Device and method for generating a signal for illuminating a fiber Bragg grating in a fiber Bragg grating sensor

Abstract

Device (102, 402, 502, 602, 702, 802) for generating a signal (103) for illuminating a fiber Bragg grating (101) in a fiber Bragg grating sensor (10), in particular for detecting train axes, wherein the device (102, 402, 502, 602, 702, 802) comprises a pump laser (109), a laser medium (110), in particular an erbium-doped fiber amplifier, and a chirped fiber Bragg grating (111), wherein the pump laser (109) is configured to pump the laser medium (110) to emit light, wherein the chirped fiber Bragg grating (111) is configured to reflect a portion of the light into the laser medium (110), and wherein the laser medium (110) is configured to reflect the portion of the To amplify the light signal (103) for illuminating the fiber Bragg grating (101) in the fiber Bragg grating sensor (10). Method for generating the signal (103).

Description

[0001] The invention relates to a device and a method for generating a signal for illuminating a fiber Bragg grating in a fiber Bragg grating sensor, in particular for the detection of traction axes.

[0002] A fiber Bragg grating sensor can detect changes in strain resulting from static or dynamic mechanical loads or temperature changes. The sensor comprises a fiber Bragg grating embedded within an optical fiber. The sensor's measuring principle is based on the fact that any change in the effective refractive index or grating period of the fiber Bragg grating results in a shift in the Bragg wavelength.

[0003] The change in Bragg wavelength depending on the load or temperature change can be determined by the following equation: ΔλB=2[Λ∂neff∂l+neff∂Λ∂l]Δl+2[Λ∂neff∂T+neff∂Λ∂T]ΔT where ∂n eff / ∂T the thermo-optical coefficient, ∂Λ / ∂T the thermal expansion of the fiber, ∂n eff / ∂l represents the variation of the effective refractive index due to the load and ∂Λ / ∂l represents the change in the lattice period.

[0004] For the detection of tensile axes, the fiber Bragg grating sensor's ability to measure strain changes is of particular interest, since the force introduced into the rail by a tensile axis leads to a temporal strain. To detect this strain, the fiber Bragg grating is attached to the side of the rail, for example, in such a way that it extends along the side of the rail at an angle of 45° to the surface through which the force is introduced.

[0005] To build a measurement system that uses a fiber Bragg grating as a sensor element, a fiber Bragg grating interrogation technique is needed to convert the spectral coding of the fiber Bragg grating into an electrical signal that contains the necessary information about the measurement quantity of the measurement system.

[0006] An example of a passive interrogation technique is passive edge filtering. The basic idea behind this technique is to convert the Bragg wavelength shift into an easily measurable power shift. To achieve this conversion, either a linearly wavelength-dependent light source or a broadband light source in combination with a linearly wavelength-dependent optical component is used.

[0007] The device for generating a signal to illuminate a fiber Bragg grating in a fiber Bragg grating sensor, particularly for detecting pull axes according to claim 1, provides a linearly wavelength-dependent light source for passive edge filtering. The device comprises a pump laser, a laser medium, in particular an erbium-doped fiber amplifier, and a chirped fiber Bragg grating. The pump laser is configured to pump the laser medium to emit light, the chirped fiber Bragg grating is configured to reflect a portion of the light back into the laser medium, and the laser medium is configured to amplify this portion of the light to form the signal for illuminating the fiber Bragg grating in the fiber Bragg grating sensor. This means the device uses the portion of the light reflected from the chirped fiber Bragg grating to generate the signal for querying the fiber Bragg grating in the fiber Bragg grating sensor.The device enables reliable scanning of the fiber Bragg grating within the fiber Bragg grating sensor at a sampling rate high enough to detect trains traveling at speeds of up to 400 km / h. This makes the device particularly suitable for train axle detection.

[0008] Preferably, the laser medium is configured to emit broadband light from a wavelength range, in particular a wavelength range from 1500 nm to 1580 nm, wherein the chirped fiber Bragg grating is configured to reflect light with wavelengths from the wavelength range, in particular between 1538 nm and 1555 nm. This means that the wavelength range comprises different wavelengths reflected by the chirped fiber Bragg grating ( Fig. 3) be reflected upon.

