Timothy J. Drapela

A comparison of far-field methods for determining mode field diameter of single-mode fibers using both Gaussian and Petermann definitions

An interlaboratory comparison is presented of far-field measurement methods for determining mode field diameter of single-mode fibers. The comparison was conducted by member of the Electronic Industries Association. Measurements were made on dispersion-unshifted and dispersion-shifted fibers at 1300 and 1550 nm. Results were calculated using both Petermann and Gaussian definitions. The Petermann definition gave better agreement than the Gaussian in all cases. A systematic offset of 0.52 mu m was observed between methods when applied to dispersion-shifted fibers. Such an offset may be caused by limited angular collection. >

A statistical model for cladding diameter of optical fibres

The National Institute of Standards and Technology has developed a contact micrometer for accurate measurement of the outer diameter of optical fibres. The contact micrometer is used to measure reference fibres that are artefacts used by the telecommunications industry for calibrating their own measurement systems. We present a model for diameters measured by the contact micrometer. Based on this model, the probability distribution of the diameters is derived and two diameter estimates are presented. We illustrate and compare the diameter estimates using simulated data.

Scanning confocal microscopy for measuring diameter and linewidth: numerical modeling

The image of a circular edge was calculated as determined by a scanning confocal microscope with fully coherent illumination. In scalar theory, the quarter-intensity point locates the geometrical-optics image of a straight edge. For a circular object, however, the quarter- intensity point is displaced from the geometrical-optics image of the edge according to the diameter of the object. For example, for an object that has a diameter of 21 resolution limits the displacement error is approximately 0.01 resolution limits. The error that results from locating the quarter-intensity point for diameters as small as 1 resolution limit is given. The error is even greater if the object is scanned off-axis. For example, the error for an object whose diameter is 21 resolution limits and which is scanned 3 resolution limits off-axis is approximately 0.45 resolution limits. Finally errors are calculated for vertical lines of width as small as 1 resolution limit.