Voltage sensing systems and methods for passive compensation of temperature related intrinsic phase shift

An electro-optical sensor for use in an electric field that self-compensates for temperature variations induced on an input beam propagating through the sensor, the sensor comprising:

• Pockels effect means having three orthogonal indices of refraction designated np1, np2, and np3 for generating a phase differential on the input beam in response to the electric field;
• compensating means optically coupled to the Pockels effect means for substantially canceling temperature sensitive variations in the phase differential of the input beam;
• and
• electric field shielding means for preventing the compensating means from exhibiting a Pockels effect.

A method of self-compensating for environmental variations induced in an input beam propagating through an electro-optical sensor subject to an electric field, the method comprising the acts of:

• selecting a Pockels crystal having three orthogonal indices of refraction designated np1, np2, and np3;
• selecting a compensating crystal possessing optical properties substantially identical to the Pockels crystal, the compensating crystal having three orthogonal indices of refraction, designated nc1, nc2, and nc3, that correspond to the similarly numbered indices of refraction of the Pockels crystal;
• rotating the compensating crystal approximately 90 degrees with respect to the Pockels crystal, such that nc1 of the compensating crystal is oriented in the same direction as np2 of the Pockels crystal and nc2 of the compensating crystal is oriented in the same direction as np1 of the Pockels crystal;
• optically coupling the compensating crystal and the Pockels crystal;
• and
• placing electric field shielding around the compensating crystal to insure the compensating crystal does not produce a Pockels effect on the input beam.

A system, in an environment having a voltage and an electric field, for measuring the voltage, the system comprising:

• a detector comprising:
• a light source for generating an input beam;
• and
• a first and second photo detector for receiving a first and second output beam;
• and
• a sensor operably connected to the detector, the sensor comprising:
• a Pockels crystal for receiving a first component of the input beam,
• wherein the Pockels crystal is oriented in the electric field such that the first component experiences a phase differential to produce an elliptically polarized output beam;
• a compensating crystal shielded from the electric field and optically connected to the Pockels crystal, the compensating crystal possessing optical properties substantially identical to the Pockels crystal and rotated approximately 90 degrees with respect to the Pockels crystal such that a portion of the phase differential attributable to temperature variations is eliminated;
• and
• a beam displacer optically connected to the compensating crystal and oriented at an angle with respect to the compensating crystal, wherein the beam displacer:
• receives the input beam from the light source and separates the input beam into the first and second components, wherein the first and second components are orthogonal and the first component impinges the compensating crystal at the angle;
• and
• receives the elliptically polarized output beam from the compensating crystal and separates the elliptically polarized output beam into the first and second output beams which represent a major axis and a minor axis of the elliptically polarized output beam;
• and
• a signal processor for receiving at least one signal from the first and second photo detectors, wherein the signal processor computes the voltage from the at least one signal.

An electro-optic sensor for measuring a voltage while subjected to an electric field generated by the voltage, the sensor comprising:

• a Pockels crystal, having Pockels crystal axes, for receiving a linearly polarized first component of an input beam, the Pockels crystal being oriented in the electric field such that the first component experiences a differential phase shift to produce an output beam having a major axis component and a minor axis component, wherein the output beam is amplitude modulated by a frequency of the electric field;
• a compensating crystal shielded from the electric field and optically connected to the Pockels crystal, the compensating crystal possessing optical properties substantially identical to the Pockels crystal and rotated approximately 90 degrees with respect to the Pockels crystal;
• a beam displacer, having beam displacer axes, oriented at an orientation angle such that the Pockels crystal axes are offset from the beam displacer axes by the orientation angle, wherein the beam displacer:
• receives an input beam and separates the light beam into a linearly polarized first component and a linearly polarized second component, wherein the linearly polarized first component is parallel to one of the beam displacer axes and impinges the Pockels crystal at the orientation angle;
• and
• receives the output beam from the Pockels crystal and separates the output beam into the major axis component and the minor axis component, whereby the voltage is determined by analyzing the amplitude of at least one of the major axis component and the minor axis component;
• and
• a prism for reflecting the linearly polarized first component which enters the Pockels crystal from the beam displacer back towards the beam displacer.