DE10242205B4 - Method and device for spatially extended detection of operating states - Google Patents

Abstract

Method for detecting operating conditions over a spatially extended region, in which radiation is emitted by at least one first radiation source (38) into at least one elongated optical medium (45), by means of a first measuring channel assembly (14) which is emitted by the at least one radiation source (38 ) is detected, and at least two measuring channel assemblies (11, 12) a reflection of a first and a second spectrum from the optical medium (45) is detected, wherein the wavelength of the first and / or second spectrum of the wavelength of the emitted Radiation differs, wherein via at least one further measuring channel assembly (13) a reflection of a third spectrum is detected, wherein the third spectrum substantially corresponds to a Rayleigh backscatter curve, characterized in that the Rayleigh attenuation of the back radiation with the Raman attenuation of the back radiation of first and second Spekt is compared in the same place, wherein the further measuring channel assembly (13) is used to measure a further physical property or size, and wherein a value for force of the optical fiber is detected when all three reflections have a change in attenuation, and a value is detected for a moisture detection when a change in the attenuation of the re-radiation of the emitted radiation is detected at the same location and no significant change in the attenuation of the re-radiation of the first and second spectrum is detected.

Description

The invention relates to a method for detecting operating states over a spatially extended area according to the preamble of claim 1 and to a device for detecting operating states over a spatially extended area according to the preamble of claim 10.

Such methods and devices include the evaluation of optically backscattered signals from an optical fiber.

For such a method and such a device, for. As for the fire monitoring of traffic tunnels, a system and a fiber optic cable is described in the brochure FP 595 eD Siemens Building Technologies AG, Männedorf, CH, where the optical fiber cable described therein has a tube made of a corrosion-resistant steel in which one or more Glass fibers are located, and wherein the tube made of corrosion-resistant steel is provided with a plastic sheath. The plastic sheath serves for the heat conduction of ambient heat to the tube made of corrosion-resistant steel as well as for the absorption of incident radiant heat in order to obtain heating of the tube made of corrosion-resistant steel in the range of thermal radiation.

A method and a device for spatially extended detection of operating states are known from EP 0 692 705 A1 known. In particular, a method and a measuring device for determining a distance-dependent temperature profile along an optical waveguide are described in detail there.

Furthermore, it is off EP 0 692 705 A1 Such a method and such a measuring device with changes to determine a distance-dependent measurement profile for detecting an effect of moisture or forces on the optical waveguide, known.

This is based in the EP 0 692 705 A1 described method for determining temperature on the detection of the intensity of the backscattered light in the spectral Raman band, while the method described there for the measurement of moisture or force from the wavelength selective extraction of Raman, preferably Rayleigh scattered light occurs.

Such a measuring system should consist of an optical transmitter (FMCW laser source), a spectral pre-filtering and a post-filtering, a fiber optic measuring section (optical waveguide) and a two-channel receiver unit, each consisting of a photodiode and a respective HF (high frequency) mixer. The two channels of the receiver unit correspond to the path of the light of the measuring tape and that of the reference band.

Parallel to the mentioned channels runs a reference channel whose light is removed by means of power coupler from the primary beam path and also meets a photodiode and is passed on to the receiver unit. The signals from the three channels then run via an interface in the numerical Weiterverabeitung, preferably in a PC. It consists of the windowing of the measurement signals, a Fast Fourier Transformation (FFT), a signal averaging and the final EDP processing.

Due to their resonator structure, laser sources have a comb-like (longitudinal) mode spectrum. The radiant power is not only guided at the emission wavelength lo (main mode) but distributed to the nearest secondary modes. The position of these extensions falls in the spectral range of the expected Raman scattered light. For this reason, the frequency-modulated laser light prior to coupling into the glass fiber cable with z. B. prefiltered an absorption filter. The backscattered light from the fiber is evaluated or prefiltered with the aid of, for example, two Wavelength Division Multiplexing (WDM) filters such that the spectral components pass at the laser wavelength lo and the Raman scattered light from the Stokes and anti-Stokes lines to the respective one Output is transferred. In the post-filtering, the laser light and the Rayleigh scattered light is suppressed, and in each case only selectively Raman scattered light is transmitted.

