After laser treatment, the GSM signals can pass again through the windows of train carriages

It is not yet clear that there is a good internet connection during train journeys. Working with a laptop or watching the latest episode of your favorite TV show on the go often isn’t nearly as good at home. Although modern trains are equipped with Wi-Fi repeaters, wagon window coatings continue to interfere with wireless communications. This coating is necessary for thermal insulation. Swiss company Now the glass They developed a laser treatment that allows them to manipulate train windows at the station, so that signals from mobile phones can better pass through them. Now the glass It is a branch of the Technical College in Lausanne, Switzerland.

The solution kills two birds with one stone. On the one hand, it prevents railway companies from having to install different repeaters each time a new communication standard comes into force. On the other hand, the thermal insulation of the carriages remains unaffected. Since the system can adjust the glass of already installed windows, there is no need to replace them.

After an initial test, Swisscom – Switzerland’s leading telecom operator – rated its signal performance positively.

“The signal on the inside is the same as on the outside. Luc Burnier, CEO and founder of says Now the glass† In addition, the technology can already be used in glass production. In this way, the trains of the future benefit from technology from day one.

Ultra-thin lines

The wearable system works directly on the glass sheet, where the laser engraves very thin lines — thinner than 25 microns — that allow wavelengths to pass through. The glaze is processed in about 15 minutes. It is not necessary to disassemble the window, the device works directly on the train, because the laser can also target curved surfaces. “At first I started scratching the lines in the glass with just a ruler. If you want to draw ultra-thin lines with high accuracy, laser technology is the preferred option,” Burnier explains.

The idea of ​​such a treatment arose from a different kind of research. Nine years ago, Burnier was part of a team from the École Polytechnique Fédérale de Lausanne – EPFL – working to improve the insulation of trains.

Stove: Heating and cooling systems make up a third of trains’ electricity consumption. That’s why we designed a glass concept that doubles the insulation performance. Despite this, the railroad partner we worked with suggested that our glass does not allow GSM signals to pass through. In association with Dr. Andreas Schuyler – the physicist and principal at the time – came up with a way to let the waves pass through. And then I started drawing lines on the glasses.”

Simple but effective

The principle behind the idea is so simple, yet so effective that it was surprising that no one thought of it. “the book Electromagnetic Displays frequency selective surfaces on the first pages. It’s so basic, it wasn’t easy to think of,” the engineer adds.

Metallic layers reflect electromagnetic waves. In order for these coatings to pass, the conductivity of the coating must be cut. The distance between the slits must be 10 or 20 times smaller than the wavelength one wants to go through. Therefore, a network must be engraved in the casing that transmits frequencies. And that’s exactly what Burnier developed.

“You can’t remove too much paint, otherwise the insulation values ​​will go down,” Burnier explains. “It was about striking a balance between allowing frequencies to pass through and leaving the isolation properties as they are.”

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Save money

Besides keeping wagons isolated, getting rid of signal amplifiers in trains is another important aspect of solving a problem Now the glass† With the railroad shift to 5G connections, all signal boosters on trains must be upgraded.

“The repeater costs about 50,000 euros. It is likely that it will be replaced by a better one in a few years. Moreover, it is not easy to provide hundreds of people with fast access to the Internet while the train is running. It is really sensitive electronics”, emphasizes Bornier.

In the event of a malfunction, the amplifiers should be checked by special technicians. In five years, that maintenance – and the costs of the speakers – is about a hundred million euros, for a country the size of Switzerland.

Now the glass It is now looking for investors to develop the system further. “Some investors have shown interest in our technology. We are looking forward to actually setting up the company, signing the first contracts and expanding across Europe,” says Bournier. The company now has four employees. Burnier expects to be able to hire more staff by the end of this year.

A second test will take place next month, in which Now the glass He will try laser treatment on a different type of carriage. In addition to the Swiss Federal Railways (SBB), other rail companies in Europe have already announced their desire to test the system. As the mobile network infrastructure continues to improve in the coming years, the communication network in trains will also benefit.

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