A team from the IO-CSIC led by researchers from the University of Alcalá (UAH), in collaboration with scientists from the Universitat Jaume I de Castellón, have developed a new sensor to monitor fiber optics with a spatial resolution higher than that used up to now . The new system, described in the journal Light: Science and Applications , makes it possible to transfer the advantages of fiber optic sensors to new fields, in addition to representing a potential saving of the energy consumed.

The authors of this research propose a new sensor distributed in fiber optics, which are used, for example, in the monitoring of train tracks or water and gas pipes, allowing measurements and identifying unforeseen events over tens of kilometers with a resolution of several meters. The system converts a standard telecommunications fiber optic, such as the one installed in homes, into a dense network of temperature, deformation or vibration sensors by connecting it to a piece of equipment called an interrogator.

"The new system is capable of improving resolution by more than two orders of magnitude, allowing information to be obtained from 10,000 independent measurement points along the fiber, two centimeters apart from each other," explains our colleague Hugo Martins, researcher at the CSIC at the Optical Institute (IO-CSIC).

“The objective of this research has been to develop a system that can monitor an optical fiber with a spatial resolution much higher than that of traditional systems, reaching resolutions of a few centimeters. This is a milestone in the field of distributed sensors, since it allows transferring the advantages of fiber optic sensors, such as lightness, immunity to electromagnetic interference, or high sensitivity, to new fields of application", emphasizes Miguel Soriano, researcher of the UAH, which has led the work.

Smart design

As a novelty, the developed system uses a type of signal known as a dual frequency comb to interrogate the optical fiber. A frequency comb is an optical signal that is characterized by having a spectrum formed by a discrete series of evenly spaced lines, reminiscent of the shape of a comb. The new interrogator uses two combs with slightly different line spacing, which modulate an optical carrier, in a similar way to how information transmitted over the fiber in telecommunications is encoded.

Since the beginning of the century, frequency combs, whose inventors were awarded the Nobel Prize in Physics in 2005, have proven to be extremely powerful and versatile measurement tools for a wide variety of applications, most notably molecular spectroscopy, the search for extrasolar planets, the construction of optical clocks or the precise measurement of distances. Vicente Durán, from the Universidad Jaume I, indicates: “This work demonstrates, for the first time, the application of ultra-dense frequency combs, generated using conventional telecommunications equipment, for the design of a distributed fiber sensor with extraordinary benefits”.

Our colleague Hugo Martins indicates: “A peculiarity of the proposed system is that the results are obtained with a detection width of a few megahertz, compared to the gigahertz typically required by similar technologies. In addition to reducing the cost of the system, this presupposes a significant potential saving in the energy consumed, because orders of magnitude less data need to be digitized and processed."

“This type of interrogator is of great interest for the monitoring of structures in aeronautical systems, such as the wings of an airplane, since it allows a deformation or integrity analysis of the different sections of said wings with an excellent resolution and sensitivity, without add weight or structural complexity”, adds María del Rosario Fernández, from the UAH.