Real-time compensatory mode control within few-mode fibers based on adaptive spatial light modulation

Few-mode fibers (FMFs) have garnered significant attention in mode-division multiplexing (MDM) systems due to their parallel mode transmission capability. To achieve efficient mode control and characterization of FMFs, we present an adaptive spatial light modulation (SLM) system based on the genetic algorithm (GA) by combing the digital holography (DH). Single exposure DH technology can achieve precise decomposition of fiber modes, laying the foundation for subsequent precise mode control. The implementation of GA optimization can effectively select the phase distribution loaded onto SLM corresponds to the expected mode field in FMFs. Through closed-loop optimization of output mode fields via a SLM, this methodology achieves high-purity linearly polarized (LP) mode generation by solely monitoring the output intensity distribution. The experimental results show that in FMFs with 5.3 µm and 8.2 µm core diameters, LP mode excitation with purity approaching 90% is demonstrated. Simultaneous excitation of composite LP mode superposition fields generates customized intensity profiles showing similarity indices nearing 0.9. This self-adaptive mode control approach eliminates complex coupling requirements while overcoming static encoding limitations, providing critical technical support for advancing MDM systems.