A High Performance Silicon Nitride Optical Delay Line With Good Expansibility

In this paper, based on the double strip silicon nitride platform, we designed and fabricated a low loss continuously tunable broadband optical delay line, which contains a 5-bit optical switched delay line and a single tunable optical ring resonator working at “off-resonance”. Optical double sideband modulation link measurement results show it can achieve continuous delay tuning of 395.5 ps and in-band delay fluctuations of about 4 ps and 1 ps were obtained in 8 GHz and 5 GHz working bandwidths, respectively. In addition, the proposed optical delay line has a low on-chip insertion loss of 3 dB and a very low optical loss delay ratio of 0.0022 dB/ps. Moreover, it's delay tuning range can be easily increased by cascading more thermo-optic switches. The delay bandwidth can be expanded by adopting the optical single sideband modulation or increasing the FSR of the optical ring resonator. This integrated tunable optical delay line with good overall performances and expand ability shows great potential for microwave photonic applications.