Temperature-Dependent Study on L-Band EDFA Characteristics Pumped at 980 nm and 1480 nm in Phosphorus and Aluminum-Rich Erbium-Doped Silica Fibers

In this paper, wepresent a comparative study on temperature-dependent spectroscopic characteristics and L-band amplifier performance for aluminum-rich erbium-doped fiber (EDF) and in-house fabricated phosphorus co-doped EDF. Different pumping configurations were studied to conclude that the pump wavelength of 980 nm with unequal forward/backward pump powers exhibited better temperature stability. Phosphorus EDF provided 19.4±1.4 dB gain and 4.6±0.2 dB noise figure (NF) from 1575–1615 nm at room temperature (RT), for a multi-channel input signal of −25 dBm in each channel, whereas the aluminum-rich EDF provided 20.3±5.1 dB gain and 5.3±0.8 dB NF. Using a single-channel input signal of −25 dBm at 1625 nm, phosphorus EDF maintained >10 dB gain with a 9.6 dB and 12 dB gain increment than aluminum-rich EDF at RT and −60 °C, respectively. The temperature-dependent gain (TDG) coefficient from 1575–1615 nm was in the range −0.006 to −0.044 dB/°C for phosphorus EDF and 0.011 to −0.023 dB/°C for aluminum-rich EDF, over the temperature range −60 to +80 °C. We propose a hybrid L-band amplifier concatenating aluminum-rich EDF with phosphorus EDF, to suppress the temperature dependence of phosphorus EDF and improve the gain bandwidth restriction of aluminum-rich EDF. The hybrid EDF exhibited multi-channel 20.9±3.9 dB gain and 3.7±0.6 dB NF from 1575–1615 nm at RT. The TDG coefficient of the hybrid EDF remained almost constant from 1585–1615 nm, contributing to a temperature-insensitive gain flatness.