Augmented Sensitive Strain Sensor With Arched Core Based on MSM Structure

High-precision axial strain sensors are extensively needed in various fields of strain measurement. In this article, a novel optical fiber strain sensor with high sensitivity is designed and experimentally testified. By introducing arched core into the single-mode fiber (SMF) with multimode–single-mode–multimode (MSM) structure, higher order cladding modes are excited and higher strain sensitivity is achieved. It is worth noting that the two resonant peaks (Dip 1: 1254.6 nm and Dip 2: 1343.2 nm) drift in opposite directions as the strain increases. The experiments prove that in the range of 0–<inline-formula> <tex-math notation="LaTeX">$240 ~\mu \varepsilon $ </tex-math></inline-formula>, the strain sensitivity of Dips 1 and 2 is 63 and −51 pm/<inline-formula> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula>, respectively. Since the two resonant peaks drift in opposite directions, the strain sensitivity of the sensor can reach 114 pm/<inline-formula> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> after stacking their corresponding sensitivities. The sensor has the ability to monitor temperature simultaneously, and the temperature sensitivity is 14 and 44 pm/°C. The temperature and strain resolution of the sensor are 0.7 °C and <inline-formula> <tex-math notation="LaTeX">$0.19~\mu \varepsilon $ </tex-math></inline-formula>, respectively. The high sensitivity and resolution of the sensor have application potential in the fields of high-precision measurement.