Sensor unit
A sensor unit has a sensor element which has a substrate and a plurality of optical components, which are integrated into the substrate, and form a plurality of integrated optical sensors. The optical sensors are an optical current sensor based on the Faraday effect, an optical voltage sensor based on the Pockels effect, an optical strain sensor and/or a wavelength sensor. Response signals from the individual sensors are evaluated in an evaluation unit, wherein the response signals from the expansion sensor and/or from the wavelength sensor are preferably used for evaluating the response signals from the other sensors.
1. A sensor unit, comprising:
a sensor element having a substrate and a plurality of integrated optical components embedded in said substrate, said plurality of integrated optical components being modified portions of said substrate;
said plurality of integrated optical components including at least one integrated measurement waveguide forming an integrated optical sensor for measuring an electric variable and at least one further integrated optical component embedded in said substrate and forming a further integrated optical sensor;
said optical sensors being selected from the group consisting of:
a) an optical current sensor based on the Faraday effect for measuring an electric current in a current-carrying conductor;
b) an optical voltage sensor based on the Pockels effect for measuring an electric voltage;
c) an optical expansion sensor for measuring an expansion; and
d) a wavelength sensor for measuring a change in an optical wavelength.
2. The sensor unit according to claim 1 , which further comprises a common evaluation unit for evaluating response signals of said optical sensors, said evaluation unit being configured to evaluate optical response signals of said voltage sensor and/or of said current sensor with incorporation of optical response signals of said expansion sensor and/or of said wavelength sensor.
3. The sensor unit according to claim 1 , wherein one of said measurement waveguides is concurrently used for a plurality of different sensors.
4. The sensor unit according to claim 1 , wherein said optical expansion sensor forms a Michelson interferometer having two waveguide arms, which are embedded in said substrate and having different optical path lengths.
5. The sensor unit according to claim 1 , wherein said two waveguide arms of said optical expansion sensor extend in a shape of circular rings concentrically to each other and have different radii of curvature defining the different optical path lengths.
6. The sensor unit according to claim 5 , wherein one of said waveguide arms is formed at the same time by a measurement waveguide for a different sensor.
7. The sensor unit according to claim 1 , wherein said wavelength sensor has one or more of the following: a Bragg grating, a resonator ring, or a directional coupler.
8. The sensor unit according to claim 1 , wherein said optical components are integrated on a common substrate in the form of a wafer, and wherein said substrate is a circular ring segment that extends at least over 180° about a circular cutout from a first end face to a second end face.
9. The sensor unit according to claim 1 , wherein said substrate has a coupling site, at least two optical fibers, and coupling elements, that connect said at least two optical fibers to said coupling site of said substrate, wherein each of said at least two optical fibers is allocated to each said optical sensor for coupling a sensor signal into said substrate and/or for coupling a response signal out of said substrate.
10. The sensor unit according to claim 1 , wherein said substrate is a non-birefringent substrate configured to produce targeted birefringence in a partial region thereof for forming an integrated optical component having birefringent function.
11. The sensor unit according to claim 10 , wherein said substrate is configured to form an integrated lambda quarter element.
12. The sensor unit according to claim 10 , wherein said integrated optical components are formed in said substrate using an ion diffusion process, and wherein said substrate is glass.
13. The sensor unit according to claim 1 , wherein said integrated optical components are selected from the group consisting of optical waveguides in straight or curved shape, polarization-changing optical components, lambda quarter elements, coupling sites for coupling light in and out, reflective surfaces and end faces, and optical gratings.
14. The sensor unit according to claim 1 , wherein said optical voltage sensor has a coupling site for a polarization-maintaining fiber that is coupled to said substrate, an integrated optical lambda quarter element, and a measurement waveguide, which is integrated in a birefringent substrate suitable for the Pockels effect.
15. The sensor unit according to claim 1 , wherein said optical voltage sensor has a coupling site for a polarization-maintaining fiber that is coupled to said substrate, an integrated optical lambda quarter element, and a combination of an optical lens and a birefringent substrate suitable for the Pockels effect.
16. The sensor unit according to claim 15 , wherein said birefringent substrate is a birefringent crystal selected from the group consisting of a lithium niobate crystal, ammonium dihydrogen phosphate, and potassium dihydrogen phosphate.
17. The sensor unit according to claim 1 , wherein said current sensor has a coupling site for a polarization-maintaining fiber that is coupled to said substrate, an optical lambda quarter element, and a curved waveguide forming the measurement waveguide.
18. The sensor unit according to claim 1 , wherein said expansion sensor has a coupling site for a single-mode optical fiber that is coupled to said substrate, and an integrated optical waveguide, in which a surface grating having a suitable grating period is introduced.
19. The sensor unit according to claim 18 , wherein a temperature-related variation of said surface grating is used for temperature measurement.
20. The sensor unit according to claim 1 , configured for current or voltage measurement in a medium voltage installation.
21. The sensor unit according to claim 1 , wherein:
said substrate is shaped as a circular ring segment which extends at least over 180° about a circular cutout from a first end face to a second end face,
said substrate has at least two embedded waveguides;
said first end face defines a coupling site;
at least two optical fibers are connected to said coupling site of said substrate by way of coupling elements for coupling a sensor signal into said waveguides and/or for coupling a response signal out of said waveguides; and
said second end face is prepared for forming a mirror at an end of at least one of said waveguides.