DE102009013795A1 - Measuring device, particularly optical measuring device, for detecting mechanical stress for detecting mechanical stress, has light source designed to emit variable optical primary radiation in wavelength - Google Patents

Abstract

The measuring device (100) has a light source (101) designed to emit a variable optical primary radiation (407) in a wavelength. The sensor elements (301,302,303) are connected to the mechanical stress (409). An optical transmission device (200) is designed to transfer the radiation emitted from the light source. An independent claim is also included for a measuring method for detecting a mechanical stress.

Description

TECHNICAL AREA

The The present invention relates to a measuring device for detection of mechanical parameters such as for example, forces, mechanical stresses, strains, etc. In particular, the concerns The present invention relates to an optical measuring device based on optical waveguides and a corresponding fiber optic measuring method.

In In many fields of technology, fiber optic sensors are far reaching common application. Advantages of optical sensors are u. a. in the non-galvanic connection between measuring device and Measuring object, a high measuring speed, a high spatial and temporal resolution and a noise immunity. Optical primary radiation emitted by a light source is applied to a sensor element modified, wherein the modified optical primary radiation as optical secondary radiation detectable and analyzable.

such Sensors for mechanical sizes are increasingly miniaturized designed, and also a large number be queried on sensors at the same time. Let such multi-sensor systems in particular by the use of optical fibers as Use optical propagation medium efficiently.

STATE OF THE ART

to Capture of mechanical variables such as Strains are typically used for strain gages, which are applied to the test object to be examined by means of adhesive. Such strain gauges are made of ohms, for example Resistive materials provided by semiconductors or constantan films, being the outside measurable electrical resistance of such strain gauges changes with the mechanical strain acting on the strain gauge.

One optical equivalent to the resistance strain gauges described above imprinted in optical waveguides or inscribed fiber Bragg gratings. In this case, light is in an optical waveguide or an optical fiber coupled, at at least one local location such a fiber Bragg grating having.

Usually an optical interference effect arises in the fiber Bragg grating in that a refractive index variation of the optical waveguide core in the area of the fiber Bragg grating is periodically modulated. Such period or period length (modulation length) is dependent mechanical strain of the optical fiber, for example, along its axis. Becomes a period length of a such refractive index modulation varies, therefore, also a filter function of the fiber Bragg grating changed.

Out a spectrum of the light reflected at the fiber Bragg grating or the transmitted through the fiber Bragg grating light can be on an elongation of the optical fiber in the fiber Bragg grating draw conclusions.

A such spectral sampling at the output of the optical fiber, d. H. after a reflection or after a transmission or through the fiber Bragg grating is disadvantageously time consuming and complicated. D. h., A spectral analysis of the reflected or transmitted light requires either a spectroscopic Arrangement or a scan of the detected light as a function the wavelength. Furthermore, on a fiber Bragg grating only a small part of the incident light power reflects or becomes the incident light power, in the case of transmission, changed only slightly by the fiber Bragg grating.

hereby there is the disadvantage of conventional, on fiber Bragg gratings based optical measuring systems characterized by having a high primary light output must be provided, with only small intensity changes Detectable in the reflected or transmitted secondary light output are.

If In addition, several fiber Bragg gratings with different center wavelength, the are arranged along an optical fiber, by a single Primary light source to be addressed, this primary light source must have a sufficiently uniform spectral Intensity over one wide wavelength range exhibit. Such light sources are complex and therefore disadvantageous Way expensive.

Further is the evaluation page extremely expensive because a spectral analysis of the reflected at one or more fiber Bragg gratings Light or the light transmitted through these are made got to. Such, for conventional fiber-optic sensors required spectral analysis unit leads in disadvantageous Way to a complex measuring system, which is prone to failure.

PRESENTATION OF THE INVENTION

The object of the present invention is to provide an improved fiber optic sensor for measuring forces and mechanical stresses. He will do this task According to the invention solved by an optical measuring device for detecting a mechanical stress with the features of claim 1.

Further The above object is achieved by a in the independent claim 12 specified method solved.

Further Embodiments of the invention will become apparent from the dependent claims.

One The essential idea of the invention is a light source to be provided, which is designed to send a in the wavelength rapidly variable optical primary radiation. With such an optical primary radiation, the filter function the sensor element, for example a fiber Bragg grating, with scanned at high speed, with an optical detector that at the sensor element reflected primary light or through the sensor element transmitted primary light detected.

In Advantageously, the optical detector can be used as a simple Photodiode without spectral resolution the detected wavelength range designed be. The optical detector is in particular for detecting a optical secondary radiation from the sensor element in dependence from the irradiated optical primary radiation and the mechanical Voltage designed.

On this way you can advantageous forces, moments, mechanical stresses, etc. recorded in high temporal resolution become. Variations of, for example, a light source intensity or otherwise Parameters of the optical measuring device can be eliminated by the fast sampling or at least greatly reduced. Further, in size and direction rapidly varying forces, Strains, compressions, etc. due to the high sampling rate efficient be recorded.

The The present invention provides an optical measuring device for detection at least one mechanical tension ready. The optical measuring device comprises a light source which is designed to emit a in the wavelength variable optical primary radiation, and at least one sensor element having the mechanical stress can be acted upon.

A optical transmission device is designed for transmission the emitted from the light source, variable in wavelength optical primary radiation towards the sensor element. An optical detector is designed for Detecting at least one optical secondary radiation from the sensor element dependent on from the irradiated optical primary radiation and the mechanical Tension. One operationally with the signal detector connected to the optical detector is used to determine the mechanical stress due to the detected optical secondary radiation.

