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Novel 800/1060 nm dual-wavelength pumping sources for Tm^sup 3+^-doped fibre amplifiers (TDFAs) are reported: a Nd^sup 3+^-doped silica fibre laser or a Nd^sup 3+^-doped microstructured silica fibre laser, both pumped near 800 nm and emitting near 1060 nm, providing the two required TDFA pump wavelengths. A new regime of pump power ratios is explored in which the 800 nm power is comparable to the 1060 nm power. Gain and noise figure are comparable with those obtained using individual pump modules at the two wavelengths.
Introduction: With the 3F4-3H4 transition optimally positioned in the S-band, Tm3+-doped fibre amplifiers (TDFAs) are promising candidates for use in S-band telecommunication [1], Because the exploited transition occurs between two excited states, more complex pump schemes are required than for erbium-doped fibre amplifiers in the C- and L-band. Dual-wavelength pumping has proven to be efficient and versatile [1-4], and the 800/1060 nm combination is particularly promising owing to its reduced pump power and fibre length requirements [1, 5], Nd3+-doped fibre lasers (NDFLs) have been studied and reviewed extensively [6], By pumping with a laser near 800 nm to create emission near 1060 and by utilising excess or unabsorbed 800 nm light, they can be used as single pump sources for such dual-wavelength pumped TDFAs.
In this Letter, we demonstrate and characterise this novel approach of using a single pump laser to produce both wavelengths required for optimum pumping of TDFAs. Two different NDFLs were explored as TDFA pumps, one using a commercially available Nd3+-doped silica fibre (NDF), the other with a Nd3+-doped microstructured silica fibre (NDMF). Small-signal fibre gain of 9 dB (NDF) and 11 dB (NDMF) was achieved with total pump powers as low as 50 and 100 mW, respectively. Noise figures were better than 4 dB.
Experimental setup: Fig. 1 presents two different NDFL and TDFA configurations explored in this work. In Fig. la, the NDFL consists of a 25 m-long NDF (INO, 100 ppm, NA 0.17, core diameter 3.4 pm, cutoff wavelength 812 nm) spliced to a 1054 nm fibre Bragg grating high reflector and output coupler (HR -99.97% reflection, OC -80% reflection). The wavelength of the Ti:Sapphire (Ti:S) laser pump source was tuned...