Optical apparatus for the spatially resolved measurement of a physical variable

Abstract

The invention relates to an apparatus for the spatially resolved measurement of a physical variable, comprising a first optical fiber (2) for the spatially resolved measurement, a first laser light source (1) for generating laser pulses, the apparatus being configured to the effect that the laser pulses are coupled into the first optical fiber (2), that the laser pulses in the first optical fiber (2) generate signals which are usable for measuring the physical variable as a result of backscattering and / or reflection, and that the generated signals are coupled out of the first optical fiber (2), an evaluation device (9) configured to the effect that the physical variable to be measured is determined in a spatially resolved manner from the signals coupled out, a second laser light source (5) for generating pump laser radiation in continuous-wave operation, the apparatus being configured to the effect that the laser radiation causes amplification of the laser pulses and / or of the signals generated in the first optical fiber (2).

Description

OPTICAL DEVICE FOR SPACE-RESOLVED MEASUREMENT OF A PHYSICAL QUANTITY

[0001] The present invention relates to a device for spatially resolved measurement of a physical quantity.

[0002] Devices of the aforementioned type are known and can be used for distributed fiber-optic sensing (DFOS) over long distances. Such long-distance DFOS systems are generally based on an OTDR (Optical Time-Domain Reflectometry) scheme, in which a nanosecond laser pulse or a sequence of laser pulses is coupled into an optical fiber that is attached to or embedded in the structure or object to be monitored. The state of the structure (temperature, strain, vibrations, or acoustic signals) is then monitored with spatial and temporal resolution by analyzing returning light signals generated by Rayleigh, Brillouin, or Raman scattering, as well as by reflections from multiple reflection centers such as fiber Bragg gratings (FBGs) or other weak reflectors in the fiber core.Raman scattering is primarily used for distributed temperature sensing (DTS). Brillouin scattering provides information about temperature and strain (distributed strain sensing - DSS). Rayleigh scattering and reflections are used to analyze vibrations, acoustic signals (distributed acoustic sensing - DAS), dynamic strain, and dynamic temperature. Important applications for long-distance DFOS include submarine power cables, overhead power lines, pipelines, railways, borders, and fences.

[0003] The optical budget, or the maximum total attenuation of the fiber optic link at which the DFOS interrogation system delivers the specified performance, and thus the The detection range of a DFOS system is limited by the coupled laser power, the strength of the scattering or reflection effect used, and the sensitivity of the detection system.

[0004] Optical amplifiers are frequently used in fiber optic telecommunications systems to extend transmission range. Optical amplifiers for telecommunications systems typically require electrical power along the fiber link. However, in many applications of distributed fiber optic sensing devices, such as high-voltage direct current submarine cables, pipelines, or long fences, no electrical power is available along the fiber link. While the power of the laser used for signal transmission can be increased when no electrical power is available along the fiber link, the usable laser power is limited by nonlinear effects, such as the occurrence of modulation instability when the laser power exceeds certain limits.

[0005] The problem underlying the present invention is the creation of a device of the type mentioned at the outset, with which spatially resolved measurement of the physical quantity over larger distances is possible.

[0006] According to the invention, this is achieved by a device having the features of claim 1. The dependent claims relate to preferred embodiments of the invention.

[0007] According to claim 1, the device comprises a first optical fiber for spatially resolved measurement, a first laser light source for generating laser pulses, wherein the device is configured to direct the laser pulses into the first The device consists of a light guide fiber coupled in such a way that the laser pulses generate signals usable for measuring the physical quantity in the first light guide fiber through backscattering and / or reflection, and that the generated signals are coupled out from the first light guide fiber. It also includes an evaluation unit configured to determine the physical quantity to be measured with spatial resolution from the coupled signals, and a second laser light source for generating a pump laser beam in continuous operation. The device is configured such that the laser beam amplifies the laser pulses and / or the signals generated in the first light guide fiber. This amplification of the laser pulses and / or the signals generated in the first light guide fiber enables the spatially resolved determination of the physical quantity to be measured even over distances of more than 50 km.

[0008] The evaluation device can, for example, be designed as described in EP 3 139 133 A1.

[0009] It is possible that the second laser light source is a semiconductor laser or a fiber laser.

[0010] The device can be configured so that the laser pulses in the first optical fiber generate a signal usable for measuring the physical quantity by Brillouin scattering and / or Rayleigh scattering and / or by reflection at multiple reflection centers, such as fiber Bragg gratings or other distributed reflectors.

