iXblue: extreme fiber optics

Last June, iXblue and the Hubert Curien laboratory (with which Télécom Saint-Étienne is associated) inaugurated LabH6: a joint research laboratory dedicated to optical fibers. This is the latest development in a partnership that has lasted since 2006 and the bursting of the dotcom bubble. iXblue rose from the ashes of a start-up specializing in fiber optics for telecoms. After the disappointments of the digital sector in the early 2000s, "we decided to take a 180° turn away from telecoms, but still in fiber optics", explains Thierry Robin, who has been involved in iXblue from the outset and is now CTO.

A daring gamble at a time when fiber optics in home networks was still in its infancy. A gamble that has also paid off. In 13 years, the young company has become a key player in the field of optical fibers in harsh environments. This success is largely due to innovations developed with the Hubert Curien laboratory. Today, the company's products are used in high-temperature conditions, under nuclear irradiation and in the vacuum of space.

Measuring nuclear irradiation

One of the major successes of this collaboration is the development of optical fibers capable of measuring the dose of nuclear radiation in an environment. Light passing through an optical fiber is naturally attenuated with the length of the fiber. This attenuation, known as optical loss, is increased when the fiber is subjected to nuclear radiation. " We know the law that links optical loss to the dose of radiation received by the fiber," points out Sylvain Girard, a researcher at the Hubert Curien laboratory. "We can therefore use an optical fiber to play the role of hundreds of dosimeters responsible for measuring radiation levels.

The use of fiber in this application has two advantages. Firstly, the data enables continuous mapping of radiation along the entire length of the fiber, where dosimeters give a point value associated with their precise location. Secondly, fiber optics offer real-time measurement, since optical loss is measured live. In contrast, dosimeters are usually left for days, or even months, at their location before the accumulated radiation value is read.

The fibers used for this kind of application are special. They need to be more sensitive to radiation, so as to be able to measure variations correctly. Research in this area has led to the development of phosphorus- or aluminum-doped fibers. This type of optical fiber is currently being installed at CERN's Large Hadron Collider (LHC) in Geneva, during the two-year shutdown lasting until 2020. " This will enable CERN to assess the vulnerability of electronic equipment to radiation, and thus avoid unplanned shutdowns due to breakdowns," emphasizes Sylvain Girard.

These optical fibers are also being evaluated at the Triumf particle gas pedal in Canada, for proton therapy. Proton therapy is a high-precision medical treatment that can be used to irradiate melanoma in the eye. The dose of radiation applied to the melanoma must be very precise. " The fiber should make it possible to measure the dose of radiation deposited in real time, and to stop when the desired value is reached," explains the researcher from Saint-Etienne. "Without the fiber, doctors only know the precise total dose received by the patient at the end of the treatment. They therefore need to accumulate three weaker irradiations one after the other to get as close as possible to the total target dose."

Resisting in space

While the fibers used in dosimetry must be sensitive to radiation in order to measure it, others must be highly resistant to it. This is the case for fibers used in space. Satellites are vulnerable to space radiation. The gyroscopes that position them use amplifying optical fibers. The collaboration between iXblue and the Hubert Curien laboratory has developed hydrogen- and cerium-loaded optical fibers. These amplifying fibers have been the subject of two patents, and their resistance has enabled them to become the benchmark for optical fibers in the space sector.

The same issue of radiation resistance arises in the nuclear industry, where it is important to measure temperature and mechanical stress at the heart of reactors. "These are environments exposed to doses of the order of a million Gray. By way of comparison, the lethal dose for a human being is 5 Gray," explains Sylvain Girard. Fiber optic sensors must therefore be extremely resistant. Here again, joint research by the company and the Hubert Curien laboratory has resulted in patents for new fibers to meet the demands of industrial companies such as Orano (formerly Areva). These fibers will also be deployed in the ITER fusion reactor project.

All this work is being pursued within the framework of LabH6, which will facilitate the industrial valorization of the research carried out by iXblue and the Hubert Curien laboratory. The stakes are high, at a time when the non-telecom uses of optical fibers are multiplying. While harsh environments such as space or nuclear power may appear to be niche sectors, optical fibers developed for these applications could find other uses. " We are currently working on high-temperature-resistant fibers for autonomous cars," says Thierry Robin. " These products are indirectly derived from our developments in radiation-resistant fibers", he adds. Having left the telecoms market and high-volume production 13 years ago, iXblue may soon be returning to it.

Our motto: "Progress in a virtuous way".

"Very quickly, we wanted to open up to the outside world and exchange ideas with scientists. Our partnership with the Hubert Curien laboratory has enabled us to make virtuous progress. Where our competitors maintain a culture of secrecy, we inform the researchers who work with us of the exact composition of our fibers. We even produce special fibers for them, for no other purpose than the scientific testing of particular compositions. Our aim is to enable academics to carry out their research by providing them with all the information they need to make progress in the field. It's this spirit that enables us to produce unique products for the space and nuclear industries.

- Thierry Robin, CTO of iXblue