Variable Optical Delay Line Using Discrete Harmonic Oscillation in Waveguide Lattices

This paper proposes a variable optical delay line based on the discrete harmonic oscillation in the waveguide lattice with a quadratic distribution of coupling coefficients. Theoretical analysis and numerical simulation have shown that the device design can achieve a time delay of up to 10 ns, with the resolution of 0.5 ns, and the 3-dB bandwidth over the whole C-band. It allows a data packet of up to 17 bits at the rate of 100 Gb/s. In this design, the propagation path is folded by up to five times (or ten times for the one-port design). Compared with the conventional fiber-delay-line buffer, this design has a small footprint (about 10 mm × 0.5 mm). A group of them can be paralleled and cascaded within a small area (e.g., 20 copies into 1 cm²) as enabled by the microfabrication. With further optimization, this design has a potential for interconnecting and signal processing applications in optical communications and computing.