Integrated-optics expansion interferometer in an extension-metrological neutral environment

• US 5,289,256 A
• Filed: 01/26/1993
• Issued: 02/22/1994
• Est. Priority Date: 02/15/1992
• Status: Expired due to Fees

• Current Assignee: Daimler-Benz AG (Mercedes-Benz Group AG)
• Original Assignee: Daimler-Benz AG (Mercedes-Benz Group AG)
• Inventors: Gramling, Hubert
• Primary Examiner(s): Turner, Samuel A.
• Assistant Examiner(s): KIM, ROBERT H
• Application Number:
  US08/009,036
• Time in Patent Office: 392 Days
• Field of Search: 356/355, 356/345, 356/352, 356/357, 356/350, 250/227.19, 250/227.27, 385/12, 385/14, 73/517 B
• US Class Current: 356/477
• CPC Class Codes: G01B 11/161 by interferometric means
• CPC Class Codes: G01B 9/02023 Indirect probing of object, e.g. via influence on cavity or fibre
• CPC Class Codes: G01B 9/02051 Integrated design, e.g. on-chip or monolithic
• CPC Class Codes: G01D 5/266 by interferometric means G01D5/353 takes precedence
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G02B 6/29355 Cascade arrangement of interferometers
• CPC Class Codes: G02B 6/43 Arrangements comprising a plurality of opto-electronic elements and associated optical interconnections

Abstract

An integrated-optics extension interferometer, in which the measuring and reference arm, the beam splitter and the beam coupler as well as entrances and exits for primary light and interference light are integrated in the baseplate, can be applied in the manner of a wire strain gauge to components to be investigated. The portions of the waveguide which form the measuring and reference arm are integrated over their entire length in the baseplate, and are disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections, in which a coupling free mutual minimum spacing of all straight active partial sections and deflecting sections of the integrated waveguides forming the measuring and reference arm respectively is observed at all locations. As a result of this, the fundamental interferometer can be applied to the surface of stressed workpieces in a manner which is as simple and space-saving as a conventional electrical-resistance wire strain gauge for extension measurements. In order to achieve an automatic compensation of the extension due to temperature, the reference arm is also expediently wound in the manner of loops and is designed to be of the same length as the measuring arm, but is disposed in an extension-metrologically neutral manner. An integrated-optics extension interferometers of double-beam construction according to Michelson or according to Mach-Zehnder and those of so-called multibeam construction according to Fabry-Perot are possible.

Claims

1. A double-beam interferometer formed using integrated-optics technology comprising:

a baseplate having waveguides integrated thereon;

an entrance optical fiber supplying primary light from a laser light source, said integrated waveguides having an entrance portion extending to an edge of the baseplate and connecting in a light-conducting manner to the entrance optical fiber;

an exit optical fiber conducting interference light away from the baseplate to a detecting device, at least one further exit portion of said integrated waveguides extending to an edge of the baseplate and connecting in a light-conducting manner to the exit optical fiber;

an integrated light splitting device disposed downstream of said entrance portion of the integrated waveguide for splitting an injected primary light onto a reference arm and a measuring arm of waveguides;

an integrated light coupler for combining light from the reference arm and from the measuring arm, said coupler merging into the at least one exit portion;

wherein the portion of the waveguide forming the reference arm and the portion forming the measuring arm are both integrated over their entire length in the baseplate, said length of the reference arm corresponding to said length of the measuring arm;

wherein at least that portion of the waveguide forming the measuring arm is disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections, in which a coupling-free mutual minimum spacing of all straight active partial sections and deflecting sections forming the measuring arm is provided; and

wherein the waveguide forming the reference arm is at least one of designed and disposed in the baseplate in such a manner that upon extension of the baseplate in a direction of the straight active partial sections of the measuring arm, said reference arm operates in an extension-metrologically neutral manner.

4. An interferometer according to claim 1, wherein the reference arm is also disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections in a length conforming to the length of the measuring arm, in which the straight active partial sections of the reference arm are disposed in a direction behaving in an extension-metrologically neutral manner in relation to the direction of the straight active partial sections of the measuring arm, preferably orthogonally to them in the baseplate and in which a coupling-free mutual minimum spacing of the straight active partial sections and deflecting section of the integrated waveguide forming the reference arm in relation to one another and in relation to the straight active partial sections and deflecting sections of the measuring arm is provided.

