We propose and demonstrate a high-performance wavelength-switchable erbium-doped fiber laser (EDFL), enabled by a figure-8 compound-ring-cavity (F8-CRC) filter for single-longitudinal-mode (SLM) selection and a polarization-managed four-channel filter (PM-FCF) for defining four lasing wavelengths. We introduce a novel methodology utilizing signal-flow graph combined with Mason’s rule to analyze a CRC filter in general and apply it to obtain the important design parameters for the F8-CRC used in this paper. By combining the functions of the F8-CRC filter and the PM-FCF assisted by the enhanced polarization hole-burning and polarization dependent loss, we achieve the EDFL with fifteen lasing states, including four single-, six dual-, four tri- and one quad-wavelength lasing operations. In particular, all the four single-wavelength operations are in stable SLM oscillation, typically with a linewidth of <600 Hz, a RIN of ≤−154.58 dB/Hz@≥3 MHz and an output power fluctuation of ≤±3.45%. In addition, all the six dual-wavelength operations have very similar performances, with the performance parameters close to those of the four single-wavelength operations, superior to our previous work and others’ similar work significantly. Finally, we achieve the wavelength-spacing tuning of dual-wavelength operations for photonic generation of tunable microwave signals, and successfully obtain a signal at 23.10 GHz as a demonstration.
A high-performance wavelength-switchable single-longitudinal-mode (SLM) fiber laser with ultra-narrow linewidth and high stability in C-band was proposed and demonstrated, mainly benefiting from the use of a wide-band chirped Moiré fiber Bragg grating (WB-CM-FBG) with 41 ultra-narrow channels. By combining the WB-CM-FBG with a manual tunable bandpass filter and using a subring cavity with a length of only 34 cm to efficiently stabilize the SLM lasing, we achieved switchable lasing operation among 41 wavelengths, with a switching-step of ~0.96 nm from 1526.592 nm to 1565.126 nm, covering the whole C-band, and obtained sub-kHz linewidth at every lasing wavelength. The high stability was validated by the measured slight fluctuations of lasing wavelength and optical power of <0.004 nm and <0.113 dB, respectively, in 1.5 h. To the best of authors’ knowledge, this is the state-of-the-art CM-FBG-based fiber laser reported with the greatest number of switchable-wavelengths covering C-band, and, what’s more, each switchable lasing wavelength was with sub-kHz linewidth. The performance of the proposed fiber laser can be improved further with good temperature compensation and vibration isolation packaging for practical applications.
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