초록 ▼

An optical frequency domain distributed strain sensor for determining the strain distribution along an optical fiber includes an optical source that provides a polarization controlled optical interrogation signal having a frequency that varies in a recurring linear manner. The interrogation signal i

An optical frequency domain distributed strain sensor for determining the strain distribution along an optical fiber includes an optical source that provides a polarization controlled optical interrogation signal having a frequency that varies in a recurring linear manner. The interrogation signal is injected into a sensor fiber embedded within a composite structure that places the fiber under strain. A portion of the interrogation signal is backscattered from the sensing fiber as a consequence of the strain experienced by the fiber and is mixed with a reference signal to produce beat frequency signals. The frequency of the beat signals is directly related the to position of backscatter in the sensing fiber while the amplitude of each beat frequency signal is directly related to the integrated strain-induced birefringence up to the backscatter point. An in-line fiber polarizer and an associated controllable polarizer control the polarization state of the interrogation signal in the sensor fiber to provide zero point sensitivity compensation and controllable testing for ambiguous strain points.

대표청구항 ▼

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 fi

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.