In this paper, we propose a new hollow-core photonic crystal fiber, which can be available for gas sensor. In addition, properties of the fiber are analyzed at the wavelength of C2H2and NH3absorption peak 1530nm and 1967nm, respectively. For both wavelengths, relative sensitivity coefficients are higher than 0.95, which makes sense in gas sensing. We also get relationship between relative sensitivity coefficient and radius of fiber core, as well as effective refractive index of the mode field.

We propose a dual-wavelength intra-cavity absorption sensor based mode competition. The sensitivity of output power to relative cavity loss in different pump current is studied experimentally by defining a sensitivity enhancement factor (SEF). A measurement sensitivity of 158.5 times that of a single-pass absorption sensor is achieved.

The surface plasmon resonance (SPR) sensor is proposed based on coating the inner surfaces of an index-guiding microstructured optical fiber (MOF) with a silver layer. Fiber core is surrounded by six large metallized holes which should facilitate the fabrication of the layered sensor structure and the infiltration of the analyte. The relationship between the sensitivity of SPR sensor and the refractive index of MOF material is demonstrated with finite element method (FEM). Numerical simulation results indicate that the sensitivity of SPR sensor decreases as the refractive index of the MOF material increasing and both spectral and intensity sensitivity are estimated to be 6.25×10-5and 6.67×10-5with low refractive index of MOF materialn=1.46.