Temperature Influence on the Radiation Responses of Erbium‐Doped Fiber Amplifiers

Abstract

The gain degradations of an Er‐doped fiber amplifier (EDFA) during the exposure of its active Er‐doped fiber to 40 keV X‐rays (≈2.7 mrad(SiO2) s−1 up to 300 krad) at three different temperatures: −40, 25, and 120 °C, are characterized. The spectral dependence of the fiber radiation‐induced attenuation (RIA) is monitored in situ in the 900–1600 nm spectral range, highlighting a combined temperature and radiation effect on the near‐infrared RIA levels and kinetics. At the system level, the kinetics of EDFA gain degradation are only slightly affected by varying the irradiation temperature for the tested backward pumping EDFA configuration. On the theoretical side, a homemade computer code based on the particle swarm optimization and the rate equations to model the radiation behavior of EDFA is used, considering only the RIA impact on its gain. Despite a good agreement between experimental and simulation results below the dose of 70 krad corresponding to current space missions, the comparison between the modeled and measured gain degradation kinetics at higher doses shows that a more precise modeling of the temperature impact on the absorption properties of the erbium ions is necessary to better reproduce the EDFA radiation behavior for future space missions.

Experimental–Simulation Analysis of a Radiation Tolerant Erbium-Doped Fiber Amplifier for Space Applications

“…Figure 6 shows the spectral RIA obtained at the maximum dose for the four different irradiation conditions, whose specifications are listed in Table 4. The obtained RIAs agree with those reported in [25,28] and are mainly due to the tail of the Al-OHC point defects, whose absorption band is centered in the visible range around 540 nm, and to a not-yetwell-known defect absorbing in the IR [25]. Thus, whereas at 980 nm, the RIA is associated with the presence of the Al-OHCs, at 1550 on the other hand, the RIA is linked to the unknown center.…”

“…Figure 6 shows the spectral RIA obtained at the maximum dose for the four different irradiation conditions, whose specifications are listed in Table 4. The obtained RIAs agree with those reported in [25,28] and are mainly due to the tail of the Al-OHC point defects, Figure 5b shows the absorption and emission cross sections, both in pristine and irradiated samples, obtained using the mathematical formula presented in Section 2.3. The increase in fiber losses leads to an increase in the absorption and emission cross sections, of 0.5 × 10 −25 m 2 at 1530 nm, at a TID of 3 kGy.…”

“…In the previous work of our research group, Aubry et al [28] showed that adding periods of high pump power during the fiber testing reduces the measured RIA at the pump and signal wavelengths. They used an experimental setup for the RIA measurements that allowed them to inject, considering time slots of 15 min, the pump signal into the FUT during the 80% of the time, while during the remaining 20%, only a low-power light source was injected to allow the RIA spectral acquisition.…”

“…Indeed, during the fiber testing, there is a lower contribution of the PB to the RIA reduction. This RIA overestimation was potentially identified as one of the causes of the slight observed disagreement between measured and simulated gain degradation kinetics on a similar EDFA, observed at high TIDs in a previous work [28]. For this reason, in this work, we developed a new experimental setup for RIA measurements, that was able to reduce the percentage of time during which the pump is not injected into the fiber.…”

Brillouin-like effects in rare-earth-doped bi-directional optical fiber amplifiers

“…Inscription is most efficient for the stationary gratings ( 0 V = , 0  =) and becomes weak at G    , when the interference pattern is shifted by a half of the grating period for the grating lifetime. The last two equations in Eq.3 are common equations from the two-level laser model 39 describing the dynamics of the pump powers. This dynamics has a minor effect on the Brillouin-like amplification but may complicate its observation.…”