High gain bismuth-doped fiber amplifier operating in the E+S band with record gain per unit length

Abstract

We experimentally demonstrate high-gain E+S band bismuth (Bi)-doped fiber amplifiers (BDFAs) using Bi-doped germanosilicate fiber (BGSF) with lengths shorter than those widely reported in the literature, ranging from 25.5 to 48m. In a double-pass amplifier configuration, a 39.9dB gain with 5.6dB noise figure (NF) is achieved at 1440nm using 35m of BGSF, for a -23dBm input signal. By reducing the fiber length to 25.5m, we achieve the highest recorded gain per unit length of 1.33dB/m, to the best of our knowledge, with 33.8dB gain and 3.7dB NF for an input signal of -23dBm. The highest power-conversion-efficiency (PCE) is 18.3%, obtained by 48m of BGSF using 375mW pump power and -10dBm signal power. From 1410-1490nm, the in-band optical signal-to-noise ratio (OSNR) is >21dB for a -23dBm input signal and >33dB for a -10dBm input signal. The temperature-dependent gain is characterized from -60 to 80°C, with the longer BGSF length exhibiting better thermal stability. Moreover, three BGSFs with an increasing GeO 2 concentration, measured to be in the range of 3.7-16mol%, are studied in detail for their absorption and luminescence characteristics. An absorption band peaking at ∼1370nm has appeared and is likely to be associated with the bismuth-active-center (BAC) connected to the Ge, BAC-Ge. By increasing the GeO 2 concentration to 16mol%, the 1370nm BAC-Ge absorption band starts to dominate over the 1405nm BAC-Si absorption band, while simultaneously the other BAC-Ge absorption band at 1640nm appears. The luminescence exhibits a wider bandwidth with an increase in GeO 2 content, favoring the E+S band amplification.

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Identifiers

ORCID for Ziwei Zhai: orcid.org/0000-0001-7128-7326

ORCID for Arindam Halder: orcid.org/0000-0002-5517-4812

ORCID for Jayanta K. Sahu: orcid.org/0000-0003-3560-6152

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