Prefers is the optical detector over an optical coupler unit optically coupled to the transmission device. In this way it is possible to efficiently receive a secondary radiation reflected from the sensor element.

In Advantageously, the light source, which is designed for Emitting one in the wavelength variable optical primary radiation, one in the wavelength tunable laser.

Of the in the wavelength Tunable laser is advantageous as a monolithically tunable Laser diode provided. Such a modulated tunable Laser diode advantageously has a reflector control for the variation of the wavelength dependent on of at least one supplied Control power on.

One Such control current is provided by a current control unit incorporated in the optical measuring device is provided generates.

The with the at least one mechanical stress acted upon sensor element is advantageously one of the group of a fiber Bragg grating, a Fabry-Perot interferometer and a thin-layer interferometer.

Preferably is the optical transmission device provided as an optical fiber. Such an optical waveguide can be a circular or a non-circular Have cross-section. In a preferred embodiment, the optical transmission device provided as a fiber optic line.

Preferably is the optical transmission device formed integrally with the sensor element. The sensor element can in an efficient manner in the optical transmission device by means of UV laser radiation are written such that refractive index variations required for measurement be provided in the region of the sensor element.

According to a further preferred embodiment, the optical measuring device further comprises a reference detector which is designed to detect a reference signal dependent on a radiation intensity of the optical primary radiation. In this way it is possible to monitor a radiation intensity of the primary light source. For this purpose, a reference signal processing is processing device, which is designed for processing the reference signal and for a corresponding control of the radiation intensity of the primary light source.

Preferred dimensions can the optical measuring device comprise a sensor device, which has at least two sensor elements. The at least two sensor elements advantageously have different wavelength response ranges from each other on, such that from the sensor elements outgoing, reflected or transmitted secondary radiation is distinguishable. The at least two sensor elements are more advantageous Way along a single optical fiber einprägbar.

According to one further preferred embodiment of the present invention has the optical measuring device further comprises a transit time detection device for determining a location of a sensor element along the optical transmission device or of the optical waveguide.

The The present invention further relates to a measuring method for measuring a mechanical stress, wherein an optical waveguide with at least one optical sensor element having a wavelength response range is provided. Furthermore, an optical primary radiation irradiated in the optical waveguide, wherein the optical sensor element is subjected to the mechanical stress. Finally, at least an optical secondary radiation from the optical waveguide depending on the irradiated optical primary radiation and the mechanical stress is detected, the primary optical radiation while of irradiation within the wavelength response range in the wavelength is varied. The method preferably detects an optical secondary radiation, which is a part of the optical reflected on the optical sensor element primary radiation equivalent.

According to one another preferred embodiment the at least one optical secondary radiation corresponds to a part of the optical sensor element transmitted optical primary radiation. Thus lets advantageously a transmission spectrum of the optical Sensor element, which by the mechanical stress on the sensor element varies, capture.

In a further preferred embodiment becomes the optical secondary radiation in the wavelength dissolved.

In Yet another preferred embodiment, the optical Primary radiation over one Tuned wavelength tuning range, which is bigger as a half width of a filter function of the at least one optical sensor element.

Preferably Tuning of the wavelength of the optical primary radiation over the half-width the filter function of the at least one optical sensor element in a period of time in a range of 10 ns to 150 ns, preferably in a time range of 100 ns (nanoseconds).

The at least one optical sensor element can be by means of UV (ultraviolet) laser radiation in the optical transmission device memorize. Thus, the optical transmission device is preferred formed integrally with one or more sensor elements.

Preferably At least two sensor elements are connected in series by means of a via transmitted optical transmission device optical primary radiation addressed.

In Advantageously, the at the at least two optical sensor elements reflected primary optical radiation by means of different wavelength response ranges of at least two optical sensor elements distinguishable from each other.

According to one another preferred embodiment includes the measuring method according to the invention a distinction from the at least two sensor elements transmitted optical primary radiation by means of different wavelength response ranges of at least two Sensor elements.

According to one another preferred embodiment of the present invention are from the at least two optical Sensor elements emitted secondary optical radiation by means of different Running times between corresponding sensor element and associated transmitting / receiving unit distinguishable from each other.

BRIEF DESCRIPTION OF THE DRAWINGS

embodiments The invention is illustrated in the drawings and in the following Description closer explained.

In show the drawings:

1 a schematic block diagram of an optical measuring device comprising an interrogator, an optical transmission device and a sensor device;

2 a section of an optical waveguide with a sensor element for viewing tion of the measuring method, according to a preferred embodiment;

3 a filter function of a fiber Bragg grating in reflection mode, ie a graph of reflection intensity as a function of wavelength;

4 a block diagram of a fiber optic measuring device with a built-in optical transmission device coupler unit, according to a preferred embodiment;

5 a schematic structure of a laser light source, which is designed to vary a wavelength of emitted laser light via reflector controls;

6 a block diagram of a fiber optic measuring device according to a preferred embodiment;

7 a block diagram of a control device for a laser light source for in 6 illustrated optical measuring device, according to a preferred embodiment;

8th a block diagram of a fiber optic measuring device according to a preferred embodiment, wherein in addition to the in 6 illustrated measuring system, a reference detector and a reference signal processing means are provided for detecting a reference signal, according to a further preferred embodiment;

9 a block diagram for illustrating a query of a plurality of sensor elements arranged in the sensor device by the interrogator device by means of a transit time method; and

10 a flow chart illustrating an optical measuring method for measuring a mechanical stress, according to a preferred embodiment of the present invention.

In In the drawings, like reference characters designate the same or the same function Components or steps.

