Analog Coherent-Optical Mobile Fronthaul With Integrated Photonic Beamforming

Abstract

We present a mobile fronthaul methodology for the analogue optical transmission of native radio signals with integrated photonic true-time delay for the beam steering of phased-array antennas. Laser-based coherent homodyne detectors and the delay dissemination through ultra-dense wavelength division multiplexing ensure a low complexity at the optical layer. We experimentally demonstrate beamsteering for a linear phased-array antenna with a 1×3 configuration at 3.5 GHz carrier frequency and prove native radio signal transmission over the 14.3-km reach coherent optical fronthaul at a low endto-end error vector magnitude of 3.3%. Experimental results are found to stand in good agreement with theoretical predictions.

Air-Filled SIW Remote Antenna Unit With True Time Delay Optical Beamforming for mmWave-Over-Fiber Systems

“…Table II shows that our mmWave RAU realizes state-of-the-art performance regarding achieved bit rate, level of integration and beam steering performance. While a plethora of optical beamforming implementations have already been proposed [31], [32], only a limited amount of reported mmWave fiber-wireless experiments [8], [11], [12], [33]- [55] effectively demonstrate optical beamforming [40]- [55]. In [44], [45], [47], [54], beam steering is realized by employing bulky external optical delay lines, which are either located at the RAU [44], [45] or at the CO [47].…”

Photonic Delay Processing With Centralized Etalon Cascade for Radio Beamsteering in Simplified 2 × 5 Phased-Array Radio Heads

“…In order not to increase the fronthaul fiber count when centralizing the required optical delay generator, multicore fibers have been proposed to accomplish a per-core delay encoding when feeding the RRH [6,7]. Continuous delay settings can also be obtained exploiting a shared dispersive media, such as the transmission fiber in [8,9], specialized fiber [10,11], or linearly chirped gratings [12][13][14][15][16][17]. In these schemes, a stable optical source is precisely tuned along a wavelength-dependent dispersion slope.…”

Radio Beamsteering for a 2×5 Remote Radio Head Assisted by a Shared Wideband Etalon Cascade

“…Optically assisted methods have been intensively researched by virtue of their broadband nature. Next to switched delays implemented on photonic integrated circuits [3], continuous delay settings build on wavelength-dependent dispersive media such as fiber [4] or linearly chirped Bragg gratings [5] or elements offering a tunable group delay at resonance, such as micro-ring resonators [6] or waveguide gratings [7]. However, the tuning mechanism can quickly become complex, and the supported RF signal bandwidth faces a limit.…”