Configurations of Pump Injection and Reinjection for Improved Amplification Efficiency of Turbo Cladding Pumped MC-EDFA

Configurations of cladding pumped MC-EDFA with pump recycling have been researched to improve optical amplification efficiency. The difference between the four researched configurations is the pump injection and re-injection method. The optical amplification performance was compared experimentally by evaluating the optical gain, noise figure, and the maximum output signal power. The results show the spatial injection and the fiber re-injection with spatial splitting configuration improved the pump recycling efficiency the most, and the configuration offered an additional 3.5 dB of optical gain and boosted the maximum output signal power by 4.0 dB compared to the standard cladding pumping without pump recycling. The improvement in the optical gain due to the pump recycling was constant at 1.0 dB in the fixed experimental set-up even if the input optical signal power was changed. The effect of the spatial intensity distribution widening due to the fiber pump combiner is considered to be effective in improving the pump recycling efficiency. An additional 0.2 dB improvement (1.2 dB in total) in the optical gain was achieved by modifying the free-space lens optics design of the spatial pump splitter.