PRECISION FABRICATION OF D-SHAPED SINGLE-MODE OPTICAL FIBERS BY IN-SITU MONITORING

A technique has been developed to locally remove, over a distance of s everal millimeters of fiber length, the cladding layer of single-mode (at the 1300 nm wavelength) optical fibers with 1 mu m depth precision by use of mechanical lapping and in situ optical transmission monitor ing. A cylinder lap dressed with diamond is used to perform high-press ure mechanical lapping. The in situ monitoring technique is based on t he specific different attenuations exhibited by higher order propagati ng modes (for 633 nm light) as the cylinder penetrates into the fiber. Advantages include relatively rapid overall processing, high lapping rate, good optical surface quality, and 1 mu m precision. Experimental results are presented and analyzed by an approximate geometrical-opti cs model.