[0009] Preferably the device is designed to transmit the signal (103, see example) Fig. 2) to generate with a spectral power density (PSD(λ)) that has at least one of the following advantageous properties: - the spectral width (Δλ) of the wavelength range is greater than or equal to the measuring range of the fiber Bragg grating sensor, - the spectral power density curve over the wavelength is strictly monotonic in the wavelength range or has a constant slope (ΔPSD / Δλ), - the spectral power density curve over the wavelength shows a rising or falling edge in the wavelength range, - The slope of the spectral power density is adjustable depending on the pump current with which the pump laser is operated.

[0010] That means, 1) The spectral power density exhibits a sufficiently large spectral width Δλ in the wavelength range for scanning across the measurement range. For example, the wavelength range has the spectral width Δλ required for the sensor's measurement range. 2) The spectral power density exhibits sufficiently high linearity in the wavelength range for interrogation, 3) The spectral power density exhibits a rising or falling edge in the wavelength range, in particular an edge that is sufficiently large for querying the fiber Bragg grating sensor, in which the fiber Bragg grating has a predetermined refractive index, 4) The slope of the spectral power density is adjustable depending on the pump current I with which the pump laser is operated. The pump laser can be operated, for example, with different pump currents I1, I2,... which result in different slopes of the spectral power density.

[0011] For example ( Fig. 4) The chirped fiber Bragg grating is arranged between the pump laser and the laser medium, wherein the laser medium is pumpable with light of a wavelength, in particular 980 nm or 1480 nm, wherein the pump laser is configured to generate the light with the wavelength, and wherein the chirped fiber Bragg grating is configured to transmit light with the wavelength.

[0012] For example ( Fig. 5) The device comprises a wavelength multiplexer, wherein the laser medium is arranged between the wavelength multiplexer and the chirped fiber Bragg grating. This represents an arrangement in which the reflected part of the light is amplified by the laser medium and then passes to the wavelength multiplexer.

[0013] The device may include an additional laser medium ( Fig. 6), wherein the device is configured to output the signal for illuminating the fiber Bragg grating in the fiber Bragg grating sensor via the additional laser medium.

[0014] For example ( Fig. 7) The device comprises a wavelength multiplexer, wherein the wavelength multiplexer is arranged between the pump laser and the laser medium and between the laser medium and the chirped fiber Bragg grating.

[0015] The device may include an additional laser medium ( Fig. 8), wherein the additional laser medium is arranged between the wavelength multiplexer and the chirped fiber Bragg grating.

[0016] Preferably the device comprises an insulator, wherein the device is configured to output the signal for illuminating the fiber Bragg grating in the fiber Bragg grating sensor via the insulator.

[0017] A method for generating a signal for illuminating a fiber Bragg grating of a fiber Bragg grating sensor, particularly for detecting pull axes, provides that a laser medium, in particular an erbium-doped fiber amplifier, is pumped with a pump laser to emit light, wherein part of the light is reflected into the laser medium with a chirped fiber Bragg grating, and wherein the part of the light is amplified with the laser medium to form the signal for illuminating the fiber Bragg grating in the fiber Bragg grating sensor.

[0018] Preferably, broadband light from a wavelength range is emitted from the laser medium, in particular a wavelength range of 1500 nm to 1580 nm, wherein light with wavelengths from the wavelength range, in particular between 1538 nm and 1555 nm, is reflected by the chirped fiber Bragg grating.

[0019] Preferably, the signal is generated with a spectral power density that exhibits at least one of the following properties: - the spectral width of the wavelength range is greater than or equal to the measuring range of the fiber Bragg grating sensor, - the spectral power density curve over the wavelength is strictly monotonic or has a constant slope in the wavelength range, - the spectral power density curve over the wavelength shows a rising or falling edge in the wavelength range, - The slope of the spectral power density is adjustable depending on the pump current with which the pump laser is operated.

[0020] The method may include the arrangement of the chirped fiber Bragg grating between the pump laser and the laser medium, wherein the laser medium is pumped with light of a wavelength, in particular 970 nm to 985 nm, e.g. 980 nm, or 1480 nm, wherein the pump laser generates the light with the wavelength, and wherein the chirped fiber Bragg grating transmits the light with the wavelength.

[0021] The process may include the arrangement of the laser medium between a wavelength multiplexer and the chirped fiber Bragg grating.

[0022] The method may include the arrangement of a wavelength multiplexer between the pump laser and the laser medium and between the laser medium and the chirped fiber Bragg grating.

