blueSPACE presented its ARoF over multi-core fibre (MCF) concept with a real-time demonstration in the laboratories of TU/e on Thursday and Friday, 19th and 20th of September.
The demonstration featured the blueSPACE ARoF baseband unit (BBU) and intermediate frequency (IF) unit for signal generation, processing and analysis as well as an analog radio-over-fiber (ARoF) fronthaul link over multi-core fiber (MCF). Optical heterodyning was used to generate the 5G mm-wave signal for transmission as well as to remotely feed a local oscillator (LO) to assist in downconversion of the received mm-wave signal. A schematic of the demo setup is shown below.
With this demonstration, blueSPACE illustrates its concept of IF ARoF fronthaul with optical heterodyning for upconversion to mm-wave at the remote site. It further showcases maximum centralization by remotely feeding the LO required for downconversion from mm-wave via the same MCF.
In detail, the downlink direction is comprised of the BBU and IF units to generate the 800MHz wide 5G NR OFDM signal and place it on a 5GHz carrier, followed by the optical downlink. The latter uses a single laser with two-tone generation in a Mach-Zehnder modulator (MZM) driven by and LO and subsequent modulation by the IF signal. Uplink transport uses one of the cores of a 10km 7-core MCF. The remote unit is simplified to only require a photodiode and amplifier before radiation.
The uplink direction benefits from the remote-fed LO, obtained by splitting off an unmodulated copy of the two-tone signal generated for the downlink, allowing downconversion without an LO at the remote site. While in a deployment, the uplink signal after downversion would be transported as an IF via the MCF, in the demonstration the optical uplink is skipped in order to show realistic system performance. That is, in a 5G deployment both down- and uplink signal will only undergo a single optical transport path and a single mm-wave transmission stage - by skipping the optical uplink, the same is achieved in the presented demo, despite no actual end user being present.
The achieved system performance can be observed in the figure below, showing the output and monitoring GUI of the BBU. Therein the recovered signal and intermediate processing steps are shown. Most relevant to observe are the recovered constellation on the bottom right, as well as the constellations along the top row, showing separate constellations for eight 100MHz wide signal bands. Finally, received signal statistics are shown in the bottom center, including the observed bit error rate (BER) of 1x10e-5. The observed performance and achieved transmission speed of ca 1.5Gbit/s show the blueSPACE system performance and suggest further capacity increases are possible.
This demonstration confirms the viability of ARoF fronthaul for high-capacity mm-wave 5G signals and validates fronthaul transport with space division multiplexing (SDM) over MCF. The demonstrated signal bandwidth of 800MHz not only surpasses the current aggregate bandwidths proposed by 3GPP, but highlights the power of analog optical fronthaul in efficiently transporting such signals destined for mm-wave 5G transmission.
Following this demonstration of ARoF fronthaul over MCF, blueSPACE will continue to develop the concept, improve performance and expand to a full end-to-end link. blueSPACE will further introduce optical beamforming for ARoF fronthaul and mm-wave signals, allowing to direct the signal at the end users and improving system performance and capacity.
The demonstration was hosted and coordinated by the Terahertz Photonic Systems group of Eindhoven University of Technology (TU/e, @TUeindhoven) and executed together with the blueSPACE project partners Eulambia (@eulmbia) and Thales. The demonstration included components developed in blueSPACE by the project partners Eulambia, Intracom (@IntracomTelecom), Optoscribe (@Optoscribe) and Thales.
blueSPACE and TU/e thank the involved project partners and colleagues at the Electrical Engineering department for making this demonstration a success!