The measuring light of the Stokes and Anti-Stokes lines of the Raman scattered light reaches the two light-sensitive diodes. The electrical signals are amplified and mixed with the modulation signal of the laser control in the low-frequency spectral range and transferred via the computer interface to the FFT analyzer.

The spectral band (as measuring band) of the absorption of the hydrogen stored in the backscatter medium and, as a reference band, a spectral band which is as far as possible without influence of the absorption of the stored hydrogen should preferably be used for a moisture measurement. The maximums of the absorption bands of the hydrogen are known and are approximately at 1,240 nm (for example, for the reversible incorporation of hydrogen in quartz) or at 1,390 nm (for example irreversible incorporation). The reference band should be as far away from the absorption bands as possible to minimize its influence.

Preferably, an optical waveguide is used as backscatter medium, which consists of a locally back and forth strand and runs at the end of the measuring section via a loop, so that both strands occupy approximately the same local position. Preferably, one of the strands is hermetically shielded against exposure to moisture, which can be achieved, for example, by placing this strand in a sheath which is impermeable to moisture (eg of stainless steel).

Preferably, for measurement of force, light of a fixed, high wavelength (about 1,550 nm or 1,650 nm) should be used, which is guided as weakly as possible by the backscatter medium and light with a wavelength as strong as possible in the backscatter medium (about 980 nm, 1,064 nm) nm, 1300 nm). In the measuring fiber physically micro bending disturbances are used for the measurement.

The second described method can also be used for temperature measurement with the method steps listed here, wherein temperature-dependent properties, in particular coefficients of expansion of the coating of optical waveguides, are utilized. Temperature-dependent coefficients of expansion cause the temperature-dependent increase or decrease of compressive forces on the optical waveguide, whereby indirectly via the force influence temperature is measurable.

That in the EP 0 692 705 A1 The measuring principle described is also referred to as optical frequency domain reflectometry and abbreviated to OFDR.

Both at the in EP 0 692 705 A1 described in the measurement procedure as well as in the other measuring methods that in the introduction to EP 0 692 705 A1 The measuring principle is based on the exploitation of intrinsic scattering processes of quartz glass fibers, namely the Raman or Brillouin scattering, is the fact that for the measurement of a parameter or a physical size in each case a complete correspondingly adapted measuring system with a corresponding investment cost is required ,

The publication DE 197 54 910 A1 describes a wavelength detector arrangement for detecting the Bragg wavelength of at least one Bragg grating in at least one FBG sensor, in which fiber couplers of each Bragg grating reflected light is guided in each case in two detector channels, in each of which a detector is included. In the 1b For example, one embodiment is directed to a plurality of Bragg gratings from one or more FBG sensors. The detectors of each pair of detector channels have narrow band spectral sensitivities which overlap each other and whose center wavelengths of maximum sensitivity span a wavelength range by the Bragg wavelength of the respective Bragg grating.

A method and a device of the type mentioned are from the US 6,285,446 B1 known. From this document, a fiber-optical sensor is known in which two measuring channel assemblies a back radiation of a Stokes and an anti-Stokes spectrum is detected from the optical medium, which differs in wavelength from the emitted radiation. In a third measuring channel assembly, the reflection of a third spectrum is detected, which corresponds to a Rayleigh backscatter curve.

From the US 5,765,948 A It is known to measure the Rayleigh attenuation, the anti-Stokes and the Stokes-Raman attenuation by means of separate measurement modules and to compare them by normalizing the Raman attenuation signals with the Rayleigh attenuation.

From the EP 0 190 001 A2 It is also known to compare the anti-Stokes Raman attenuation with the Rayleigh attenuation.

The invention is therefore based on the object of developing methods and devices of the type mentioned in such a way that the field of application of such methods and devices is extended and can be used in particular in terms of improved efficiency in other areas.