[0023] Preferably, the signal for illuminating the fiber Bragg grating in the fiber Bragg grating sensor is output via an insulator.

[0024] Further advantageous embodiments can be found in the following description and the drawing. The drawing shows: Fig. 1 A schematic representation of a fiber Bragg grating measuring system with a fiber Bragg grating in a fiber Bragg grating sensor and a device for generating a signal to illuminate the fiber Bragg grating, Fig. 2 an exemplary spectral power density, Fig. 3 an exemplary reflectivity spectrum of a chirped fiber Bragg grating, Fig. 4 a schematic representation of an exemplary first embodiment of the device, Fig. 5 a schematic representation of an exemplary second embodiment of the device, Fig. 6 a schematic representation of an exemplary third embodiment of the device, Fig. 7 a schematic representation of an exemplary fourth embodiment of the device, Fig. 8 a schematic representation of an exemplary fifth embodiment of the device Fig. 9. A flowchart showing the steps of a procedure for generating the signal.

[0025] Fig. Figure 1 schematically depicts a fiber Bragg grating measuring system 100 with a fiber Bragg grating 101 in a fiber Bragg grating sensor 10 and a device 102 for generating a signal 103 to illuminate the fiber Bragg grating 101. The sensor itself is in the Fig. Figure 1 is not shown. The sensor is, for example, a mechanical device comprising the fiber Bragg grating 101. The fiber Bragg grating measuring system 100 can be used, for example, for the detection of tensile axes.

[0026] The fiber Bragg grating measuring system 100 comprises a wavelength multiplexer 104, which is arranged between the device 102 and the fiber Bragg grating 101 of the fiber Bragg grating measuring system 100.

[0027] The fiber Bragg grating 101 is arranged in an optical fiber and exhibits a refractive index modulation along the optical fiber. This refractive index modulation determines which wavelengths the fiber Bragg grating 101 transmits as the transmitted part 105 of the signal and which wavelengths the fiber Bragg grating 101 reflects as the reflected part 106 of the signal 103. The fiber Bragg grating 101 is manufactured with a refractive index modulation that allows a predetermined wavelength to be reflected from the fiber Bragg grating 101 at a specified temperature without any mechanical stress being applied to it.

[0028] The measuring range of the fiber Bragg grating measuring system 100 depends on a wavelength range in which the fiber Bragg grating 101 reflects light due to the refractive index modulation which changes depending on the mechanical load and / or depending on the temperature.

[0029] According to a first example, the fiber Bragg grating 101 is designed to reflect light with a wavelength in a first wavelength range between 1547 nm and 1562 nm, depending on a mechanical load and / or depending on the temperature in the measuring range. The fiber Bragg grating 101 is, for example, manufactured with a refractive index modulation for the reflection of light with a wavelength of 1554 nm.

[0030] According to a second example, the fiber Bragg grating 101 is designed to reflect light with a wavelength in a second wavelength range between 1538 nm and 1555 nm, depending on a mechanical load and / or depending on the temperature within the measurement range. For example, the fiber Bragg grating 101 is manufactured with a refractive index modulation for the reflection of light with a wavelength of 1549 nm.

[0031] The fiber Bragg grating measuring system 100 comprises a device 107 configured to convert the reflected part 106 of the signal 103 into an electrical signal 108 that characterizes a power of the reflected part 106 of the signal 103.

[0032] A change in the electrical signal 108 indicates a power shift, which results from a Bragg wavelength shift in the fiber Bragg grating 101 due to the refractive index modulation in the fiber Bragg grating 101 caused by load or temperature change.

[0033] The device 102 for generating the signal 103 for illuminating the fiber Bragg grating 101 comprises a pump laser 109, a laser medium 110 and a chirped fiber Bragg grating 111.

[0034] The laser medium 110 and the pump laser 109 are configured for the optical 980 nm window in this example.

[0035] The pump laser 109, for example, generates light with a wavelength of 980 nm. The laser medium 110 includes, for example, an erbium-doped fiber amplifier.

[0036] The wavelength of 980 nm is one example. The laser medium 110 and the pump laser 109 can also be configured for other optical windows, such as the 850 nm window, the 1300 nm window, or the 1550 nm window. Cables for the 850 nm window are relatively inexpensive and are mainly used for short distances. The second optical window exhibits lower attenuation and is therefore suitable for somewhat longer ranges. The third optical window is used for long distances to enable extended ranges.

