 and the grid 12 causing a wavelength shift. Alternatively, if the pressure P2 is greater than P1 the diaphragm 274 flexes outwards as indicated by the dotted lines 279. Referring to Fig. 18, an alternative embodiment of the present invention has a housing 300 having a view section. circular side and an internal chamber 306. The general shape of the housing 300 may be a sphere or a cylinder or other shapes having a circular cross-section. The tube 20 with the figure 10 and the grid 12 inserted into it is joined to the internal diameter of the housing 300. Figure 10 leaves the housing 300 at points of direct feeding 316, which can be direct hermetic supplies, as described above . As the external pressure P 1 increases, the diameter of the housing 300 decreases and the tube 20 is compressed which results in a shift in the reflection wavelength of the grid 12 as described above. The amount of wavelength displacement for a given pressure change will depend on the properties of the housing material 300 of the tube 20, for example, Poisson's ratio, Young's modulus, etc. , as described above. If the housing 300 and the tube 20 are of a similar material, eg, glass, the tube 20 can be part of or be fused to the housing 300 as a sample by dotted lines 302. In that case, the voltages between the housing 300 and tube 20 can also be smaller. Also, tube 20 may have a canine bone shape as indicated by dotted lines 304 or other shapes as described herein. Referring to Figure 11, for any of the embodiments described herein, instead of an individual grid inserted into the tube 20, two or more grids 150, 152 can be embedded in Figure 10 which is inserted in the tube 20. The grids 150, 152 may have the same reflection wavelengths and / or profiles or different wavelengths and / or profiles. The multiple grids 150, 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 Mutlipoint Fiber Laser Sensor", U.S. Patent No. 5,564,832, entitled "Birefringent Active Fiber" Laser "or U.S. Patent No. 5,666,372" Tuned Fiber Laser Compression "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 grids 150, 152 form an optical cavity and the fiber 10 at least between the grids 150, 152 (and may also include the grid 150, 152 and / or the fiber outside the grids if desired) would be contaminated with a rare earth impurifier, for example, erbium and / or ytterbium, etc. and the laser action wavelength would shift as the pressure changed.

Referring to Figure 30, another type of selectable fiber laser that can be used is selectable distributed feedback fiber (DFB) laser 154, as described in VC Lauridsen, et al, "Desgin of DFB Fiber Lasers", Electronic Letters, October 15, 1998, Vol. 34, No, 21, pp 2028-2030; P. Varming, et al, "Erbium Doped Fiber DGB Laser With Permanent for 2 Phase-Shift Induced by UV Post-Processing", IOOC'95, Tech. Digest, Vol. 5, PDI-3, 1995; U.S. Patent No. 5, 771, 251, "Optical Fiber Distributed Laser Feedback", for Kringlebotn et al, or U.S. Patent No. 5, 51 1, 083, "Polarized Fiber Laser Source ", for D'Amato et al. In that case, the grid 12 is etched into a fiber impurified with rare earth and configured to have a phase shift of? / 2 (where? Is the wavelength of the laser action) at a predetermined location 180 near the center of the grid 12 providing a well-defined resonance condition that can be continuously selected in the single longitudinal mode operation without mode restriction, as is known. Alternatively, instead of an individual grid, the two recesses 150, 152 can be placed close enough to form a cavity having a length of (N +? A) ?, where N is an integer (including 0) and the gratings 150, 152 are a fiber doped with rare earth.

Alternatively, the DFB laser 154 may be located on the fiber 10 between the grid pair 150, 152 (FIG. 11) where the fiber 10 is contaminated with a rare earth impurifier along at least a portion of the distance between the fibers. the grids 150, 152. Said configuration is referred to as an "interactive fiber laser", as described by JJ Pan et al, "Interactive Fiber Lasers with Low Noise and Controlled Output Power", E-tek Dynamics, Inc., San Jose, CA, website www.e-tek.com/products/whitepapers. Other single or multiple fiber laser configurations may be placed on the fiber 10 if desired.

Referring to Figure 21, a plurality of pressure sensors 20, 110, 112, described herein, each having at least one grid 12 inserted therein, can be connected in series by the common optical fiber 10 for measuring Multiple pressure points as distributed sensors. Any known multiplexing techniques can be used to distinguish a sensor signal from another sensor signal, such as wavelength division multiplexing (WDM) or time division multiplexing (TDM) or other multiplexing techniques. In that case, the grid 12 on each sensor may have a different reflection wavelength.