[0011] Furthermore, the physical quantity to be measured can be a temperature and / or a strain and / or a vibration and / or an acoustic signal, for example a dynamically changing temperature and / or a dynamically changing strain.

[0012] The device can be configured to amplify the laser pulses and / or the generated signals by means of a Raman effect. This is known as Raman amplification. Specifically, it is provided that the first laser light source generates laser pulses with a first wavelength during operation of the device, and that the second laser light source generates pump laser radiation with a second wavelength during operation of the device, wherein the first wavelength is greater than the second wavelength, and in particular, where the magnitude of the wavelength difference between the first and second wavelengths corresponds to possible wavelength shifts in the Raman spectrum of the core material of the first optical fiber.Raman amplification occurs when a pump laser beam with a shorter wavelength travels in an optical fiber in either the same or opposite direction to the laser pulses or signal to be amplified, and when the frequency difference between the pump laser beam and the laser pulses or signal to be amplified corresponds to a band in the Raman spectrum of the fiber material. It is possible to amplify the laser pulses and the returning signals simultaneously using the same pump laser beam. Besides increasing the distance over which spatially resolved determination of the physical quantity is possible, Raman amplification offers the advantage that no electrical energy or additional optical components are required for amplification along the fiber segment used for the measurement.

[0013] It can also be provided that the wavelength difference between the first and second wavelengths is not located at the maximum of the Raman spectrum of the core material of the first optical fiber. This reduces the Raman gain and the depletion of the pump Laser radiation is reduced and Raman amplification remains efficient even at greater distances.

[0014] It is possible that Raman amplification occurs not only through a first-order Raman effect, but alternatively or additionally through a higher-order Raman effect. In a second-order Raman effect, laser beams with two different wavelengths are introduced. These can be, in particular, a first laser beam with a wavelength of approximately 1480 nm and a lower power of, for example, 1 mW, and a second laser beam with a shorter wavelength, which is suitable for amplifying the first laser beam. Systems with a third-order Raman effect are also possible. The advantage of higher-order Raman effects is that the maximum power at 1480 nm is only reached at a considerable distance from the second laser light source.

[0015] The device may comprise a second optical fiber and a coupling device, wherein the second optical fiber is connected to the first optical fiber via the coupling device, and wherein the device is configured such that the pump laser radiation generated by the second laser light source is coupled into the second optical fiber and from the second optical fiber is coupled into the first optical fiber via the coupling device, in particular wherein the coupling device is configured as a wavelength multiplexer or as a multi-port circulator. It may be provided that the coupling device is spaced apart from the first laser light source, wherein the length of a first section of the first optical fiber from the first laser light source to the coupling device is between 1 km and 100 km, in particular between 5 km and 75 km, preferably between 10 km and 50 km.This design means that the amplification of the laser pulses and / or signals only begins after the. The coupling device can be positioned at a considerable distance from the first laser light source, such that the laser pulses, although already attenuated by propagation through the first section of the first optical fiber to the coupling device, are still sufficiently strong to ensure spatially resolved determination of the physical quantity to be measured. In particular, the power of the laser pulses coupled into the first optical fiber can be chosen to be so low as to avoid nonlinear effects.

[0016] It may be provided that the first optical fiber has a second section extending away from the coupling device for coupling the pump laser radiation from the first section of the first optical fiber. In this second section, the amplification of the laser pulses and / or the signals generated by backscattering and / or reflection from the laser pulses then begins.

[0017] The device may comprise at least one active optical fiber, which is particularly erbium-doped, and may be configured such that the pump laser radiation in the at least one active optical fiber amplifies the laser pulses and / or the signals generated in the first optical fiber. It may be provided that, during operation of the device, the second laser light source generates pump laser radiation with a second wavelength, which can be absorbed by the erbium ions in the core material of the optical fiber in such a way that a population inversion with more ions in a higher energy state than in a lower energy state can be achieved. This can be achieved, for example, with second wavelengths between 1430 nm and 1500 nm. The additional active In a range where the pump laser radiation no longer contributes sufficiently to effectively amplify the laser pulses and / or signals via Raman amplification, optical fibers can achieve effective amplification of the laser pulses and / or signals via the erbium-doped fiber amplifier (EDFA) that forms the active optical fiber. The pump power remaining after attenuation by the fiber only needs to be high enough to generate a population inversion, which is typically the case at powers of just a few mW, such as 1 mW to 10 mW.Due to the low duty cycle of the pulsed first laser light source with laser pulses in the nanosecond range and the extremely weak reflected signal, the active optical fiber—unlike, for example, telecommunications systems—operates entirely in the low-signal amplification range, where population inversion is practically unaffected by signal amplification. Although the power of the laser pulses in the active optical fiber can be higher than the power of the pump laser radiation, population inversion is not affected because a large portion of the pump energy is accumulated in the active optical fiber with excited states that have lifetimes of, for example, 10 ms.