[0037] Erbium is an example of the type of doping of the optical fiber in the laser medium 110. Other types of doping, e.g. doping with titanium, chromium, cobalt, neodymium or ytterbium, can be provided for a fiber Bragg grating 101 with appropriately adapted refractive index modulation using a pump laser with a suitable wavelength for excitation.

[0038] The laser medium 110 is configured to emit light in a wavelength range that includes wavelengths suitable for illuminating the fiber Bragg grating 101 during a measurement with the fiber Bragg grating measuring system 100. Wavelengths suitable for interrogation lie within a suitable wavelength range, i.e., the wavelength range in which the fiber Bragg grating 101 reflects light due to the refractive index modulation in the fiber Bragg grating 101, which changes depending on the mechanical stress and / or temperature.

[0039] In the wavelength range suitable for querying, the spectral power density PSD(λ) exhibits a rising or falling edge.

[0040] In the wavelength range suitable for querying, the spectral power density PSD(λ) additionally exhibits at least one of the following properties: - a linear progression of the rising or falling flank, - the spectral width of the wavelength range is greater than or equal to the measuring range of the fiber Bragg grating sensor 10, - the spectral power density curve over the wavelength is strictly monotonic in the wavelength range or exhibits a constant slope ΔPSD / Δλ, - the spectral power density curve over the wavelength shows a rising or falling edge in the wavelength range, - The spectral power density curve over the wavelength exhibits an edge in the wavelength range, with a low power fluctuation along the edge. - The slope of the spectral power density is adjustable depending on the pump current with which the pump laser is operated.

[0041] The flank is created by combining the laser medium 110 with the chirped fiber Bragg grating 101.

[0042] The reflectivity spectrum of the chirped fiber Bragg grating 101 has an influence on this. The following parameters, for example, have an influence on the reflectivity spectrum: the period of the grating modulation in the chirped fiber Bragg grating 101, the size of the modulation depth of the chirped fiber Bragg grating 101, and the number of grating periods in the chirped fiber Bragg grating 101.

[0043] The characteristics of the laser medium 110 have an influence on this. For example, the following parameters influence the characteristics: the emission and absorption cross sections of the laser medium 110, the length of the laser medium 110, and the pumping power.

[0044] The combination of the laser medium 110 with the chirped fiber Bragg grating 101 represents a feedback system, i.e. the part of the light reflected by the chirped fiber Bragg grating 101 is also amplified.

[0045] The parameters are determined, for example, in a numerical simulation.

[0046] It may be provided that the slope of the spectral power density is adjustable depending on a pump current I with which the pump laser 109 is operated.

[0047] Fig. Figure 2 represents an exemplary spectral power density PSD 200 versus wavelength λ. In the wavelength range 201, with wavelength λ increasing from zero, the spectral power density PSD 200 exhibits a sawtooth waveform with a rising edge followed by a falling edge towards zero.

[0048] The rising edge begins, for example, at 1538 nm. The falling edge ends, for example, at 1552 nm. The chirped fiber Bragg grating 111 is arranged in an optical fiber and exhibits a refractive index modulation along the optical fiber with a variation in the refractive index modulation along the optical fiber. The variation in the refractive index modulation determines which wavelengths the chirped fiber Bragg grating 101 transmits and which wavelengths the chirped fiber Bragg grating 111 reflects.

[0049] The chirped fiber Bragg grating 111 is designed to reflect a portion of the light, i.e., light of the wavelengths reflected by the chirped fiber Bragg grating 111, into the laser medium 110.

[0050] The chirped fiber Bragg grating 111 is designed to reflect light with wavelengths from the wavelength range.

[0051] In Fig. Figure 3 shows the reflectivity R of the chirped fiber Bragg grating 111 in percent versus wavelength λ in nanometers. The reflectivity R is maximal in the wavelength range 201. The reflectivity R curve is flat in the wavelength range 201. For example, the reflectivity R for generating signal 103 with the value shown in Fig. The spectral power density shown in Figure 2 is maximal and flat in the wavelength range 201 between 1540 nm and 1550 nm. Outside the wavelength range 201, the reflectivity R is minimal, i.e., at zero percent.

[0052] This means that, in the first example, the chirped fiber Bragg grating 111 can be designed to reflect light with wavelengths from the first wavelength range of 1547 nm to 1562 nm.

