Research on Continuously Tunable Optical Delay Line based on Cascaded Micro-ring Resonators

Optical delay line is the key component of broadband optically controlled phased array. It can overcome the inherent aperture effect and transition time limitations of traditional phased array radar technology, electronic countermeasures, all-optical signal processing and optical communication. Through the analysis of frequency response characteristics of the micro-ring, the influencing factors such as coupling coefficient, round trip loss and round-trip delay time, and their mechanism for the delay characteristics of optical micro-ring have been investigated. The Mach-Zehnder interferometer (MZI) is proposed to achieve the continuous tuning of delay time combining with the phase shifter on the ring waveguide. At the same time, the phase correction on the ring waveguide is used to balance the effect of extra phase on the frequency shift brought by the MZI coupling structure. A three-ring cascaded micro-ring resonators is designed based on SOI optical waveguide with the thickness of 220nm. The results of the target response demonstrate that the adjustable delay time can achieve 67ps and the tuning accuracy is less than 0.1ps.