A Compact, Low Loss Integrated Continuous-Time Electro Optic-Pll With Maximum Range Of > 3.3m

Continuous time (CT) Electro Optic Phase Locked Loops (EOPLLs) can significantly reduce the differential delay required in a Mach-Zehnder Interferometer (MZI) which is used to detect the chirp slope, thereby reducing the MZI area and associated loss. However, CT-EOPLLs produce inter-modulation tone at (f(ref) + f(beat)) which creates spurs at offsets of +/-(f(ref) + f(beat)), +/- 2(f(ref) + f(beat)), +/- 3( f(ref) + f(beat))...from the expected beat tone at the ranging output. In this work, we present a CT-EO-PLL which not only breaks the fundamental trade-off between chirp bandwidth and MZI delay, but also completely eliminates spurs from the PLL and laser output by using IQ single-sideband (SSB) and harmonic reject (HR) mixing. This EO-PLL, integrated in CMOS technology, suppresses the spurs at beat note by > 25dB, enabling us to detect an object at a maximum range of > 3.3m, with a precision of 558 mu m at 2m distance. (C) 2019 The Author(s)