Temperature-Insensitive Micro Fabry–PÉrot Strain Sensor Fabricated by Chemically Etching Er-Doped Fiber

Micro extrinsic Fabry-Perot interferometric (MEFPI) sensors are fabricated by chemically etching Er-doped fibers with mixed hydrochloric (HCl) and hydrofluoric (HF) acid and fusion splicing. Compared with MEFPI sensors fabricated by etched single-mode fibers, the sensor performance is greatly improved by the chemical reaction between HCl acid and doped Er
₂
O
₃
. A maximum visibility of ~24 dB is obtained, comparable to that of MEFPI sensors fabricated by excimer lasers. Our MEFPI sensor has high mechanical strength as the etching rate difference between fiber core and cladding is enlarged. Preliminary results indicate that this kind of sensor is insensitive to temperature while highly sensitive to strain, with sensitivities of ~0.65 pm/degC and ~3.15 pm/muepsiv, respectively.