Optical fiber acceleration sensor

Abstract

A fiber-optic acceleration sensor for determining an acceleration along an axis, the fiber-optic acceleration sensor comprising: an optical fiber having a fiber end face; and a vibrating diaphragm having a diaphragm frame, a deflection mass and a connecting bridge; wherein the vibrating diaphragm is arranged to at least partially reflect primary radiation emerging from the fiber end face; and wherein the connecting bridge connects the diaphragm frame and the deflection mass at at least two different axial positions from one another.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application generally relate to an optical fiber acceleration sensor, in particular for determining an acceleration along an axis, and to a method for manufacturing an optical fiber acceleration sensor. In particular, embodiments relate to an optical fiber acceleration sensor system and to a wind power plant. BACKGROUND

[0002] Measuring, monitoring or regulating the acceleration of a measurement object is of great significance in many areas of industrial applications. Conventional acceleration measuring systems use a spring-mass system to determine the acceleration and are based on detecting a deflection of the measurement object from a rest position. In particular, in optical fiber measuring systems the deflection of a diaphragm can be detected from a change in the optical properties. In order to make such optical fiber measuring systems more sensitive, the spring action of the diaphragm is often changed or the diaphragm is additionally loaded with a mass, which in many cases leads to an asymmetric configuration of the spring-mass system.

[0003] However, the solutions known to date for measuring acceleration have different disadvantages. In particular, conventional optical fiber measuring systems have a lateral sensitivity with respect to rotational acceleration or a low stability or a low sensitivity. SUMMARY

[0004] One aspect relates to an optical fiber acceleration sensor for determining an acceleration along an axis, the optical fiber acceleration sensor comprising an optical fiber having a fiber end face, and a vibrating diaphragm having a diaphragm frame, a deflection mass and a connecting bridge, wherein the vibrating diaphragm is designed to at least partially reflect primary radiation emerging from the fiber end face, and wherein the connecting bridge connects the diaphragm frame and the deflection mass at at least two different axial positions from one another.

[0005] Another aspect relates to an optical fiber acceleration sensor system having at least two optical fiber acceleration sensors according to the embodiments described herein, wherein the optical fiber acceleration sensor system is designed for determining an acceleration along at least two axes.

[0006] Yet another aspect relates to a wind power plant having at least one optical fiber acceleration sensor according to the embodiments described herein or at least one optical fiber acceleration sensor system according to the embodiments described herein.

[0007] Another aspect relates to a method for manufacturing an optical fiber acceleration sensor for determining an acceleration along an axis, in particular an optical fiber acceleration sensor according to the embodiments described herein, the method comprising: providing a transparent substrate; and selectively laser etching a diaphragm from the transparent substrate, wherein the diaphragm has a diaphragm frame, a deflection mass, and a connecting bridge, and wherein the connecting bridge connects the diaphragm frame and the deflection mass at at least two different axial positions from each other. BRIEF DESCRIPTION OF DRAWINGS

[0008] Embodiments are shown in the drawings and are explained in detail in the following description:

[0009] Figure 1 Schematically showing an optical fiber acceleration sensor according to one embodiment with the associated beam path;

[0010] Figure 2 Schematically showing a diaphragm of an optical fiber acceleration sensor according to one embodiment;

[0011] Figure 3 Schematically showing a part of a wind power plant with a rotor blade and an optical fiber acceleration sensor arranged thereon;

[0012] Figure 4 Schematically showing a rotor of a wind power plant with a rotor blade and an optical fiber acceleration sensor according to the embodiments described herein;

[0013] Figure 5 Schematically showing a measurement system for an optical fiber measurement system according to the embodiments described herein;

[0014] Figure 6 Schematically showing another measurement system according to the embodiments described herein; and

[0015] Figure 7 Schematically showing a flow chart for illustrating a method for manufacturing an optical fiber acceleration sensor according to the embodiments described herein.

[0016] In the drawings, the same reference notations indicate the same or functionally similar components or steps. For the sake of clarity, not all features of a type are necessarily labeled with a reference notation, e.g. Figure 1 the connecting bridge (reference numeral: 125) in. DETAILED DESCRIPTION

[0017] Reference will now be made in detail to the various embodiments of the application, one or more examples of which are illustrated in the drawings. The expression "or" is used herein to mean "and / or", unless explicitly indicated otherwise.

[0018] Optical fiber sensors have a large application potential, which are based on acceleration-dependent changes of light, for example light intensity or light phase, which propagate through an optical fiber. Thus, optical fiber acceleration measurements are advantageous in regions of measurement objects which are exposed to lightning strikes and thus cannot be measured electrically. In a purposeful manner, any electrical lines along the measurement object are avoided here, so that data detection can be carried out in a purely optical manner.

