Fiber optic angular rate sensor including digital phase modulation

• US 5,400,142 A
• Filed: 05/03/1994
• Issued: 03/21/1995
• Est. Priority Date: 05/03/1994
• Status: Expired due to Fees

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Alliedsignal Inc. (Honeywell International Inc.)
• Inventors: Lavin, Thomas J.
• Primary Examiner(s): Lee, John D.
• Application Number:
  US08/237,526
• Time in Patent Office: 322 Days
• Field of Search: 356/349, 356/350, 385/1-3, 385/12, 385/13, 385/14, 385/16
• US Class Current: 356/464
• CPC Class Codes: G01C 19/721 Details

Abstract

A digital phase modulation arrangement for a fiber optic angular rate sensor utilizes Pockels electro-optical effect operating in the transverse mode. Light travels around a fiber optic coil in clockwise and counterclockwise directions. An error signal corresponding to the phase difference between the clockwise and counterclockwise traveling light is applied to a digital processor which provides a plurality of logic bits. The logic bits are applied to voltage/phase transducers arranged on an integrated optics chip. The voltage/phase transducers are switched from an applied reference voltage to a particular voltage level to induce a phase change through Pockels electro-optical effect.

Claims

1. In a fiber optic angular rate sensor of the type wherein light from a light source travels around a fiber optic coil in clockwise and counterclockwise directions, and a digital error signal is provided corresponding to the phase difference between the clockwise and counterclockwise traveling light, a phase modulation arrangement comprising:

digital processor means responsive to the error signal applied thereto for providing a plurality of logic bits;

an integrated optics chip having a confined light path for the light traveling around the fiber optic coil and including a corresponding plurality of voltage/phase transducers;

said integrated optics chip further including a corresponding plurality of switching means, wherein each of the switching means switches a respective voltage/phase transducer from an applied reference voltage to a particular voltage level to induce a phase change through Pockels electro-optical effect operating in the transverse mode.

2. In a fiber optic angular rate sensor of the type wherein light from a light source travels around a fiber optic coil in clockwise and counterclockwise directions and a detector detects the clockwise and counterclockwise light and provides an analog electrical error signal corresponding to the phase difference between said clockwise and counterclockwise traveling light, phase modulation means comprising:

an analog to digital converter for converting the analog error signal to a digital signal;

digital processor means connected to the analog to digital converter and responsive to the digital signal therefrom for providing a plurality of logic bits; and

voltage/phase transducer means arranged on an integrated optics chip having a confined light path for the light traveling around the fiber optic coil and switching means connected to the digital processor means and responsive to the logic bits provided by said digital processor means for switching the voltage/phase transducer means from an applied reference voltage level to a particular voltage level through Pockels electro-optical effect operating in the transverse mode to induce a phase change.

3. Phase modulation means as described by claim 2, wherein:

the integrated optics chip is arranged to exhibit a linear relationship between the reference voltage level and a phase delay imparted to the confined light path for the light traveling around the fiber optic coil.

4. Phase modulation means as described by claim 3, wherein:

the integrated optics chip includes a substrate and a plurality of phase control terminals and a grounded terminal on the substrate; and

the effective index of refraction of the confined light path is increased by the application of the logic bits to respective control terminals so that said terminals are at a particular voltage relative to the grounded terminal.

5. In a fiber optic rate sensor of the type wherein light from a light source travels around a fiber optic coil in clockwise and counterclockwise directions, and an analog electrical error signal is provided corresponding to the phase difference between the clockwise and counterclockwise traveling light, a phase modulation arrangement comprising:

means for converting the analog electrical error signal to a digital signal;

means connected to the converting means for processing the digital signal therefrom to provide a plurality of logic bits;

voltage/phase transducer means arranged as an integrated optics chip having a confined light path for the light traveling around the fiber optic coil;

said voltage/phase transducer means including a plurality of voltage to phase transducers, each of said plurality of transducers having a different gain, and a plurality of switching means;

each of said plurality of switching means being actuated by a logic bit of the plurality of logic bits to activate a corresponding voltage/phase transducer of the plurality of said transducers, whereby said transducers are switched from an applied reference voltage to a particular voltage level to induce a phase change through Pockels electro-optical effect operating in the transverse mode.

6. For a fiber optic angular rate sensor of the type including directing light from a light source for traveling around a fiber optic coil in clockwise and counterclockwise directions, detecting the clockwise and counterclockwise traveling light, and providing an electrical error signal corresponding to the phase difference between said clockwise and counterclockwise traveling light, a phase modulation method comprising:

converting the analog error signal to a digital signal;

processing the digital signal for providing a plurality of logic bits;

arranging voltage/phase transducer means on an integrated optics chip having a confined light path for the light traveling around the fiber optic coil;

arranging switching means on the integrated optics chip in operative relation with the voltage/phase transducer means and the plurality of logic bits; and

using the logic bits for actuating the switching means for switching the voltage/phase transducer means from an applied reference voltage level to a particular voltage level through Pockels electro optical effect operating in the transverse mode.

7. A method as described by claim 6, including:

arranging the integrated optics chip for exhibiting a linear relationship between the reference voltage level and a phase delay imparted to the confined light path for the light traveling around the fiber optic coil.

8. A method as described by claim 7, including:

forming the integrated optics chip from a substrate and providing a plurality of phase control terminals and a grounded terminal on the substrate; and

applying the logic bits to respective control terminals so that said terminals are at a particular voltage relative to the ground terminal.