Blonder, GregJohnson, Bertrand H.2019-07-092019-07-091993-04-061991-12-23Greg Blonder, Bertrand H Johnson. "Wet chemical etching technique for optical fibers." U.S. Patent 5,200,024-A.US-5200024-Ahttps://hdl.handle.net/2144/36334A wet chemical etching technique is disclosed for forming a lensed optical fiber. In particular, the fiber is placed in a mixture comprising buffered hydrofluoric acid (e.g., HF and NH4 F) and a treating agent comprising acetic acid or citric acid. The relative concentrations of the constituents are adjusted so that a double conical lens is formed which requires no further operations (such as fire polishing) to provide coupling efficiencies of about 80% with a standard deviation of less than ±2%.Patent429593