[0019] According to the embodiments described herein, an optical fiber acceleration sensor with an optical fiber and a diaphragm is used to measure accelerations with a high resolution. The diaphragm, for example a deflection mass of the diaphragm and a fiber end face of the optical fiber, can be reflectively embodied. Thus, an optical resonator of a Fabry-Perot interferometer can be configured, for example, by the optical fiber and the diaphragm. Upon acceleration of the optical fiber acceleration sensor, the deflection mass of the diaphragm can be deflected relative to the diaphragm frame, wherein, inter alia, the interference wavelength of the optical resonator can be changed. Via the change in the interference wavelength, an acceleration can be detected.

[0020] Examples of measurement objects in which an acceleration measurement should be carried out without electrical lines are rotor blades of wind power installations or wings of aircraft. With suitable mounting technology, distributed optical fiber acceleration sensors can be used to detect accelerations, for example vibrations, at such measurement objects. Thus, for example, wind power installations are subjected to complex control, which is based on sensor data from the wind power installation itself, for example on reliable acceleration data. The risk of lightning damage by means of optical fiber transmission of optical signals is reduced. Thus, an optical fiber acceleration sensor can be provided, which allows installation in radially outer regions of a rotor blade without increasing the risk of lightning damage.

[0021] Figure 1 An optical fiber acceleration sensor 110 is shown schematically, which can be embodied as a Fabry-Perot interferometer. In particular, the optical fiber acceleration sensor 110 is shown in a longitudinal section along an axis 127 along which the optical fiber acceleration sensor 110 can measure an acceleration. The beam path is also shown for the purpose of illustrating the principle of the application. The optical fiber acceleration sensor 110 comprises an optical fiber 112 with a fiber end face 131 and a diaphragm 103. For the sake of simplicity, only a portion of the optical fiber 112 is shown in Figure 1 The fiber cladding and the fiber protection sleeve are not shown for the sake of overview.

[0022] A cavity 107 is formed between the fiber end face 131 and the diaphragm 103, in particular between the fiber end face 131 and the deflection mass 123. The diaphragm 103 comprises a diaphragm frame 121, a connecting bridge 125 and the deflection mass 123. The diaphragm frame 121 is arranged at least substantially position- fixed with respect to the fiber end face 131. For example, the diaphragm 121 is rigidly connected with the optical fiber 112. The deflection mass 123 is connected with the diaphragm 121 via the connecting bridge 125. The connecting bridge can be configured as an elastic element between the diaphragm frame 121 and the deflection mass 123. Upon acceleration of the fiber-optic acceleration sensor 110, the deflection mass 123 can be deflected with respect to the diaphragm frame 121. In particular, the deflection mass 123 can be deflected along the axis 127. According to embodiments, the deflection mass 123 can be configured at least substantially cylindrically, wherein for example a cylinder axis of the cylindrical deflection mass 123 extends along the axis 127.

[0023] According to embodiments, the diaphragm 103 has a reflective diaphragm face. In particular, the reflective diaphragm face is oriented perpendicular to the axis 127. In Figure 1 In particular, the reflective diaphragm face and the fiber end face 131 are oriented at least substantially parallel to each other. The fiber end face 131 can be configured reflective. In further embodiments, a further reflective face is arranged in the light path between the fiber end face 131 and the diaphragm 103.

[0024] “Reflective” or “mirror” is in particular to be understood herein such that at least a portion of the intensity of an incident light beam is reflected, for example at least 0.5% of the share of the incident light beam, in particular at least 1% or at least 2%.

[0025] In Figure 1 In particular, a first incident beam 143 from the optical fiber 112 is incident on the fiber end face 131. A first portion of the first incident beam 143 is reflected on the fiber end face 131 back into the optical fiber 112 as a first reflected beam 145. A second portion of the first incident beam 143 is transmitted on the fiber end face 131 into the cavity 107 between the fiber end face 131 and the diaphragm 103 as a second incident beam 147, in particular as a primary radiation from the optical fiber 112. The second incident beam 147 is incident on the diaphragm 103, in particular on the deflection mass 123 of the diaphragm 103. The second incident beam 147 is at least partially reflected on the reflective diaphragm face, in Figure 1The light is reflected, for example, on the axial diaphragm face 133 of the deflection mass 123 facing the cavity 107. In particular, at least a portion of the second incident beam 147, for example as a second reflected beam 149, is reflected back into the cavity 107 and in the direction of the optical fiber 112. The share of the second reflected beam 149 that is transmitted through the fiber end face 131 can interfere in the optical fiber 112, for example, with the first reflected beam 143. Furthermore, the light can be reflected multiple times between the fiber end face 131 and the deflection mass 123. The fiber end face 131 of the optical fiber 112 serves in particular as a reflection face for the light from the optical fiber 112, as a light exit face that emits light in the direction of the diaphragm 103 from the optical fiber, and as a light entrance face for absorbing light that is reflected back into the optical fiber 112 from the cavity 107.

