100 GHz-Carrier Broadband OFDM Radio Transmission Enabled by Photonic Integrated Optical Clock Synthesizer

We report on the performance of a monolithically integrated silicon photonics <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula>100 GHz-carrier synthesizer, and its application in a radio transmission system. The photonic integrated circuit (PIC) includes an optical frequency comb generation stage driven by a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 20-GHz reference clock, followed by an innovative multi-resonant distributed feedback resonator-based optical filter for selecting the two comb components generating the target <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 100 GHz-carrier wave in an off-chip photodiode. Phase noise (PN) characterization of the synthesized W-band signal indicates operation in agreement with ideal frequency multiplication of the employed reference clock. In addition, the flat-tops spectral feature of the photonic integrated filter allows the output frequency to be tuned in the range 96 — 100 GHz without significant PN degradation. A 97-GHz optical local oscillator is then used to up-convert and succesfully transmit broadband wireless data signals with different complex modulation formats, including single-carrier and orthogonal frequency division multiplexed (OFDM) QPSK and 16-QAM, with net information rate up to 4 Gb/s.