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New concept of distributed fiber optic sensors

on March 23, 2020

illuminatedFiber optic technology promotes a new era of the Internet because optical fibers transmit huge amounts of data information all around the world. Herewith, fibers are regarded as an excellent platform for fiber optic sensors. It is possible to spread fiber sensors over hundreds of kilometers, simply install within structures, and even in a severe environment where the application of electricity is forbidden. Nevertheless,  optical fiber sensors have some inevitable problems as well.

The operating principle of an optical measurement is based on the light that touches the medium under test but conventional optical fibers are developed to perform the exact opposite. To be more precise, the design of optical fibers includes a glass cladding, with a much thinner, inner core. Herewith, the light is sent at the inner core, and every effort is made to keep light from leaking outside. “A substance under test, in most cases, lies outside the much larger cladding. Unfortunately, guided light does not touch upon much of the outside world.”

The only solution to the problem is coupling to the cladding modes that need for the inscription of permanent, periodic perturbations in the optical fiber medium (fiber Bragg gratings). FBGs are written at specific, discrete locations. Fiber optic sensor has limits to point-measurements only because their erasement or movement are prohibited. Optical fiber sensors are perfect in spatially-distributed analysis, in which every fiber optic segment operates as an independent measurement node. Additionally, it is possible to use two strong optical waves into the optical fiber instead as an alternative to the fiber Bragg gratings.

Also, there are Brillouin dynamic gratings, which can be switched on and off at will compared to standard FBGs. It is possible to short segments of arbitrary locations, and scan along the optical fiber. The thing is that the developed distributed fiber optic sensor is considered to be a first of its kind. Researchers have overcome some challenges: they succeeded to demonstrate the accurate measurement of refractive index outside the cladding boundary of traditional, unmodified optical fiber resulting in an 8cm spatial resolution. Herewith, the analysis demonstrates proper identification of short fiber optic sections immersed in water and ethanol, and clearly distinguished between the two. 

The researchers claim that it is a new concept of distributed fiber optic sensors. Such fiber sensors allow overcoming a decades-long challenge: fiber optic sensors perform the distributed mapping of refractive index outside the cladding of conventional optical fiber, where light does not achieve. The applications of distributed fiber optic sensors include leak detection in critical infrastructure, and process monitoring in the petrochemical industry, desalination plants, food and beverage production and more.

Optromix is a manufacturer of innovative fiber optic products for the global market. The company provides the most technologically advanced fiber optic solutions for the clients. Optromix produces a wide range of fiber optic devices, including cutting-edge customized fiber optic Bragg grating product line and fiber Bragg grating sensor systems. Moreover, Optromix is a top choice among the manufacturers of fiber Bragg grating monitoring systems. If you have any questions, please contact us at

editorNew concept of distributed fiber optic sensors

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