[0026] By the interference of the reflected beams, in particular the first reflected beam 145, the second reflected beam 149 or the multiple reflected beams, an interference pattern according to the Fabry-Perot effect can be formed. The interference pattern can be used to determine the acceleration acting on the fiber-optic acceleration sensor 110. For example, the cavity length 111 of the cavity 107 or the deflection of the deflection mass 123 can be determined and, from this, the acceleration of the fiber-optic acceleration sensor 110. In further embodiments, the acceleration can be determined from the interference pattern via a mathematical function or a look-up table.

[0027] In a Fabry-Perot interferometer, as it is also illustrated in Figure 1 a free spectral range FSR is provided, in which the wavelength interval can be determined unambiguously. This means that when measuring in the free spectral range, there is no ambiguity in the measurement signal. In Figure 1 The cavity length 111, d, shown in

[0028] where Δλ = λ1- λ2,

[0029] where Δλ represents the difference in wavelength between the two interference minima at λ1and λ2, n represents the refractive index of the medium, for example air, enclosed in the cavity, and θ represents the angle between the surface normal of the reflection face and the direction of light propagation in the optical resonator.

[0030] The phase difference between the reflected beams, i.e. the first reflected beam 145, the second reflected beam 149 or the multiply reflected beam, is determined by the cavity length 111. In particular, the phase difference is determined by the spacing d between the fiber end face 131 and the reflective diaphragm face, e.g. the axial diaphragm face 133. In other words, the interferometer is configured such that light can enter into the cavity 107 and is reflected at the vibrating diaphragm 103. The reflective diaphragm face, the fiber end face 131 and the cavity 107 thus form an optical resonator, e.g. an optical resonator of a Fabry-Perot interferometer. The light reflected into the optical fiber 112 shows an interference spectrum, in particular interference maxima or interference minima, the number or the position of which is related to the cavity length 111, in particular to the spacing d between the fiber end face 131 and the reflective diaphragm face. By analyzing the position of the interference maxima or interference minima in the reflection spectrum, a change in the cavity length 111 or, in particular, an acceleration-dependent deflection of the deflection mass 123 can be determined.

[0031] According to an embodiment, the reflective diaphragm face is arranged on the deflection mass. In particular, the reflective diaphragm face, e.g. the axial diaphragm face 133, is oriented perpendicular to the axis 127. In particular, the reflective diaphragm face and the fiber end face 131 are oriented at least substantially parallel to each other.

[0032] According to an embodiment, the vibrating diaphragm 103 is arranged such that, in the event of an acceleration acting on the optical fiber acceleration sensor 110, the deflection mass 123 is deflected, e.g. relative to a rest position of the deflection mass 123. In particular, the deflection mass 123 is deflected in the event of an acceleration oriented along the axis 127 or in the event of an acceleration comprising a component oriented along the axis 127. Figure 1 and Figure 2 According to an embodiment, the connecting bridge 125 connects the diaphragm frame 121 and the deflection mass 123 in at least two axial positions different from each other. The expression "axial" is understood here in particular with respect to the axis 127. The connecting bridge 125 can be arranged as a resilient element between the diaphragm frame 121 and the deflection mass 123. The vibrating diaphragm 103 is in particular arranged such that, in the event of an acceleration acting on the optical fiber acceleration sensor 110, the deflection mass 123 is deflected, e.g. relative to a rest position of the deflection mass 123. In particular, the deflection mass 123 is deflected in the event of an acceleration oriented along the axis 127 or in the event of an acceleration comprising a component oriented along the axis 127.

[0033] For example, by connecting the deflection mass 123 with the diaphragm frame 121, a deflection of the deflection mass 123 can be at least substantially reduced to a movement of the deflection mass 123 along the axis 127. In particular, a tilting of the deflection mass 123 can be reduced. Furthermore, a lateral sensitivity of the fiber-optic acceleration sensor 110, for example in case of a rotational acceleration, can be reduced compared to known acceleration sensors. Another advantage can be that the mass of the deflection mass 123 extends along the axis 127 and can have a larger mass, in particular without an asymmetric distribution of the mass with respect to the axis 127. For example, the fiber-optic acceleration sensor 110 can have a higher sensitivity, in particular due to the larger mass. Furthermore, a stability of the diaphragm 103 can be increased, for example by the deflection mass 123 being connected with the diaphragm frame 121 at at least two axial positions.

