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The radiation-induced Bragg wavelength shift (BWS) was measured with type I gratings made of 12 fibers with very different composition, i.e., of fibers with an extremely different radiation-induced attenuation. With two of the fibers fabrication parameters like laser intensity, hydrogen loading, and annealing conditions after grating inscription were varied. With another fiber type I and type II gratings were made by a completely different process. With gratings made under identical conditions of the 12 fibers the radiation-induced BWS only varied by about a factor of three. Varying the fabrication parameters led to BWS differences up to nearly a factor of ten.
We have measured for the first time the shift of the Bragg wavelength and other parameters of fibre Bragg gratings (FBGs) exposed to radiation at different wavelengths up to a dose of 100 kGy. The results show that the FBG sensitivity to radiation increases from 820 nm to 1516 nm so that FBGs with higher Bragg wavelength, e.g. 1.55 µm, are good candidates for high dose radiation sensing: no saturation was observed up to 100 kGy and the measured wavelength shift was fairly independent on the radiation dose rate.
The sensitivity of low loss perfluorinated polymer optical fiber (PF-POF) to gamma radiation is investigated for on line radiation monitoring purposes. The radiation induced attenuation (RIA) of a commercial PF-POF based on Cytop material is measured in the visible spectral region. The fiber RIA shows strong wavelength dependence with rapid increase towards the blue side of the spectrum. The wide range of radiation sensitivities is available via careful selection of appropriate monitoring wavelength. The accessible sensitivities span from 1.99 ± 0.01 dBm⁻¹/kGy measured at 890 nm to 140.9 ± 0.6 dBm⁻¹/kGy measured at 460 nm. The fairly high radiation sensitivity as well as its wide tunability makes the fiber a promising candidate for a broad range of applications.
Radiation induced attenuation in perfluorinated polymer optical fibres for dosimetry applications
(2016)
Real-time measurement of radiation-induced attenuation (RIA) in a commercial perfluorinated polymer optical fibre (PF-POF) is performed with regard to on-line radiation monitoring purposes. Spectral character and dose dependence of fibre’s RIA is measured in 450-900 nm spectral region. Fibre exhibited high radiation sensitivity in the visible region with strong increase towards the UV wavelengths. Good linearity and high sensitivity reaching up to 130 dBm-1/kGy was demonstrated in the VIS region for a low dose range. This of the shelf PF-POF could be therefore interesting for on-line remote dosimetry applications.
Impact of gamma radiation on transmission of a commercial Cytop polymer optical fibre (Lucina, Asahi Glass Company) is investigated. Spectral dependence of radiation induced attenuation in the investigated fibre is measured in the VIS-NIR spectral region. Besides attenuation increase, radiation is found to increase fibre susceptibility to water as well. While pristine Cytop fibre is rather humidity insensitive, strong humidity related absorption in the NIR region is observed after fibre irradiation. Selective irradiation of separate fibre sections is proposed as a way of fibre humidity sensitization and quasi-distributed water detection is demonstrated using optical time domain reflectometry at 1310 nm.
In the last decades, considerable attention has been paid to the development of polymer optical fibers (POFs) that may, in certain cases, represent more suitable or cost effective alternative to their glass based counterparts. Due to some of their unique properties, POFs have found their applications in the area of data transmission, lighting as well as optical sensing. Compared to the glass based fiber sensors, POFs are more robust and flexible yielding sensors suitable also for larger strain applications. They have better biocompatibility and are generally more acceptable for medical applications. In addition, POFs can provide higher inherent sensitivity to some of the more alternative measurands such as humidity or ionizing radiation.
Over the last three years, BAM’s Division 8.6 has been participating in the European FP7 project “TRIPOD” devoted to the development of POF technology for sensing applications. Project activities and main technological achievements will be reviewed. Special attention will be paid to the utilization of optical fiber sensors in radiation environments. In the recent years, ionizing radiation has found numerous applications also outside the nuclear industry, e.g. in material processing, sterilization or medical applications. With increasing importance of radiation processes, demand for suitable monitoring techniques is rising as well. Among available dosimetry solutions, optical fiber based dosimeters offer numerous advantages such as electromagnetic immunity, small dimensions and possibility of remote and real time monitoring. A concept of attenuation based radiation sensing with perfluorinated POFs will be investigated and presented as a potential candidate for low cost easy to use on line radiation monitoring system.
Application importance of ionizing radiation has been growing steadily over the last decades. Extensive utilization of ionizing radiation generates demand for development of suitable monitoring techniques. Radiation monitoring systems based on optical fibers offer several key advantages such as small footprint, possibility of remote and real-time measurement as well as electromagnetic immunity. In this contribution, we investigate radiation-induced attenuation (RIA)-based sensing with perfluorinated polymer optical fibers (PF-POFs). The RIA response of two commercial PF-POFs is assessed in a low dose region and performance and limitations of the system are discussed. The concept represents a potential high-sensitivity, low-cost and easy-to-use on-line radiation monitoring system with distributed detection capability.
Sensitivity of two commercial perfluorinated (PF) polymer optical fibers (POFs) to gamma radiation was measured, compared and exploited for dosimetry purposes. Fiber radiation induced attenuation (RIA) was found to be highly wavelength dependent and pronounced towards the UV part of the spectrum. PF-POFs were shown to be highly radiation sensitive and RIA-based on-line radiation monitoring with sensitivity as high as 135 dBm-1/kGy was demonstrated at 460 nm with co-extruded PF-POF. In addition, thanks to low inherent attenuation in the near-infrared region, possibility of distributed radiation detection with PF-POFs was demonstrated for the first time, utilizing optical time domain reflectometry.
Application importance of ionizing radiation has been growing steadily over the last decades. Extensive utilization of ionizing radiation generates demand for development of suitable monitoring techniques. Radiation monitoring systems based on optical fibers offer several key advantages such as small footprint, possibility of remote and real-time measurement as well as electromagnetic immunity. In this contribution, we investigate radiation-induced attenuation (RIA)-based sensing with perfluorinated polymer optical fibers (PF-POFs). The RIA response of two commercial PF-POFs is assessed in a low dose region and performance and limitations of the system are discussed. The concept represents a potential high-sensitivity, low-cost and easy-to-use on-line radiation monitoring system with distributed detection capability