[0018] It is entirely possible that more than one active optical fiber is used. These active optical fibers can be spaced apart from each other.

[0019] It can be provided that at least one active optical fiber connects to the second section of the first optical fiber on the side facing away from the first section of the first optical fiber, in particular wherein a third section of the first optical fiber connects to the active optical fiber on the side facing away from the second section of the first optical fiber. connects. In this third section, the laser pulses, amplified in the at least one active optical fiber, for example up to the limit given by the nonlinear effects, then enter, so that the third section can extend over a comparatively large length.

[0020] It may well be provided that a first of the active optical fibers is arranged between the second and the third section of the first optical fiber and that a second of the active optical fibers connects to the third section of the first optical fiber on the side facing away from the second section of the first optical fiber, in particular wherein a fourth section of the first optical fiber connects to the second active optical fiber on the side facing away from the third section of the first optical fiber.

[0021] The length of the second section of the first optical fiber, from the coupling device for coupling the pump laser radiation to the active optical fiber, can be between 10 km and 180 km, particularly between 50 km and 150 km, and preferably between 100 km and 130 km. It is particularly possible for the total length of the first, second, and third sections of the first optical fiber to be more than 100 km, particularly more than 150 km, and preferably between 150 km and 500 km, for example, approximately 250 km.

[0022] It is possible that the second laser light source comprises a plurality of laser devices, wherein at least two of the laser devices of the second laser light source generate pump laser radiations with different wavelengths and / or polarizations during operation of the device, in particular wherein the device is configured such that the The laser beams emanating from the individual laser devices are coupled to each other, preferably by wavelength division multiplexing and / or polarization coupling, before being coupled into the second optical fiber. By coupling several laser beams with different wavelengths, significantly higher pumping powers can be achieved than with pump lasers operating at a single wavelength. It is entirely possible to compose the pump laser beam from considerably more than four different wavelengths.

[0023] The device can be configured to couple signals traveling back in the first optical fiber, particularly by means of a circulator included in the device, preferably a multi-port circulator, into the second optical fiber, from which they are coupled out and fed to the evaluation unit for spatially resolved determination of the physical quantity to be measured. In this way, even very weak signals can travel from the coupling device to the evaluation unit in the second optical fiber instead of the first, where they can be amplified by the pump laser radiation propagating in the second optical fiber. This allows the total possible length of the measuring path provided by the first optical fiber to be further extended.

[0024] It is possible that the device is configured to partially couple pump laser radiation, coupled into the first optical fiber via the coupling device, into the first section of the first optical fiber, in particular wherein the device for this partial coupling of the pump laser radiation comprises a multi-port circulator and / or a fiber Bragg grating. This variant contributes to ensuring that the laser pulses and / or the generated signals are also amplified in the first section of the first optical fiber by the pump laser radiation.

[0025] The first and / or second optical fiber can be single-mode fibers. In particular, the entire fiber optic assembly of the device can be based on single-mode fibers and passive fiber optic components such as polarization combiners, wavelength multiplexers, and bandpass filters. The use of multimode fibers and / or free-space optics is also entirely possible.

[0026] Further features and advantages of exemplary embodiments of the invention are described below with reference to the drawings. The same reference numerals are used for identical or similar parts and for parts with identical or similar functions. The drawings show: Fig. 1 shows a schematic view of a first embodiment of a device according to the invention; Fig. 2 shows a schematic view of a second embodiment of a device according to the invention; Fig. 3 shows a schematic view of a third embodiment of a device according to the invention; Fig. 4 shows a schematic view of a fourth embodiment of a device according to the invention; Fig. 5 shows a schematic view of a fifth embodiment of a device according to the invention; Fig. 6 is a diagram in which the signal power generated by a device according to the invention is plotted logarithmically against the distance in km.

