Fig. 7From: Autocompensating measurement-device-independent quantum cryptography in space division multiplexing optical fibersOFD device for codirectional modes. Light comes from the two cores of a MCF and is directed, via, for example, photonic lanterns, to a pair of parallel single-mode fibers. In one of them, an optic fiber delay is placed, introducing a delay τ in one of the modes. Photons exit the SMFs through another PL and they are introduced back into the cores of an MCFBack to article page