[0034] According to some embodiments, the connecting bridge 125 between the diaphragm frame 121 and the deflection mass 123 is configured as a meandering arm. In particular, the connecting bridge 125 has a first connection site 151 with the diaphragm frame 121 and a second connection site 153 with the deflection mass 123, respectively, wherein the first connection site 151 is offset with respect to the second connection site 153 along a circumferential direction around the axis 127. In embodiments, the meandering arm comprises at least three arm sections, wherein at least two arm sections are at least substantially radially oriented and at least one arm section is at least substantially oriented along a circumferential direction around the axis 127. “At least substantially radially” is for example understood as a deviation of at most 30°, in particular at most 20° or at most 10° compared to a radial direction. “At least substantially along a circumferential direction” is for example understood as a deviation of at most 30°, in particular at most 20° or at most 10° compared to a circumferential direction. For example, the connecting bridge 125 of the diaphragm 103 shown in Figure 2 is configured as a meandering arm.

[0035] According to embodiments, the diaphragm 103 comprises at least two, in particular at least three connecting bridges 125 at at least two axial positions, respectively. For example, the diaphragm 103 comprises exactly three or exactly four connecting bridges 125 at at least two axial positions, respectively. In Figure 2 exemplary embodiments, the diaphragm 103 comprises three connecting bridges 125 at two axial positions, respectively.

[0036] According to some embodiments, the connecting bridge 125 comprises a first connecting bridge in a first axial position of the at least two axial positions and a second connecting bridge in a second axial position of the at least two axial positions, wherein the first connecting bridge is arranged offset with respect to the second connecting bridge in a circumferential direction around the axis 127. For example, the respective first connection sites 151 of the first and second connecting bridges can be arranged offset with respect to each other in the circumferential direction, or the respective second connection sites 153 of the first and second connecting bridges can be arranged offset with respect to each other in the circumferential direction. In Figure 2 In embodiments, the connecting bridges 125 are arranged offset in the circumferential direction around the axis 127. For example, the respective connecting bridges 125, for example the respective first connection sites 151 between the connecting bridges 125 and the diaphragm frame 121 or the respective second connection sites 153 between the connecting bridges 125 and the deflection weight 123, are arranged in two axial positions in the circumferential direction offset by 60° with respect to each other. By arranging the connecting bridges 125 offset in the circumferential direction, for example a lateral sensitivity of a deflection of the deflection weight 123 can be reduced.

[0037] In embodiments, the axial length of the deflection weight 123 or the axial spacing 155 between the at least two axial positions is at least 0.1 mm, in particular at least 0.2 mm or at least 0.5 mm, or at most 5 mm, in particular at most 3 mm or at most 1.5 mm. According to embodiments, the diaphragm 103 has a diameter transverse to the axis 127 of at least 1 mm, in particular at least 2 mm, or at most 10 mm, in particular at most 7 mm or at most 5 mm. In embodiments, the diaphragm 103 has a natural frequency of at least 5 kHz, in particular at least 10 kHz, or at most 500 kHz, in particular at most 200 kHz or at most 100 kHz.

[0038] According to embodiments, the diaphragm is set up for a mechanical deflection of the deflection weight of at least 0.25 nm / G, in particular at least 0.5 nm / G or at least 1 nm / G, or at most 40 nm / G, in particular at most 30 nm / G, at most 25 nm / G or for example at most 20 nm / G. In this context, “G” stands for the gravitational acceleration, for example rounded to 9.81 m / s 2 .

[0039] In some embodiments, the diaphragm 103 is made in one piece. In particular, the diaphragm 103 is made of a unique material, for example of a unique transparent material. By being made of a unique material, for example a stress in the diaphragm 103 can be avoided. According to embodiments, the diaphragm 103 is made of glass, in particular of quartz glass or borosilicate glass.

[0040] In an embodiment, the diaphragm 103 is made by selective laser etching ("SLE"). In selective laser etching, for example, a substrate, in particular a glass substrate made of quartz glass or borosilicate glass, is provided. The shape of the diaphragm 103 is first imprinted into the substrate by means of a laser, wherein in particular the region of the substrate around the diaphragm 103 is modified, for example chemically, by means of laser radiation. The modified region of the substrate can then be selectively etched. In particular, the modified region of the substrate can be removed at a higher etching rate than the unmodified structure of the diaphragm 103 imprinted into the substrate.

