Real-Time Bending Sensing Based on a Strong-Coupled SCF Structure and Time-Stretch Technique

The real-time interrogation of optical fiber sensors is highly desirable in a wide range of applications that require precise and dynamic measurements. Herein, a novel real-time bending interrogation based on a strong-coupled seven-core fiber (SC-SCF) structure and time-stretch technique has been experimentally demonstrated. The proposed SC-SCF-based Mach-Zehnder interferometer (MZI) plays a role of comb filter with the advantage of low insertion loss and highly sensitive bending response. The time-stretch technique is accomplished using a wideband and high-power femtosecond all-PM fiber laser source that based on the self-similar amplification method. Due to the mechanism of wavelength-to-time mapping, real-time spectrum-encoded waveform of bending response can be obtained at an interrogation speed of 79.23 MHz. By monitoring the time shift of bending response, a bending sensitivity of −2.19629 ns/m<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula> and a bending resolution of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$56.914~\mu $ </tex-math></inline-formula>m<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula> can be achieved. Furthermore, the compact size and high sensitivity of our real-time interrogation technique give it a competitive edge in the fields, where fast measurements are crucial.