A Tunable Focus Lens-Based Variable Optical Delay Line for Free-Space and Fiber-Optic Applications

We present a novel variable optical delay line (VODL) design for free-space and fiber-optic applications. The design employs multiple electronically controlled tunable lenses (ECTLs) to vary the optical path of a beam between two fixed locations. The use of ECTLs entirely eliminates bulk motion of optical elements as variable signal delay is achieved by electronically tuning the focal lengths of the ECTLs. For each unique set of focal length values the beam follows a different path through the system which results in an ECTL-induced variable signal delay between the VODL input and output ports. The design provides a repeatable digitally controlled short variable signal delay as well as a small signal delay step size for short delay measurements.