[0041] According to some embodiments, the diaphragm 103, in particular the deflection mass 123, has a high-reflective coating. "High-reflective" is to be understood herein in particular as meaning that at least 50% of the incident light, for example at least 70% or at least 90% of the incident light, is reflected. For example, the axial diaphragm face 133 of the deflection mass 123 facing the cavity 107 can be coated by a high-reflective coating, for example as shown in Figure 1 In further embodiments, the rear diaphragm face facing away from the cavity 107 can be coated by a high-reflective coating. By providing a high-reflective coating, for example, a higher intensity of the reflected light can be provided.

[0042] According to embodiments, the high-reflective coating can be made, for example, by evaporating a metal or metal alloy layer on the diaphragm 103, in particular on the deflection mass 123. In other embodiments, the diaphragm 103 does not have a high-reflective coating. For example, the light incident on the diaphragm 103 can be at least partially reflected on the surface of the diaphragm 103, for example at the transition between the glass and the air.

[0043] In an embodiment, the deflection mass 123 comprises an axial diaphragm face 133 facing the cavity 107 and a lattice defect region behind the axial diaphragm face 133 for diffusely scattering light. The axial diaphragm face 133 is configured as a reflective diaphragm face. In the lattice defect region, light transmitted through the axial diaphragm face 133 can be diffusely scattered. For example, the lattice defects of the lattice defect region can be written into the deflection mass 123 by means of a laser.

[0044] According to some embodiments, the fiber-optic acceleration sensor 110 is set up as a Fabry-Perot interferometer. The fiber end face 131 of the optical fiber 112 forms a first mirror of the Fabry-Perot interferometer, and the diaphragm 103, in particular the deflection mass 123, forms a second mirror of the Fabry-Perot interferometer.

[0045] In an embodiment, the optical fiber 112 is configured as a glass fiber or a polymer conductor, wherein materials such as optical polymers, polymethyl methacrylate, polycarbonate, quartz glass, ethylene tetrafluoroethylene, etc., which are doped if necessary, can be used. In particular, the optical fiber 112 can be configured as an SMF-28 fiber.

[0046] The optical fiber 112 is held by a fiber holder 161 of the optical fiber acceleration sensor 110. The fiber holder 161 can be arranged in a sensor housing (not shown) of the optical fiber acceleration sensor 110. The sensor housing can in particular enclose a volume around the diaphragm 103. According to an embodiment, the fiber holder 161 is arranged in a measurement position with respect to the diaphragm 103 together with the optical fiber 112, in particular with an end piece of the optical fiber 112 having the fiber end face 131. In particular, the optical fiber 112 is fixed on the fiber holder 161 by means of gluing or welding.

[0047] According to some embodiments, the end piece of the optical fiber acceleration sensor 110 or of the optical fiber 112 has at least one optical beam shaping component, for example on the fiber end face 131, in order to shape the light beam exiting from the optical fiber 112. For example, the optical beam shaping component comprises at least one of the following components: a graded-index lens (GRIN lens), a prism, a spherical lens, a cylindrical lens, and any combination thereof. According to another embodiment, the optical fiber 112 can be configured as a single-mode optical fiber.

[0048] According to an embodiment, an optical fiber acceleration sensor system is provided, which has at least two optical fiber acceleration sensors according to the embodiments described herein, wherein the optical fiber acceleration sensor system is set up for determining accelerations along at least two axes. The acceleration sensor system can in particular comprise two or three optical fiber acceleration sensors. In an embodiment, the at least two axes of the at least two optical fiber acceleration sensors are oriented non-parallel, in particular at least substantially orthogonal to each other. The optical fiber acceleration sensor system can for example be arranged in or on a rotor blade.

[0049] According to embodiments, a wind power plant is proposed having at least one fiber-optic acceleration sensor according to the embodiments described herein or at least one fiber-optic acceleration sensor system according to the embodiments described herein. In particular, the wind power plant comprises a rotor blade, wherein at least one fiber-optic acceleration sensor or at least one fiber-optic acceleration sensor system is arranged in or on the rotor blade. According to embodiments, the wind power plant comprises two or three rotor blades, wherein at least one fiber-optic acceleration sensor or at least one fiber-optic acceleration sensor system is arranged on each rotor blade. One advantage can be that the fiber-optic acceleration sensor according to the embodiments described herein has a low lateral sensitivity with respect to rotational accelerations, which occur in particular in the rotor blade when the wind power plant is in operation.

