MZI-based wavelength-shift detection system with tunable-FBG

Proposed and demonstrated in this letter is a scheme of fiber Bragg grating (FBG) sensor interrogation system based on all fiber Mach-Zehnder Interferometer (MZI) edge filter and tunable-FBG, of which the Bragg period is tunable through a one-dimensional adjustor. Wavelengths message of FBG sensor and the tunable-FBG are transformed into powers message by a pair of the filtering edges of the filter, respectively; and the wavelength difference between the FBG sensor and the tunable-FBG can be obtained through differing the two pairs powers message. In measured experiments, the results show that the precision of the proposed system is 0.02nm in a range of 1nm. The wavelength measurement range can be improved by adjusting the length difference of the two interference arms of the filter.