[0027] It is not necessary for a device according to the invention to have all the features described below. It is also possible for a device according to the invention to have only individual features of the embodiments described below.

[0028] The embodiment of the device shown in Fig. 1 comprises a first laser light source 1, which emits laser pulses with a length in the nanosecond range, for example with a length of a few The device can generate laser pulses in nanoseconds and with a first wavelength of approximately 1,550 nm. It further comprises a first optical fiber 2 into which the laser pulses are coupled. The first optical fiber 2 has a first section 3 into which the laser pulses are coupled at its end, particularly on the left side in Fig. 1. The first optical fiber 2 further comprises a second section 4, which adjoins the first section 3.

[0029] The first optical fiber 2 comprises a fiber core and a cladding. The fiber core can essentially consist of quartz glass with optional doping.

[0030] The device is configured such that the laser pulses in the first optical fiber 2 generate a signal usable for measuring a physical quantity through Brillouin scattering and / or Rayleigh scattering and / or reflection at multiple reflection centers, such as fiber Bragg gratings or other distributed reflectors. The physical quantity to be measured can be temperature and / or strain and / or vibration and / or an acoustic signal, for example, a dynamically changing temperature and / or a dynamically changing strain.

[0031] The device further comprises a second laser light source 5, which can generate a pump laser beam in continuous wave mode with a second wavelength between approximately 1,430 nm and approximately 1,500 nm. The device further comprises a second optical fiber 6, into which the pump laser beam is coupled. The pump laser beam serves to amplify the laser pulses and / or the signals generated in the first optical fiber 2, as will be described in more detail below.

[0032] The device further comprises a coupling device 7, which is configured in particular as a wavelength multiplexer. The second optical fiber 6 is connected to the first optical fiber 2 via the coupling device 7 in the connection area of ​​the first and second sections 3, 4.

[0033] The length of a first section 3 of the first optical fiber 2 from the first laser light source 1 to the coupling device 7 can be between 1 km and 100 km, in particular between 5 km and 75 km, preferably between 10 km and 50 km. In the junction of the first and second sections 3, 4 of the first optical fiber 2, pump laser radiation generated by the second laser light source 5 is coupled into the first optical fiber 2. This design ensures that the amplification of the laser pulses and / or signals only begins in the second section 4 of the first optical fiber 2, and thus at a considerable distance from the first laser light source 1.

[0034] The pump laser radiation can amplify the laser pulses and / or the generated signals through a Raman effect. This is known as Raman amplification. The wavelength difference of approximately 50 nm to 120 nm between the first wavelength (approximately 1,550 nm) and the second wavelength (between approximately 1,430 nm and approximately 1,500 nm) corresponds to possible wavelength shifts in the Raman spectrum of the core material of the first optical fiber 2, particularly the quartz glass from which the core may be made. It is possible to amplify the laser pulses and the returning signals simultaneously using the same pump laser radiation.

[0035] In particular, the selected wavelength difference is not located at the maximum of the Raman spectrum of the core material of the first optical fiber 2. This results in a lower Raman gain. The depletion of the pump laser radiation is reduced, and the Raman amplification remains efficient even at greater distances. Due to the Raman amplification, the length of the second section 4 of the first optical fiber 2 can be up to 200 km, preferably between 50 km and 100 km.

[0036] The signals generated in the first optical fiber 2 travel back to the left in the first optical fiber 2 in Fig. 1 and are coupled out via a coupling device 8, for example designed as a circulator, and fed to an evaluation device 9, which in particular comprises a photodetector. An evaluation device configured to determine the physical quantity to be measured with spatial resolution from the coupled signals is well known and will not be described further below. The evaluation device can, for example, be designed as described in EP 3 139 133 A1.

[0037] The second embodiment of the device shown in Fig. 2 corresponds to the first embodiment shown in Fig. 1 up to the end of the second section 4 of the first optical fiber 2. In contrast to the first embodiment, the second embodiment additionally comprises an active optical fiber 10 and a third section 11 of the first optical fiber 2. The active optical fiber 10 connects to the second section 4 on the side facing away from the first section 3. The third section 11 connects to the active optical fiber 10 on the side facing away from the second section 4.