[0050] Figure 3 A wind power plant 200 is shown as an application example for a fiber-optic acceleration sensor 110 according to the embodiments described herein, for example with reference to Figure 1 and Figure 2 The wind power plant 200 comprises a tower 202 and a nacelle 203. On the nacelle 203 a rotor 500 is fixed. The rotor 500 comprises a hub 205 on which rotor blades 100 are fixed. As shown in Figure 3 at least one sensor unit 110 for fiber-optic acceleration measurement is arranged on the rotor blade 100. The sensor unit 110 is connected via an optical fiber 112 with an evaluation unit 114. The evaluation unit 114 provides a signal, for example, to a control unit 204 of the wind power plant 200 for controlling or regulating the wind power plant 200. The rotor blade 100 has a blade axis 101 along which it extends in longitudinal direction. The length of the rotor blade 100 extends from a blade flange to a blade tip, wherein in this region no electrical lines are suitably present. In contrast, the fiber-optic acceleration sensor can be arbitrarily positioned along the longitudinal extension of the rotor blade. For example, the fiber-optic acceleration sensor 110 can be arranged at a radial position in an outer region of the rotor blade 100.

[0051] According to some embodiments, the optical signal, for example an interference spectrum, is transmitted to the evaluation unit 114 by means of the optical fiber 112. Each rotor blade 100 can have an individual acceleration, in particular a vibration or oscillation. Therefore, according to some embodiments, at least one fiber-optic acceleration sensor 110 is provided in each rotor blade 100.

[0052] In order to provide the fiber-optic acceleration sensor 110, for example, as described in Figure 1As shown in the middle, it is particularly simple to provide the fiber-optic acceleration sensor 110 on the rotor blade, in particular in the outer radial region of the rotor blade, which advantageously has a small size in a cross section perpendicular to the axis 127. The maximum dimension in a cross section perpendicular to the axis 127 can be, for example, 10 mm or less.

[0053] Figure 4 As an application example of the fiber-optic acceleration sensor 110, a rotor 500 of a wind turbine is shown, on which acceleration measurements can be carried out. The rotor 500 has a hub 205 and rotor blades 100 arranged thereon. The acceleration sensor 110 is provided in at least one rotor blade 100. The signal of the fiber-optic acceleration sensor 110 is conducted via the optical fiber 112 to a distributor 501. The distributor 501 can be, for example, a field distributor, at which the signals of different sensors are provided. The distributor 501 can be arranged on a blade bulkhead of the rotor blade 100 and can be configured for plugging in and unplugging out the signal cable of the sensor, for example the optical fiber 112 of the fiber-optic acceleration sensor 110. Furthermore, a sensor cable for plugging in and unplugging out from the field distributor to a measuring device or evaluation unit 114 can be provided. According to some embodiments, the distributor 501 is arranged on a blade bulkhead or in a blade root.

[0054] As shown in Figure 4 The transport light guide 503, for example another optical fiber, can be guided from the distributor 501 to the evaluation unit 114, as shown in

[0055] Figure 4 The fiber-optic acceleration sensor 110 is shown in each rotor blade 100. It is furthermore possible to measure the acceleration at a plurality of positions along the blade axis 101 of the rotor blade 100 at a plurality of positions along the blade axis 101 of the rotor blade 100. For this purpose, a plurality of fiber-optic acceleration sensors 110 can be provided at the respective positions. It can furthermore be purposeful to use the fiber-optic acceleration sensor 110 in the region of the rotor blade tip of the wind turbine, i.e. in the radially outermost region of the rotor 500. For this purpose, the optical fiber 112 should be laid to the blade tip when retrofitting the fiber-optic acceleration sensor 110.

[0056] Figure 5A measurement system 600 with fiber-optic acceleration sensors 110 according to embodiments described herein is schematically shown. The measurement system 600 comprises one or more fiber-optic acceleration sensors 110. The measurement system 600 has an electromagnetic radiation source 602, for example a primary light source. The source 602 serves to provide optical radiation capable of irradiating at least one fiber-optic acceleration sensor 110. For this purpose, an optical transmission fiber or light guide 603 is provided between the primary light source 602 and a first fiber coupler 604. The fiber coupler 604 couples the primary light into the optical fiber 112. The source 602 can be, for example, a broadband light source, a laser, an LED (light emitting diode), an SLD (Superlumineszenzdiode), an ASE light source (Amplified Spontaneous Emission-Lichtquelle) or a SOA (Semiconductor Optical Amplifier). A plurality of sources of the same or different type can also be used in the embodiments described herein.

[0057] According to embodiments, the optical fiber 112 of the fiber-optic acceleration sensor 110 is optically coupled to an optical resonator 302 of the fiber-optic acceleration sensor 110, wherein the optical resonator 302 comprises, inter alia, the fiber end face 131 of the optical fiber 112, the diaphragm 103 and the cavity 107 formed between the fiber end face 131 and the reflective diaphragm face. The light shot back by the at least one fiber-optic acceleration sensor 110 is in turn conducted via the fiber coupler 604, which conducts the light via a further transmission fiber 605 into a beam splitter 606. The beam splitter 606 splits the light shot back in order to be detected by means of a first detector 607 and a second detector 608. In this case, the signal detected on the second detector 608 is first filtered by means of an optical filter device 609. By means of the filter device 609, the position of the interference maxima or minima output from the optical resonator 302 or the wavelength change caused by the optical resonator 302 and thus the acceleration can be detected.

