Optical Fibers that Can 'Feel' the Materials Around Them
July 31, 2018 | EPFLEstimated reading time: 2 minutes
EPFL researchers have developed an optical fiber capable of detecting what sort of material or liquid they have come into contact with. In recent years optical fibers have served as sensors to detect changes in temperature, like a thermometer, and pressure, like an artificial nerve. This technique is particularly useful in structures such as bridges and gas pipelines.
EPFL researchers have now come up with a new method that enables optical fibers to identify whether they are in contact with a liquid or a solid. This is achieved by simply generating a sound wave with the help from a light beam within the fiber.
A Sensor that Doesn’t Disturb the Light
No wider than a strand of hair, an optical fiber made of glass transmits light that varies according to four parameters: intensity, phase, polarization and wavelength. These parameters are altered when the fiber is stretched or the temperature changes, enabling the fiber to act like a sensor by detecting cracks in structures or abnormal temperatures. But up to now it was not possible to determine what was happening around the fiber without having light escape the fibre, which disrupts its path.
The method developed at EPFL uses a sound wave generated inside the fiber. It is a hyper-frequency wave that regularly bounces off the fiber’s walls. This echo varies at different locations depending on the material the wave comes into contact with. The echoes leave an imprint on the light that can be read when the beam exits the fiber, making it possible to map out the fiber’s surroundings. This imprint is so faint that it hardly disturbs the light propagating within the fiber. The method could be used to sense what is going on around a fiber and send light-based information at the same time.
The researchers have already immersed their fibers in water and then in alcohol, before leaving them out in the open air. Each time, their system was capable of correctly identifying the change in the surroundings. “Our technique will make it possible to detect water leakages, as well as the density and salinity of fluids that come into contact with the fiber. There are many potential applications,” says Thévenaz.
Spatial and Temporal Detection
These changes in the surroundings are located thanks to a simple time-based method. “Each wave impulse is generated with a slight time lag. And this delay is reflected upon the beam’s arrival. If there were any disturbances along the way, we can both see what they were and determine their location,” explains Thévenaz. “For the moment, we can locate disturbances to within around ten meters, but we have the technical means to increase our accuracy to one meter.”
The idea of using a sound wave in optical fibers initially came from the team’s partner researchers at Bar-Ilan University in Israel. Joint research projects should follow.
Suggested Items
D Coupon Testing and Data Insights With GreenSource Fabrication
04/17/2024 | Marcy LaRont, PCB007 MagazineMarcy LaRont spoke with Steve Karas of GreenSource Fabrication at the SMTA UHDI conference in March. He presented a case study that GreenSource undertook with a customer on critical via reliability with advanced materials and used the experience to highlight the importance and effectiveness of D coupon testing. He also discussed GreenSource’s approach to data aggregation and a new system they developed to use collected data effectively.
Real Time with... IPC APEX EXPO 2024: Exploring Silicone Solutions with R&D Director of CHT
04/17/2024 | Real Time with...IPC APEX EXPOIn this interview, Gerry Ellis, the R&D director for CHT, discusses the product range offered by his company. He explains the challenges in creating base formulations, the drive to make products more user-friendly, and the various application techniques involved. Ellis also highlights the key market segments and the significance of providing efficient solutions to customers.
The World of Electronics and Standards: A Conversation with Frank Honyotski, STI
04/03/2024 | Marcy LaRont, PCB007 MagazineMarcy LaRont of I-Connect007 speaks with Frank Honyotski of STI Electronics, who discusses the services offered by STI, including training, engineering, and failure analysis. He highlights his involvement with IPC standards development and emphasizes the importance of industry professionals engaging in standards development.
Demand Rebounds, Global LED Industry Revenue Expected to Grow 3% in 2024 with Market Focus on Automotive Displays
04/01/2024 | TrendForceTrendForce’s latest LED industry report indicates that the global market is set to recover in 2024, with estimated revenues reaching US$13 billion—marking a YoY growth of 3%.
Orbex Secures Patent for 'Petal Fold' Reusable Rocket Technology
03/29/2024 | OrbexOrbex has successfully patented its REFLIGHT reusable rocket technology following patent approval in several European markets, based on the patent grant by the European Patent Office, as well as in the United States.