5. An interferometer according to claim 1, wherein the deflecting sections between two successively following straight active partial sections within the integrated waveguide forming the measuring arm or within that forming the reference arm are respectively formed by a semicircular arcuate piece or by a pair of quadrant-shaped arcuate pieces, disposed in mirror image, with a straight connecting piece disposed therebetween.

6. An interferometer according to claim 4, wherein the deflecting sections between two successively following straight active partial sections within the integrated waveguide forming the measuring arm or within that forming the reference arm are respectively formed by a semicircular arcuate piece or by a pair of quadrant-shaped arcuate pieces, disposed in mirror image, with a straight connecting piece disposed therebetween.

7. An interferometer according to claim 1, wherein the deflecting sections between two successively following straight active partial sections within the integrated waveguide forming the measuring arm or within that forming the reference arm are respectively formed by a connecting piece which extends rectilinearly and which adjoins orthogonally with a sharp edge onto the respective active partial sections and by deflecting mirrors disposed at each of the two thus formed corners of waveguide sections, wherein the deflecting mirrors are in turn formed by the reflecting, preferably totally reflecting lateral surface of a respective slot incorporated into the baseplate orthogonally to the glass surface and at a 45°

angle to the combining active partial or connecting sections.

8. An interferometer according to claim 4, wherein the deflecting sections between two successively following straight active partial sections within the integrated waveguide forming the measuring arm or within that forming the reference arm are respectively formed by a connecting piece which extends rectilinearly and which adjoins orthogonally with a sharp edge onto the respective active partial sections and by deflecting mirrors disposed at each of the two thus formed corners of waveguide sections, wherein the deflecting mirrors are in turn formed by the reflecting, preferably totally reflecting lateral surface of a respective slot incorporated into the baseplate orthogonally to the glass surface and at a 45°

angle to the combining active partial or connecting sections.

9. An interferometer according to claim 5, wherein the loops, composed of straight active partial sections and circular-arcuate deflecting sections of the waveguide forming the measuring arm and/or of that forming the reference arm are disposed in the form of at least one oval double spiral, in which a waveguide, extending to and fro in a U shape and the parallel limb portions of which merge into one another via an end loop, is disposed so as to be wound in each instance in an oval spiral in which a waveguide partial section extends from the outermost active partial section of the one double spiral without crossover to the adjacent double spiral.

10. An interferometer according to claim 5, wherein the loops, composed of straight active partial sections and circular-arcuate deflecting sections of the waveguide forming the measuring arm and/or of that forming the reference arm or one of the resonators are disposed in the form of at least one oval spiral, in which a waveguide partial section extends from the innermost active partial section, crossing the other active partial sections of the one side of the oval spiral, to a region situated outside the oval spiral.

11. An interferometer according to claim 1, wherein with a design of the interferometer as a Michelson interferometer, the light splitting device and the light coupler are structurally combined in a single waveguide configuration, and specifically preferably in a so-called 3×

3 directional coupler with three waveguides passed side-by-side at coupling spacing over a defined length, in which the central, blunt-ended waveguide of the 3×

3 directional coupler represents the entrance portion and the two other waveguides of the 3×

3 directional coupler merge on the one hand into the measuring arm provided at the end surface with a reflector or into the reference arm of the waveguides, provided at the end surface with a reflector, and on the other hand merge into the exit portions, in which at the two exit portions two interference signals which are phase-shifted preferably by 120°

are present.

12. An interferometer according to claim 4, wherein with a design of the interferometer as a Michelson interferometer, the light splitting device and the light coupler are structurally combined in a single waveguide configuration, and specifically preferably in a so-called 3×

3 directional coupler with three waveguides passed side-by-side at coupling spacing over a defined length, in which the central, blunt-ended waveguide of the 3×

3 directional coupler represents the entrance portion and the two other waveguides of the 3×

3 directional coupler merge on the one hand into the measuring arm provided at the end surface with a reflector or into the reference arm of the waveguides, provided at the end surface with a reflector, and on the other hand merge into the exit portions, in which at the two exit portions two interference signals which are phase-shifted preferably by 120°

are present.

