1480 nm Diode-Pumped Er3+:Yb3+ Co-Doped Phospho-Alumino-Silicate Fiber for Extending the L-Band Gain Up to 1625 nm

In this article, we report erbium/ytterbium (Er/Yb) co-doped phospho-alumino-silicate fibers (EYDFs) fabricated by the modified chemical vapor deposition (MCVD) and solution doping technique, to extend the L-band gain up to 1625 nm. Fibers with different doping concentrations and Yb-to-Er ratios were studied in terms of the spectroscopic properties and optical amplification in the L-band when pumped at 1480 nm. A higher Yb-to-Er ratio suppressed the signal-induced excited-state absorption (ESA) effect and also improved the amplifier gain in the L-band. A maximum gain of 15.5 dB at 1625 nm was achieved for the fiber with an Yb-to-Er ratio of 3.5. The gain coefficient was 0.039 dB/mW and the saturation output power was 21.5 dBm at 1600 nm. On the other hand, one highly doped fiber with the Er
₂
O
₃
concentration of 0.5 mol% and an Yb-to-Er ratio of 2 was demonstrated to have the controlled Er concentration quenching and a reduced amplifier device length, exhibiting 12.9 dB gain and 6.3 dB noise figure (NF) at 1625 nm, with <5.8 dB NF from 1575 to 1623 nm. What's more, the temperature-dependent amplifier performance was studied, over the temperature range of −60 to 80 °C. The temperature-dependent-gain (TDG) coefficient and its zero-point wavelength were reported. An increased L-band gain was achieved by cooling the fiber.