| 摘要 |
<p>METHOD FOR MEASURING THE PARAMETERS OF OPTICAL FIBERS The present invention relates to a method of measuring the diameter, DC, of the core of a clad optical fiber, given the thickness of the cladding layer, t, and the refractive indices of the cladding and of the core, m1 and m2 respectively. The method is comprised of directing a beam of spatially coherent, monochromatic radiation at the fiber thereby to generate a complex scattering pattern at least a portion of the pattern must include contributions from the diffraction, the reflection and the refraction of the beam by the fiber. The scattering pattern is spatially, radially disposed about the fiber and has a fringe pattern intensity modulated superimposed thereon. The method further includes, at a given reference angle .THETA.R, measuring the modulation pattern over an angle range .DELTA..THETA.R, where .THETA.R satisfies the relationship .THETA.R + 1/2 .DELTA..THETA.R < .THETA.F, where .THETA.F is the cut-off angle which, in turn, satisfies the relation m1 cos(.THETA.F/2) = 1. The method further includes the step of determining the core-to-fiber diameter ratio, R, by comparing the measured modulation pattern with modulation patterns priorly observed for clad optical fibers of the same core and cladding indices, measured at the same scattering angle range .DELTA.OR and then computing the core diameter DC from the equation DC = 2Rt(1 - R).</p> |
