This invention provides a tunable delay of an optical signal having a carrier with an angular frequency .omega..sub.0 and a single side band having a signal band with a median angular frequency .omega..sub.r. The delay line comprises at least a first, a second and a third integrated resonators coupled sequentially to a waveguide. The first and the second resonators have angular resonant frequencies .omega..sub.1=.omega..sub.r-.DELTA..omega. and .omega..sub.2=.omega..sub.r+.DELTA..omega. respectively, where .DELTA..omega. is a deviation from the median frequency. The third resonator provides a phase delay difference between the phase at the optical carrier .omega..sub.0 and the phase at the median frequency .omega..sub.r equal to (.omega..sub.r-.omega..sub.0)T.sub.d, where T.sub.d is the time delay. The device provides an equal group delay to all frequency components in the output signal and also equal phase delay for all frequency components of an RF signal when the optical signal is downconverted at a photodetector. The device may find applications controlling the time delay to antenna elements in a phased array system.