Synthetic photonic lantern characterization and power regulation with intensity superposition mode decomposition.

Photonic lanterns (PLs) enable to convert the spatial modes, making it possible to simply add/drop modes in multimode division multiplexing (MDM) systems. The parameters of PLs have a significant impact on the modal purity, signal quality, transmission distance, and efficiency. This paper proposes a method for the synthetic characterization and power regulation of PLs with multi-channel intensity superposition mode decomposition (MD). The observation reveals that the single channel on the charge-coupled device (CCD) comprises a combination of the fundamental and higher mode fields. However, when the multi-channel is input together, the intensity of each few-mode spot is superimposed on the CCD, and the parameters that cannot be acquired by a single channel can be obtained through the detection of multi-channel input. This offers a novel avenue for optimizing the PLs. Thus, the insertion loss (IL), modal dependent loss (MDL), mode conversion efficiency (MCE), crosstalk, and mode multiplexing power ratio difference (MMPRD) can be obtained. Furthermore, the power regulation is implemented based on the multi-channel intensity superposition MD. The difference between the two modes before power control at the output of the PL is 0.28 dB. However, after implementing power control measurements, this difference was reduced to 0.05 dB, facilitating power equalization throughout the entire communication system.