High output Er³⁺/Yb³⁺ co-doped optical amplifiers pumped by diode-pumped Nd³⁺ lasers

As the erbium-doped optical fiber amplifier has gained acceptance in the telecommunications industry, the majority of attention has focussed on the choice of the semiconductor pump source, especially with regards to lifetime and power scalability. High output power erbium optical amplifiers have been demonstrated with both 980 and 1480 nm pump diodes. However there are serious questions regarding power scalability once more than two pump diodes are required. A +22.3dBm output power amplifier has been reported using four 1480 nm pump diodes. This configuration however required the use of polarization preserving diode pigtails and bulk polarization combining optics, which had a high insertion loss and introduce non-negligible reflections in the amplifier system