We demonstrate an all-fiber 7 × 1 signal combiner with an output core diameter of 50 μm for high power incoherent beam combining of seven self-made Yb-doped single-mode fiber lasers around a wavelength of 1080 nm and output power of 2 kW. 14.1 kW combined output power is achieved with a total transmission efficiency of higher than 98.5% and a beam quality of M = 5.37, which is close to the theoretical results based on finite-difference beam propagation technique. To the best of our knowledge, this is the highest output power ever reported for all-fiber structure beam combining generation, which indicates the feasibility and potential of >10 kW high brightness incoherent beam combining based on an all-fiber signal combiner.
In this study, we present systematic numerical and experimental analysis of high-power C-band light pumping in extended L-band erbium-doped fiber amplifiers (EDFAs). We investigate, for the first time to the best of our knowledge, how C-band light sources can be used as pump sources to extend the bandwidth of L-band EDFAs beyond 1610 nm. Results show that, when using a C-band light source as the sole pump, efficient amplification is obtained over the extended L-band, but at the expense of a higher noise figure. However, the advantage of C-band pumping in terms of power conversion efficiency can be exploited when using a two-stage EDFA, with a first stage pumped by 1480 nm to maintain good noise figure performance and a high-power C-band light source (up to several hundred mW) as the pump source for the second stage. Thus, a 20 dB gain covering 1570–1618 nm with a maximum noise figure of 5.7 dB is demonstrated.
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