WAYS TO PERFORM THE INVENTION

in the Below are embodiments of the present invention described in more detail.

It is a measuring device for detecting at least one mechanical Voltage provided, which is a light source, at least one Sensor element, an optical transmission device and includes an optical detector. One from the light source emitted optical primary radiation is during an irradiation within a wavelength response range of the sensor element varied.

1 shows an optical measuring device 100 which consists of three subunits, ie an interrogator device 105 , in which essentially transmit, receive and evaluation components are included, an optical transmission device 200 for transmitting optical radiation and a sensor device 300 for the detection of mechanical stresses 409 , The sensor device 300 has at least one sensor element 301 on, which with the measured mechanical stress 409 can be acted upon.

In the in 1 shown sensor device 300 are three sensor elements, ie a first sensor element 301 , a second sensor element 302 and an nth sensor element 303 shown. It should be noted here that a plurality of sensor elements in a number n in the sensor device 300 can be provided.

The optical measuring device 100 has electronic components that are essentially in the Interrogatoreinrichtung 105 are included. The remaining components, ie the transmission device 200 and the sensor device 300 , operate on an optical basis, ie light, which is in the transmission device 200 is irradiated, becomes the sensor device 300 or the sensor elements 301 . 302 . 303 passed on and is there by the mechanical tension 409 changed before it is redirected.

That from the sensor elements 301 . 302 . 303 emitted, changed primary light is thus transmitted through the transmission device 200 back to the interrogator device 105 directed. The mechanical tension 409 pointing to a sensor element 301 . 302 . 303 is below with reference to 2 explained in more detail.

Although this in 1 is not shown, it should be noted that the optical transmission device 200 is not limited to a single optical waveguide, that is, it can be provided two or more optical waveguides. Below, for example, with reference to 4 described that a single optical fiber to a sensor element 301 is advantageous when an optical coupler unit is used.

In the following, the interrogator device 105 to query the in the sensor elements 301 . 302 . 303 the sensor device 300 modified primary light described in more detail. The interrogator Facility 105 has a light source 101 on which an optical primary radiation 407 to the input of the optical transmission device 200 sending out. From the optical transmission device, for example from the sensor elements 301 . 302 . 303 Reflected primary light is from the transmission device 200 as an optical secondary radiation 408 output and from an optical detector 102 detected.

A central control device 103 controls the optical light source 101 and the optical detector 102 , The optical detector 102 For example, according to a preferred embodiment of the present invention, it may be provided as a simple photodiode for light intensity measurement. In this way, a fast optical data acquisition is possible. The optical light source, which may be provided as a laser according to a preferred embodiment, will be described below with reference to FIG 5 described in more detail. So serves the controller 103 including a control of the emission wavelength of the light source 101 ,

The control device 103 is within the interrogator device 105 with an input-output unit 104 connected, over which one of the mechanical tension 409 corresponding measurement signal 406 can be issued or via which control commands 410 can be entered.

The interrogator device 105 further comprises a transit time detection device 113 on, which with the control device 103 interacts. The transit time acquisition device 113 serves to detect a transit time of a light signal from the interrogator 105 to an individual sensor element 301 . 302 . 303 and back to determine a location position of the individual sensor element over a transit time measurement. The time-of-flight measurement method will be described below with reference to FIG 9 explained in more detail.

A Such term acquisition is particularly advantageous if the optical primary radiation is pulsed and / or if a phase relationship between light waves of optical primary radiation and secondary optical radiation is determinable.

The optical transmission device 200 for transmitting optical radiation between the interrogator device 105 and the sensor device 300 is provided as an optical waveguide according to a preferred embodiment of the present invention. It should be noted here that the optical waveguide 200 which, as described below, comprises the at least one sensor element 301 . 302 . 303 may include, but is not limited to, an optical waveguide having a circular cross-section.

An optical transmission device designed as an optical waveguide 200 Rather, it may have any cross section, such as an elliptical cross section, a rectangular cross section, a triangular cross section, etc.

According to a preferred embodiment of the present invention, the optical transmission device 200 individually or the optical transmission device 200 together with at least one sensor element 301 . 302 . 303 as an optical fiber, preferably an optical fiber. Furthermore, it is possible to provide the optical transmission device with or without sensor element as a polymer optical waveguide.

The at least one sensor element 301 . 302 . 303 that the sensor device 300 is at least one of the group of a fiber Bragg grating, a Fabry-Perot interferometer and a thin-layer interferometer. Such optical measuring devices are known to those skilled in the art, so that in order to avoid a redundant description, such optical sensor elements will not be discussed in more detail here. Furthermore, it is possible to use the optical transmission device 200 as mentioned, integral with at least one optical sensor element 301 . 302 . 303 train.

Thus, the optical waveguide, which is the optical transmission device 200 forms, at the same time carrier of the at least one sensor element 301 . 302 . 303 as it is in 2 is shown, and transmission means.

Is now more than one sensor element 301 . 302 . 303 in the optical waveguide 200 integrated, can be at the at least two optical sensor elements 301 . 302 . 303 reflected primary optical radiation by means of different wavelength response ranges 706 (please refer 3 ) differ from each other.

Furthermore, although it is possible in 1 not shown is radiation through the sensor elements 301 . 302 . 303 is transmitted, in which case the through the sensor elements 301 . 302 . 303 transmitted optical primary radiation by means of different wavelength response ranges 706 (please refer 3 ) of the at least two optical sensor elements 301 . 302 . 303 distinguishable from each other.