Referring to Figures 22 and 23, alternatively, two or more figures 10, 350, each having at least one key 12, 352 thereon, respectively, may be introduced into the tube 20. In that case, the hole in the tube 20 before heating and the fusing may be different from circular, for example, square, triangular, etc. Also, the hole in the tube 20 need not be centered along the center line of the tube 20.

Referring to Figure 24, alternatively, instead of the fibers 10, 350 touching each other as shown in Figure 23, the fibers 10, 350 may be separated in the tube by a predetermined distance. The distance may be any desired distance between the fibers 10, 350. Likewise, for any of the embodiments shown herein, as described above, part or all of the optical fiber and / or grating may be fused within, partially within or on the external surface of the tube 20, as indicated by the fibers 500, 502, 504 respectively.

Referring to Figure 25, alternatively, the tube 20 can be collapsible and fused onto the fiber 10 only where the grid 12 is located. In that case, if the tube 20 is larger than the grid 12, the internal tapered or fluted regions 22 described above may exist and the areas 19 between the tube 20 and the fiber 10 may be filled with a filler material, as described previously.

Referring to FIGS. 9, 10, any of the sensor configurations described herein (collectively shown as a sensor 110) may be placed within a housing 112 having a pressure port 114 carrying a pressure P1 within a chamber. 116 which exposes sensor 110 to pressure P1. The sensor 110 may be attached to at least one wall 118 of the housing 112 as shown in Figure 9.

Referring to Figure 10, instead of attaching it to one side of the sensor 110 to a wall of the housing 112, the sensor 110 may be suspended within the housing 112 by support 120, 122 connected to one or more of the walls of the housing 112. and at one end of the sensor 110 (or from the middle or any other desired point along the sensor 110). The fiber 110 is fed through two hermetic direct feeds 111, 113. Likewise, the fiber 10 may have some gap 117 between the sensor 110 and the direct feeds 111, 113. Likewise, the sensor 110 may be a delta-P sensor. if a second pressure P2 is brought to the sensor 110 as indicated by the lines 124.

Alternatively, instead of the supports 120, 122, the sensor 110 may be suspended by the fluid in the chamber 116, for example, a viscous fluid, grease, silicone oil or other fluids that provide insulation against impact and / or vibration and they prevent the sensor 110 from hitting them. inner walls of the housing 112. Instead of or in addition to using a fluid to suspend the sensor 110, radial and / or axial compatible separators (or seats) 130, 131 respectively can be provided between the sensor 110 and the internal walls of the housing 1. The spacers, 130, 131 may be floating or attached to the inner housing walls. Also, small solid granular pellets or gel capsules (the compatible bubble membrane fluid) 132 can also be used. The separators 130, 131 or pellets / capsules 132 can be made of a compatible material such as Teflon®, polyimide, silicone or other compatible materials. Alternatively, a network or lattice support similar to receptacle 134 can be attached to opposite walls of housing 12 on opposite axial sides of sensor 1 10, which holds sensor 1 10 between the internal walls of housing 1 12 which allows some movement of the housing. sensor 1 10 and allows the pressure to be transferred to the sensor 1 10. Also, instead of the radial spacers 130, the radial space Ds between the sensor 1 10 and the internal walls of the housing 1 12 can be small (approximately 3mm), if desired, with a layer or film of the fluid to act as a protective layer. Any other techniques for suspending the sensor 1 10 within the housing 1 12 that provide impact and vibration isolation and allow the pressure P 1 to be transferred to the sensor 1 10 can be used.

Referring to Figure 27, alternatively, the sensor 1 10 may be partially in and partially out of the pressurized chamber 1 16. In that case, the portion exposed to the pressure 48 of the sensor 1 10 would be exposed to the pressure P 1 of the axial extended portion 251 having the temperature grid 250 may be outside the chamber 16 and isolated from the pressure P 1. Also, in that case, there may be an optional additional portion 121 additional to the housing 1 12 to protect the axial extended portion 251, which creates a chamber 125 and the fiber 10 comes out through a direct feed 123. Alternatively, the grid temperature 250 may be exposed to pressure P 1, as described above.

