POSTFABRICATION RESONANCE PEAK POSITIONING OF LONG-PERIOD CLADDING-MODE-COUPLED GRATINGS

A simple, flexible method of postfabrication positioning of resonance wavelengths of long-period cladding-mode-coupled gratings is proposed. This method is based on changing the outer fiber diameter. Reducing t he diameter by etching the fiber in HF acid shifts the loss peaks to h igher wavelengths. A shift as large as 130 nm after 5 min of HF etchin g was observed for our strongest grating peak, corresponding to the cl adding mode HE(19). The experimental results are in excellent agreemen t with model calculations. (C) 1996 Optical Society of America.