[0053] This means that in the second example, the chirped fiber Bragg grating 111 can be designed to reflect light with wavelengths from the second wavelength range of 1538 nm to 1555 nm.

[0054] The laser medium 110 is designed to amplify the part of the light reflected into the laser medium 110 for illumination of the fiber Bragg grating 101 in the fiber Bragg grating sensor.

[0055] The device 102 provides a light source for the fiber Bragg grating measuring system 100. The light source provides light for the fiber Bragg grating 101 within the measuring range of the fiber Bragg grating measuring system 100.

[0056] The following are exemplary embodiments of device 102.

[0057] Fig. Figure 4 schematically represents an exemplary first embodiment 402 of the device 102.

[0058] According to the first embodiment 402, the chirped fiber Bragg grating 111 is arranged between the pump laser 109 and the laser medium 110.

[0059] The laser medium 110 can be pumped with light of wavelength 980 nm.

[0060] The pump laser 109 is designed to generate light with a wavelength of 980 nm.

[0061] The chirped fiber Bragg grating 111 is designed to transmit light with a wavelength of 980 nm. This means that the chirped fiber Bragg grating 111 is a bandstop filter that reflects light in the stopband of the bandstop filter and transmits all other wavelengths.

[0062] The device 102 according to the first embodiment 402 has an insulator 112.

[0063] The device 102 according to the first embodiment 402 is configured to output the signal 103 for illumination of the fiber Bragg grating 101 in the fiber Bragg grating measuring system 100 via the insulator 112.

[0064] Fig. Figure 5 schematically represents an exemplary second embodiment 502 of the device 102.

[0065] The device 102 according to the second embodiment 502 comprises the pump laser 109, the laser medium 110, the chirped fiber Bragg grating 111, the insulator 112 and a wavelength multiplexer 113.

[0066] The laser medium 110 is arranged between the wavelength multiplexer 113 and the chirped fiber Bragg grating 111. The laser medium 110 can be the optical link or part of the optical link.

[0067] Fig. Figure 6 schematically represents an exemplary third embodiment 602 of the device 102.

[0068] The device 102 according to the third embodiment 602 is configured like the device 102 according to the second embodiment 502 and additionally comprises a laser medium 114 arranged between the wavelength multiplexer 113 and the isolator 112. The laser medium 114 may be the optical link or part of the optical link.

[0069] The laser medium 114 is designed in the same way as the laser medium 110 in this example.

[0070] Fig. Figure 7 schematically represents an exemplary fourth embodiment 702 of the device 102.

[0071] The device 102 according to the fourth embodiment 702 comprises the pump laser 109, the laser medium 110, the chirped fiber Bragg grating, the insulator 112 and a Wavelength multiplexer 115. The wavelength multiplexer 115 is arranged between the pump laser 109 and the laser medium 110 and between the laser medium 110 and the chirped fiber Bragg grating 111.

[0072] The laser medium 110 is arranged between the wavelength multiplexer 115 and the insulator 112.

[0073] The device 102 according to the fourth embodiment 702 is configured to output the signal 103 for illumination of the fiber Bragg grating 101 in the fiber Bragg grating measuring system 100 via the insulator 112.

[0074] The insulator 112 can, instead of being located inside the device 102, also be located outside the device 102, e.g. between the device 102 and the fiber Bragg grid 101, depending on the specific embodiment.

[0075] Fig. Figure 8 schematically represents an exemplary fifth embodiment 802 of the device 102.

[0076] The device 102 according to the fifth embodiment 802 is configured like the device 102 according to the fourth embodiment 702 and additionally comprises a laser medium 116 arranged between the wavelength multiplexer 115 and the chirped fiber Bragg grating 111. The laser medium 116 may be the optical link or part of the optical link.

[0077] The laser medium 116 is designed in the same way as the laser medium 110 in this example.

[0078] In designs with two laser media, it may be provided that both laser media are designed differently from each other, particularly with regard to their length.

[0079] In Fig. Figure 9 shows a flowchart with steps of a procedure for generating the signal 103 for illuminating a fiber Bragg grating 101 of the fiber Bragg grating sensor 10 in the fiber Bragg grating measuring system 100, in particular for the detection of pull axes.

[0080] The procedure includes step 901.

