## 6 Conclusions  
In this work, we presented a novel switchable and tunable multi-wavelength ring fiber laser that uses a structure comprising SMF/TCEDF/SMF as a WSF. The proposed ring cavity design features a filter, enabling tunable and switchable laser line emissions that go from single to quadruple wavelengths, achieved by adjusting the curvature on the MZI. Our findings indicate a tuning range of 7.62 nm with an SMSR of 49.80 dB for a  
Figure 15: Stability tests of the triple emissions. (**a**) On the first switch, (**b**) power variation, (**c**) wavelength variation, (**a**) test on the second switch, (**b**) power variation, (**c**) wavelength variation.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Ref.** & **Main Characteristics** & **Emission Lines** & **Tuning (nm)** & **SMSR (dB)** \\ \hline
[7] & Cascade structure—Sagnac loop filter (SLF)/twin core photonic & 1 & 23.04 & 57 \\  & crystal fiber (TCPCF) & 2 & 19 & 40 \\  & MZI & 2 & 3.43 & 30 \\
[8] & (SMF/PCF/SMF) & 3 & - & 28 \\  & 1 & 40 & 32.68 \\
[11] & Sagnac loop and MZI filter—SMF/TCF/SMF & 2 & 13 & 33.5 \\  & 3 & - & 34.51 \\  & 1 & - & 51 \\  & 2 & 12.6 & 55.2 \\
[36] & Double SMF tapers/thulium-doped fiber (TDF) from the ASE & 3 & - & 52 \\  & 4 & - & 48 \\  & 5 & - & 48 \\
[37] & MZI—SMF/with a segment of select cutoff fiber (SCF)/SMF & 1 & 4.88 & 55.3 \\
[38] & SMF/TCPCF/SMF—MZI & 1 & 23.04 & 45 \\  & 2 & 33.82 & 42 \\  & 1 & 7.62 & 49.8 \\  & MZI—core-offset & 2-narrow & 2.33 & 40.36 \\ This work & SMF/TCEDF/SMF & 2 & 8.8 & 42.35 \\  & 3 & - & 36.83 \\  & 4 & - & 39.96 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparison between similar works using a sensor in a laser cavity to generate switchable and tunable multi-wavelength emission lines.  
single lasing line emission, complemented by a peak power and wavelength fluctuation of less than 0.87 dB and 0.26 nm, respectively. Furthermore, we successfully obtained quadruple lasing lines at specific wavelengths, 1557.99 nm, 1558.89 nm, 1564.02 nm, and 1564.78 nm, with SMSR values of 29.07 dB, 31.98 dB, 39.96 dB, and 34.11 dB, respectively. Additionally, for triple-emission lines at 1558.27 nm, 1558.85 nm, and 1564.81 nm, the SMSR values were 29.15 dB, 31.16 dB, and 26.83 dB, respectively. We also observed a dual-narrow wavelength lasing line at \(\lambda_{\rm 1B}=\) 1564.56 nm and \(\lambda_{\rm 1A}=\) 1563.71 nm, with a tuning range of 3.22 nm and SMSR values of 36.59 dB and 39.12 dB, respectively. Lastly, a dual wavelength with \(\lambda_{\rm 1A}=\) 1572.53 nm and \(\lambda_{\rm 4 IB}=\) 1585.69 nm and an SMSR of 36.59 dB and 39.12 dB was achieved. The intrinsic flexibility, versatility, and adaptability of these multi-wavelength lasers make them essential tools across multiple sectors, including telecommunications, sensors, materials science, medicine, and research. In particular, they are highly invaluable in studies due to their ability to provide a stable range of emissions across several tunable wavelengths. Our study demonstrates the consistent repeatability in tuning and switching among the multiple lines of the proposed laser using the WSF.  
Conceptualization, C.P.-M. and J.G.-G.; methodology, J.L.C.-P.; software, M.V.-T.; validation, R.R.-L. and J.M.E.-A.; formal analysis, J.M.S.-H.; investigation, L.T.-C.; resources, V.H.O.-M.; data curation, E.I.G.-H.; writing--original draft preparation, C.P.-M.; writing--review and editing, J.G.-G.; visualization, P.A.H.-C.; supervision, E.P.-C.-M.; project administration, I.B.G.-V. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.  
[PERSON] is grateful for the support provided by the Consejo Nacional de Humanidades, Ciencias y Tecnologias (CONAHCYT) of Mexico with grant No. 745773.  
The authors declare no conflicts of interest.