This object is achieved by a method for detecting operating conditions of the type mentioned above with the characterizing features of claim 1 and by a device for detecting operating conditions of the type mentioned above with the characterizing features of claim 10. The subclaims relate to preferred embodiments of the invention.

According to claim 1 it is provided that the Rayleigh attenuation of the return radiation is compared with the Raman attenuation of the re-radiation of the first and second spectrum at the same location, wherein the further measurement channel assembly is used to measure a further physical property or quantity, and wherein a value for a force load of the optical waveguide is detected when all three reflections have a change in attenuation, and a value for a humidity detection is detected if a change in the attenuation of the re-radiation of the emitted radiation is detected at the same location and no significant change in the attenuation of the reverberation of the first and second spectrum is detected. According to Claim 10 is provided that the device is designed such that the Rayleigh attenuation of the return radiation can be compared with the Raman attenuation of the re-radiation of the first and second spectrum at the same location, wherein the further measurement channel assembly can be used for a further physical Property or size can be measured, and wherein a value for a force load of the optical waveguide can be detected when all three reflections have a change in attenuation, and a value for a moisture detection can be detected, if at the same location a change in the attenuation of the reflection of the emitted radiation is detected and no significant change in the attenuation of the reflectance of the first and second spectrum is detected.

The development according to the invention makes it possible to substantially improve the accuracy and long-term stability of such a measuring system and method without requiring additional measuring infrastructure in the object to be monitored. The improvement can be achieved with the known fiber optic cables, even using those that are already laid.

Thereby, the scope of such a measurement method and system is extended with regard to applications in which z. B. for process monitoring a higher measurement accuracy and in particular a higher accuracy of the detected absolute values are required. Such applications may be in chemical plant engineering, especially in the petrochemical industry, where thermally out-of-control processes or resulting fires can have disastrous consequences.

Furthermore, it is possible by the construction according to the invention to also detect a plurality of physical variables with a single measuring system and thus without significant additional costs.

In a particularly preferred embodiment of the method and the device, it is provided to provide a device with which a plurality of optical waveguides, in particular temporally successively, can be connected to the evaluation device of the device.

This not only makes it possible to monitor and diagnose complex systems, such as As in the off-shore area in the oil and gas extraction, production and transport, but also in other high-tech objects, such as aircraft, and particularly safety-critical large structures, such as dams or traffic tunnels that cross geological fault lines, much more efficient, longer and can be operated more safely.

The inventive construction, it is possible to capture complex state variables of a technical object with the aid of fiber optic sensors with low equipment and evaluation effort, evaluate with little effort and clearly presented.

In a further development according to the invention of a measuring method and a device of the type mentioned in the introduction, the measuring device and the method are characterized in that an optical waveguide is provided which has so-called fiber grating sensor at one or more points, d. H. Optical grating, which are introduced, for example, by laser engraving in the optical waveguide, and preferably comprises one or more wavelength detectors, for example, a wavelength detector SSO-WS-7.56-TO5i Fa. SILICON Sensor GmbH, or a holographic grating with CCD line.

In particular, when using a plurality of such fiber grating sensor, it is particularly useful to provide these grids with different lattice spacings.

By changing the wavelength irradiated into the fiber, it is possible to "address" the individual fiber grating sensor and to obtain a very precise information about the actual temperature prevailing at the location of the respective fiber grating sensor via a temperature-induced change in the known grid spacing.

The inventive construction, it is possible to make a recalibration without the hitherto considered necessary high equipment cost for a second reference measuring system an occasional review of the normal temperature measurement to compensate with the tolerances in glass fiber production but also in particular aging processes of the glass fiber and environmental influences. Particularly advantageous embodiment of the invention in such applications in which the normal optical fiber is not or only with difficulty accessible and therefore a recalibration in a conventional way by checking the actual temperature at certain reference points with a separate reference measuring system is not possible.

Due to the formation of the invention, it is not only possible to make a recalibration where the optical fiber is difficult to access, but by eliminating the capital outlay for a separate reference measuring system, the useful life of a measuring system of the type mentioned can be significantly extended and thus the economy in the commitment in the long term, even where the expense of recalibration has been waived for cost reasons.

