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Temperature and strain properties of photonic bandgap fiber sensors

Photonic bandgap fiber have progressed rapidly in recent years and is of great interest for optical fiber sensors applications because of the bandgap effect, high thermos-optical coefficient and birefringence coefficient. The high temperature and stain sensitive is attractive and significant for sensors application. Optimal design themicro-structure of all-solid photonic bandgap fiber with is necessary to for fiber sensors. Theoretical research of sensing theory and sensitive properties for PBGF sensor systematically and deeply has not been reported. The temperature and strain sensitive properties of the all-solid photonic bandgap fiber with different Ge-rod diameter and space are analyzed in this paper. Mode distribution and white light transmittance spectrum are calculated by COMSOL software with finite element method. Both core mode and cladding modes of the photonic bandgap fiber are analyzed for different parameters. Then the optical mode filed is coupled with thermal field and stress field respectively. Temperature and strain sensitivities are obtained based on the above simulation. The simulating results show that bandgap position at short wavelength side is sensitive with temperature and transverse bending stress, while the cladding modes are more sensitive to the longitudinal stress. The temperature and strain sensitive properties are compared with the different parameter fibers. Finally an all solid photonic bandgap fiber sensor with optimized parameter is designed and the temperature and strain properties are also stated. The designed photonic bandgap fiber sensor will be available for tunnel and bridge engineering in temperature and stress sensing area. Further experimental verification will be proceed in next step.