Abstract: The present invention provides a dual fiber Bragg grating strain sensor system, which comprises a broadband light source, a power reading unit, and a sensor unit having a first fiber Bragg grating and a second fiber Bragg grating placed adjacent to each other; wherein the broadband light reaches said sensor unit through said power reading unit, the light that corresponds to the intersection between the spectra of the two FBGs is backreflected and is detected by an optical power meter/detector at the detection port.

Abstract: The present invention provides a dual fiber Bragg grating strain sensor system, which comprises a broadband light source, a power reading unit, and a sensor unit having a first fiber Bragg grating and a second fiber Bragg grating placed adjacent to each other; wherein the broadband light reaches said sensor unit through said power reading unit, the light that corresponds to the intersection between the spectra of the two FBGs is backreflected and is detected by an optical power meter/detector at the detection port.

Abstract: A fiber-optic switchable wavelength filter comprises a fiber grating positioned in the thin section of the fiber, a horn with the tip attached to the side of the fiber, and a piezoelectric transducer fixed to the bottom of the horn. Upon receiving a voltage signal, the piezoelectric transducer can create acoustic wave in the horn, wherein the amplitude of the acoustic vibration in the horn is controlled by the magnitude of the voltage signal. The vibration energy is transferred and focused from the horn to the fiber, such that the operation wavelength is switched by changing the reflectivity of the optical signal at the Bragg wavelength and the reflectivity of the optical signal at the cladding-mode coupling wavelength.

Abstract: A reflectivity-tunable fiber reflector is disclosed. The Bragg reflectivity of the fiber grating is modulated by exciting the transverse vibration of the fiber through an acoustic wave. The excitation of the transverse vibration, leading to fiber grating tilting and fiber micro-bending, induces the coupling of the fiber core mode into cladding modes. This leads to the reduction of core-mode power and hence that of Bragg reflection. This mechanism is applied by this invention to control the reflectivity of a fiber optic Bragg grating after fabrication. The fiber reflector is suitable for fiber-compatible acousto-optical switching.