Composite integrity monitoring

Claim 1

A method of composite integrity monitoring by sensing strain distributed along an optical fiber, comprising the steps of: providing a composite structure, and an optical fiber, said structure comprising composite material, said optical fiber being embedded in said composite material, said optical fiber being subjected to strain; launching initial frequency varying modulated optical energy having a selectively controllable polarization state into said optical fiber; providing a reference signal representative of the modulated optical energy; mixing a portion of the optical energy backscattered from the fiber with a portion of the reference signal to produce a beat signal, the frequency of which is representative of strain at a location along the fiber; sensing the polarization state of the backscattered optical energy; and controlling the polarization state of said initial optical energy launched in response to said beat signal.

Claim 2

A method of composite integrity monitoring by sensing strain distributed along an optical fiber, comprising the steps of: providing a composite structure, and an optical fiber, said structure comprising composite material, said optical fiber being embedded in said composite material, said optical fiber being subjected to strain; launching initial frequency varying modulated optical energy having a selectively controllable polarization state into said optical fiber; providing a reference signal representative of the modulated optical energy; mixing a portion of the optical energy backscattered from the fiber with a portion of the reference signal to produce a beat signal, the frequency of which is representative of strain at a location along the fiber; sensing the polarization state of the backscattered optical energy; and controlling the polarization state of said initial optical energy launched in response to said beat signal.

Claim 7

A method of composite integrity monitoring by sensing strain at a selected location along an optical fiber, comprising the steps of: providing a composite structure, and an optical fiber, said structure comprising composite material, said optical fiber being embedded in said composite material, said optical fiber being subjected to strain; launching initial frequency varying optical energy having a selectively controllable polarization state into said optical fiber; providing a reference signal representative of the modulated optical energy; sensing the polarization state of the backscattered optical energy from the fiber below a selected frequency; controlling the polarization state of said initial optical energy launched in response to said sensed polarization state of the backscattered energy to minimize backscatter; and increasing the selected frequency to correspond to a selected location and mixing a portion of the optical energy backscattered from the fiber with a portion of the reference signal to produce a beat signal representative of strain at the selected location.

Claim 8

A method of composite integrity monitoring by sensing strain at a selected location along an optical fiber, comprising the steps of: providing a composite structure, and an optical fiber, said structure comprising composite material, said optical fiber being embedded in said composite material, said optical fiber being subjected to strain; launching initial frequency varying optical energy having a selectively controllable polarization state into said optical fiber; providing a reference signal representative of the modulated optical energy; sensing the polarization state of the backscattered optical energy from the fiber below a selected frequency; controlling the polarization state of said initial optical energy launched in response to said sensed polarization state of the backscattered energy to minimize backscatter; and increasing the selected frequency to correspond to a selected location and mixing a portion of the optical energy backscattered from the fiber with a portion of the reference signal to produce a beat signal representative of strain at the selected location.

Claim 12

A method of composite integrity monitoring by sensing strain at successive selected locations along an optical fiber, comprising the steps of: providing a composite structure, and an optical fiber, said structure comprising composite material, said optical fiber being embedded in said composite material, said optical fiber being subjected to strain; launching initial frequency varying optical energy having a selectively controllable polarization state into said optical fiber; providing a reference signal representative of the modulated optical energy; sensing the polarization state of the backscattered optical energy from the fiber below a selected frequency; controlling the polarization state of said initial optical energy launched in response to said sensed polarization state of the backscattered energy to minimize backscatter; increasing the selected frequency to correspond to a selected location and mixing a portion of the optical energy backscattered from the fiber with a portion of the reference signal to produce a beat signal representative of strain at the selected location; and repeating the second, third, and fourth steps at selectively incremented frequencies.

Claim 13

A method of composite integrity monitoring by sensing strain at successive selected locations along an optical fiber, comprising the steps of: providing a composite structure, and an optical fiber, said structure comprising composite material, said optical fiber being embedded in said composite material, said optical fiber being subjected to strain; launching initial frequency varying optical energy having a selectively controllable polarization state into said optical fiber; providing a reference signal representative of the modulated optical energy; sensing the polarization state of the backscattered optical energy from the fiber below a selected frequency; controlling the polarization state of said initial optical energy launched in response to said sensed polarization state of the backscattered energy to minimize backscatter; increasing the selected frequency to correspond to a selected location and mixing a portion of the optical energy backscattered from the fiber with a portion of the reference signal to produce a beat signal representative of strain at the selected location; and repeating the second, third, and fourth steps at selectively incremented frequencies.