Radiation hardening techniques for rare-earth-based optical fibers and amplifiers

Abstract

Er/Yb doped fibers and amplifiers have been shown to be very radiation sensitive, limiting their integration in space. We present an approach including successive hardening techniques to enhance their radiation tolerance. The efficiency of our approach is demonstrated by comparing the radiation responses of optical amplifiers made with same lengths of different rare-earth doped fibers and exposed to gamma-rays. Previous studies indicated that such amplifiers suffered significant degradation for doses exceeding 10 krad. Applying our techniques significantly enhances the amplifier radiation resistance, resulting in a very limited degradation up to 50 krad. Our optimization techniques concern the fiber composition, some possible pre-treatments and the interest of simulation tools used to harden by design the amplifiers. We showed that adding cerium inside the fiber phosphosilicate-based core strongly decreases the fiber radiation sensitivity compared to the standard fiber. For both fibers, a pre-treatment with hydrogen permits to enhance again the fiber resistance. Furthermore, simulations tools can also be used to improve the tolerance of the fiber amplifier by helping identifying the best amplifier configuration for operation in the radiative environment.

A Review of High-Power Semiconductor Optical Amplifiers in the 1550 nm Band

“…Semiconductor optical amplifiers are one to two orders of magnitude more resistant to radiation than fiber optic amplifiers, without any special improvements in radiation resistance [9][10][11][12][13][14]. High-power, low-cost, and integrated SOA devices are eminently suitable for carrying space loads for space laser communication.…”