A preferred embodiment of the method according to the invention for designing a cost-effective moisture and / or force measurement is characterized in that the attenuation of the return radiation at an emitted wavelength of at least one radiation source of about 1240 nm and / or about 1390 nm on the at least one further measuring channel assembly detected In particular, if at least two measuring channel assemblies, a back radiation of a first and a second spectrum is detected from the optical medium, wherein the wavelength of the first and / or second spectrum of the wavelength of the emitted radiation by about 65 to 75 nm, preferably differs by 70 nm, to a higher and / or a lower wavelength.

According to the invention, the Rayleigh attenuation of the return radiation is compared with the Raman attenuation of the re-radiation of the first and second spectrum at the same location, wherein a value for a force load of the optical waveguide is detected when all three reverberations have a change in attenuation, and a value for a moisture detection is detected if a change in the attenuation of the reflected radiation of the emitted radiation is detected at the same location and no significant change in the attenuation of the reflection of the first and second spectrum is detected, in particular if an additional optical waveguide for measuring moisture is provided.

For the detection of an elongation of the optical waveguide, it is particularly advantageous if the method and the device is characterized in that there is further provided a further radiation source, preferably in the form of an additional laser, of the optical radiation in the elongated optical medium opposite Direction of the radiation emitted by the first radiation source, and providing a spectrum analyzer connected to the first and the further radiation source for determining a frequency difference between the radiation of the first and the further radiation source, in particular when detecting the Brillouin amplification spectrum and the Brillouin-Stokes Frequency.

This is particularly true if the method is further characterized by the step of correlating the detected effect of Brillouin scattering with a temperature measurement due to Raman scattering to determine a local strain profile along the optical medium.

The invention can be used particularly economically with a sensor cable for use with a method according to the invention and / or a device according to the invention if the sensor cable has a plurality of optical waveguides, of which at least one is suitable for determining moisture and / or force as described above, and / or if the sensor cable has a plurality of optical waveguides, of which at least one is suitable for determining temperature by a method described above and at least one further optical waveguide for determining an elongation by a method mentioned above, in particular in an optical waveguide with a plurality of fiber grating sensors.

The invention will be explained in more detail with reference to embodiments illustrated in FIGS. Show it:

1 a schematic diagram of a structure of a device according to the invention,

2 a schematic representation of an alternative construction of a device according to the invention,

3 a cross-sectional view through a power cable with sensor cable elements;

4 a cross-sectional view through another sensor cable; and

5 a cross-sectional view through another sensor cable for example, integration in a power cable according to 3 ,

According to the current state of technological development, a wide variety of optical and fiber optic sensors exist. In many cases, locally distributed measuring systems have proved to be suitable for use on extended measuring objects for technical and economic reasons. Locally distributed measuring systems are those in which physical parameters are not detected at individual discrete locations, in particular by individual sensors, but over extended sensors continuously along the sensor. For this purpose, in particular the use of optical waveguides (fiber optic cables) is known and expedient, in which certain sizes can be detected as a function of, for example, the glass fiber length. This technique thus enables seamless measurement over many kilometers with a local resolution of less than one meter. The costs per cell are considerably lower compared to conventional sensor networks with point-measuring sensors.

Commercially, two measuring systems with locally distributed sensors are currently being used either based on Raman scattering for localized temperature measurement or Brillouin scattering, which can be used for both distributed temperature measurement and distributed strain sensor. Starting point for a construction according to the invention is one of EP 0 692 705 A1 known structure of an OFDR Raman temperature measuring system.

The measuring system consists of an evaluation unit, sometimes also referred to as optical radar, and an optical fiber cable as a linear temperature sensor. The optical radar works with laser light, which is coupled into the sensor cable. By thermal molecular vibrations of the optical waveguide material results in a scattering of the laser light with inelastic properties, the Raman scattering. In order to be able to determine this temperature-dependent light scattering along the fiber at each location, an OFDR method is reproduced EP 0 692 705 A1 used. Optionally, a computer can be used to parameterize and configure the measuring system and visually display the evaluation of the measured data.