[0081] In step 901, the pump current I with which the pump laser 109 is operated is specified. Then, step 902 is executed. This means that the operating point of the pump laser 109 is initially set. Adjustments are made, for example, by modifying the pump current I if the operating point deviates too far from the initially set operating point.

[0082] The sensitivity of the fiber Bragg grating measuring system 100 depends on the slope of the spectral power density edge in the wavelength range and the reflectivity of the fiber Bragg grating 101. The reflectivity of the fiber Bragg grating is proportional to the refractive index modulation and the grating length.

[0083] The sensitivity is proportional to the product of the slope of the power spectrum in the wavelength range and the refractive index of the fiber Bragg grating 101.

[0084] For example, the pump current I required to achieve a specified sensitivity is determined. For instance, the pump current I required to achieve the specified sensitivity of the fiber Bragg grating measuring system 100 is determined as a function of the slope of the spectral power density edge in the wavelength range and / or as a function of the reflectivity of the fiber Bragg grating 101. The pump current I is determined, for example, as a function of the product.

[0085] The procedure includes step 902.

[0086] In step 9702, the pump laser 109 is operated with the pump current I.

[0087] The pump laser 109 pumps the laser medium 110.

[0088] The laser medium 110 generates light via spontaneous emission.

[0089] The light from the spontaneous emission is amplified in the laser medium 110. Part of this amplified spontaneous emission is reflected from the chirped fiber Bragg grating 111 into the laser medium 110.

[0090] The reflected portion of the amplified spontaneous emission is further amplified by the laser medium 110, thus generating the signal 103 with which the fiber Bragg grating 101 in the fiber Bragg grating sensor 10 is illuminated. The signal 103 exhibits the aforementioned properties, particularly with regard to its edge.

[0091] This means that the portion of the light amplified by the laser medium 110 from the spontaneous emission in the laser medium 110 is reflected back into the laser medium 110 by the chirped fiber Bragg grating 111 and amplified again.

[0092] The portion of the light is amplified with the laser medium 110 to form the signal 103 for illuminating the fiber Bragg grating 101 in the fiber Bragg grating sensor 10.

[0093] The signal 103 is generated, for example, with the device 102 according to one of the exemplary embodiments.

[0094] Step 901 is then executed.

[0095] The device 102 and the method are used, for example, for the detection of traction axles. This means that the fiber Bragg grating 101 in the fiber Bragg grating sensor 10 determines a change in strain resulting from a force introduced into a rail by a traction axle. To detect this strain, the fiber Bragg grating 101 is attached to the side of the rail, for example, such that it extends at an angle of 45° to the surface through which the force is introduced.

[0096] The fiber Bragg grating 101 is queried, for example, using the device 102 in the procedure.

