MODELING AN EVANESCENT FIELD ABSORPTION OPTICAL-FIBER SENSOR

Using the weakly guiding and exact field solutions of an optical fiber , we wrote a FORTRAN program to determine the fractional power that re aches the end of an optical fiber with an absorptive cladding. We have assumed that each mode of the fiber is equally excited. This correspo nds to incoherent source excitation. The results were compared to a pr evious approximation published by Payne and Hale in 1993. We have foun d that, at low V-numbers, V<20, Payne and Hale's approximation deviate by more than 20% from the weakly guiding solution. At high V-numbers, the approximation deviates by less than 10%, When compared to Payne a nd Hale's approximation, both the weakly guiding and exact solutions a re closer to the data points obtained experimentally by Degrandpre and Burgess in 1988. Although closer than Payne and Hale's approximation, our solution still deviates from the Degrandpre and Burgess results. The difference may result from the assumption that all modes were exci ted equally, Another possibility was the fact that we have neglected l eaky modes in our treatment.