Environmentally stable Fabry-Perot-type strain sensor based on hollow-core photonic bandgap fiber

We design and demonstrate a miniature all-fiber Fabry-Perot (F-P) interferometric sensor based on hollow-core photonic bandgap fiber where the strain is gauged by measuring the spectrum shift of the reflected optical signal. The F-P cavity in the order of millimeters is fabricated by simple techniques of cleaving and fusion splicing. The sensitivity of the sensor is 1.55 pm/mu epsilon at the wavelength of 1550 nm and the contrast of the intensity reaches 4-6 dB. Temperature and bend insensitivity and excellent repeatability of the sensor make it convenient for a wide range of applications.