13. An interferometer according to claim 1, wherein with a design of the interferometer as a Mach-Zehnder interferometer, the light-splitting device is designed in the form of a branching of a waveguide, in which one of the two branching-off waveguides merges into the measuring arm and the other merges into the reference arm and in that the light coupler combining the light from the measuring arm and from the reference arm is designed in the form of a directional coupler, preferably in the form of a so-called 3×

3 directional coupler with three waveguides passed side-by-side at coupling spacing over a defined length, in which the central blunt-ended waveguide of the 3×

3 directional coupler represents one of three exit portions and the two other waveguides, situated on the outside of the 3×

3 directional coupler, merge on the one hand into the measuring arm or into the reference arm of the waveguides and on the other hand merge into further exit portions, in which at the in total three exit portions three interference signals which are phase-shifted preferably by 120°

are present.

14. An interferometer according to claim 4, wherein with a design of the interferometer as a Mach-Zehnder interferometer, the light-splitting device is designed in the form of a branching of a waveguide, in which one of the two branching-off waveguides merges into the measuring arm and the other merges into the reference arm and in that the light coupler combining the light from the measuring arm and from the reference arm is designed in the form of a directional coupler, preferably in the form of a so-called 3×

3 directional coupler with three waveguides passed side-by-side at coupling spacing over a defined length, in which the central, blunt-ended waveguide of the 3×

3 directional coupler represents one of three exit portions and the two other waveguides, situated on the outside of the 3×

3 directional coupler, merge on the one hand into the measuring arm or into the reference arm of the waveguides and on the other hand merge into further exit portions, in which at the in total three exit portions three interference signals which are phase-shifted preferably by 120°

are present.

15. An interferometer according to claim 1, wherein said interferometer is used as an extension measuring element which can be applied to the surface of a mechanically stressed component in the manner of a wire strain gauge known per se, and which is subjected to the component deformation near the surface.

18. An interferometer according to claim 4, wherein said interferometer is used as an extension measuring element which can be applied to the surface of a mechanically stressed component in the manner of a wire strain gauge known per se, and which is subjected to the component deformation near the surface.

2. An interferometer of the Fabry-Perot type formed using integrated-optics technology, comprising:

a baseplate having waveguides integrated therein;

an entrance optical fiber supplying primary light from a laser light source, said integrated waveguides having an entrance portion extending to an edge of the baseplate and connecting in a light-conducting manner to the entrance optical fiber;

an exit optical fiber conducting interference light away from the baseplate to a detecting device, at least one further exit portion of said integrated waveguides extending to an edge of the baseplate and connecting in a light-conducting manner to the exit optical fiber;

a Y-shaped combining element combining the entrance portion and the exit portion into a common waveguide;

a resonator optically disposed downstream of the common waveguide of the combining element, said resonator being formed from a partially transmitting mirror which is integrated into the baseplate and which stands orthogonally to the waveguide and an end mirror disposed at the other end of the resonator waveguide;

wherein the resonator waveguide is disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections, in which a coupling-free mutual minimum spacing of all straight active partial sections and deflecting sections of the integrated waveguide forming the resonator is provided.

3. An interferometer according to claim 2, wherein two resonators with resonator waveguides of mutually equal length are integrated into the baseplate, in which the resonator waveguides of both resonators are disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections in the baseplate and a coupling-free mutual minimum spacing of all straight active partial sections and deflecting sections is provided both within each individual resonator and also between the two resonators;

and

wherein the straight active partial sections of the one resonator are disposed in a direction behaving in an extension-metrologically neutral manner in relation to the direction of the straight active partial sections of the other resonator, preferably orthogonally to them in the baseplate.

16. An interferometer according to claim 2, wherein said interferometer is used as an extension measuring element which can be applied to the surface of a mechanically stressed component in the manner of a wire strain gauge known per se, and which is subjected to the component deformation near the surface.