It should be understood that the fiberglass fiberglass pressure sensor of the present invention can be used in compressive compression or tension (for example, where axial compression occurs with increasing pressure) or in tension or stress formation., for example where the axial lengthening (increase in tension) or a decrease in length (decrease in tension) occur with the increase in pressure depending on the configuration. An example of a tension based system would be where the tube 20 is attached to a transducer mechanism based on tension and axially stretched. For example, the canine bone geometry (as in FIG. 8), the internal surfaces of the sections 32 can be pulled in opposite axial directions to place the grid 12 in tension. A voltage-based configuration is also described in commonly owned co-pending US Patent Application Serial No. 08/925, 598 entitled "High Sensitivity Fiber Optic Pressure Sensor for Use in Harsh Environments" for Robert J. Maron, described herein in the prior art section and incorporated herein by reference (in that case, the grid is prestressed in tension and the tension decreases with the increase in pressure). Other configurations based on tension using the grid inserted in the tube described herein may also be used. Alternatively, for configurations where the axial forces are less than the radial forces by a predetermined amount (based on the properties of the material), the tube 20 can be operated in tension (such as when the axial ends of the tube 20 are outside the field of pressure, see the description of figures 5, 6 and 16).

Also, if the elastic element (eg bellows or diaphragm) described herein has a very low rigidity relative to the tube 20, only a small amount of force will be reduced through the elastic element (or will be lost). In that case, the sensor can be used as a force transducer (Ibf).

In addition, for any of the embodiments shown herein, instead of the fiber 10 passing through the sensor housing or the tube 20, the fiber 10 can be single ended ie only one end of the fiber 10 comes out of accommodation or the tube 20. In that case, one end of the fiber 10 would be at the exit point of the fiber 10 from the tube 20 or before the exit point. Alternatively, the fiber 10 can exit from both sides of the tube 20 although one end of the fiber 10 would terminate before leaving the housing.

Also, it should be understood that the grids of the invention can be used in reflection and / or transmission depending on whether the light reflected or transmitted from the grid is used to measure the magnitude under measurement. Also, the term "tube" as used herein may also represent a block of material having the properties described herein.

The chambers or regions 34, 64, 74, 100, 1 16, 202, 306, 406 described herein can be filled with natural air or they can be evacuated (or be at another pressure), or they can be filled partially or completely with a fluid (liquid or gas), for example an oil. The type of filler fluid will depend on the desired thermal time constant, viscosity and other fluid properties based on the desired application.

Also, it should be understood that in the operation, an instrumentation box (not shown), connected to the optical fiber 10 having a broadband source, a scanned laser light source or other suitable known optical source and having an analyzer of Suitable spectrum or other known optoelectronic measuring equipment, all well known in the art, can be used to provide the incident light 14 and to decode and measure the resulting wavelength or other optical parameter shift of the return light (reflected 16). and / or transmitted 18) from the sensor (s) described herein, as described in US Pat. Nos. 5,401, 956, 5,426,297 or 5,513,913, or other known optical instrumentation techniques.

Referring to Figure 31, alternatively, a portion of or all of the fiber grating introduced into the tube 20 can be replaced by a large diameter silica wave guide grid 600, such as that described in the patent application of The United States of America serial number (case number CiDRA CC-0230), entitled "Large Diameter Optical Waveguide, Grating and Laser", which is incorporated herein by reference. The waveguide 600 has a core 612 (equivalent to the core of the fiber 10) and a coating 614 (equivalent to the fused combination of the tube 20 and the coating of the fiber 10) and having the grid 12 embedded therein. The overall length L1 of the waveguide 600 and the waveguide diameter d2 are set identical to those described above for the tube 20 (i.e. so that the tube 20 will not deform over the selection range of the length of wave of the desired grid) and the outer diameter of the waveguide is at least 0.3 mm. An optical fiber 622 (equivalent to the fiber 10 in Figure 1) having a coating 626 and a core 625 that propagates the light signal 14, is split or otherwise optically coupled to one or both of the axial ends 628 of the waveguide 600 using any technique known or to be developed to split the fibers or couple the light from an optical fiber into a larger waveguide, which provides optical losses acceptable to the application.