The peculiarity of the OFDR Raman temperature method is that the local temperature profile along the optical waveguide results from the calculation of the Fourier transform of the Raman scattered light backscattered on the fiber. The amplitudes of the resulting Raman backscatter curves are proportional to the Raman scattering intensity of the considered spatial element. After correcting the attenuation dependence of the glass fiber, the fiber temperature along the sensor cable is obtained from the amplitude ratio of the Stokes measuring channel and the Antistokes measuring channel.

Significant advantages of the known OFDR technique are the practically continuous operation of the laser source and the narrow-band detection of the optical backscatter signal. This technical advantage allows the use of inexpensive semiconductor laser diodes and the use of inexpensive electronic modules for signal processing.

An example of the structure of an OFDR evaluation device according to the present invention is shown in FIG 1 shown. The illustrated measuring device essentially comprises four main assemblies: a power supply 1 , a signal processor module 2 , a laser module 3 that the laser source is in the form of a laser diode 38 and the electronics required to drive them, as well as the measuring channel assemblies 11 . 12 . 13 , and 14 , The measuring channel modules 11 and 12 include in a known manner two measuring channels and a reference channel with the measuring channel assembly 14 for detecting the spectral position of the laser source 38 or in the optical fiber 45 radiated signal. Potential-free inputs and outputs 5 and 6 as well as connections for data communication 7 serve for the integration of peripheral devices, a status display 8th for the information of a user.

Each of the measuring channel assemblies 11 to 14 is realized by an assembly comprising corresponding photodetectors, optical filters and electronic components, as well as an internal temperature reference and preferably means for selectively connecting a plurality of at the terminals 18 to 23 connectable light waveguides 45 with one or more measuring channel modules 11 to 13 in the form of a so-called fiber optic switch 17 , The fiber optic switch 17 enables efficient fiber optic connection of the measurement channel assemblies 11 to 13 with optical fibers 45 as sensor fibers.

By means of software control, the optical switch 17 activated and the temperature profile of the sensor fibers 45 be determined in chronological order. The measuring time of the device is mainly determined by the set range, the local resolution (the number of measuring points over the sensor length) and the temperature accuracy of the device. In the case of a realized device, the measurement number is about 1,000 measurement points, a local resolution of the sensor of one meter and a temperature accuracy of ± 1 K per optical fiber 45 between 10 and 20 seconds.

Typically in the measuring channel assemblies 11 and 12 used optical filter 34 . 35 have a pass-through curve according to a Gaussian function while the filter 37 for the reference channel (measuring channel module 14 ) is substantially optimized for side channel rejection.

For the invention provided additional measuring channel assembly 13 For the Störgrößenerfassung invention also a filter with optimization on side suppression (Rayleigh 36 ) are provided to detect interference by the interspersed light, for example, by the reflection at the end of the optical waveguide 45 , in particular plug and fresnel reflections arise.

For the use of the present invention additional measuring channel assembly 13 For the recalibration, it may be appropriate to provide a filter with a ramp characteristic or a comb filter in order to decrease a frequency range via a temperature variation of the laser light source 38 by comparison with the amplitude of the measuring channel assembly 13 to obtain a detection of the wavelength of the incident light in a ramp filter or by counting the traversed maximum comb filter. One or more wavelength detectors can also be used to detect the wavelength of the emitted radiation, for example a wavelength detector SSO-WS-7.56-TO5i from SILICON Sensor GmbH, or else a holographic grating with a CCD line.