17. An interferometer according to claim 3, wherein said interferometer is used as an extension measuring element which can be applied to the surface of a mechanically stressed component in the manner of a wire strain gauge known per se, and which is subjected to the component deformation near the surface.

19. A double-beam interferometer formed using integrated-optics technology, comprising:

a baseplate having waveguides integrated thereon;

an entrance optical fiber supplying primary light from a laser light source, said integrated waveguides having an entrance portion extending to an edge of the baseplate and connecting in a light-conducting manner to the entrance optical fiber;

an exit optical fiber conducting interference light away from the baseplate to a detecting device, at least one further exit portion of said integrated waveguides extending to an edge of the baseplate and connecting in a light-conducting manner to the exit optical fiber;

an integrated light splitting device disposed downstream of said entrance portion of the integrated waveguide for splitting an injected primary light onto a reference arm and a measuring arm of waveguides;

an integrated light coupler for combining light from the reference arm and from the measuring arm, said coupler merging into the at least one exit portion;

wherein the portion of the waveguide forming the reference arm and the portion forming the measuring arm are both integrated over their entire length in the baseplate;

wherein at least that portion of the waveguide forming the measuring arm is disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections, in which a coupling-free mutual minimum spacing of all straight active partial sections and deflecting sections forming the measuring arm is provided;

wherein the waveguide forming the reference arm is at least one of designed and disposed in the baseplate in such a manner that upon extension of the base plate in a direction of the straight active partial sections of the measuring arm, said reference arm operates in an extension-metrologically neutral manner; and

wherein the reference arm is also disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections in a length conforming to the length of the measuring arm, in which the straight active partial sections of the reference arm are disposed in a direction behaving in an extension-metrologically neutral manner in relation to the direction of the straight active partial sections of the measuring arm, preferably orthogonally to them in the baseplate and in which a coupling-free mutual minimum spacing of the straight active partial sections and deflecting sections of the integrated waveguide forming the reference arm in relation to one another and in relation to the straight active partial sections and deflecting sections of the measuring arm is provided.

20. An interferometer of the Fabry-Perot type formed using integrated-optics technology, comprising:

a baseplate having with waveguides integrated therein;

an entrance optical fiber supplying primary light from a laser light source, said integrated waveguides having an entrance portion extending to an edge of the baseplate and connecting in a light-conducting manner to the entrance optical fiber;

an exit optical fiber conducting interference light away from the baseplate to a detecting device, at least one further exit portion of said integrated waveguides extending to an edge of the baseplate and connecting in a light-conducting manner to the exit optical fiber;

a Y-shaped combining element combining the entrance portion and the exit portion into a common waveguide;

a resonator optically disposed downstream of the common waveguide of the combining element, said resonator being formed from a partially transmitting mirror which is integrated into the baseplate and which stands orthogonally to the waveguide and an end mirror disposed at the other end of the resonator waveguide;

wherein the resonator waveguide is disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections, in which a coupling-free mutual minimum spacing of all straight active partial sections and deflecting sections of the integrated waveguide forming the resonator is provided;

wherein two resonators with resonator waveguides of mutually equal length are integrated into the baseplate, in which the resonator waveguides of both resonators are disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections in the baseplate and a coupling-free mutual minimum spacing of all straight active partial sections and deflecting sections is provided both within each individual resonator and also between the two resonators; and

wherein the straight active partial sections of the one resonator are disposed in a direction behaving in an extension-metrologically neutral manner in relation to the direction of the straight active partial sections of the other resonator, preferably orthogonally to them in the baseplate.

21. A double-beam interferometer formed using integrated-optics technology, comprising:

a baseplate having waveguides integrated thereon;

an entrance optical fiber supplying primary light from a laser light source, said integrated waveguides having an entrance portion extending to an edge of the baseplate and connecting in a light-conducting manner to the entrance optical fiber;

an exit optical fiber conducting interference light away from the baseplate to a detecting device, at least one further exit portion of said integrated waveguides extending to an edge of the baseplate and connecting in a light-conducting manner to the exit optical fiber;

an integrated light splitting device disposed downstream of said entrance portion of the integrated waveguide for splitting an injected primary light onto a reference arm and a measuring arm of waveguides;

