Fabrication of chirped fibre gratings using etched tapers

A technique for fabricating fibre gratings with an accurately controlled chirp profile is demonstrated. The technique involves writing a grating over a section of fibre, the cladding of which has been tapered by etching it in HF acid. A strain gradient along the taper is used to produce the chirp either during or after writing. Linearly chirped gratings with bandwidths up to 4.8 nm have been demonstrated. Transmission filters have also been demonstrated when a step is made in the taper