Claims

[1] Device (102, 402, 502, 602, 702, 802) for generating a signal (103) for illuminating a fiber Bragg grating (101) in a fiber Bragg grating sensor (10) in particular for detecting train axes, characterized by , that the device (102, 402, 502, 602, 702, 802) comprises a pump laser (109), a laser medium (110), in particular an erbium-doped fiber amplifier, and a chirped fiber Bragg grating (111), wherein the pump laser (109) is configured to pump the laser medium (110) to emit light, wherein the chirped fiber Bragg grating (111) is configured to reflect part of the light into the laser medium (110), and wherein the laser medium (110) is configured to amplify the part of the light to form the signal (103) for illuminating the fiber Bragg grating (101) in the fiber Bragg grating sensor (10). [2] The device (102, 402, 502, 602, 702, 802) according to claim 1, characterized by, that the laser medium (110) is configured to emit broadband light from a wavelength range, in particular a wavelength range from 1500 nm to 1580 nm, wherein the chirped fiber Bragg grating (111) is configured to reflect light with wavelengths from the wavelength range, in particular between 1538 nm and 1555 nm. [3] Device (102, 402, 502, 602, 702, 802) according to claim 2, characterized by , that the device (102, 402, 502, 602, 702, 802) is configured to generate the signal (103) with a spectral power density that has at least one of the following properties: - the spectral width of the wavelength range is greater than or equal to the measuring range of the fiber Bragg grating sensor (10), - the spectral power density curve over the wavelength is strictly monotonic or has a constant slope in the wavelength range, - the spectral power density curve over the wavelength shows a rising or falling edge in the wavelength range, - the slope of the spectral power density is adjustable depending on the pump current with which the pump laser (109) is operated. [4] The device (102, 402) according to one of claims 1 to 3, characterized by , that the chirped fiber Bragg grating (111) is arranged between the pump laser (109) and the laser medium (110), wherein the laser medium (110) is pumpable with light of a wavelength, in particular 980 nm or 1480 nm, wherein the pump laser (109) is configured to generate the light with the wavelength, and wherein the chirped fiber Bragg grating (111) is configured to transmit light with the wavelength. [5] The device (102, 502, 602) according to any one of claims 1 to 3, characterized by, that the device (102, 502, 602) comprises a wavelength multiplexer (113), wherein the laser medium (110) is arranged between the wavelength multiplexer (113) and the chirped fiber Bragg grating (111). [6] The device (102, 602) according to claim 5, characterized by , that the device (102, 602) comprises an additional laser medium (114), wherein the device (102, 602) is configured to output the signal (103) for illumination of the fiber Bragg grating (101) in the fiber Bragg grating sensor (10) via the additional laser medium (114). [7] The device (102, 702) according to one of claims 1 to 3, characterized by , that the device (102, 702) comprises a wavelength multiplexer (115), wherein the wavelength multiplexer (115) is arranged between the pump laser (109) and the laser medium (110) and between the laser medium (110) and the chirped fiber Bragg grating (111). [8] The device (102, 802) according to claim 7, characterized by, that the device (102, 802) comprises an additional laser medium (116), wherein the additional laser medium (114) is arranged between the wavelength multiplexer (115) and the chirped fiber Bragg grating (111). [9] The device (102, 402, 502, 602, 702, 802) according to any one of the preceding claims, characterized by , that the device (102, 402, 502, 602, 702, 802) comprises an insulator (112), wherein the device (102, 402, 502, 602, 702, 802) is configured to output the signal (103) for illuminating the fiber Bragg grating (101) in the fiber Bragg grating sensor (10) via the insulator (112). [10] A method for generating a signal (103) for illuminating a fiber Bragg grating (101) of a fiber Bragg grating sensor (10) in particular for detecting train axes, characterized by, that a laser medium (110), in particular an erbium-doped fiber amplifier, is pumped with a pump laser (109) to emit light, wherein part of the light is reflected into the laser medium (110) with a chirped fiber Bragg grating (111), wherein the part of the light is amplified with the laser medium (110) to the signal (103) for illumination of the fiber Bragg grating (101) in the fiber Bragg grating sensor (902). [11] The method according to claim 10, characterized by , that broadband light from a wavelength range is emitted from the laser medium (110) (902), in particular a wavelength range of 1500 nm to 1580 nm, wherein light with wavelengths from the wavelength range, in particular between 1538 nm and 1555 nm, is reflected by the chirped fiber Bragg grating. [12] The method according to claim 11, characterized by, that the signal (103) is generated with a spectral power density that has at least one of the following properties: - the spectral width of the wavelength range is greater than or equal to the measuring range of the fiber Bragg grating sensor (10), - the spectral power density curve over the wavelength is strictly monotonic or has a constant slope in the wavelength range, - the spectral power density curve over the wavelength shows a rising or falling edge in the wavelength range, - the slope of the spectral power density is adjustable depending on the pump current with which the pump laser (109) is operated. [13] The method according to any one of claims 10 to 12, characterized by, that the chirped fiber Bragg grating (111) is arranged between the pump laser (109) and the laser medium (110), wherein the laser medium (110) is pumped with light of a wavelength, in particular 970 nm to 985 nm, e.g. 980 nm or 1480 nm, wherein the pump laser (109) generates the light with the wavelength, wherein the chirped fiber Bragg grating (111) transmits the light with the wavelength. [14] The method according to any one of claims 10 to 12, characterized by , that the laser medium (110) is arranged between a wavelength multiplexer (113) and the chirped fiber Bragg grating (111). [15] The method according to any one of claims 10 to 12, characterized by , that a wavelength multiplexer (115) is arranged between the pump laser (109) and the laser medium (110) and between the laser medium (110) and the chirped fiber Bragg grating (111). [16] The method according to any one of claims 10 to 15, characterized by, that the signal (103) for illuminating the fiber Bragg grating (101) in the fiber Bragg grating sensor (10) is output via an insulator (112).

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