an integrated light coupler for combining light from the reference arm and from the measuring arm, said coupler merging into the at least one exit portion;

wherein the portion of the waveguide forming the reference arm and the portion forming the measuring arm are both integrated over their entire length in the baseplate;

wherein at least that portion of the waveguide forming the measuring arm is disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections, in which a coupling-free mutual minimum spacing of all straight active partial sections and deflecting sections forming the measuring arm is provided;

wherein the waveguide forming the reference arm is at least one of designed and disposed in the baseplate in such a manner that upon extension of the baseplate in a direction of the straight active partial sections of the measuring arm, said reference arm operates in an extension-metrologically neutral manner;

wherein the reference arm is also disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections in a length conforming to the length of the measuring arm, in which the straight active partial sections of the reference arm are disposed in a direction behaving in an extension-metrologically neutral manner in relation to the direction of the straight active partial sections of the measuring arm, preferably orthogonally to them in the baseplase and in which a coupling-free mutual minimum spacing of the straight active partial sections and deflecting sections of the integrated waveguide forming the reference arm in relation to one another and in relation to the straight active partial sections and deflecting sections of the measuring arm is provided; and

wherein the deflecting sections between two successively following straight active partial sections within the integrated waveguide forming the measuring arm or within that forming the reference arm are respectively formed by a semicircular arcuate piece or by a pair of quadrant-shaped arcuate pieces, disposed in mirror image, with a straight connecting piece disposed therebetween.

22. A double-beam interferometer formed using integrated-optics technology, comprising:

a baseplate having waveguides integrated thereon;

an entrance optical fiber supplying primary light from a laser light source, said integrated waveguides having an entrance portion extending to an edge of the baseplate and connecting in a light-conducting manner to the entrance optical fiber,

an exit optical fiber conducting interference light away from the baseplate to a detecting device, at least one further exit portion of said integrated waveguides extending to an edge of the baseplate and connecting in a light-conducting manner to the exit optical fiber;

an integrated light splitting device disposed downstream of said entrance portion of the integrated waveguide for splitting an injected primary light onto a reference arm and a measuring arm of waveguides;

an integrated light coupler for combining light from the reference arm and from the measuring arm, said coupler merging into the at least one exit portion;

wherein the portion of the waveguide forming the reference arm and the portion forming the measuring arm are both integrated over their entire length in the baseplate;

wherein at least that portion of the waveguide forming the measuring arm is disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections, in which a coupling-free mutual minimum spacing of all straight active partial sections and deflecting sections forming the measuring arm is provided;

wherein the waveguide forming the reference arm is at least one of designed and disposed in the baseplate in such a manner that upon extension of the baseplate in a direction of the straight active partial sections of the measuring arm, said reference arm operates in an extension-metrologically neutral manner;

wherein the reference arm is also disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections in a length conforming to the length of the measuring arm, in which the straight active partial sections of the reference arm are disposed in a direction behaving in an extension-metrologically neutral manner in relation to the direction of the straight active partial sections of the measuring arm, preferably orthogonally to them in the baseplate and in which a coupling-free mutual minimum spacing of the straight active partial sections and deflecting sections of the integrated waveguide forming the reference arm in relation to one another and in relation to the straight active partial sections and deflecting sections of the measuring arm is provided;

wherein the deflecting sections between two successively following straight active partial sections within the integrated waveguide forming the measuring arm or within that forming the reference arm are respectively formed by a semicircular arcuate piece or by a pair of quadrant-shaped arcuate pieces, disposed in mirror image, with a straight connecting piece disposed therebetween; and

wherein the loops, composed of straight active partial sections and circular-arcuate deflecting sections of the waveguide forming the measuring arm and/or of that forming the reference arm are disposed in the form of at least one oval spiral, in which a waveguide partial section extends from the innermost active partial section, crossing the other active partial sections of the one side of the oval spiral, to a region situated outside the oval spiral.