[0058] Generally, the measurement system, as in the following for example for the fiber-optic acceleration sensor 110, comprises a control unit 610. The control unit 610 is configured to control the measurement system 600 and / or the fiber-optic acceleration sensor 110. The control unit 610 is configured to control the primary light source 602 and / or the fiber coupler 604 and / or the beam splitter 606 and / or the first detector 607 and / or the second detector 608 and / or the filter device 609. Figure 6As shown in the measurement system 700, it is also possible to provide this without the beam splitter 606 or detector 607. However, detector 607 enables the normalization of the measurement signal from fiber optic accelerometer 110 with respect to other intensity fluctuations, such as fluctuations in the intensity of source 602, fluctuations due to reflections at the interfaces between the various optical guides, fluctuations due to reflections at the interface between fiber optic 112 and fiber optic coupler 604, or other intensity fluctuations. This normalization improves measurement accuracy and reduces the correlation with the length of fiber optic 112 provided between evaluation unit 114 and fiber optic accelerometer 110 during measurement system operation.

[0059] Figure 6 One embodiment of the evaluation unit 114 is shown, wherein the signal from the fiber optic accelerometer 110 is guided to the evaluation unit 114 via fiber optic cable 112. Figure 6 The diagram also shows a light source 602, which can optionally be provided in the evaluation unit. However, the light source 602 can also be provided independently of or outside the evaluation unit 114. The optical signal from the fiber optic accelerometer 110, particularly an optical interference signal having a maximum and minimum interference value, can be converted into an electrical signal using a detector, such as a converter 702. The evaluation unit 114 can include a photoelectric converter for converting the optical signal into an electrical signal. For example, a photodiode, photomultiplier (PM), or other photodetector can be used as the converter. The electrical signal can be filtered using an analog anti-aliasing filter 703. After analog filtering using an analog anti-aliasing filter or a low-pass filter 703, the signal is digitized using an analog-to-digital converter 704. Figure 6 A digital evaluation unit 706 is also shown, which may include, for example, a CPU, memory, and other elements for digital data processing.

[0060] The optical filtering device 609, or an additional optical filtering device for filtering the interference spectrum or for detecting the maximum and minimum interference values, may include an optical filter selected from: one or more edge filters, thin-layer filters, fiber Bragg gratings, arrayed waveguide gratings (AWGs), echelle gratings, grating devices, prisms, and any combination thereof.

[0061] According to one embodiment that can be combined with other embodiments described herein, it is feasible, by means of the described evaluation unit 114, to resolve wavelength shifts up to 2 pm. Regarding the minimum interference, this means a change of 0.001 μm in the cavity length 111.

[0062] According to an embodiment, a method 800 for manufacturing an optical fiber accelerometer for determining acceleration along an axis is provided, such as, for example, in...Figure 7 The method 800 comprises, in a block 810, providing a transparent substrate. The substrate can be made of glass, for example of quartz glass or borosilicate glass. In a block 820, a diaphragm is selectively laser-etched from the transparent substrate, wherein the diaphragm comprises a diaphragm frame, a deflection mass and a connecting bridge, and wherein the connecting bridge connects the diaphragm frame and the deflection mass at at least two different axial positions from each other.

[0063] The diaphragm can be constituted according to the embodiments described herein. The selective laser-etching comprises, for example, imprinting the structure of the diaphragm into the substrate. The imprinting comprises, for example, modifying the area of the substrate surrounding the structure of the diaphragm, in particular by chemical modification by laser radiation. The selective laser-etching can also comprise selectively etching the area of the substrate modified by laser radiation. In particular, the modified area of the substrate can be etched into the substrate with a higher etching rate using an etchant. By selectively etching the modified area, the diaphragm can be etched from the substrate.

[0064] According to an embodiment, the method 800 can further comprise arranging the diaphragm relative to a fiber end face of an optical fiber. In particular, the diaphragm frame of the diaphragm and the optical fiber can be connected with a sensor housing. In particular, the diaphragm and the optical fiber can be arranged such that the fiber end face is oriented at least substantially perpendicular to the axis.

[0065] Although the application has been described above with reference to exemplary embodiments, the application is not limited to this, but can be modified in various ways. The application is also not limited to the application possibilities mentioned.

