Development of a dual-tapered Փ-OTDR sensor with enhanced temperature sensitivity and extended dynamic range

A competitive dual-tapered Φ-OTDR sensor is proposed to enhance the sensitivity of the fiber under test. Experimental results demonstrate that employing two 1.5 cm-long tapers with a 20 µ m diameter embedded in a 20 m fiber sensor not only improves overall performance but also increases its efficiency. The sensor was experimentally characterized by immersing the dual-tapered 20 m fiber in a distilled water bath with a gradually increasing temperature starting from 20 °C. It exhibited an extended dynamic temperature range of approximately 20 °C, achieving a minimum temporal shift resolution of 0.14 µ s °C −1 , a minimum detectable phase shift of 3.89 × 10 −3 ± 6 × 10 −4 rad and a minimum detectable sensitivity of 0.01 V °C −1 . However, due to a saturation effect, the operational temperature range of the fabricated Φ-OTDR sensor was limited to below 40 °C. The refractive index measurements obtained from the raw Φ-OTDR signals as a function of temperature were compared with theoretical values, showing a maximum deviation of 1.52 × 10 −2 % at 36 °C. These findings highlight the enhanced performance, precision and reliability of the proposed sensor design.