[0038] The active optical fiber 10 is doped with erbium, so that the pump laser radiation in the active optical fiber 10 amplifies the laser pulses and / or the radiation generated in the first optical fiber 2. Signals are generated. The pump laser radiation with a wavelength in the range between approximately 1,430 nm and approximately 1,500 nm can be absorbed by the erbium ions in the material of the core of the active optical fiber 10 in such a way that a population inversion is achieved with more ions in a higher energy state than in a lower energy state.

[0039] The additional active optical fiber 10 enables effective amplification of the laser pulses and / or signals via the erbium-doped fiber amplifier (EDFA) forming the active optical fiber 10 at the end of the second section 4 of the first optical fiber 2, where the pump laser radiation contributes very little to effective amplification of the laser pulses and / or signals via Raman amplification. The pump power remaining after attenuation by the first two sections 3, 4 of the first optical fiber 2 only needs to be high enough to generate a population inversion, which is typically the case at powers of only a few mW, such as 1 mW to 10 mW.

[0040] The length of the second section 4 of the first optical fiber 3 can be between 10 km and 180 km, in particular between 50 km and 150 km, preferably between 100 km and 130 km. Furthermore, the total length of the first, second, and third sections 3, 4, 1 1 of the first optical fiber 2 can be more than 100 km, in particular more than 150 km, preferably between 150 km and 500 km, for example, about 250 km. The third embodiment of the device shown in Fig. 3 corresponds to the second embodiment of the device shown in Fig. 2, except for the design of the second laser light source 5. In contrast to the second embodiment, in the third embodiment the second laser light source 5 comprises four laser devices 5a, 5b, 5c, 5d. Each of the Laser devices 5a, 5b, 5c, 5d generate a pump laser radiation whose wavelength and / or polarization differs from the wavelengths and / or polarization of the pump laser radiations generated by the other laser devices 5a, 5b, 5c, 5d. The wavelengths are arranged in a range between approximately 1430 nm and approximately 1500 nm. In particular, pumping occurs with two different wavelengths, each with two different, preferably mutually orthogonal, linear polarizations. It is also possible to compose the pump laser radiation from significantly more than four different wavelengths.

[0041] It can also be provided that the pump laser radiation from at least one of the laser devices is coupled into the first optical fiber at a greater distance from the first laser light source than the pump laser radiation from at least one of the second laser devices. In this case, the pump laser radiations from at least one first laser device and at least one second laser device are coupled into different second optical fibers and guided to the coupling devices. This avoids nonlinear effects in the second optical fiber or fibers.

[0042] The device comprises two polarization couplers 12a, 12b and an additional wavelength multiplexer 12c, by which the laser beams emitted from the individual laser devices 5a, 5b, 5c, 5d are coupled to each other before being coupled into the second optical fiber 6. By coupling several laser beams with different wavelengths, significantly higher pump powers can be achieved than with pump lasers that operate at a single wavelength.

[0043] The fourth embodiment of the device shown in Fig. 4 corresponds, except for the connection between the first and the second section 3, 4 of the first optical fiber 2 and except for the coupling out and feeding of the generated signals to the coupling device 9, to the second embodiment of the device shown in Fig. 2.

[0044] In contrast to the second embodiment, in the fourth embodiment the second section 4 of the first optical fiber 2 is connected via a 3-port circulator 13 to both the first section 3 and the second optical fiber 6. A short fiber section 14 and a further wavelength multiplexer 15 are provided between the 3-port circulator 13 and the second optical fiber 6.

[0045] Due to the chosen design, signals returning from the first optical fiber 2 are coupled into the second optical fiber 6 via the short fiber section 14 and the wavelength multiplexer 15 in the second section 4 of the first optical fiber 2. In the second optical fiber 10, the signals travel to the left in Fig. 4 and are coupled out of the second optical fiber 6 at the end facing the second laser light source 5 and fed to the evaluation unit 9 via a further wavelength multiplexer 16.

[0046] The fifth embodiment of the device shown in Fig. 5 corresponds essentially to the fourth embodiment of the device shown in Fig. 4, except for the connection between the first and the second section 3, 4 of the first optical fiber 2 and except for an additional fiber Bragg grating.

[0047] In contrast to the fourth embodiment, the fifth embodiment provides a 4-port circulator 17 instead of the 3-port circulator 13. The 4-port circulator 17 replaces, as in The coupling device provided in the first four embodiments is described in more detail below.