The large-diameter waveguide with the grid 600 can be used in the same manner as the grid inserted in the tube 20 that is used in the present where the fiber 10 is analogous to (and interchangeable with) the core 612 of the guide 600 wave, For example, the waveguide 600 can be recorded, ground, or polished to achieve the "canine bone" shape described herein with the tube 20. Alternatively, the "canine bone" shape can be obtained by the heating and melting two outer tubes 640, 642 on opposite ends of the waveguide 600, as described heretofore with FIG. 2. All alternative embodiments described herein for the tube 20 and the grid inserted into the tube are also applicable for waveguide 600 when feasible, including having a fiber laser or DFB fiber laser, multiple fibers (or cores), various geometries, etc.

The fiber grating introduced in tube 20 and the large diameter waveguide grating 600 can each also be referred to herein as an "optical detector elements", the grid inserted in tube 20 and the waveguide grating large diameter 600 have substantially the same composition and properties at the locations where the tube 20 is fused to the fiber 10, since the transverse (or transverse) cross-section of the grid inserted in tube 20 and the waveguide grating diameter large 600 are contiguous (or monolithic) and are substantially of the same material through the cross section, for example, a vitreous material, such as impurified or non-contaminated silica. Also, in those locations, both have an optical core and a large coating.

Likewise, the waveguide 600 and the grid inserted in tube 20 can be used together to form any of the determined modes of the detector elements described herein. In particular one or more axial portions of the sensing element may be a grating inserted into a tube or fiber and / or one or more different axial portions may be the waveguide 600 which are axially divided or fused or otherwise mechanically and optically coupled together so that the core of the waveguide is aligned with the core of the fiber fused to the tube. For example, a central region of the detector element may be the large waveguide and one or both of the axial ends may be the fiber introduced into the tube which are fused together as indicated by dotted lines 650, 652 or vice versa (FIGS. , 30, 31).

It should be understood that the dimensions, geometries and materials described for any of the embodiments herein are for illustrative purposes only and as such, other dimensions, geometries or materials may be used if desired, depending on the application, size, performance, requirements of manufacture or design, or other factors in view of the teachings herein.

Furthermore, it should be understood, that unless otherwise specified herein, any of the features, alternative embodiments or modifications described with respect to a particular embodiment herein may be applied, utilized or incorporated also with another embodiment described in the foregoing. I presented. Also, the drawings shown herein are not drawn to scale. .

Although the invention has been described and illustrated with respect to illustrative embodiments thereof, the foregoing and other additions and omissions may be made herein and thereto without departing from the spirit and scope of the present invention.

Claims (62)

1. A pressure sensor, comprising: an optical sensing element, having at least one pressure reflecting element positioned thereon, the reflex pressure element having a pressure reflex wavelength; the sensing element that is axially tensioned due to a change in external pressure, the axial tension causing a change in the reflective wavelength of the pressure and the change in the reflective wavelength of the pressure which is indicative of said change in pressure; and at least a portion of the sensing element having a transverse cross section that is contiguous and made substantially of the same material and having an external transverse dimension of at least 0.3 mm.

The apparatus according to claim 1, characterized in that the detector element comprises: an optical fiber, having the reflective element embedded therein; and a tube having the optical fiber and the reflective element inserted therein along a longitudinal axis of said tube, the tube being fused to at least a portion of the fiber.

The apparatus according to claim 1, characterized in that the detector element comprises a large diameter optical waveguide having an outer coating and an internal core placed therein and an external waveguide dimension of at least 0.3 mm.

The pressure sensor according to claim 1, characterized in that the detector element comprises: a tube fused to at least a portion of an optical fiber along a longitudinal axis of the tube; a large diameter optical waveguide having an outer coating and an internal core placed therein; and the tube and waveguide that are axially fused and optically coupled together.

The pressure sensor according to claim 4, characterized in that the reflective element is embedded in the fiber and inserted into the tube along the longitudinal axis of the tube.

6. The pressure sensor according to claim 4, characterized in that the reflective element is placed in the optical waveguide.

7. The pressure sensor according to claim 1, characterized in that the material comprises a vitreous material.

The pressure sensor according to claim 1, further comprising a housing attached to at least a portion of said detector element which applies an axial tension on the detector element due to said change in pressure.

9. The pressure sensor according to claim 1, characterized in that the sensing element is tensioned in compression.

10. The pressure sensor in accordance with the claim 2, characterized in that the tube is fused to the optical fiber where the reflecting element is located. eleven .

