Comparison of radiation-induced passive and dynamic responses in two erbium-doped fiber lasers

Erbium-doped fiber lasers (EDFLs) may soon find applications in space as high bit rate optical communication systems and photonic analog-to-digital converters (ADCs). The rapid advancement in digital signal processing systems has led to an increased interest in the direct digitization of high-frequency analog signals. The potential high bandwidth, reduced weight, and reduced power requirements makes photonics an attractive technology for wide-band signal conversion as well as for use in space-based platforms. It is anticipated that photonic ADCs will be able to operate at sampling rates and resolutions far greater than current electronic ADCs. The high repetition rates and narrow pulse widths produced by EDFLs allow for high-speed impulse sampling of analog signals thus making it a vital component of a photonic ADC. In this paper we compare the results of exposing two differently constructed erbium-doped mode-locked fiber lasers (EDFLs) to gamma-rays. Each experiment is fully explained. The performance of EDFL1 was characterized in a passive fashion, i.e. before and after the irradiation. EDFL2´s performance was monitored in situ. The onset, growth and extent of ionization induced damage under time-resolved operational conditions is presented. The in situ studies clearly revealed ionization induced shifts of the EDFL optical spectrum to shorter wavelengths and with corresponding changes to the emission spectral width. The results of the evaluation will allow for further optimization of an EDFL for use in space-based architectures and applications.