938 Gb/s, 5–150 GHz Ultra-Wideband Transmission Over the Air Using Combined Electronic and Photonic-Assisted Signal Generation

The next-generation radio access network (RAN) requires high speed wireless transmission between base stations exceeding <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\geq$</tex-math></inline-formula> 100 Gb/s to connect access points and hubs. This has motivated research exploring how to fully utilize wireless spectrum from sub-6 GHz to millimeter (mm) waveband (e.g. D-band up to 170 GHz) for data transmission, using either all-electronic or optoelectronic approaches. However, to date, all-electronic and optoelectronic methods have been used separately due to the challenge of generating broad-band signals with synchronized carrier frequencies. Here, we demonstrate an ultra-wide 145 GHz bandwidth wireless transmission of orthogonal frequency-division multiplexing (OFDM) signals over the air, covering 5–150 GHz frequency region. This is achieved by combining the merits of high-speed electronics and microwave photonics technologies. Specifically, the signals over 5–75 GHz are generated using high speed digital-to-analog converters. The high frequency mm-wave band signals, including W-band (75–110 GHz) and D-band (110–150 GHz) signals, are generated by mixing optically modulated signals with frequency-locked lasers on high-speed photodiodes. By frequency-locking two pairs of narrow linewidth lasers and referring to a common quartz oscillator, we generated W-band and D-band signals with stable carrier frequency and reduced phase noise compared to free-running lasers, maximizing the use of spectrum. By using OFDM format and bit loading, we achieve 938 Gb/s transmission data rate with less than 300 MHz gap between different RF and mm-wave bands.