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Remedies to Thermal Radiation in Fused Silica Optical Fibers

Borzycki Krzysztof, Jaworski Marek, Kossek Tomasz

Journal of Telecommunications and Information Technology

2023

nr 1

88--96

During fire incidents, optical fibers located with-in a fire-resistant cable are usually exposed to temperatures of 800◦C to 1000◦C. Hot fibers generate narrowband thermal (incandescent) radiation and collect broadband thermal radiation originating from the heated surroundings. The power of the second component, initially negligible, increases with time due to the rising number of fiber cracks and other defects acting as couplers for external radiation. Thermal radiation may interfere with fiber attenuation measurements performed during a fire test, but is rather unlikely to prevent data transmission with typical GbE and 10 GbE transceivers during a fire. This problem may be remedied by combining the following methods: using single mode fibers instead of multimode fibers, using bandpass filters to block thermal radiation, and selecting proper transmitter power, wavelength and photodetector.

High Temperature Effects in Fused Silica Optical Fibers

Borzycki Krzysztof, Jaworski Marek, Kossek Tomasz

Journal of Telecommunications and Information Technology

2021

nr 3

56--71

Fire-resistant fiber optic cables used in safety and monitoring systems playing an essential role in fire fighting and building evacuation procedures are required to temporarily maintain optical continuity when exposed to fire. However, the use of fused silica fiber at temperatures between 800◦C and 1000◦C is associated with two highly undesirable phenomena. Thermal radiation (incandescence) of optical fibers, with its intensity and spectral distribution being proportional to additional attenuation observed in the fiber’s hydroxyl absorption bands (“water peaks”) is one of them. The other consists in penetration of thermal radiation from the surroundings into the fiber, due to defects in glass, causing light scattering and resulting in fiber brittleness. Thermal radiation is a source of interference in fiber attenuation measurements performed during fire tests and affects normal operation of fiber optic data links in the event of a fire. In this article, results of laboratory tests performed on a telecom single mode and multimode fibers subjected to temperatures of up to 1000◦C are presented.