22 December 1989 In-Situ Monitoring Of D-Type Fiber Etching
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A method to efficiently gauge the etching depth in a D-type fiber is presented. A more exact method of determining the etching depth of a fiber could prove beneficial in many applications where the core or cladding of a fiber must be exposed to allow interaction between external materials and devices, and the light which propagates in the fiber. D-type fibers are etched by removing the outer protective layers of the fiber and then placing them in a solution of hydrofluoric acid (HF). Both the flat and semicircular portions of the fiber are etched. The etching has a negligible effect on the overall radius of the fiber, but on the flat side the etching process exposes the cladding and core because of their proximity to the flat surface. The required depth to which the core and cladding must be etched depends on the application. To obtain reproducible results the etching process must be carefully monitored and controlled. Monitoring of the etching process is achieved by observing the output from a section of the D-type fiber into which laser light has been focused. It has been noted that the output from the fiber varies slowly as a function of etching time for quite a while and begins to oscillate quite dramatically before it it declines to zero. This previously unreported oscillation is similar from fiber to fiber and can be used to monitor and control the depth to which a fiber is etched. The paper proposes an explanation for the observed oscillatory behavior and how it can be used to produce more accurate etching times and desired cladding thicknesses.
© (1989) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Richard H. Selfridge, Richard H. Selfridge, Gregg T. Pugmire, Gregg T. Pugmire, Michael Curtis, Michael Curtis, "In-Situ Monitoring Of D-Type Fiber Etching", Proc. SPIE 1168, Current Developments in Optical Engineering and Commercial Optics, (22 December 1989); doi: 10.1117/12.962994; https://doi.org/10.1117/12.962994

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