A Net-gain Integrated Microwave Photonic Circuit for Energy-Efficient Wireless Access Network

Wireless communication technology has profoundly transformed our daily lives by widespread connectivity. To meet the surging demand for data throughput and spectral efficiency, wireless networks are evolving toward higher-frequency bands, including millimeter-wave and terahertz. However, this shift imposes fundamental limitations in spatial coverage due to the decreasing wavelength of electromagnetics. Increased path loss and reduced propagation range necessitate ultra-dense base station deployments to ensure seamless coverage. Such densification places unprecedented stress on link interconnects from central units to base stations, where conventional copper cable-based solutions suffer from severe frequency-dependent attenuation, bulkiness, and environmental vulnerability.Microwave photonics (MWP) offers a compelling solution by shifting the RF transmission tasks into optical domain, broadly known as radio over fiber (RoF). Leveraging the inherent advantages of photonic systems, this technology has been widely deployed as fronthaul in current 4/5G networks. However, their performance is currently constrained by the limited conversion efficiency of electro-optic (E/O) and opto-electric (O/E) interfaces. The bottleneck results in signal deterioration, driving the extensive deployment of power-hungry electronic amplifiers for loss compensation. This not only increases energy consumption but complicates system design, especially in ultra-dense wireless access scenarios envisioned for future networks.To address these challenges, this project aims to develop highly efficient chip-scaleE/O/E interfaces to empower wireless access networks with substantial gain and low noise, eliminating the need for power-hungry amplifiers. The proposed research leverages the PI's expertise in integrated MWP based on thin-film lithium niobate(TFLN) platform, where he has previously demonstrated an ultrafast MWP signal processing engine (H. Feng et al., Nature 2024). Specifically, the proposed RoF link involves the optimized E/O conversion circuits based on TFLN platform, and the high-power handling O/E interface based on III-V uni-traveling-carrier photodiode(UTCPD). The exquisite synergy of these building blocks will evolve the RoF links from mere ‘signal pipelines’ to ‘signal booster’. This technology will be accompanied by two proof-of-concept demonstrations, including power amplifier-free data link transmission to achieve energy-efficient fronthaul and electronic-amplifier-free optoelectronic oscillation to provide high-quality carrier sources. These demonstrations highlight the transformative potential of the net-gain MWP link in revolutionizing wireless access architecture.The proposed system aims to deliver green solutions for future wireless communication networks, enabling energy-efficient data transmission and ultra-low phase noise signal generation. This technology could be further extended to millimeter-wave radar and satellite communications, laying the foundation for future Integrated Sensing and Communication and ubiquitous Internet of Things.