2 shows a portion of an optical waveguide 304 which is a sensor element designed as a fiber Bragg grating 301 includes. It should be noted here that the optical waveguide 304 the optical transmission supply device 200 can correspond, ie that it is possible, the sensor element 301 integral with the optical transmission device 200 (please refer 1 ) train. As indicated by a double arrow with the reference numeral 409 indicated, a mechanical stress acts, for example, in the direction of an optical axis 505 of the optical waveguide 304 ,

In this way, the trained as a fiber Bragg grating sensor element 301 in the direction of the optical. axis 505 stretched or compressed. Further, it is possible to propagate light within the area of the optical sensor element 301 by forces, moments and mechanical stresses that affect directions different from the optical axis 505 of the optical fiber 304 Act. As an application of such mechanical stresses that are not in the optical axis 505 of the optical fiber 304 are not relevant to the understanding of the present invention, a description of these effects will not be discussed here.

The optical sensor element 301 can in the optical fiber 304 For example, be inscribed by means of laser radiation in the ultraviolet spectral range. Such an embossing of a fiber Bragg grating can be provided by a refractive index change caused by UV radiation in the region of the sensor element. For this purpose, an in 2 not shown UV laser beam split into two sub-beams, which are crossed at a predetermined angle in the sensor location volume. A resulting interference pattern caused by the crossed UV laser beams is then approximately equal to that in FIG 2 shown modulated refractive index curve in the region of the sensor element 301 ,

As in 2 shown, becomes an incident light wave 501 from the left into the optical waveguide 304 coupled, wherein the incident light wave 501 in the optical waveguide 304 spreads and also the area of the optical sensor element 301 reached. In one by the modulation period of the fiber Bragg grating of the sensor element 301 predetermined wavelength range can now be a reflected light wave 502 be caused, which to Einkoppelstelle the incident light wave 501 is reflected back.

Furthermore, it is possible that a transmitted light wave 503 through the fiber Bragg grating of the sensor element 301 is blasted through. The intensity of the reflected light wave 502 as a function of the wavelength, ie the course of a filter function 700 of the optical sensor element 301 , will be referred to below with reference to 3 described.

In the area of the sensor element 301 in which there is an optical interference effect within the optical waveguide 304 is formed, typically the period of the refractive index of the fiber core is modulated. Such a modulation period can be due to the mechanical stress 409 along the optical axis 505 that is, such a modulation period is shortened at a mechanical compression of the optical fiber and accordingly at a mechanical elongation of the optical waveguide 304 increased.

Furthermore, by the application of the sensor element 301 in the optical fiber 304 with a mechanical tension 409 the refractive index in the region of the fiber Bragg grating be changed, which also has a change in the modulation period result. An elongation of the optical waveguide 304 thus also has an elongation of the fiber Bragg grating result. A wavelength of the reflected light wave 502 thus also changes depending on a grid spacing of the fiber Bragg grating.

As with the sensor device 300 of the 1 As illustrated, an optical waveguide may include a plurality of sensor elements arranged in series. When multiple fiber Bragg gratings are integrated into an optical waveguide, it is preferable to design a modulation period of the individual gratings differently.

In this way, certain spectral ranges of corresponding grating and thus corresponding positions within the optical waveguide can be a sensor location of an individual sensor element 301 . 302 . 303 assign. Such sensor elements 301 . 302 . 303 ( 1 ) So spectrally encoded, so that in the individual sensor elements 301 . 302 . 303 reflected light waves 502 have different spectral distributions, such that the individual of the individual sensor elements 301 . 302 . 303 spectrally distinguish originating sensor signals.

It It should be noted here that, although in the present Description of light waves or optical waves is the speech, the spectral range of such optical radiation next to the optical visible area also the near and far infrared area as well may include the near and far ultraviolet range.

The at least one optical secondary radiation can correspond both to a part of the optical primary radiation reflected at the optical sensor element and also to a part of the optical primary radiation transmitted through the optical sensor element. That is, the transmitted light wave 503 and the reflected light wave 502 can both from the incident light wave 501 as well as the application of the mechanical stress 409 in their intensity and their wavelength response range 706 ( 3 ) can be varied.

If at least two optical sensor elements 301 . 302 . 303 serially by means of the optical transmission device 200 transmitted optical primary radiation 407 ( 1 ), which can be addressed to the at least two optical sensor elements 301 . 302 . 303 reflected primary optical radiation 407 by means of different wavelength response ranges 706 the at least two optical sensor elements 301 . 302 . 303 be differentiated from each other.

Likewise, the through the at least two optical sensor elements 301 . 302 . 303 transmitted optical primary radiation 407 by means of different wavelength response ranges 706 the at least two optical sensor elements 301 . 302 . 303 be differentiated from each other.

3 shows a filter function 700 a trained as a fiber Bragg grating sensor element 301 . 302 . 303 (please refer 1 ). The filter function typically describes a reflection intensity 702 of optical radiation reflected at the fiber Bragg grating as a function of wavelength 701 (Λ).

As in 3 shown, assigns the filter function 700 of the fiber Bragg grating one by one center wavelength 703 symmetrical shape in which in 3 Case shown a so-called Gaussian profile. Such a Gaussian profile has a full width at half maximum (FWHM), which is denoted by the reference numeral 704 is designated.

Individual sampling points 705 are along the filter function 700 characterized by vertical lines at different wavelength positions. It should be noted here that the in 3 shown filter function 700 corresponds to the course of an intensity having an optical primary radiation reflected at the fiber Bragg grating. It is known to the person skilled in the art that an optical grating arrangement which corresponds to the fiber Bragg grating has a Gaussian filter function 700 having.

