This paper describes the detailed characterization of a novel InP-Si3N4 dual laser module with results revealing relative intensity noise (RIN) as low as −165 dB/Hz and wide wavelength tunability (100 nm). The hybrid coupled laser is deployed in an unamplified 28 GBd 8 level pulse amplitude modulation (PAM) short-reach data center (DC) transmission system. System performance, which is experimentally evaluated in terms of received signal bit error ratio (BER), demonstrates the ability of the proposed laser module to support PAM-8 transmission across a 100 nm tuning range with less than 1 dB variance in receiver sensitivity over the operating wavelength range. Comparative performance studies not only indicate that the proposed source can outperform a commercial external cavity laser (ECL) in an intensity modulation/direct detection (IM/DD) link but also highlight the critical impact of RIN in the design of advanced modulation short-reach systems.

The future evolution of wireless networks, throughout the 5G era and beyond, will require the expansion and augmentation of millimetre-wave systems for both terrestrial and satellite communications. Photonic technologies offer a cost efficient and high bandwidth platform for millimetre-wave carrier generation and distribution, but can introduce high levels of phase noise through optical heterodyning, which is highly problematic for mobile signal waveforms. In this work, a detailed analytical model of a hybrid photonic/mm-wave system is developed and discussed. Through careful system design, the system is found to support both 5G compatible multi-carrier (OFDM) and single carrier (APSK) modulation at 60 GHz. APSK is found to offer higher tolerance mm-wave phase noise compared to OFDM, ultimately easing optical linewidth restrictions to ∼30 kHz. The model is extended to include a novel millimetre wave phase noise cancelling receiver, which is shown to significantly alleviate these restrictions even further—enabling phase noise free mm-wave operation for optical linewidths up to ∼2 MHz. Detailed analysis and discussion of this extended system lead to the establishment of a theoretical relationship between the mm-wave receiver design and the achievable system performance in terms of error vector magnitude (EVM). Excellent matching of the predicted theoretical with simulated performances is shown.

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Orthogonal chirp-division multiplexing is deployed as a novel waveform in an optical/millimeter-wave system. Enhanced channel estimation gives a 5-dB receiver sensitivity improvement over a conventional OFDM implementation, and compatibility with 256-QAM at 60-GHz is experimentally demonstrated.

A hybrid integrated InP-Si3N4 dual tunable laser module is deployed as a highly flexible source for converged optical/mm-wave fronthaul. Experimental results show the wavelength flexible delivery of 5G signals over analog radio-over-fiber, incorporating wireless transmission at 60 GHz, with received EVMs as low as 5%. Fig. 2: (i) Superimposed spectra of wavelengths after 2 nm OBPF with respective constellations of the demodulated 60.75 GHz mm-wave signal and EVM values, (ii) EVM performance of the received signal with respect to the wavelength.