An eccentric core optical fiber (ECOF) for distributed evanescent field sensing is proposed. The finite element method (FEM) is utilized to analyze characteristics of the ECOF, including the fractional power of coating and core. A strong evanescent field exits in the coating of the ECOF due to a small distance between the core and the coating. The sensitivity or resolution of this kind sensing fiber is analyzed. The sensitivity is ~0.25dB/RIU or resolution of 4×10−3 in the range of 1.4-1.42. The sensing length is in the range of 16m-160m.
Modal fields, propagation constant and power distribution of single-mode eccentric core optical fiber are calculated
based on the weakly wave-guiding approximation. The calculation of the propagation constant and power distribution is
in terms of the change of the coating refractive index and eccentric distance. It is found that the evanescent field power
depends on the coating refractive index and eccentric distance. In eccentric core side coating, the higher coating
refractive index, the stronger evanescent field power and the larger eccentric distance, the weaker evanescent field
power. The present results will be useful for deciding the geometric structure of the fiber to achieve maximum power of
the evanescent field in eccentric core side coating to enhance the sensing sensitivity.