Radiation tests on polymer optical fibers
Polymer optical fiber is found in various fields such as lighting, data transmission in an industrial environment, sensors, medicine, audio cables.These plastic fibers are made of PMMA (Polymethyl Methacrylate), a thermoplastic polymer offering very high light transparency in the visible range. These plastic optical fibers also have the distinction of resisting electromagnetic disturbances but also of being easy to handle unlike optical fibers based on silica. They also represent an economical alternative to optical fibers based on silica and are often used to transport light from one place to another. These fibers can be exposed in environments with high radiative stresses.
We wanted to test whether these plastic optical fibers were sensitive to X-ray irradiation. Indeed, the fibers can be put in extreme conditions whetherin space, nuclear. When the optical fibers are sensitive to radiation, we observe a phenomenon of radio darkening with a degradation of transmission of the fiber; these are linked to the appearance of an absorption band on theoperating spectrum of the fiber.
Radiation results on polymer optical fiber
The Institute of Physics of Nice (INPHYNI, University of the Côte d'Azur -UMR 7010 of CNRS) carried out this test by exposing this optical fiber in PMMA to an irradiation of X photons. The fiber used was a plastic optical fiber PMMAof diameter 250µm, from the Toray brand with the reference PGR FB250. Thisfiber was irradiated for 1 hour over a length of 1.5 cm at X-rays with an average energy of 45 keV at a dose rate of 636.5 Gy / min, the dose (or fluence) being expressed in Gray. (1 Gy = 1J / kg). A green emitting laser diode (wavelength 519nm) was connected to the input of the PMMA plastic optical fiber (length of the PMMA fiber: 1 m) to then measure the light intensity atthe output of the plastic fiber PMMA.
The laboratory did not detect after 1 hour of irradiation any decrease in the intensity transmitted in the green as shown in the diagram below.
These PMMA fibers have shown no sensitivity to X-rays for the wavelength of green. On the other hand, no radio-induced emission was detected since there was no re-emission of light under X-ray irradiation.
By comparison, an optical fiber based on silica would have shown a rapid decrease in the transmission after switching on the X-rays. Although this PMMAplastic fiber has only been exposed for a limited time, it can be considered asa fiber completely insensitive to X-rays knowing that the dose received wasalready large (more than 33kGy received in 1 hour).
Please consult us our polymer optical fibers, optical fiber cords, light guides from Toray brand..