Spatial mode compensation technique using progressive phase conjugation

We propose a spatial mode compensation method using progressive phase conjugation (PPC) to establish a dynamic control technology for mode distribution in multi-mode fiber (MMF). PPC is a phase conjugate generation technology that can be far away from the signal source and does not require an additional reference beam. We confirm the basic operation of the proposed scheme by considering the coupling efficiency between the compensated spatial mode component and incident mode. We quantitatively evaluate the mode recovery from the mixed state of LP11, LP22, LP02, and LP31 to LP01, the fundamental mode. Using a random optical diffuser to uniformly scatter the intensity distribution of the signal beam, high compensation performance can be obtained because the influence of the mode intensity distribution is reduced.