Variable group delay and pulse reshaping of high bandwidth optical signals

We present the dispersive characteristics of an electronically tunable optical filter, with application toward delaying high speed digital and analog signals. Square waves can be dynamically delayed and reshaped through a change in injection current to the filter. Since the filter is of an all-pass nature, its usable bandwidth is limited primarily by the phase response (dispersion). We show that for 2-GHz square waves, dispersion is not a limiting factor and the filter can be operated over the full range of delays. At 5 GHz, the pulses can still be delayed, however the range of operation is dispersion limited. Additionally, at 5 GHz this dispersion can be harnessed for pulse reshaping applications. The filter is studied both experimentally and theoretically, demonstrating good agreement.