Temperature-insensitive optical fiber strain sensor with ultra-low detection limit based on capillary-taper temperature compensation structure.

An optical fiber strain sensor based on capillary-taper compensation structure was proposed. The theoretical simulation by using the finite element analysis method shows a matching condition between the capillary length and the interference-cavity length to achieve the zero temperature crosstalk. Meanwhile, the strain sensitivity can also be improved greatly at the matching condition. We then set up an insertion controller system with high accuracy to make sure the interference-cavity length can match the capillary length. Finally the fiber strain sensor with both ultra-low temperature-crosstalk (0.05 pm/°C) and ultra-high sensitivity (214.35 pm/με) was achieved, and the experimental results agreed well with the calculated results. The "ladder-mode" and repeatability experiments showed that the proposed sensor was actually with the ultra-low detection limit of 0.047 µɛ.