1880-nm Broadband ASE Generation With Bismuth–Thulium Codoped Fiber

A broadband amplified spontaneous emission (ASE) generation in 1880-nm region is demonstrated by employing a newly developed single-mode Tm-Bi codoped fiber (TBF) in conjunction with 793-nm pumping for the first time. The TBF was obtained by drawing a preform, which was fabricated using a deposition of porous layer by the modified chemical vapor deposition (MCVD) process in conjunction with solution doping technique. The highest Bi
³⁺
and Tm
³⁺
concentrations of 0.35 wt.% and 0.9 wt.%, respectively, were successfully achieved to generate ASE centered at 1880-nm region. The ASE peaked at - 47.2 dBm with 3-dB spectral width ranging from 1817 to 1984 nm with 1.0-m-long TBF and 200-mW 793-nm pump power, which was generated due to the transition of thulium ions from
³
F
₄
to
³
H
₆
with some assistance from bismuth to thulium ion energy transfer. The use of a secondary pump of 1550 nm is also shown to improve the ASE generation.