The pressure sensor in accordance with the claim 2, characterized in that the tube is fused to the optical fiber on opposite axial sides of said reflective element.

12. The pressure sensor in accordance with the claim 1, characterized in that the reflective element is a Bragg grid.

13. The pressure sensor in accordance with the claim 1, characterized in that the reflective element has a characteristic wavelength and wherein the sensing element comprises a shape that provides a predetermined sensitivity for a displacement in said wavelength due to a change in force on the tube.

The pressure sensor according to claim 13, characterized in that the detector element comprises a canine bone shape.

The pressure sensor according to claim 1, characterized in that the sensing element comprises a canine bone shape and comprises an external tube fused to at least a portion of the large sections of said canine bone shape on opposite axial sides of the reflective element.

16. The pressure sensor according to claim 1, characterized in that at least a portion of said detector element comprises an indic cylindrical shape.

17. The pressure sensor according to claim 1, characterized in that the detector element is made of silica.

The pressure sensor according to claim 1, characterized in that the detector element comprises a sleeve mounted around at least a portion of said detector element.

19. The pressure sensor according to claim 1, characterized in that the detector element comprises at least one axially extended end.

20. The pressure sensor according to claim 1, characterized in that the sensing element comprises at least one external tapered axial section. twenty-one .

The pressure sensor according to claim 1, characterized in that the detector element comprises at least an internal tapered axial section.

22. The pressure sensor according to claim 1, further comprising a temperature reflecting element positioned in the detector element in thermal proximity to said pressure reflecting element and having a temperature reflecting wavelength that changes with the temperature.

23. The pressure sensor according to claim 22, characterized in that the temperature reflection wavelength does not change in response to a change in said pressure wavelength due to a change in pressure.

24. The pressure sensor according to claim 22, characterized in that the temperature reflecting wavelength changes in response to a change in pressure wavelength due to a change in pressure in a different range than the changes in length pressure wave due to the same pressure change.

25. The pressure sensor in accordance with the claim 2, characterized in that the tube comprises a plurality of said optical fibers introduced therein.

26. The pressure sensor in accordance with the claim 3, characterized in that the waveguide comprises a plurality of optical cores inserted therein.

27. The pressure sensor according to claim 1, characterized in that the detector element comprises a plurality of reflective elements placed therein.

The pressure sensor according to claim 1, characterized in that the detector element comprises at least one pair of reflective elements placed therein and at least a portion of said detector element is doped with a rare earth dopant between the pair of elements to form a laser.

29. The apparatus according to claim 28, characterized in that said laser performs laser action at a wavelength of laser action that changes as the force changes on the detector element.

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

31 The apparatus according to claim 30, characterized in that the laser DFB performs laser action at a wavelength of laser action that changes as the force changes on the detector element.

32. The pressure sensor in accordance with the claim 1, further comprising an outer housing surrounding the sensing element and suspending means placed between the sensing element and the external housing for suspending said detector element within said housing.

33. The pressure sensor in accordance with the claim 32, characterized in that the suspension means comprise a fluid.

34. The pressure sensor according to claim 32, characterized in that the suspension means comprise spacers in a fluid.

35. A method for detecting pressure, comprising: obtaining an optical detector element having at least one pressure reflective element positioned thereon along a longitudinal axis of said detector element, the pressure reflective element having a wavelength of pressure reflection; and axially tensioning the detector element due to a change in pressure, said axial tension causing a change in said pressure reflex wavelength, and the change in the pressure reflex wavelength which is indicative of said change in pressure; and at least a portion of said detector element having a transverse cross section that is contiguous and made substantially of the same material and having an external transverse dimension of at least 0.3 mm.

36. The method according to claim 35, characterized in that the detector element comprises: an optical fiber, having the reflective element embedded therein; and a tube having the optical fiber and the reflective element inserted therein along a longitudinal axis of said tube, the tube being fused to at least a portion of the fiber.

37. The method according to claim 35, characterized in that the detector element comprises a large diameter optical waveguide having an external coating and an internal core placed therein and an external waveguide dimension of at least 0.3 mm.

38. The method according to claim 35, characterized in that the tensioning step comprises compressing said detector element axially.

