| Summary: | 碩士 === 國立臺灣大學 === 電機工程研究所 === 84 === The propagation characteristics of symmetrical 2x2 fused fiber-
optic couplers made of two identical fibers are theoretically
investigated using the surface integral equation method (SIEM)
in this research. By nonuniformly dividing the boundary contour
of the dumbbell-shaped cross-section of the coupler, the
accurate coupling characteristics, including the coupling
coefficients of x and y polarization states and the form
birefringence, have been calculated. For the more strongly
fused couplers, an improved model of the coupler's cross-
section, which is no longer dumbbell-shaped, has been adopted.
A three-dimensional electromagnetic model for the fused tapered
couplers has been developed by combining the SIEM and the step-
like approximation method for the tapered structure. The
simulation results agree well with the measured coupling
behaviors of the practical fused couplers fabricated in our
group. The characteristics of the couplers with different
structure parameters are analysed in detail. Using the 3-D
modeling, the fused couplers with various functions can be
designed.
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