While the half width 704 the filter function 700 among other things, the number of Durchbrechungsindex fluctuations along that of the optical fiber 304 evoked reflection zones is the central wavelength or the center wavelength 703 of a fiber Bragg grating given by the above-mentioned modulation period Λ. A so-called Bragg wavelength λ _B is given by the following relationship: λ B = 2 · n k · Λ

Here, n _{k is} the effective refractive index of the fundamental mode of the core of the optical fiber and Λ the (spatial) grating period (modulation period) of the fiber Bragg grating. The spectral width, by the half width 704 the filter function depends on the extent of the fiber Bragg grating in the direction of the optical axis and the size of the refractive index change. Optical primary radiation whose wavelength is within the wavelength response range 706 is reflected, in such a way that the in 3 shown intensity curve 702 over the wavelength 701 results.

Further shows 3 to illustrate the measuring method according to the invention, a laser line 308 , which compared to the half width 704 the filter function 700 has a negligible half-width, ie the laser line, for example, by a as in 5 is shown spectrally extremely narrow band compared to the half-width of the fiber Bragg grating.

According to the measuring method according to the invention now in the optical waveguide 304 irradiated and to the sensor element 301 ( 2 ) guided optical primary radiation during the irradiation over the wavelength response range 706 the filter function 700 pushed, ie the wavelength of the laser radiation is at least over the reference numeral 706 marked wavelength range is scanned (scanned).

Individual sampling points 705 which is the optical detector 102 the interrogator device 105 ( 1 ) are sampled according to its sampling rate, are also in 3 by circles along the Gaussian filter function 700 characterized. It should be noted that the in 3 shown intensities in a reflection at the fiber Bragg grating occur, ie it is the reflected light wave 502 as part of the incident light wave (laser light wave) 501 detected as in 2 illustrated. That is, only within the wavelength response range 706 can be a reflection intensity according to the filter function shown 700 at the entrance of the optical waveguide 304 to be obtained.

In certain applications, although not shown in the figures of the present specification, an intensity transmitted through a fiber Bragg grating is also detectable. In this case, would be in a sampling of the filter function 700 by means of the laser line 708 in an in 3 shown scanning direction 707 only outside the wavelength response range 706 transmitted while the transmitted intensity is near the center wavelength 703 would have a minimum value, ie the in 3 shown function would be inverted.

According to a preferred embodiment of the present invention, a sampling of the filter function is performed 700 through the laser line 708 using a like in 5 shown light source with such high speed that advantageously thermal effects can be neglected. In this way, disturbances in the measurement of mechanical stresses are suppressed. Although in 3 only a filter function 700 a single sensor element 301 can be shown in the optical waveguide 304 ( 2 ) several sensor elements 301 . 302 . 303 ( 1 ) can be arranged one behind the other.

Preferably, the individual, successively arranged sensor elements 301 . 302 . 303 respective filter functions 700 on, their center wavelengths 703 differ. In this way, a spectral distinction of the individual, from the individual sensor elements 301 . 302 . 303 back-reflected optical primary radiation possible. Tuning the wavelength of the optical primary radiation over the half width of the filter function 700 For example, in the by a reference numeral 707 in the in 3 indicated direction, preferably takes place in a very short period of time in a range of a few tens of nanoseconds (ns) to about 150 ns, preferably in a period of about 100 ns.

A vote of the laser line 708 takes place in a tuning direction 707 over the wavelength tuning range, which may be greater than the half width 704 the filter function 700 , Furthermore, it is possible to resolve the received in reflection or transmission optical secondary radiation even in the wavelength. Such a wavelength resolution of the optical secondary radiation can be particularly advantageous if the half-width of the irradiating laser line is not small in comparison to the half-width 704 the filter function 700 is.

Preferably, the at least two optical sensor elements 301 . 302 . 303 reflected primary optical radiation by means of different wavelength response ranges 706 the at least two optical sensor elements 301 . 302 . 303 spectrally distinguishable from each other. The same differentiation possibilities apply to an operation of the sensor element designed as a fiber Bragg grating or of the multiplicity of sensor elements in transmission.

If at least two optical sensor elements 301 . 302 . 303 are operated in transmission, which by the at least two optical sensor elements 301 . 302 . 303 transmitted optical primary radiation through different wavelength response ranges 706 the corresponding filter functions 700 a different spectral behavior, whereby the secondary optical radiations are distinguishable from each other.

4 Fig. 10 is a block diagram illustrating an optical measuring apparatus 100 according to a preferred embodiment. The example formed as a laser light source 101 sends an optical primary radiation 407 via an optical transmission device 200 to a coupler unit 201 , The coupler unit 201 can be designed as a 3 dB coupler, ie a light intensity which is irradiated at an input of the coupler element divides in the ratio 50:50 on opposite outputs of the coupler unit 201 on.

Thus, it is possible via a single transmission device 200 , which is an integrally arranged coupler unit 201 has, both the optical primary radiation 407 to the at least one sensor element 301 lead as well as the sensor element 301 outgoing optical secondary radiation to the optical detector 102 which is also at an output of the coupler unit 201 connected.

The coupler unit 201 is about another optical transmission device 200 with the optical detector 102 connected, such that a measurement signal 406 as a function of the optical primary radiation 407 and one on the sensor element 301 applied mechanical stress 409 is obtained. Since the measuring device according to the invention is based on the wavelength of the (laser) light source 101 To vary, a simple receiving photodiode can be used as the optical detector 102 serve.

5 schematically illustrates a trained as a laser light source 600 for carrying out the method according to the invention. The laser light source 600 has a laser light exit window 605 on, by which emitted laser light 607 exit and as optical primary radiation 407 can be used for the measurement ( 4 ). The laser light source 600 also includes a laser coupler 604 which turns the internal laser beam (intra-cavity) into a first laser reflector 601 and a second laser reflector 602 passes.

