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J. Eur. Opt. Society-Rapid Publ. 22, 54( 2026)
Fig. 3. Optical peak power for each emission wavelength as a function of the HWP adjustment, with the QWP held fixed.
power for the emission wavelengths can be achieved depending on the paddle positions. Therefore, by simultaneously adjusting both paddles, an optimization process can be performed to obtain the desired output combinations.
The results of the tuning process for all lasing configurations at a bias current of 300 mA are shown in Figure 4. Figure 4a corresponds to the no-lasing configuration, where both emission wavelengths exhibit a power level below �45 dBm. In contrast, the single-wavelength emission configurations presented in Figures 4b and 4c show that both emission lines exceed a peak optical power of �15 dBm, resulting in an optical signal-to-noise ratio( OSNR) greater than 55 dB in both cases, as well as a main lobe-to-sidelobe suppression ratio( MSSR) exceeding 40 dB. Finally, Figure 4d illustrates the dual-wavelength configuration, where the peak output power of each emission wavelength is �11.84 dBm. The power difference measured in this configuration is less than 0.01 dB, and the OSNR for both wavelengths is higher than 60 dB. These parameters align with established standards for high-performance lasersensing in the C [ 25 ], O [ 26 ], and L-bands [ 3 ].
Table 1 provides a comprehensive summary of the results obtained for all configurations across the three bias current levels. The data include the power OSNR of each emission line, along with the power difference between both lines for each configuration. The results are consistent across all cases, with only minor variations attributed to increased available power at higher bias currents. In all non-lasing cases, line suppression exceeds 42 dB, while in all single-line emission configurations, the MSSR is at least of 37 dB and the OSNR is greater than 55 dB. For the dualwavelength emission configuration, the OSNR surpasses 58 dB in all cases, with the maximum power difference between emission lines remaining below 0.5 dB and reaching as low as 0.01 dB in one instance, demonstrating an exceptional level of output equalization. It is worth noting that these results could be further improved with enhanced polarization control, which was limited in this study by the motorized controller ' s minimum rotation angle of 0.2 °. Nonetheless, the results validate the proposed system and demonstrate its ability to maintain high performance under varying operational conditions.
Fig
. 4. Output spectra measured in the optical domain for the:( a) no-lasing,( b) single-wavelength at 1590 nm( c) singlewavelength at 1610 nm and( d) dual wavelength lasing configurations, for a biasing current of 300 mA at the BOA.
Fig. 5.( a) Output peak powers for a dual-wavelength configuration in free-running mode;( b) mean peak power;( c) 1590 nm and( d) 1610 nm peak for the dual-wavelength configuration with the stabilization loop activated, indicating the CL at 95 %( dashed lines).
The dual-wavelength configuration with a 300 mA bias current was chosen to evaluate the stability of the system. First, output spectra were captured every 45 s for a total of 2.5 h, without any adjustments of the PC during all the experiment duration. The registered evolution of the two wavelengths peak powers is plotted in Figure 5a, showing that the system is not able to preserve the dual-wavelength emission, since the 1610 nm line power progressively decreases and eventually falls drastically after approximately 2 h, becoming then the laser a single line device. This behavior prevents the use of this free-operating