# Pilot-tone assisted 16-QAM photonic wireless bridge operating at 250 GHz

## TL;DR

This paper demonstrates a 250 GHz photonic wireless bridge using pilot-tone assisted 16-QAM modulation, achieving 50 Gbit/s over short distances and promising longer-range applications with future technology improvements.

## Contribution

It introduces a pilot-tone assisted carrier recovery method for high-frequency photonic wireless links, enabling high data rates with phase noise mitigation at 250 GHz.

## Key findings

- Achieved 50 Gbit/s data rate in a single-channel setup.
- Demonstrated WDM operation across 224-294 GHz band.
- Estimated potential for >1000 m transmission distance with advanced technology.

## Abstract

A photonic wireless bridge operating at a carrier frequency of 250 GHz is proposed and demonstrated. To mitigate the phase noise of the free-running lasers present in such a link, the tone-assisted carrier recovery is used. Compared to the blind phase noise compensation (PNC) algorithm, this technique exhibited penalties of 0.15 dB and 0.46 dB when used with aggregated Lorentzian linewidths of 28 kHz and 359 kHz, respectively, and 20 GBd 16-quadrature amplitude modulation (QAM) signals. The wireless bridge is also demonstrated in a wavelength division multiplexing (WDM) scenario, where 5 optical channels are generated and sent to the Tx remote antenna unit (RAU). In this configuration, the full band from 224 GHz to 294 GHz is used. Finally, a 50 Gbit/s transmission is achieved with the proposed wireless bridge in single channel configuration. The wireless transmission distance is limited to 10 cm due to the low power emitted by the uni-travelling carrier photodiode used in the experiments. However, link budget calculations based on state-of-the-art THz technology show that distances >1000 m can be achieved with this approach.