Both laser reflectors each have reflector controls, ie the first laser reflector 601 is through a first reflector control 608 controlled while the second laser reflector 602 through a second reflector control 609 is controlled. The reflector controls 608 . 609 be through appropriate control currents 403 . 404 ie a first wavelength control current 403 and a second wavelength control current 404 controlled. The first and second wavelength control currents 403 . 404 Be by one below, with reference to 7 explained power control unit provided.

One in the corresponding laser reflectors 601 . 602 The predominant electro-optical effect known to those skilled in the art ensures that there is a refractive index in the first and second laser reflectors 601 . 602 depending on the supplied wavelength control current 403 respectively. 404 changes. Such a change in the refractive index within a laser resonator causes an emission wavelength of the emitted laser light 607 is varied.

A like in 5 shown, monolithic constructed laser allows a very rapid detuning of the wavelength of the emitted laser light over, for example, with reference to 3 shown wavelength response range 706 , so that thermal effects, which also cause a wavelength variation of the emitted laser light 607 can not play a role. By using the in 5 shown laser light source 600 Thus, according to a preferred embodiment, it is possible to provide primary optical radiation with high wavelength stability and fast wavelength variation capability.

6 shows a block diagram of an optical measuring device 100 , in addition to the in 4 shown block image components of the interrogator 105 ( 1 ) a driver device 106 , a signal processing device 107 and a data processing unit 108 are shown.

The optical light source (laser light source) 101 is determined by predetermined light source operating parameters 401 set. Such light sources or operating parameters include the setting of an operating current, an operating temperature, etc. The driver device 106 indicating the light source operating parameters 401 is provided by the controller 103 driven.

As already with reference to 1 explained, is the control device 103 with the input-output unit 104 the interrogator device 105 connected. The input-output unit 104 For example, as in the in 6 shown embodiment, with a data processing unit 108 or be connected to a PC, in which a data processing can be performed.

The optical detector 102 , which via the optical transmission device 200 the measuring signal 406 receives and converts into an electrical output signal is with the signal processing means 107 connected corresponding to a scan of the laser line via the filter function 700 (see above) outputs a corresponding intensity signal.

This intensity signal becomes the control device 103 and via the input-output unit 109 to the data processing unit 108 forwarded. The optical coupler unit 201 is optically to the transmission equipment 200 coupled and configured one of the sensor element 301 to receive reflected secondary radiation. It should also be noted that the signal processing device 107 can be designed as a scanning unit, which intensity values in synchronism with the variation of an emission wavelength of the laser light source 101 certainly.

7 illustrates a block diagram of components that are suitable for driving the laser light source 101 , The laser light source 101 according to a preferred embodiment of the present invention receives a signal which general light source operating parameters 401 and another signal representing a wavelength control current 402 provides.

The light source operating parameters 401 be, as already above with reference to the 1 and 6 mentioned by the driver device 106 provided. The driver device 106 receives a driver control signal from one in the controller 103 included driver control unit 112 , According to the invention, the control device 103 now designed such that in addition to the driver control unit 112 a power control unit 111 which is capable of providing a wavelength control current 402 and which is further capable of this wavelength control current 402 to vary in a short time. Depending on a variation of the wavelength control current 402 becomes an emission wavelength of the emitted laser light 607 variable in the nanosecond range. By the in 7 As shown, it is possible to use the laser line 708 , as in 3 shown over the wavelength response range 706 the fiber Bragg grating or the filter function 700 to scan.

In particular, the in 5 shown laser light source (monolithically tunable laser diode) 600 suitable for quickly detuning the emission wavelength of the emitted laser light 607 provide. By a suitable current control, it is thus possible to change the emission wavelength of the laser light source (ie, the monolithically tunable laser or the monolithically tunable laser diode) quickly (ie in egg a range of a few tens of nanoseconds) in order to query in a short time the reflection or transmission spectrum of a sensor element designed as a fiber Bragg grating. Such an interrogator or interrogation method has the advantage that, if a laser diode of this kind is tuned through, any thermal influences which may occur are negligible.

The monolithically tunable laser can emit a set of discrete wavelengths when a predetermined set of wavelength control currents 402 provided. The dependence of the laser emission wavelength on the set of wavelength control currents can be predetermined and determined in one measurement. To a predetermined spectral range or a wavelength response range of the optical sensor element 301 . 302 . 303 interrogate, a variety of known, discrete wavelengths by the laser light source 101 generated.

In order to achieve a fast sequence of the discrete wavelengths or a fast wavelength variation, sufficiently fast digital / analogue converter devices in the in 6 shown signal processing device 107 provided. Preferably, the time duration in which a set of wavelength control currents 402 at the laser light source 101 is present, extremely short. As a result, the temperature of the laser light source and thus other parameters, such as emission wavelength and / or emission intensity of the emitted laser light 607 , not changed, such that a constant intensity value results at a constant wavelength.

8th shows a block diagram illustrating an optical measuring device 100 according to a further preferred embodiment. Unlike the in 6 shown optical measuring device has the in 8th shown optical measuring device 100 a reference detector 109 on. The reference detector 109 is about another optical transmission device 200 with a remaining fourth port of the optical coupler unit 201 connected.

The optical coupler unit 201 gives at its fourth port an optical output signal, the intensity of the optical primary radiation 407 corresponds, ie a reference signal 405 , The reference signal 405 is determined by one in the reference detector 109 provided photodiode converted into an electrical signal which a reference signal processing means 110 which is operatively connected to the reference detector 109 connected is.

