Real-Time Strain Interrogation Based on an STS Structure and Wavelength-to-Time Mapping

A novel real-time interrogation technique based on an SMF-TMF-SMF (STS) structure and wavelength-to-time (WTT) mapping is proposed and experimentally demonstrated. An ultrashort optical pulse is first spectrally shaped by the homemade STS comb filter, which is formed by inserting a section of two-mode fiber (TMF) into single-mode fibers (SMF) using core-offset splicing. Linear WTT mapping is realized by employing a dispersive element and the spectrally-shaped waveform is mapped to the time domain. By monitoring the strain-encoded time shift, an ultrafast strain interrogation system with a measurement speed of 100 MHz and a strain sensitivity of 0.3 ps/ $\mu \varepsilon $ is obtained.