Abstract
A continuously tunable optical delay line with low delay ripple based on four cascaded tunable silicon nitride microring resonators for Ka-band beamforming network is proposed. The delay responses of the tunable optical delay line were investigated theoretically and experimentally. And a maximum delay tuning range of 300.3 ps, 169.4 ps and 88.6 ps were achieved when the delay bandwidth is set as 2 GHz, 5 GHz and 10 GHz respectively. In addition, low delay ripple about 8.5 ps and low additional loss less than 3.6 dB were obtained. Moreover, the maximum delay tuning range was increased to about 395 ps by combining the off-resonance region of the cascaded MRRs.
Highlights
With the growth in wireless communication, the Ka-band has enormous potential for its wide bandwidth and compact antenna size
We proposed a continuously tunable optical delay lines (ODLs) consisting of cascaded four Si3N4 microring resonators (MRRs), which can realize larger delay tuning range with larger delay bandwidth and smaller delay ripples
The modulator working at the quadrature bias was driven by the radio frequency (RF) signals from the vector network analyzer (Agilent N5242A) and the optical double sideband modulation (ODSB) was obtained
Summary
With the growth in wireless communication, the Ka-band (frequency ranges from 26.5 GHz to 40 GHz) has enormous potential for its wide bandwidth and compact antenna size. The ODL structures based on optical switchable waveguides and tunable MRRs are relative simple and easy to fabricate Both of them can be realized on the CMOS compatible platforms such as the silicon on insulator (SOI) and silicon nitride (Si3N4). By combining the resonant and off-resonance regions of three cascaded Si3N4 MRRs, a 209 ps tuning range with bandwidth of 6 GHz was realized by precise tuning all the MRRs [20], to reduce the system complexity, binary tree structure was adopted to realize the 1 × 4 optical beamforming network (OBFN) in that work. We proposed a continuously tunable ODL consisting of cascaded four Si3N4 MRRs, which can realize larger delay tuning range with larger delay bandwidth and smaller delay ripples. The fabrication and packaging cost are much lower than the SOI MRRs
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