Such a reference signal detecting device, as in 8th has the advantage that any variations in emission intensity of the laser light source 101 can be eliminated or at least reduced by making these variations separately and independently of those of the optical sensor element 301 emitted secondary optical radiation 408 as a reference signal 405 are detectable. The output signal of the reference signal processing device 110 , which may be configured similar to the signal processing device 107 , becomes the controller 103 fed. The rest, in 8th Components shown correspond to those already with reference to 6 shown and described. These components, to avoid redundant description, are incorporated herein by reference 8th not explained again.

9 is a block diagram of an optical measuring device 100 according to another preferred embodiment of the present invention. As in 9 is a sensor device 300 via an optical transmission device 200 with an interrogator device 105 connected. The interrogator device 105 includes numerous components referred to herein with reference to 1 . 6 and 9 have been described and with reference to 9 in order to avoid a redundant description, will not be explained again.

In particular, the interrogator device 105 , in the 9 is shown, a transit time detection device 113 on, already referring to 1 has been described. The transit time acquisition device 113 detects a transit time of one or more light waves between the interrogator 105 and a sensor element 301 . 302 . 303 the sensor device 300 ,

As in 9 are shown, n are sensor elements 301 . 302 , ..., 303 integral with the optical transmission device 200 (Optical waveguide) formed and serially along the optical transmission device 200 arranged. The individual sensor elements 301 . 302 , ..., 303 have different geometric distances to the Interrogatoreinrichtung 105 on, ie a first sensor element 301 has a distance d1, a second sensor element 302 has a distance d2 and an nth sensor element 303 has a distance d3. The different distances d1, d2,..., D3 lead to different transit times of the optical signal between the interrogator device 105 and the respective one. sensor element 301 . 302 , ..., 303 ,

About such a transit time detection device 113 is a determination of a sensor location of the at least one optical sensor element along the optical transmission device 200 possible. Thus, the optical secondary radiation emitted from the at least two optical sensor elements can be distinguished from one another by means of different transit times between the respective optical sensor element and the associated transmitter / receiver unit.

10 FIG. 10 is a flow chart illustrating an optical measurement method for measuring a stress according to a preferred embodiment of the present invention. FIG. This in 10 The flowchart shown essentially comprises six steps S1 to S6.

The Procedure starts at a step S1 and proceeds to a Step S2, in which an optical waveguide is provided, having at least one optical sensor element. The optical sensor element has a predetermined and specifiable wavelength tuning range.

In a subsequent step S3, an optical primary radiation is radiated into the optical waveguide. The optical primary radiation reaches the sensor element 301 over the optical waveguide 304 . 200 , In a subsequent step S4, the at least one optical sensor element 301 . 302 . 303 with a mechanical tension 409 applied.

Finally, in a subsequent step S5, at least one optical secondary radiation is detected from the optical waveguide. This secondary radiation essentially depends on the incident primary optical radiation and the mechanical stress on the sensor element 301 . 302 . 303 has been applied in the above step S4.

The optical primary radiation is doing this during of irradiation at least within the wavelength response range varies in wavelength. Subsequently the procedure is ended in a step S6.

The use of a laser as a light source 101 has the particular advantage that laser radiation has a high spectral power density. In this way it is possible to use the filter function 700 the fiber Bragg grating of one or more sensor elements 301 . 302 . 303 to scan with high accuracy.

By the extremely fast scanning of the primary optical radiation during the Radiating over the wavelength response range the at least one sensor element has the advantage that a very fast measuring optical measuring system can be realized can.

The use of a monolithically tunable laser diode as a light source 101 in the described optical measuring device 100 ensures a measurement without the influence of disturbing vibrations, thermal variations, fluctuations in the operating parameters, etc ..

Furthermore, an extremely cost-effective optical measuring system can be realized, since for the detection of the at least one sensor element 301 . 302 . 303 emitted optical secondary radiation only a fast photodiode is required, which can be dispensed spectroscopic evaluation by means of Spektrometeranordnung.

Even though the present invention above based on preferred embodiments It is not limited to this, but in many ways modifiable.

Also the invention is not limited to the aforementioned applications limited.

100

optical measuring device

101

Transmitter unit / light source

102

Receiver unit / detector

103

control device

104

Input-output unit

105

Interrogatoreinrichtung

106

driving means

107

Signal processing device

108

Data processing unit / PC

109

reference detector

110

Reference signal-processing device

111

Current control unit

112

Drive controller

113

Run time detecting means

200

transmission equipment

201

coupler

300

sensor device

301

(First) sensor element

302

second sensor element

303

nth sensor element

304

optical waveguides

401

Light sources operating parameters

402

Wavelength control current

403

first Wavelength control current

404

second Wavelength control current

405

reference signal

406

measuring signal

407

optical primary radiation

408

optical secondary radiation

409

mechanical tension

410

command

501

incident light wave

502

reflected light wave

503

transmitted light wave

505

optical axis

600

Laser light source

601

first laser reflector

602

second laser reflector

603

active laser medium

604

laser coupler

605

Laser light emission window

606

laser housing

607

emitted laser light

608

first Reflector control

609

second Reflector control

700

filter function

701

wavelength

702

reflection intensity

703

Center wavelength

704

FWHM (FWHM)

705

sampling

706

Wavelength response range

707

scan

708

laser line

Claims (22)

