Silicon Photonic Integrated Broadband Continuously Tunable Optical Delay Line

We designed and fabricated an integrated broadband optically tunable delay line (OTDL) combined with a 6-bit switched waveguide for discrete delay tuning and a long spiral waveguide for continuous delay tuning. The variable optical attenuator is added after the Mach-Zehnder interferometer (MZI) based switch to suppress optical crosstalk to the target delay path caused by the limited extinction ratio of the MZI. The thermal isolation trenches are adopted to reduce power consumption of the optical switch. The long spiral waveguide based on Archimedean spiral structure with small bending loss realizes continuous delay adjustment within 0 ∼ 1ps by using the thermo-optical effect. The fabricated OTDL chip footprint is 2.5×1.1mm
²
. After being packaged, the OTDL chip is tested with the continuous time tuning in the range of 0 ∼ 64ps.