Ultra-sensitive optical fiber sensor based on intermodal interference and temperature calibration for trace detection of copper (II) ions.

An ultrahigh sensitive optical fiber sensor for trace detection of Cu concentration in aqueous solution with temperature calibration has been developed in this article. Based on the intermodal interference, the sensor is coated with a hydrogel sensing membrane with specific binding to Cu on the no-core fiber/single mode fiber/no-core fiber structure by using our new spray coating method. The imidazole group in the sensing film combines with Cu to produce chelation, which changes the refractive index of the sensing film.