Signal processing algorithms improve turbulence in free-space optical tests

New signal processing algorithms have been shown to be able to mitigate the effects of turbulence in free-space optical experiments, potentially bringing the “free space” internet one step closer. reality.

The team of researchers, from the Aston Institute of Photonic Technology at Aston University and the University of Glasgow, used commercially available photonic lanterns, a commercial transponder and a space light modulator to simulate perturbations. By applying noise suppression consecutively digital signal processing algorithm, they achieved record results.

The findings were published in Light Wave Technology Magazine.

Space looks optical technology transmits data wirelessly in the form of light in the air around us—called “space looks“—for use in telecommunications or computer networks. Because optical communication in free space does not require the installation of expensive optical cables, it is considered an exciting development in bringing communications to where infrastructure is limited.

But since the data is sent as light pulses, weather conditions can cause problems. A bright sunny day or heavy fog can cause diffraction or flicker beam of lightcreate disturbances that cause data loss.

The researchers transmitted multiple data signals simultaneously using spatially differently shaped light beams using so-called photonic lanterns. Perturbations change the shape of the beam, often losing signal if only a single simple shape is transmitted and detected, but by detecting light with these shapes with a second lantern, many More light is collected at the receiver and the original data can be rearranged. This can greatly reduce the impact of atmosphere on received data quality, in a technique known as Multiple Input Multiple Output (MIMO) digital signal processing.

Professor Andrew Ellis at Aston University said: “When using a single beam, when a single beam is transmitted, a disturbance similar to a hot sunny day destroys the signal 50% of the time. By passing multiple beams of different shapes through the same telescope and detecting different shapes, we not only increased availability by more than 99%, but also increased capacity to more than 500 Gbit/s, or over 500 ultra-fast Pure-Fiber broadband links.”

A project investigating real-world applications of FSO technology is currently underway in South Africa, where researchers from Aston University and the University of Glasgow are working with the University of the Witwatersrand in Johannesburg to try to bring internet access to communities living in informal settlements and schools. in difficult areas.

The Fiber Before the Fiber project aims to provide the internet performance of a Pure-Fiber connection without the installation of cables. It uses a free space optical communication system that can link to remote sites using wireless optical site signals to link to nearby fiber optic sources in affluent suburbs. than.

Professor Ellis said, “Our role in the project was to examine the impact and educational benefits of free-space optics on students, who will eventually be able to access the internet.”