Rapid ultrafine-tunable optical delay line at the 1.55-mum wavelength

A fast, ultrafine-tunable delay line at 1550 nm is demonstrated by use of acousto-optic pulse shaping. Delays of up to 30 ps can be achieved without any optical readjustment. The delay is linear to the rf center frequency applied to the acousto-optic modulator and is fully electronic. It takes only 3micros to switch between different time slots, irrespective of the time separation in the tuning range of 30 ps; for a smaller tuning range the tuning speed can be faster. The tuning resolution and range depend on the choice of system parameters. The pulse energy can be regulated by rf power.