Fibre-optic variable delay lines

Abstract

A technique is presented for fabricating large numbers of evanescently coupled taps on a single-mode fibre. An output fibre can be adjusted between any of the taps, resulting in a discretely variable delay. The concept was demonstrated with a 7 tap device which had a 2.5 ns delay between taps and a tap uniformity of ± 1.6 dB. A technique for making continuously variable delay lines is presented.