Measuring device ( 100 ) for detecting at least one mechanical stress ( 409 ) comprising: a light source ( 101 ) designed to emit a wavelength-variable optical primary radiation ( 407 ); at least one sensor element ( 301 . 302 . 303 ), with the mechanical tension ( 409 ) can be acted upon; an optical transmission device ( 200 ), designed for transmission from the light source ( 101 ) emitted in the wavelength variable optical primary radiation ( 407 ) to the sensor element ( 301 . 302 . 303 ); an optical detector ( 102 ) designed to detect at least one optical secondary radiation ( 408 ) from the sensor element ( 301 . 302 . 303 ) as a function of the irradiated optical primary radiation ( 407 ) and the mechanical stress ( 409 ); and one operationally with the optical detector ( 102 ) connected signal processing device ( 107 ) for determining the mechanical stress ( 409 ). Measuring device ( 100 ) according to claim 1, wherein the optical detector ( 102 ) via an optical coupler unit ( 201 ) visually to the transmission device ( 200 ) and is adapted to receive one of the sensor element ( 301 . 302 . 303 ) reflected secondary radiation ( 408 ) to recieve. Measuring device ( 100 ) according to claim 1 or 2, wherein the light source ( 101 ) comprises a wavelength tunable laser. Measuring device ( 100 ) according to claim 3, wherein the wavelength tunable laser is designed as a monolithically tunable laser diode comprising at least one reflector control element ( 608 . 609 ) for varying the wavelength as a function of a control current ( 402 . 403 ) having. Measuring device ( 100 ) according to claim 3 or 4, further comprising a current control unit for providing the control current ( 402 . 403 ). Measuring device ( 100 ) according to at least one of the preceding claims, wherein the sensor element ( 301 . 302 . 303 ) comprises at least one of a group of a fiber Bragg grating, a Fabry-Perot interferometer, and a thin film interferometer. Measuring device ( 100 ) according to at least one of the preceding claims, wherein the optical transmission device ( 200 ) as an optical fiber ( 304 ). Measuring device ( 100 ) according to at least one of the preceding claims, wherein optical transmission means ( 200 ) integral with the sensor element ( 301 . 302 . 303 ) is trained. Measuring device ( 100 ) according to at least one of the preceding claims, further comprising: a reference detector ( 102 ) which is designed to detect one of a radiation intensity of the optical primary radiation ( 407 ) dependent reference signal ( 405 ); and a reference signal processing device ( 110 ) which is designed to process the reference signal ( 405 ). Measuring device ( 100 ) according to at least one of the preceding claims, further comprising a sensor device ( 300 ), which at least two sensor elements ( 301 . 302 . 303 ), wherein the sensor elements ( 301 . 302 . 303 ) have mutually different wavelength response ranges. Measuring device ( 100 ) according to at least one of the preceding claims, further comprising a transit time detection device for determining a sensor location of the at least one optical sensor element along the optical transmission device ( 200 ). Measuring method for measuring a mechanical stress ( 409 ), comprising the steps of: providing an optical waveguide ( 304 ) with at least one optical sensor element ( 301 . 302 . 303 ) having a wavelength response range; Irradiation of an optical primary radiation ( 407 ) in the optical waveguide ( 304 ); Applying the optical sensor element with the mechanical tension ( 409 ); and detecting at least one optical secondary radiation ( 408 ) from the optical waveguide ( 304 ) as a function of the irradiated optical primary radiation ( 407 ) and the mechanical stress ( 409 ), wherein the optical primary radiation ( 407 ) is varied in wavelength during irradiation over the wavelength response range of the sensor element. Measuring method according to claim 12, wherein the at least one optical secondary radiation ( 408 ) a part of the optical sensor element ( 301 . 302 . 303 ) reflected primary optical radiation ( 407 ) corresponds. Measuring method according to claim 12, wherein the at least one optical secondary radiation ( 408 ) a part of the through the optical sensor element ( 301 . 302 . 303 ) transmitted optical primary radiation ( 407 ) corresponds. Measuring method according to at least one of claims 12 to 14, wherein the secondary optical radiation ( 408 ) is resolved in wavelength. Measuring method according to at least one of claims 12 to 15, wherein the optical primary radiation ( 407 ) is tuned over a wavelength tuning range which is greater than a Habwertsbreite a filter function of the at least one optical sensor element. The measuring method according to claim 16, wherein the tuning of the wavelength of the optical primary radiation ( 407 ) is performed over the half width of the filter function of the at least one optical sensor element in a period in a range of 10 ns to 150 ns, preferably in about 100 ns. Measuring method according to at least one of claims 12 to 17, wherein the optical sensor element ( 301 . 302 . 303 ) by means of UV laser radiation in the optical transmission device ( 200 ) is impressed. Measuring method according to at least one of claims 12 to 18, wherein at least two optical sensor elements ( 301 . 302 . 303 ) serially by means of an optical transmission device ( 200 ) transmitted optical primary radiation ( 407 ) be addressed. The measuring method according to claim 19, wherein the at least two optical sensor elements ( 301 . 302 . 303 ) reflected primary optical radiation ( 407 ) by means of different wavelength response ranges of the at least two optical sensor elements ( 301 . 302 . 303 ) are distinguishable from each other. The measuring method according to claim 19, wherein the at least two optical sensor elements ( 301 . 302 . 303 ) transmitted optical primary radiation ( 407 ) by means of different wavelength response ranges of the at least two optical sensor elements ( 301 . 302 . 303 ) are distinguishable from each other. Measuring method according to at least one of claims 18 to 21, wherein the at least two optical sensor elements ( 301 . 302 . 303 ) emitted secondary optical radiation ( 408 ) by means of different transit times between the respective optical sensor element ( 301 . 302 . 303 ) and associated transceiver unit are distinguishable from each other.