Abstract

In this paper we review our work to achieve S-band amplification using only erbium doped silica fibers. To this end, double-pass and single pass erbium doped depressed cladding fiber amplifier designed for S band operation are evaluated under changes of the input optical power, pumping power and fiber bending radius. The double pass configuration employs the usual combination of a circulator and a Faraday rotator mirror while the single pass is based on the co-propagating scheme. The amplifiers were characterized in terms of gain and noise figure. It is demonstrated that the double pass topology shows much improved gain performance compared to the single pass configuration although the noise figure is slightly degraded by counter-propagating ASE. Next, the amplifier double pass topology is properly modified to achieve signal amplification simultaneously over S, C and L bands. An embedded dispersion compensating fiber is included and the experimental characterization is carried out in terms gain and noise figure over the CWDM wavelength grid. By providing optical gain to seven CWDM channels spectrally located between 1490 and 1610 nm, the amplifier can extend the reach of a 16-channel CWDM optical bus well beyond the 100 km limit. The system results are then compared to those obtained by using a SOA (semiconductor optical amplifier), under the same experimental conditions.

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