Abstract
A hybrid double cladding erbium–ytterbium co-doped fiber (EYDF) amplifier with a single-mode-multimode-single-mode (SMS) active fiber is demonstrated in this study. The hybrid gain fiber with an SMS structure is composed of two kinds of EYDFs with 6 and 12 μm core diameters. The transmission spectra of the SMS fiber structure were theoretically analyzed and the simulation results indicated that the maximum loss in the 1~1.1 μm band where the Yb-band amplified spontaneous emission (Yb-ASE) located, was much larger than that of the 1.5-μm band because of the wavelength difference. The power performance and spectra properties of the hybrid fiber amplifier were theoretically and experimentally analyzed and compared with a typical uniform fiber amplifier under the same conditions. The experimental results demonstrated that this hybrid fiber amplifier can suppress the Yb-ASE by over 12 dB and increase the slope efficiency by more than 2%, but the ASE in the 1.5-μm band increases by 2~3 dB. This work provides a possible method to enable EYDF amplifiers to suppress the Yb-ASE and overcome the pump bottleneck effect.
Highlights
A single-frequency fiber laser at 1.55 μm wavelength with narrow linewidth, low fiber transmission loss, and eye-safe properties has great application in many fields, such as LIDAR, coherence optical communication, high sensitivity fiber sensors, and so on [1,2]
In 2007, the bottleneck effect was observed for the first time in an erbium–ytterbium co-doped fiber oscillator by Jeong et al [5] and it has attracted the interest of researchers since
The efficiency of the amplifier can be improved by 2.7% because of Yb-band amplified spontaneous emission (Yb-ASE) suppression and the additional gain provided by the SMS active fiber structure
Summary
A single-frequency fiber laser at 1.55 μm wavelength with narrow linewidth, low fiber transmission loss, and eye-safe properties has great application in many fields, such as LIDAR, coherence optical communication, high sensitivity fiber sensors, and so on [1,2]. The feedback of auxiliary 1-μm signal can effectively reduce the intensity of Yb-ASE, this method needs additional components or laser source, which will increase the cost and insertion loss of the amplifier. Another effective way to improve the limitation of the bottleneck effect is by optimizing the pump wavelength. The efficiency of the amplifier can be improved by 2.7% because of Yb-ASE suppression and the additional gain provided by the SMS active fiber structure This provides a monolithic structure for the EYDF amplifier to overcome the pump bottleneck effect and achieves high efficiency and high-power output
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