Single coherence peak extraction among synthesized periodical peaks by different beat frequencies for elongation of measurement range in multiplexed long-length distributed FBG sensors

摘要

A scheme to extract only one coherence peak among multiple peaks synthesized in synthesis of optical coherence function (SOCF) technique is proposed, and elongation of measurement range of multiplexed distributed long-length FBG sensors is demonstrated. In the SOCF systems, distributed measurement is carried out by sweeping the position of a coherence peak synthesized with optical frequency modulation of a laser source. Since, only one coherence peak is allowed to exist in the measurement range for the distributed measurement, the measurement range was limited within the interval of the peaks. In the proposed scheme, only one peak can be extracted among the multiple coherence peaks by using different heterodyne beat frequency caused in each peak when the laser center frequency is swept in high speed for shaping the FBG reflection spectrum. Extracted single peak is successfully swept over the conventional measurement range in our multiplexed distributed long-length FBG sensor system.