## 3 Experimental Results
The dual-wavelength lasing involves wavelengths of 1529.65 nm and 1532.65 nm with a wavelength spacing of 3 nm, as shown in Figure 5b. There are eight nodes between the lasing wavelengths located at the half-upper-waist of the interference lobes. Despite this, it is noteworthy that the laser was not successfully excited at points on these eight nodes. The main reason for this is that the lasing wavelength aligns most accurately with the peak of the sub-interference, while the other eight nodes do not align as precisely with the peak of the sub-interference. Figure 6a-d illustrate the fluctuation of the wavelength position of the dual-wavelength laser in the cases of Figures 4a,b and 5a,b and the change in the power value corresponding to the peak of the lasing wavelength every minute, respectively. In Figure 6, it is evident that each wavelength position of different dual-wavelength laser cases fluctuates by less than 0.1 nm. The maximum change in the value corresponding to the peak of each lasing wavelength exceeds 3 dB due to the lack of temperature control for the EDFA in this scheme. The temperature variation of the EDFA impacts its output spectrum [69] and consequently affects the stability of the lasing wavelength output in this fiber ring laser setup. Figure 7 shows the case of triple-wavelength lasers; Figure 7a shows their spectra recorded every 10 min; and Figure 7b shows their wavelength position fluctuations and power variations at different times. The triple-wavelength lasers emit light at 1530.1 nm, 1531.22 nm, and 1532.34 nm, with a consistent 1.12 nm spacing between wavelengths. The fluctuation of each wavelength of triple-wavelength lasers is consistently less than 0.1 nm every 10 min, and the power corresponding to the peak of the lasing wavelength does not change by more than 2 dB. Figure 3: (**a**) Dual-wavelength laser with variable spacing and consistent center position of dual wavelengths. (**b**) Dual-wavelength laser with intertwined wavelength positions. (**c**,**d**) Dual-wave-length laser with regular positional tuning and similar wavelength spacing (the subplot is a superimposed drawing of the spectrum that does not correspond to the power scale of the vertical axis). Maintaining a clear separation between telecommunication channels is essential to avoiding crosstalk. The wavelength separation of WDM in the C-band is usually 0.8 nm (100 GHz) or 0.4 nm (50 GHz). However, with the development of wavelength selective switch (WSS) components, it will be possible to support WDM with wavelength intervals less than 0.4 nm. WSS utilizes switch arrays that operate on wavelength-dispersed light to decouple or complex any single wavelength to a selected common or output port [70]. In a recent study [71], data communication in the C-band using two WDM channels at 0.3 nm intervals has been successfully demonstrated by WSS. Hence, this program can be effectively implemented in real-world scenarios. Furthermore, minimizing fiber loss, monitoring system temperature, monitoring laser output power, and adjusting the looped-in system's power will be essential for maintaining stability in laser power output during practical applications. Moreover, the operations of TDLI and TBF can cover the 1520-1570 nm wavelength range. Consequently, it is theoretically feasible to use other bands of EDFA to amplify and produce lasers within the respective bands. Figure 4: (**a**,**b**) The same dual-wavelength laser with different interferences and the spectral observation at different times. Figure 5: (**a**) Dual-wavelength laser with the narrowest wavelength spacing. (**b**) Dual-wavelength laser with several interfering lobes between the lasing wavelengths. Figure 6: **(a,b)** The wavelength position and the power corresponding to the peak of the lasing wavelength per minute are obtained from Figure 4a,b, respectively. **(c,d)** The wavelength position and the power corresponding to the peak of the lasing wavelength per minute are obtained from Figure 5a,b, respectively.