Optical Communication in High-Radiation Environments
Joint research confirms reliable data transmission after gamma irradiation up to 198 kGy
Reliable communication is essential wherever safety, monitoring and control systems must operate under demanding environmental conditions. This is particularly relevant for nuclear power plants, radioactive-waste repositories, nuclear medicine and other critical-infrastructure applications, where optical cables may be exposed to ionising radiation throughout their service life.
OPTOKON Kable participated in a joint research project with the Czech Technical University in Prague and the Nuclear Research Institute Rez to investigate how gamma radiation affects the performance of optical cables with single-mode fibres. The findings have been published in the peer-reviewed journal Radiation Physics and Chemistry.
Testing the cable under gamma irradiation
The research focused on an experimental optical cable containing four G.657.A1 single-mode fibres with a germanium-doped core and pure-silica cladding. The cable design includes a double jacket and was developed for demanding outdoor and industrial applications.
Three 130-metre cable samples were exposed to gamma radiation from cobalt-60 sources at the Nuclear Research Institute Rez. One hundred metres of each cable were irradiated, while the remaining length was used for measurement connections.
The tests covered total gamma doses of:
- 67.7 kGy at a dose rate of 0.89 kGy/h
- 98.4 kGy at a dose rate of 6.4 Gy/h
- 198.0 kGy at a dose rate of 0.76 kGy/h
For comparison, the anticipated cumulative dose at a planned cable route in the Dukovany Nuclear Power Plant is approximately 17 kGy over the expected operating lifetime. The research therefore examined cable behaviour at radiation levels substantially higher than this application-specific requirement.
Measuring attenuation and communication performance
During and after irradiation, the team measured changes in optical attenuation at wavelengths of 1310 nm, 1383 nm, 1490 nm, 1550 nm and 1625 nm.
Gamma radiation increases attenuation in optical fibres because it creates microscopic defects in the glass structure. These defects absorb part of the transmitted optical signal. After irradiation ends, the attenuation begins to decrease through a recovery process in which some of the radiation-induced defects gradually recombine or become inactive.
Alongside attenuation measurements, the study verified actual data transmission during irradiation. At the highest tested dose of 198.0 kGy, data transmission at 1310 nm was measured over a 100-metre cable length.
The result was 944 Mbit/s, compared with an initial speed of 946 Mbit/s. This confirms that even after exposure to the highest tested gamma dose, the optical cable maintained data transmission close to 1 Gbit/s.
Why 1310 nm matters
One of the most important outcomes concerns the selected operating wavelength.
The lowest radiation-induced attenuation was observed at 1310 nm. Higher attenuation was measured at longer wavelengths, including 1490 nm and 1550 nm. For communication systems intended for radiation-intensive environments, operation in the O-band, approximately 1260-1360 nm, may therefore offer a practical advantage over operation in the C-band around 1550 nm.
This is an important consideration for system designers. Selecting the right wavelength can help maintain optical communication performance in applications where radiation exposure cannot be avoided.
Total dose is the key factor
The research also evaluated the influence of dose rate, meaning how quickly a cable receives radiation exposure.
For the tested cable construction, the results showed that the total absorbed gamma dose had a more significant effect on attenuation than the dose rate itself. Although lower dose rates produced slightly lower attenuation changes, the difference was not dominant under the tested conditions.
This insight supports more accurate planning of qualification tests and long-term cable deployment in radiation-intensive environments.
From research to critical applications
The study demonstrates that optical communication can remain operational in challenging gamma-radiation environments, even when optical attenuation increases. It also highlights why cable performance must be assessed as a complete system rather than by considering the optical fibre alone.
Cable construction, protective materials, fibre design and operating wavelength all influence performance under irradiation.
For OPTOKON, participation in this research is part of a broader commitment to developing and validating reliable communication solutions for environments where dependable data transmission is critical.
Read the full peer-reviewed article, “The effect of gamma-ray irradiation on optical cables with Ge-doped single-mode fibers,” in Radiation Physics and Chemistry here.
