Multi-parameter measurement under fiber bending based on directional resonance coupling in photonic crystal fibers

摘要

A multi-parameter sensor with enhanced sensitivity based on magnetic fluids infiltrated photonic crystal fiber is proposed. The sensing performances are investigated using the mode coupling theory and finite element method. Four symmetrical defective channels are assembled into the photonic crystal fiber to produce two resonant transmission dips lambda(CV) and lambda(CH) in vertical and horizontal directions, respectively. Each dip can be split into two relatively shallow dips (lambda(CV1),lambda(CV2)) or (lambda(CH1),lambda(CH2)) when the photonic crystal fiber is bent. Interestingly, the values of (lambda(CH2)- lambda(CH1)) and (lambda(CV2),lambda(CV1)) are associated with corresponding bend-curvature but almost unaffected by external temperature or magnetic field. On the contrary, the values of (lambda(CH2)+lambda(CH1))/2 and (lambda(CV2)- lambda(CV1))/2 are sensitive to temperature or magnetic field regardless of the bending condition. Based on above characteristics and the dependence of the magnetic fluids refractive index on temperature and magnetic field, the proposed sensor can measure not only the bend-curvature and bend-direction, but also the temperature and magnetic field.