Radiation Resistant Erbium Doped Optical Fiber for Space Applications

Transcription

1 Radiation Resistant Erbium Doped Optical Fiber for Space Applications J. Thomas 1, M. Myara 1, P. Signoret 1, A. Pastouret 2, E. Burov 2, D. Boivin 2, O. Cavani 2, M. Sotom 3, M. Maignan 3, O. Gilard 4 ICSO - Ajaccio October 10 th (2012)

2 2 Summary 1.Motivations 2.Some Design Rules for Radiation-Resistant EDFAs 3.Our Solution : Erbium-doped Nanoparticles 4.Fibers and Amplifiers under test 5.Experimental Results 6.Conclusion & Perspectives

3 3 1. Motivations WDM technology in the Context of Space Applications Optical WDM technology low cost/mature Applications: inter-satellite communication, embeded RF signal routing, lidar, Most photonic components validated except the Erbium-Doped Fiber. Two Main Locks Accelerated test methods for irradiated EDFs assessment Enhanced chemical/manufacturing processes for Erbium-Doped Fibers (EDF) Hardening Typical Space Mission: Gamma + Protons similar to gamma irrad. at 3mGy/h during 15 years (total dose 450 Gy)

4 4 1. Motivations Degradation of passive optical fibers Due to absorbing defects in the Silica Network Amplified by the inclusion of co-doping atoms RIA s origin in the visible/uv range (absorption tail) Degradation of active Er-doped fibers Mainly due to Al co-doping atom, leads to gain reduction Reducing Al induces quenching, thus reduces the gain too

5 5 2. Requirements for Radiation Resistant Erbium doped fiber Overall influence of the radiations = RIA(dB/m) x Amplifier Length (m) Radiation-Resistant High-Power Amplifier = Low RIA & Short Length [Er] Quenching, Low RIA Short Amplifier, Strong RIA Long Amplifier, Low RIA Long Amplifier, Strong RIA Always lead to low-gain amplifier, before or after irradiation [Al] No solution with classical fabrication processes Erbium-Doped Nanoparticules technology permits to solve this tricky problem!

6 6 3. Prysmian Group / Draka solution : NP technology Schematic concept Polyme r coa ting = 250 m NP Erbium doped fiber (NP EDF) Muc h le s s Al c onte nt Er e nvironme nt inde pe nde nt of c ore glas s c ompos ition = 4 to 8 m Keep NP integ rity up to doped- fibe r NP EDF NP size and shape control Fe w nm tens nm + Stable suspension in commun solve nt MCVD process + NP structure adaptations Clad Co re NP Synthesis Fib e r Dra wing = 20 mm Pre form Ma nufa cturing NP glass Incorpora tion Doped NP Soft chemica l or physical synthesis according to N P kind NP fiber doping process Pastouret et al., in proc. SPIE 7195 (2009) Erbium doped alumina NPs have been firstly designed for C-band WDM EDFAs. Improved amplifying efficiency compared to more conventional fibers Boivin et al., in proc. SPIE 7914 (2011) Concept applied to Er doped silica NPs for Radhard EDFAs application

7 7 4. Fibers / Amplifier under test RIA / Optimal length balance implies to test amplifier gain too! EDFA Configuration under test : Optimal Length Fibers/Amplifiers under test Standard Fibers NP-Fibers Highly doped Al-Free Fibers All amplifiers exhibit similar output power (~ 17 dbm) before irradiation.

8 5. Experimental Setup & Irradiation Conditions Performed at 10Gy/h (Co 60 source) Allows real-time / in-line evaluation of the degradation Allows both RIA (sub-nw limit) and EDFA gain measurement Very moderate photobleaching during measurements Not accurate for NF measurements (optical switches reflections) 8

9 9 6. Experimental Results RIA Results Fiber Name Er abs. (db/m) Al. (wt%) Opt. Length (m) RIA 980 nm (db/m/gy) RIA 1550 nm (db/m/gy) Al-NB 4.7 < Al-LB NP-Al NP-Si NP-Si Low [Al] leads to low RIA Gain Decrease NP process permits ultra-low RIA Best fiber have low [Al] and short length Confirmation of Gusarov rule weigthed by RIA values! At comparable [Al], NP technology provides better tolerance Singular behaviour for NP-Al!

10 6. Experimental Results Optimal Length Evolution pre/post irradiation Heavily Al-doped fiber Non-Al-doped fiber Optimal length of a RH amplifier should be chosen considering the post irradiation optimal length (and not the pre irradiation one!) 10

11 6. Experimental Results Noise Factor vs Dose Insufficient inhomogeneous broadening for very low noise and multiple-channel applications NF degradation smaller for NP-Si+ 11

12 12 7. Conclusion Radiation resistance tests of 5 EDFs with different compositions and manufacturing process: - gain & NF measurement in saturation regime - RIA for pump & signal in small-signal regime - cutback measurements done after irradiation Gain degradation: - highest for standard process with high [Al] - lowest for Al-free NP-fibers (idem for RIA) First demonstration of the feasability of Radiation-Hardened single channel EDFA for space applications Perspectives: for WDM & low noise operations, optimisations are needed - introduction of small [Al] within the nanoparticle - minimal hydrogenation to compensate for induced RIA

13 Thanks for your attention. 13