39. The method according to claim 36, characterized in that the tube is fused to the optical fiber where the reflective element is located.

40. The method according to claim 36, characterized in that the tube is fused to the optical fiber on opposite axial sides of the reflective element.

41 The method according to claim 35, characterized in that the reflective element is a Bragg grid.

42. The method according to claim 35, characterized in that the reflecting element has a characteristic wavelength and wherein the sensing element has a shape that provides a predetermined sensitivity for a displacement in said wavelength due to a change in force on the detector element.

43. The method according to claim 35, characterized in that the detector element has a canine bone shape.

44. The method according to claim 35, characterized in that the detector element has a canine bone shape and wherein the detector element has an external tube fused to at least a portion of the large sections of the canine bone shape in opposite axial sides of the reflective element.

45. The method according to claim 35, characterized in that at least a portion of said detector element has an indic cylindrical shape.

46. The method according to claim 35, characterized in that the detector element is made of a vitreous material.

47. The method according to claim 35, characterized in that the detector element comprises at least one axially extended end.

48. The method according to claim 35, characterized in that the sensing element comprises at least an external tapered axial section.

49. The method according to claim 35, characterized in that the sensing element comprises at least an internal tapered axial section.

50. The method according to claim 35, characterized in that the detector element comprises a temperature sensing element placed therein and in the thermal proximity to said pressure reflecting element, and having a temperature reflecting wavelength that change with temperature.

51 The method according to claim 50, characterized in that the temperature reflection wavelength does not change substantially in response to a change in pressure wavelength due to a change in said pressure.

52. The method according to claim 50, characterized in that the temperature reflecting wavelength changes in response to a change in said pressure wavelength due to a change in said pressure in a different range than the change in length. pressure wave due to the same change in pressure.

53. The method according to claim 35, characterized in that the detector element has a plurality of said optical fibers introduced into said tube.

54. The method according to claim 35, characterized in that the waveguide has a plurality of said optical cores therein.

55. The method according to claim 35, characterized in that the detector element has a plurality of reflective elements placed therein.

56. The method according to claim 35, characterized in that the detector element has at least one pair of reflective elements placed therein and at least a portion of said detector element is doped with a rare earth dopant between the pair of elements to form a laser.

57. The method according to claim 53, characterized in that the laser performs laser action at a wavelength of laser action that changes as the force changes on the detector element.

58. The method according to claim 35, characterized in that at least a portion of said detector element is doped with a rare earth dopant where the reflective element is located and the reflective element is configured to form a laser DFB.

59. The method according to claim 55, characterized in that the laser DFB performs laser action at a wavelength of laser action that changes as the force changes on the detector element.

60. The method according to claim 35, further comprising a step of suspending the detector element within an external housing.

61 The method according to claim 57, characterized in that the suspension step comprises the suspension in a fluid.

62. The method according to claim 57, characterized in that the suspension stage comprises the suspension between separators in a fluid. SUMMARY A fiber grating pressure sensor includes an optical sensing element 20, 600 which includes an optical fiber having a Bragg grid 12 printed thereon which is inserted into and fused to at least a portion of a vitreous capillary tube. 20 and / or a large diameter wave guide grid 600 having a core and a wide coating and having an external transverse dimension of at least 0.3 mm. The light 14 is incident on the grid 12 and the light 16 is reflected from the grid 12 at a wavelength? 1. The detector element 20, 600 may be used by itself as a sensor or located within a housing 48, 60, 90, 270, 300. When the external pressure P is increased, the grid 12 is compressed and the reflection wavelength? 1 changes. The shape of the sensing element 20, 600 may have other geometries, for example a "canine bone" shape, to improve the sensitivity of the displacement by? 1 due to the applied external pressure and may be fused to an external protection 50. At least a portion of the sensing element may be impurified between a pair of grids 150, 152 to form a laser selected by compression or the grid 12 or grids 150, 152 may be constructed as a selectable DFB laser. Also, the axial ends of the element 20, 600 where the fiber 10 can have an internal tapered region 22 and / or a tapered axial (ribbed) section 27 to provide improved tension release or tensile strength for the fiber 10. A temperature grid 270 can be used to measure the temperature and allow a temperature-corrected pressure measurement. The sensor can be suspended within an external housing 112, by means of a fluid, separators or other means. The invention can also be used as a force transducer.