For measuring an elongation of an optical fiber 45 or a fiber bundle, the Brillouin scattering can be used for the already prescribed temperature measurement. The Brillouin scattering is a light scattering on acoustic waves. By acoustic waves on the fiber 45 An optical grating is generated in the atomic structure of the quartz circular fiber. Due to the finite group velocity of the acoustic waves along the fiber 45 This causes the backscattered wave of the incident pumping light source 38 has a lower frequency. The frequency difference between the pump and Stokes wave corresponds to the frequency of the acoustic wave and is referred to as the Brillouin-Stokes frequency, and through a spectrum analyzer 44 detected. The superimposition of the Stokes and the pump wave creates an interaction between the two waves, which leads to an electrostrictive effect and to the excitation of new acoustic waves in the fiber. These in turn cause an increase in the Stokes wave and a further increase in backscatter. From a certain threshold power of the pump wave, this process grows like an avalanche. It comes to stimulated Brillouin scattering with a (lorenzförmigen) spectral gain profile. The frequency position of the maximum of the gain spectrum is temperature and strain dependent. In principle, therefore, it can not be distinguished by measuring only the Brillouin scattering whether the measured change is due to a temperature or strain change.

The Brillouin gain spectrum and thus the Brillouin-Stokes frequency can be spatially resolved along the fiber by optical reflectometry 45 be measured.

The ambiguity of the detected effect of the Brillouin scattering can be canceled out by the correlation with a temperature measurement due to the Raman scattering, so that a spatially distributed measurement of temperature and strain is simultaneously possible by the combined device according to the invention. By integrating in a single measuring system, this can be realized much cheaper than with conventional systems.

This can be done in 1 described device to be extended, as in 2 is described. In this case, the device has an additional laser light source 40 on and a fiberglass 45 is at the connections 18 and 22 of the fiber optic switch 17 connected.

3 shows a cross section through a high voltage power cable with multiple optical fibers 45 for condition monitoring of the cable. The overhead line comprises a central tube 55 in which of a thermally conductive gel filler 51 embedded three optical fibers 54 . 52 . 59 are arranged. The central tube 55 is through the rope veins 58 surrounded, in turn, in a filler 53 embedded by an outer jacket 56 are surrounded.

It is on the top of the overhead line, the introduction of a glass fiber 50 intended for pressure measurement, via which the sag of the overhead line cable can be detected. In the area of the lower periphery is an optical fiber 57 provided with a moisture-permeable jacket over which the moisture load of the cable can be detected. In the core of the overhead cable, ideally, there are three optical fibers 54 . 52 and 59 one of which is for measuring temperature, strain and a reference measurement for recalibration. About the temperature measurement can be deduced on the current load of the cable, the results of the moisture and strain measurement conclusions on a mechanical load on the cable, z. B. by Eisbehang. About the strain measurement can be in particular an age-related extension of the cable recognize, in the loss of elasticity, the risk of cable breakage at impact load, z. B. severe storm gusts, or the risk of touching ground or trees, etc. exists.

Claims (18)

