Fiber optic electric field sensor/phase modulator
AssigneeOptical Technologies, Inc.
InventorsEdward F. Carome, Charles M. Davis
Life of this patent
Estimating the term…
Abstract
The invention relates to a technique for detecting electric fields by modulating the phase of an optical beam. A length of optical fiber is jacketed with or attached to piezoelectric material that is poled perpendicular to the length of the fiber. An electric field is applied across the piezoelectric element, i.e. in the direction of poling, resulting in a change in the element thickness and a change in the axial dimension, which, in turn, changes the length of the optical fiber. The change in fiber length is accompanied by a smaller change in the refractive index of the fiber. The result is a shift in the optical phase.
Claims26
An antenna system for receiving r.f. electric fields, the system comprising:
- (a) a source of coherent light;
- (b) at least a first and a second optical fiber operatively connected with the coherent light source for transmitting coherent light therefrom;
- (c) photodetector means operatively connected with the optical fibers for detecting the coherent light transmitted therethrough;
- and,
- (d) an electric field-responsive sensor operatively connected with at least the first optical fiber, the sensor including:
- (i) an electric field receiving piezoelectric element which is unshielded by electrodes such that electric fields are free to impinge directly thereon, the piezoelectric element being poled such that the incident electric fields cause corresponding length changes in the piezoelectric element,
- (ii) means for attaching the piezoelectric element to the first optical fiber such that the length changes of the piezoelectric member cause a corresponding length changes of the first optical fiber, whereby the incident electric fields change the length of the optical path between the coherent source and the photodetector means through the first optical fiber which, in turn, changes the relative phase of the coherent light transmitted through the first and second optical fibers in correspondence to the incident electric field.
An optical fiber sensor system for sensing electric fields, the system comprising:
- (a) at least two optical fibers, each optical fiber being adapted to extend between a source of coherent light and a detector means for detecting the relative phase of coherent light transmitted therethrough;
- and,
- (b) a piezoelectric direct electric field sensor means operatively connected with at least one of the optical fibers for changing the length of said one optical fiber in response to changes in an incident electric field, whereby the change in length of the one optical fiber causes a corresponding change in the relative phase of the coherent light transmitted through the optical fibers.
A method of receiving electric fields comprising:
- transmitting coherent light through at least two optical fibers;
- comparing the relative phase of the coherent light transmitted through the two fibers;
- piezoelectrically exerting a longitudinal strain along one of the optical fibers, which optical strain varies in proportion to an incident electric field, the longitudinal strain altering the physical properties of the one optical fiber including the length of the one optic fiber in correspondence to the incident electric field, whereby the incident electric field causes a change in the relative lengths of the two optical fibers which, in turn, changes the relative phase between the coherent light transmitted through the two optic fibers in correspondence to the incident electric fields;
- and,
- determining a change in the relative phase of the coherent light transmitted through the two optic fibers which corresponds to the incident electric field.
Dependencies are inferred from the claim text.