Photonic Beamformers Research Articles

Multi-Beam Microwave Photonic Beamforming Based on Self-Coherent Detection of a WDM Signal

The increasing ubiquity of mobile services is driving wireless communications to fully exploit spatial-division multiplexing (SDM). However, SDM’s key enabling technology – the beamformer – is hindered by scalability hurdles that electronic technologies have failed to overcome. This manuscript tackles this challenge by introducing a novel photonic beamforming architecture, which leverages and combines key techniques of both past photonic beamformers and cutting-edge optical communications. The proposed architecture makes use of wavelength-division multiplexing, coherent detection, and programmable photonic processing to realize a truly scalable photonic beamformer. The proposed architecture is analytically and numerically validated, as well as experimentally demonstrated. The experimental validation includes a practical demonstration of two RF beams at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$12 \,\mathrm{G}\mathrm{Hz}$</tex-math></inline-formula> , each carrying a 1 GBd QPSK signal, being independently beamformed, and down-converted to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$5 \,\mathrm{G}\mathrm{Hz}$</tex-math></inline-formula> .

Silicon integrated microwave photonic beamformer

Optical beam-forming networks (OBFNs) based on optical true-time delay lines (OTTDLs) are well known as the promising candidate for solving the bandwidth limitation of traditional electronic phased array antennas (PAAs) due to beam squinting. Here we report, to the best of our knowledge, the first monolithic 1 × 8 microwave photonic beamformer, based on switchable OTTDLs on the silicon-on-insulator platform. The chip consists of a modulator, an eight-channel OBFN, and eight photodetectors, thus including hundreds of active and passive components in total. It has a wide operating bandwidth from 8 to 18 GHz, which is almost two orders larger than that of electronic PAAs. The beam can be steered to 31 distinguishable angles in the range from − 75.51 ∘ to 75.64°, based on the beam pattern calculation with the measured radiofrequency response. The response time for beam steering is 56 µs. These results represent a significant step toward the realization of integrated microwave photonic beamformers that can satisfy compact-size and low-power consumption requirements for the future radar and wireless communication systems.

Reconfigurable monitoring and control system for tunable optical delay lines.

In this Letter, we propose a monitoring and control system (MCS) for operating tunable optical delay lines (TODLs), regardless of their operation principle and implementation technology. The monitoring system resorts to two out-of-band pilot tones added to the input optical signal. The amplitude and phase difference between tones are retrieved to the control system, which calculates and applies the TODL control signals. The MCS was validated using a Mach-Zehnder delay interferometer-based TODL, implemented in three different silicon photonic integrated circuits (PICs). The three PICs resort to different kinds of phase shifters based on thermo-optic, carrier-injection, and carrier-depletion effects. The proposed MCS enabled tuning the delay within the entire range of the TODL in all tested PICs. The scalability of the MCS for large-scale photonic beamformers is discussed.