Method for detecting operating conditions over a spatially extended area, in which at least one first radiation source ( 38 ) radiation into at least one elongate optical medium ( 45 ) is transmitted by means of a first measuring channel assembly ( 14 ) from the at least one radiation source ( 38 ) emitted radiation, and via at least two measuring channel assemblies ( 11 . 12 ) a re-radiation of a first and a second spectrum from the optical medium ( 45 ), wherein the wavelength of the first and / or second spectrum differs from the wavelength of the emitted radiation, whereby at least one further measuring channel module ( 13 ) a third spectrum is detected, the third spectrum substantially corresponding to a Rayleigh backscatter curve, characterized in that the Rayleigh attenuation of the return radiation is compared with the Raman attenuation of the re-radiation of the first and second spectrum at the same location, the further measurement channel assembly ( 13 ) is used to measure another physical property or quantity, and a value for force of the optical fiber is detected when all three reflections have a change in attenuation, and a value for humidity detection is detected when at the same location a change of the Damping of the re-radiation of the emitted radiation is detected and no significant change in the attenuation of the reflection of the first and second spectrum is detected. Method according to claim 1, characterized in that at least one first radiation source ( 38 ) optical radiation in at least one connectable elongate optical medium in the form of an optical waveguide ( 45 ) having at one or more points over its longitudinal extent one or more so-called fiber grating sensors known lattice constant, and wherein the wavelength of the radiation from the first radiation source ( 38 ) and a signal is detected, wherein the wavelength of the detected signal associated with one or more reflection maxima of the fiber grating sensors and compared with a predetermined output value, wherein the displacement of the detected wavelength of a reflection maximum to the associated predetermined output value converted into a temperature information which is assigned to the position of the respective fiber grating sensor. Method according to one of claims 1 or 2, characterized in that the attenuation of the return radiation at an emitted wavelength of the at least one radiation source ( 38 ) of about 1240 nm and / or about 1390 nm via the at least one further measuring channel module ( 13 ) is detected. The method of claim 3, wherein the wavelength of the first and / or second spectrum differs from the wavelength of the emitted radiation by 65 to 75 nm at a higher and / or a lower wavelength. A method according to claim 2, characterized in that a plurality of fiber grating sensors each have different lattice constants. Method according to one of the preceding claims, characterized in that an additional optical waveguide ( 57 ) is intended for moisture measurement. Method according to one of the preceding claims, characterized in that furthermore a further radiation source ( 40 ) from the optical radiation into the elongated optical medium ( 45 ) against the direction of that of the first radiation source ( 38 ) emitted radiation, and providing one with the first and the further radiation source ( 40 ) spectrum analyzer ( 44 ) for determining a frequency difference between the radiation of the first and the further radiation source ( 38 . 40 ). The method of claim 1, further characterized by detecting the Brillouin gain spectrum and the Brillouin-Stokes frequency. The method of claim 8 further characterized by the step of correlating the detected effect of Brillouin scattering with a temperature measurement due to Raman scattering to determine a local strain profile along the optical medium ( 45 ). Device for detecting operating conditions over a spatially extended area, comprising at least one radiation source ( 38 ) for emitting an optical radiation, at least one elongate optical medium ( 45 ), a measuring channel assembly ( 14 ) for detecting the from the at least one radiation source ( 38 ) emitted radiation, and at least two measuring channel assemblies ( 11 . 12 ) for detecting the reflection of a first and a second spectrum from the optical medium ( 45 ), wherein the wavelength of the first and / or second spectrum differs from the wavelength of the emitted radiation, the device comprising at least one further measuring channel assembly ( 13 ) for detecting back radiation of a third spectrum, wherein the third spectrum substantially corresponds to a Rayleigh backscatter curve, characterized in that the device is designed such that the Rayleigh attenuation of the back radiation with the Raman attenuation of the back radiation of the first and second Spectrum can be compared at the same location, with the other measurement channel assembly ( 13 ) can be used to measure another physical property or quantity, and a value of force of the optical fiber can be detected when all three reflections have a change in attenuation and a value for moisture detection can be detected when in the same location a change in the attenuation of the re-radiation of the emitted radiation is detected and no significant change in the attenuation of the re-radiation of the first and second spectrum is detected. Device according to claim 10, characterized by a device ( 17 ) optional Connection of a plurality of optical waveguides ( 45 ) with one or more measuring channel assemblies ( 11 . 12 . 13 ). Device according to claim 11, characterized in that the device ( 17 ) for a temporally successive connection of the optical waveguides ( 45 ) with one or more measuring channel assemblies ( 11 . 12 . 13 ) is designed. Device according to one of claims 11 or 12, characterized in that the optical waveguide ( 45 ) has at one or more points over its longitudinal extent one or more so-called fiber grating sensors. Apparatus according to claim 13, characterized in that it comprises one or more wavelength detectors. Apparatus according to claim 13, characterized in that the one or more fiber grating sensors having optical waveguide is an additional optical waveguide. Device according to one of claims 13 or 15, characterized in that a plurality of fiber grating sensors each have different lattice constants. Device according to one of claims 10 to 16, characterized in that an additional optical waveguide ( 57 ) is intended for moisture measurement. Device according to one of the preceding claims 10 to 17, characterized in that further comprises a further radiation source ( 40 ) from the optical radiation into the elongated optical medium ( 45 ) against the direction of that of the first radiation source ( 38 ) emitted radiation, and providing one with the first and the further radiation source ( 40 ) spectrum analyzer ( 44 ) for determining a frequency difference between the radiation of the first and the further radiation source ( 38 . 40 ).

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