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SAN CARLOS DE BARILOCHE.- In terms of telecommunications, one of the greatest and most urgent challenges in the world is to extend the current capabilities of the equipment to supply the growing demand for connectivity that modern society has. Among other projects in development, Argentine experts are working in this Patagonian city to find technologies that complement those already in use, which are reaching their ceiling. On that path, photonics is positioned as the ideal candidate to complement the use of conventional radio frequencies.
“He electromagnetic communications spectrum is highly saturatedespecially satellite, because free space is shared – warns the researcher from Conicet and the National Atomic Energy Commission (CNEA) Pablo Costanzo Case, referring to the frequencies used to transmit information between devices wirelessly. “This differentiates it from fiber optics, which is a confined medium: if one has a channel, you can put another optical fiber next to it, which is another channel that runs in parallel and does not interfere with the first, and it is also possible to double the communication capacity,” he explains. To establish communication between the Earth and satellites (such as those used to provide TV or satellite internet service), “what is usually done is to transmit electromagnetic waves of radio frequency, microwaves or even higher frequencies, as well known as millimeter waves. All that spectrum, which is shared and regulated, is finite. And it’s full -he clarifies-. “Communications satellites encounter a saturation of the electromagnetic spectrum.”
Costanzo Caso, settled in Bariloche ten years ago, currently heads the Telecommunications Engineering Department of the Balseiro Institute. And he warns that there are many ways to find solutions to the need to transmit more and more information between the Earth’s surface and satellites in orbit: one of them consists of “widening the highway further and using new lanes.” The transmission of radio waves (at megahertz frequencies) is followed by microwaves (of some gigahertz), then millimeter waves, which are higher frequencies, of tens of gigahertz, and beyond that are optical frequencies, in which terahertz or infrared region, which is non-ionizing radiation.
“What we are looking for now is use a region of the spectrum that has much higher frequencies, linked to infrared light, and that is not saturated. This gives us the possibility of transmitting more information and more efficiently,” says Costanzo Caso.
Based on the experience with fiber optic networks that the Balseiro Telecommunications Engineering Department has, they began to work in collaboration with an American company, Skyloom (founded by Argentinians Santiago Tempone and Marcos Franceschini)for the design of a network of low orbit satellites that communicate with each other optically by encoding the intensity of the transmitted light.
“These satellites circle the Earth many times a day. So, the visibility time you have in each geographical region is reduced, something that makes continuous data service difficult – clarifies Costanzo Caso, in reference to the satellites that, seen from the ground, cross the sky from one side of the horizon to the other. , about 500 km high. That is why it is key not only for low orbit satellites to communicate with each other, but, in turn, to be able to communicate with a geostationary satellite, which has 24-hour visibility with a certain place on Earth. In this way, an indirect transmission is generated,” explains the engineer.
And he gets excited: “We are designing an optical link that communicates the low orbit satellite of that network – any or all of them – with the geostationary satellite located 40 thousand kilometers away. In general, the solutions that companies have are non-coherent links, the equivalent of turning a laser (transmitter) on and off. The truth is that there are other, more efficient ways of transmitting and encoding information, which are not only related to the intensity of light, but also to the frequency of light, phase changes and polarization, that is, how it is oriented that electric field, if it is horizontal, vertical, circular, etc.
In the Bariloche laboratory they emulated a link between two satellites with a coherent communication system that uses various dimensions to encode, such as amplitude, frequency, phase and polarization. That significantly increases the amount of information that can be transmittedsince the information is encoded in many parts of the signal.
“We have been developing this technology for many years and we have grown in the reliability, complexity and robustness of the implemented system, which is of better quality and has a greater capacity to transmit information,” adds Costanzo Caso.
When referring to the projects they are carrying out in optical and microwave communications systems, the researcher states that, Throughout the world, interest is growing in finding alternatives to transmit the greatest amount of information possible per second: “In the laboratory we reached a milestone, which is to make these optical communications (generate signals, transmit and receive them error-free) at a speed of 128 gigabits per second, the equivalent of transmitting 128 billion pulses per second. The optical system in our laboratory is working, we transmit over a fiber of about 100 km, and we are working on solving many aspects so that this link can be technically developed.”
Thanks to the demonstrated capacity, many companies and institutions appeared interested in the electronics needed to process such an amount of information. “One of the biggest challenges today in a digital world is that this signal, which is transmitted analogically through fiber optics, is digitized to be processed or stored. Data transducers are needed, that convert in both directions: from digital to analog and from analog to digital. “We have been working with the Fulgor Foundation to demonstrate a technique that can convert signals from the analog world to the digital world, and vice versa, in a bandwidth of around 100 gigahertz,” he adds.
The idea is make a prototype in the laboratory that will later serve as a technological demonstrator to generate, for example, a chip that allows this development to be implemented commercially. Likewise, the nearly 30 members of the Telecommunications Engineering Department – including researchers, professionals and scholarship holders – seek to design new devices for these optical communication systems.
“In an optical communication system, both in the transmitter and in the receiver, there is electronic technology that processes the signals and then converts them to the optical domain to establish the link with light signals. Therefore, within the optical link I have light and I can use photonic technology to process that transmitted light. We work on the design of integrated optical and fiber optic circuits: we want to make chips that process light directly. Today it is one of the “hottest” topics in the world of telecommunications, because it is the technology that will support what is to come. Electronics are also saturated, finding their limit in processing speed, storage capacity and transmission, so they need alternative or hybrid solutions, with photonic and electronic components to sustain growth and demand,” says the researcher.
At Conicet and CNEA they know that the development of telecommunications impacts other areas of science, education, health, justice and security, in addition to generating new business opportunities and ventures linked to the production of goods and services. . In the last ten years they focused on creating a space with state-of-the-art laboratories at the national level where they train specialized human resources.
“Today’s world is an essentially digital world -reflects-. What we see, the tools we have, the applications we use and what we do on a daily basis is strongly influenced by the new technologies and tools that appear, such as Artificial Intelligence. We, telecommunications professionals, focus, based on our knowledge, on generating solutions and providing technological support to all these tools and applications that surprise us day after day.”