[0066] It is noted at this point that the aspects and embodiments described herein can be suitably combined with each other and individual aspects can be omitted where this is meaningful and feasible within the scope of the professional handling. Modifications and additions to the aspects described herein will occur to those skilled in the art.

Claims

1. A fiber optic accelerometer for determining acceleration along an axis, the fiber optic accelerometer comprising: Optical fiber with fiber end faces; and A vibrating diaphragm having a diaphragm frame, a deflection weight, and a connecting bridge; The vibrating diaphragm is configured to at least partially reflect primary radiation emitted from the fiber end face; and The connecting bridge connects the diaphragm frame and the deflection weight at at least two different axial positions. The fiber optic accelerometer sensor mentioned above is a Fabry-Perot interferometer; The fiber end face of the optical fiber forms the first reflecting mirror of the Fabry-Perot interferometer; and The vibrating diaphragm forms the second reflecting mirror of the Fabry-Perot interferometer.

2. The fiber optic accelerometer sensor according to claim 1, The connecting bridge between the diaphragm frame and the deflection weight is configured as a toggle arm.

3. The fiber optic accelerometer sensor according to claim 1 or 2, The vibrating diaphragm includes at least two connecting bridges at at least two axial positions.

4. The fiber optic accelerometer sensor according to claim 3, The vibrating diaphragm includes at least three connecting bridges at at least two axial positions.

5. The fiber optic accelerometer sensor according to claim 1 or 2, The connecting bridge includes a first connecting bridge at a first axial position in at least two axial positions, and a second connecting bridge at a second axial position in at least two axial positions; and the first connecting bridge is offset relative to the second connecting bridge in a circumferential direction around the axis.

6. The fiber optic accelerometer according to claim 1 or 2, The axial spacing between at least two axial positions is at least 0.1 mm and / or at most 5 mm.

7. The fiber optic accelerometer sensor according to claim 6, The axial spacing between at least two axial positions is at least 0.2 mm.

8. The fiber optic accelerometer sensor according to claim 6, The axial spacing between at least two axial positions is at most 3 mm.

9. The fiber optic accelerometer according to claim 1 or 2, The vibrating diaphragm is configured to provide a mechanical deflection of at least 0.25 nm / G and / or at most 40 nm / G for the deflection weight.

10. The fiber optic accelerometer sensor according to claim 9, The vibrating diaphragm is configured to provide a mechanical deflection of at least 0.5 nm / G for the deflecting weight.

11. The fiber optic accelerometer sensor according to claim 9, The vibrating diaphragm is configured to provide a mechanical deflection of up to 30 nm / G for the deflection weight.

12. The fiber optic accelerometer according to claim 1 or 2, The vibrating diaphragm is made in one piece, and / or the vibrating diaphragm is made of glass.

13. The fiber optic accelerometer sensor according to claim 12, The vibrating diaphragm is made of quartz glass.

14. The fiber optic accelerometer according to claim 1 or 2, The vibrating diaphragm is made by selective laser etching.

15. The fiber optic accelerometer according to claim 1 or 2, The vibrating diaphragm described therein has a highly reflective coating.

16. The fiber optic accelerometer according to claim 1 or 2, The deflecting weights described therein have a highly reflective coating.

17. The fiber optic accelerometer according to claim 1 or 2, wherein the fiber optic accelerometer includes a cavity formed between the fiber end face and the vibrating diaphragm; wherein the deflection weight includes an axial diaphragm surface facing the cavity; and wherein the deflection weight includes a lattice defect region for diffuse light scattering after the axial diaphragm surface.

18. A fiber optic accelerometer system having at least two fiber optic accelerometers according to any one of claims 1 to 17, wherein the fiber optic accelerometer system is configured to determine acceleration along at least two axes.

19. A wind power facility having at least one fiber optic accelerometer sensor according to any one of claims 1 to 17 or at least one fiber optic accelerometer sensor system according to claim 18.

20. The wind power facility according to claim 19, wherein the wind power facility includes rotor blades; wherein the at least one fiber optic accelerometer or the at least one fiber optic accelerometer system is disposed in or on the rotor blades.

21. A method for manufacturing an optical fiber accelerometer for determining acceleration along an axis, wherein the optical fiber accelerometer is an optical fiber accelerometer according to any one of claims 1 to 17, the method comprising: - Provide transparent substrates; and - Selectively etch a vibrating diaphragm from the transparent substrate, wherein the vibrating diaphragm includes a diaphragm frame, a deflection weight, and a connecting bridge; and wherein the connecting bridge connects the diaphragm frame and the deflection weight at at least two axial positions that are different from each other.

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