In-line electro-optic voltage sensor

A fiber optic voltage sensor comprising:

• a light source;
• a polarizer connected to said light source;
• a birefringence modulator connected to said polarizer;
• an electro-optic sensor connected to said birefringence modulator;
• a delay line connected to said electro-optic sensor;
• a quarter-wave device connected to said delay line;
• and
• a reflective device connected to said quarter-wave device.

An optical voltage sensor comprising:

• a light source;
• a polarizer proximate to said light source;
• a first splitter proximate to said polarizer;
• an electric field sensitive phase shifter proximate to said splitter;
• a delay line proximate to said electric field sensitive phase shifter;
• a first quarter-wave device connected to said delay line;
• a reflective termination connected to said quarter-wave device;
• a second quarter-wave device proximate to said first splitter;
• a second splitter proximate to said second quarter-wave device;
• a first detector proximate to said second splitter;
• a second detector proximate to said second splitter;
• and
• a signal processor connected to said first and second detectors.

A voltage sensor comprising:

• means for providing light;
• means for polarizing light, connected to said means for providing light;
• first means for splitting light, connected to said means for polarizing light;
• means for phase shifting light in response to an electric field of a voltage;
• means for delaying and reflecting light in an opposite polarization;
• means for receiving and phase shifting reflected light from said first means for splitting light;
• second means for splitting light, the light being split into a first beam of a first polarization and a second beam of a second polarization;
• first means for converting the first beam into a first electrical signal;
• second means for converting the second beam into a second electrical signal;
• and
• means for processing the first and second electrical signals into a third electrical signal indicative of the electric field of the voltage.

A voltage sensor comprising:

• a light source;
• a polarizer connected to said light source;
• a birefringence modulator connected to said polarizer;
• an electro-optic sensor connected to said birefringence modulator;
• a delay line connected to said electro-optic sensor;
• and
• a quarter-wave reflective termination connected to said delay line.

A voltage sensor wherein:

• light from a source goes to a polarizer;
• light of a first linear polarization exits from said polarizer in a first polarization maintaining optical fiber;
• light of the first linear polarization goes to a second polarization optical fiber via a connection having axes of said first and second polarization maintaining optical fibers aligned at about 45 degrees, thereby resulting in light of the first linear polarization and a second linear polarization in said second polarization maintaining optical fiber;
• light of the first and second linear polarizations goes from said second polarization maintaining fiber to a birefringence modulator;
• said birefringence modulator provides a bias modulation, caused by a bias modulation signal from a signal processor, of a birefringence between first and second polarization axes of a light medium in said birefringence modulator, thereby affecting the phase relationship between light of the first and second polarizations;
• light from said birefringence modulator goes through a third polarization maintaining fiber to an electro-optic sensor;
• said electro-optic sensor provides a modulation of birefringence between the first and second polarization axes of a light medium in said electro-optic sensor, the modulation caused by an electric field of a voltage being measured, thereby resulting in a non-reciprocal phase shift between light of the first and second polarizations;
• light from said electro-optic sensor goes to a delay line and a quarter-wave optical termination that reflects light of the first polarization as light of the second polarization and reflects light of the second polarization as light of the first polarization;
• light of second and first polarizations returns through said delay line to said electro-optic sensor;
• said electro-optic sensor again provides a modulation of birefringence between the first and second polarization axes of the light medium in said electro-optic sensor, thus resulting in further non-reciprocal phase shift between light of the first and second polarizations;
• light from said electro-optic modulator goes through said third polarization maintaining fiber to said birefringence modulator for further bias modulation of the phase relationship between the light of the first and second polarizations;
• light from said birefringence modulator goes through said second polarization maintaining fiber onto said first polarization maintaining fiber via the connection of said first and second polarization maintaining fibers;
• light from said first polarization maintaining fiber goes through said polarizer;
• and
• light from said polarizer goes to a detector that provides a first electrical signal representative of the light, to a processor;
• a second electrical signal from said processor goes to an integrator;
• and
• a third electrical signal from said integrator indicates an intensity of the electric field that in turn indicates a magnitude of the voltage to be measured.

A voltage sensor comprising:

• a light source;
• a polarizer connected to said light source;
• a Faraday rotator connected to said polarizer;
• an electro-optic sensor connected to said Faraday rotator;
• a delay line connected to said electro-optic sensor;
• and
• a quarter-wave reflective termination connected to said delay line;
• and
• wherein said electro-optic sensor is proximate to an electric field of a voltage to be measured.

A voltage sensor comprising:

• a light source for providing a first beam;
• a polarizer for polarizing the first beam to a first polarization;
• a beam splitter for passing a portion of the first beam which is a second beam;
• an electro-optic sensor having birefringence axes aligned at about 45 degrees relative to axes of said polarizer, for receiving a first portion of the second beam in the first polarization and a second portion of the second beam in a second polarization, and for birefringently phase modulating the second beam;
• a delay line connected to said electro-optic sensor having polarization axes aligned with each other, for delaying the second beam;
• a first quarter-wave plate connected to said delay line having polarization axes aligned at about 45 degrees, wherein the second beam is reflected back having the first portion in the second polarization and the second portion in the first polarization;
• a second quarter-wave plate, aligned with said electro-optic sensor, for receiving a third beam which is a portion of the second beam reflected by the said first quarter-wave plate through said delay line, electro-optical sensor, and reflected by said beam splitter through said second quarter-wave plate, wherein a first portion of the third beam is of the first polarization and a second portion of the third beam is in the second polarization, and said quarter-wave is for providing about a 90 degree bias phase shift between the first and second portions of said third beam;
• a second beam splitter for receiving the third beam from said second quarter-wave plate, and splitting the third beam into the first and second portions;
• a first detector for converting the first portion of the third beam into a first electrical signal;
• a second detector for converting the second portion of the third beam into a second electrical signal;
• and
• a signal processor connected to said first and second detectors, for processing the first and second electrical signals into a signal representing a non-reciprocal phase shift that is proportional to a time derivative of the electric field of the voltage to be measured.