{'fraction_non_alphanumeric': 0.027833001988071572, 'fraction_numerical': 0.016302186878727636, 'mean_word_length': 4.616071428571429, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Study of Silicate-based Erbium-Doped Fiber for Extending to L-band and Its Amplification Performance

With the continuous development of mobile internet, cloud computing, Internet of things and 5G, the annual growth rate of the existing communication transmission capacity is far from meeting the growing demand. The gain bandwidth of L-band EDFA has become the main restriction reason for bandwidth extension. Due to its negative effect on the gain and noise figure after 1580 nm, the excited state absorption(ESA) is regarded as a key factor that directly limits the L-band expansion of erbium-doped fiber amplifiers. If the ESA coefficient has the same value as the stimulated emission coefficient, the net gain coefficient becomes zero. At the same time, signal amplification can not be obtained no matter how to adjust the pump power and fiber length. Improvements from the perspective of erbium-doped fibers, such as changing the host glass and doping components, are extremely beneficial to L-band extension based on simple amplifier configurations. In the present study, an erbium-doped fiber extending to the L-band was fabricated by MCVD technology. The saturation curve of the fiber was measured, and then the rate of clustering was obtained. In addition, the absorption and emission coefficients of the fiber were tested by the truncation method, then the effect of ESA was studied. We demonstrated that modulating the ratio of P to Al in the fiber core has a significant inhibitory effect on the ESA of Er3+. To better characterize the amplification performance of the fiber, a single-stage and a multi-stage amplifier system were built respectively. At an input signal injection with a power of -9 dBm, the fiber exhibited a gain of 10.5 dB with a maximum noise figure of 5.9 dB at 1625.3 nm, based on a single-stage amplifier system under a 980 nm forward-pumping excitation. It declares that the amplification performance of the fiber in the long-wavelength has improved, which is consistent with the conclusion of the suppression effect on ESA. By optimizing the fiber length for the first, second and third stages to 19 m, 26 m and 10 m, respectively, a gain of 23.4 dB was obtained at the longest wavelength. The maximum noise figure was 6.3 dB, and the saturation output power is 24.8 dBm. In the meantime, the pump conversion efficiency reached 13%. It is the first report that shows the L-band extended silicate-based erbium-doped fiber can achieve long-wavelength gain extension to 1625.3 nm.