[0048] The second section 4 of the first optical fiber 2 is connected via the 4-port circulator 17 to both the first section 3 and the second optical fiber 5. However, there is an additional connection between the second optical fiber 6 and the 4-port circulator 17, which is established by another fiber section 18.

[0049] The pump laser radiation passes through this further fiber section 18 to the 4-port circulator 17 and is coupled by it into the first section 3 of the first optical fiber 2. In this first section 3, the pump laser radiation travels backwards or to the left in Fig. 5 until it reaches a fiber Bragg grating 19, which is arranged in a region of the first section 3 of the first optical fiber 2 adjacent to the 4-port circulator 17.

[0050] The fiber Bragg grating 19 is designed such that the larger proportion of the pump laser radiation, in particular about 80% of the pump laser radiation, is reflected back to the right in the direction of the 4-port circulator 17, whereas a smaller proportion of the pump laser radiation, in particular about 20% of the pump laser radiation, passes through the fiber Bragg grating 19 to the left in the direction of the first laser light source 1.

[0051] The portion of the pump laser radiation reflected back to the right towards the 4-port circulator 17 is coupled by the 4-port circulator 17 into the second section 4 of the first optical fiber 2. The signals generated in the second and third sections 4, 1 1 of the first optical fiber 2 are transmitted by the 4-port circulator 17 via the short fiber section 14 and The wavelength multiplexer 15 is coupled into the second optical fiber 6.

[0052] In the fifth embodiment, the signals also run to the left in the second optical fiber 5 in Fig. 5 and are coupled out of the second optical fiber 6 at the end facing the second laser light source 5 and fed to the evaluation unit 9 via a further wavelength multiplexer 16.

[0053] Fig. 6 shows a diagram in which the signal power generated by a device according to the invention is plotted logarithmically against the distance in km. The diagram shows that the power 20 of the signal generated by Brillouin scattering decreases exponentially in a first region 21, which corresponds to a linear decrease in the logarithmic representation of Fig. 6. The signals of the first region 21 are generated in the first section 3 of the first optical fiber 2.

[0054] At a distance of approximately 20 km from the first laser light source 1, the signal power in a second region 22 increases due to Raman amplification until it decays exponentially again at the end of the second region. The signals of the second region 22 are generated in the second section 4 of the first optical fiber 2.

[0055] The active optical fiber 10 is located at a distance of 120 km from the first optical fiber. A correspondingly strong increase in signal strength is observed at 120 km, which then transitions into an exponential decay in a third region 23 of the signal. The signals of the third region 23 are generated in the third section 1 1 of the first optical fiber 2.

[0056] Overall, it is shown that a device according to the invention can still generate signals at distances of more than 200 km which can be used for the spatially resolved determination of the physical quantity to be measured.