23. An interferometer of the Fabry-Perot type formed using integrated-optics technology, comprising:

a baseplate having waveguides integrated therein;

an entrance optical fiber supplying primary light form a laser light source, said integrated waveguides having an entrance portion extending to an edge of the baseplate and connecting in a light-conducting manner to the entrance optical fiber;

an exit optical fiber conducting interference light away from the baseplate to a detecting device, at least one further exit portion of said integrated waveguides extending to an edge of the baseplate and connecting in a light-conducting manner to the exit optical fiber;

a Y-shaped combining element combining the entrance portion and the exit portion into a common waveguide;

a resonator optically disposed downstream of the common waveguide of the combining element, said resonator being formed from a partially transmitting mirror which is integrated into the baseplate and which stands orthogonally to the waveguide and an end mirror disposed at the other end of the resonator waveguide;

wherein the resonator waveguide is disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections, in which a coupling-free mutual minimum spacing of all straight active partial sections and deflecting sections of the integrated waveguide forming the resonator is provided;

wherein two resonators with resonator waveguides of mutually equal length are integrated into the baseplate, in which the resonator waveguides of both resonators are disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections in the baseplate and a coupling-free mutual minimum spacing of all straight active partial sections and deflecting sections is provided both within each individual resonator and also between the two resonators,

wherein the straight active partial sections of the one resonator are disposed in a direction behaving in an extension-metrologically neutral manner in relation to the direction of the straight active partial sections of the other resonator, preferably orthogonally to them in the baseplate;

wherein the deflecting sections between two successively following straight active partial sections within the integrated waveguide forming the measuring arm or within that forming the reference arm are respectively formed by a semicircular arcuate piece or by a pair of quadrant-shaped arcuate pieces, disposed in mirror image, with a straight connecting, piece disposed therebetween; and

wherein the loops, composed of straight active partial sections and intermediate deflecting sections of the waveguide forming the resonator are disposed in the form of at least one oval double spiral, in which a waveguide, extending to and fro in a U shape and the parallel limb portions of which merge into one another via an end loop, is disposed so as to be wound in each instance in an oval spiral, in which a waveguide partial section extends from the outermost active partial section of the one double spiral without crossover to the adjacent double spiral.

24. An interferometer of the Fabry-Perot type formed using integrated-optics technology, comprising:

a baseplate having with waveguides integrated therein;

an entrance optical fiber supplying primary light from a laser light source, said integrated waveguides having an entrance portion extending to an edge of the baseplate and connecting in a light-conducting manner to the entrance optical fiber;

an exit optical fiber conducting interference light away from the baseplate to a detecting device, at least one further exit portion of said integrated waveguides extending to an edge of the baseplate and connecting in a light-conducting manner to the exit optical fiber;

a Y-shaped combining element combining the entrance portion and the exit portion into a common waveguide;

a resonator optically disposed downstream of the common waveguide of the combining element, said resonator being formed from a partially transmitting mirror which is integrated into the baseplate and which stands orthogonally to the waveguide and an end mirror disposed at the other end of the resonator waveguide;

wherein the resonator waveguide is disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections, in which a coupling-free mutual minimum spacing of all straight active partial sections and deflecting sections of the integrated waveguide forming the resonator is provided;

wherein two resonators with resonator waveguides of mutually equal length are integrated into the baseplate, in which the resonator waveguides of both resonators are disposed in a plurality of loops with mutually parallel oriented straight active partial sections and intermediate deflecting sections in the baseplate and a coupling-free mutual minimum spacing of all straight active partial sections and deflecting sections is provided both within each individual resonator and also between the two resonators;

wherein the straight active partial sections of the one resonator are disposed in a direction behaving in an extension-metrologically neutral manner in relation to the direction of the straight active partial sections of the other resonator, preferably orthogonally to them in the baseplate;

wherein the deflecting sections between two successively following straight active partial sections within the integrated waveguide forming the measuring arm or within that forming the reference arm are respectively formed by a semicircular arcuate piece or by a pair of quadrant-shaped arcuate pieces, disposed in mirror image, with a straight connecting piece disposed therebetween; and

wherein the loops, composed of straight active partial sections and intermediate deflecting sections of the waveguide forming the resonator are disposed in the form of at least one oval spiral, in which a waveguide partial sections extends from the innermost active partial section, crossing the other active partial sections of the one side of the oval spiral, to a region situated outside the oval spiral.