Claims

Claims: Device for spatially resolved measurement of a physical quantity, comprising a first optical fiber (2) for spatially resolved measurement, a first laser light source (1) for generating laser pulses, wherein the device is configured such that the laser pulses are coupled into the first optical fiber (2), that the laser pulses generate signals usable for measuring the physical quantity in the first optical fiber (2) by backscattering and / or reflection, and that the generated signals are coupled out of the first optical fiber (2), an evaluation device (9) configured to determine the physical quantity to be measured with spatial resolution from the coupled-out signals, a second laser light source (5) for generating a pump-type laser radiation in continuous operation, wherein the device is configured tothat the laser radiation causes an amplification of the laser pulses and / or the signals generated in the first optical fiber (2). Device according to claim 1, characterized in that the device is configured such that the laser pulses in the first optical fiber (2) generate a signal usable for measuring the physical quantity by Brillouin scattering and / or by Rayleigh scattering and / or by reflection at multiple reflection centers, such as fiber Bragg gratings or other distributed reflectors. A device according to claim 1 or 2, characterized in that the physical quantity to be measured is a temperature and / or a strain and / or a vibration and / or an acoustic signal, for example, a dynamically changing temperature and / or a dynamically changing strain. A device according to any one of claims 1 to 3, characterized in that the device is configured to amplify the laser pulses and / or the generated signals by means of a Raman effect.Device according to claim 4, characterized in that the first laser light source (1 ) generates laser pulses with a first wavelength during operation of the device and that the second laser light source (5) generates a pump laser radiation with a second wavelength during operation of the device, wherein the first wavelength is larger than the second wavelength, in particular wherein the magnitude of the wavelength difference between the first and the second wavelength corresponds to possible wavelength shifts in the Raman spectrum of the material of the core of the first optical fiber (2).Device according to one of claims 4 or 5, characterized in that the wavelength difference between the first and the second wavelength is not located in the maximum of the Raman spectrum of the material of the core of the first optical fiber, in particular wherein the distance between the maximum of the Raman spectrum and the wavelength difference between the first and the second wavelength is between 10 nm and 40 nm. Device according to one of claims 1 to 6, characterized in that the device comprises a second optical fiber (6) and a coupling device (7), wherein the second optical fiber (6) is connected to the first optical fiber (2) via the coupling device (7), and wherein the device is configured to couple the pump laser radiation generated by the second laser light source (5) into the second optical fiber (6) and from the second optical fiber (6) into the first optical fiber (2) via the coupling device (7), in particular wherein the coupling device (7) is configured as a wavelength multiplexer or as a multi-port circulator.Device according to claim 7, characterized in that the coupling device (7) is spaced apart from the first laser light source (1), wherein the length of a first section (3) of the first optical fiber (2) from the first laser light source (1) to the coupling device (7) is between 1 km and 100 km, in particular between 5 km and 75 km, preferably between 10 km and 50 km. Device according to any one of claims 1 to 8, characterized in that the first optical fiber (2) has a second section (4) which extends away from the coupling device (7) for coupling the pump laser radiation from the first section (3) of the first optical fiber (2).Device according to one of claims 1 to 9, characterized in that the device comprises at least one active optical fiber (10), which is in particular doped with erbium, wherein the device is arranged to ensure that the pump laser radiation is directed into the at least one active optical fiber. (10) causes an amplification of the laser pulses and / or the signals generated in the first optical fiber (2).

1. Device according to claim 10, characterized in that the device is configured to achieve population inversion in at least one active optical fiber (10) due to a duty cycle of less than 0.1% of the pulsed first laser light source (1), even with low powers of pump laser radiation, wherein in particular the laser pulses have a length in the range of 10 to 1,000 ns and the weak reflected signals have a power between 1 pW and 1,000 pW, preferably wherein the pump laser radiation has a power in the range of 1 mW to 100 mW. 2.Device according to claim 10 or 11, characterized in that at least one active optical fiber (10) connects to the second section (4) of the first optical fiber (2) on the side facing away from the first section (3) of the first optical fiber (2), in particular wherein a third section (11) of the first optical fiber (2) connects to the at least one active optical fiber (10) on the side facing away from the second section (4) of the first optical fiber (2).

3. Device according to claim 12, characterized in that the length of the second section (4) of the first optical fiber (2) from the coupling device (7) for coupling the pump laser radiation to the active optical fiber (10) is between 10 km and 180 km, in particular between 50 km and 150 km, preferably between 100 km and 130 km. Device according to one of claims 12 or 13, characterized in that the total length of the first and the second and at least a third section (3, 4, 1 1 ) of the first optical fiber (2) is more than 100 km, in particular more than 150 km, preferably between 150 km and 500 km, for example about 250 km.Device according to one of claims 1 to 14, characterized in that the second laser light source (5) comprises a plurality of laser devices (5a, 5b, 5c, 5d), wherein at least two of the laser devices (5a, 5b, 5c, 5d) of the second laser light source (5) generate pump laser radiations with different wavelengths and / or polarizations during operation of the device, in particular wherein the device is configured to couple the laser radiations emitted by the individual laser devices (5a, 5b, 5c, 5d) to each other, preferably by wavelength division multiplexing and / or polarization coupling, before they are coupled into the second optical fiber (6).Device according to any one of claims 1 to 15, characterized in that the device is configured to couple signals traveling back in the first optical fiber (2), in particular by means of a circulator encompassed by the device, preferably a multi-port circulator, into the second optical fiber (6), from which they are coupled out and supplied to the evaluation unit (9) for spatially resolved determination of the physical quantity to be measured. Device according to any one of claims 8 to 16, characterized in that the device is configured to transmit signals via... The coupling device (7) is to partially couple the pump p-laser radiation coupled into the first optical fiber (2) into the first section (3) of the first optical fiber (2), in particular wherein the device for this partial coupling of the pump-laser radiation comprises a multi-port circulator and / or a fiber Bragg grating (19).

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