Carrying Data on the Orbital Angular Momentum of Light

The use of fiber optic cable in support of bandwidth expansion has become de rigeur. Not only does optical fiber offer tremendous bandwidth, it is also low in attenuation, small in cross section, inexpensive, and impervious to electromagnetic interference, and there are significant economies of scale on components developed for the myriad of optical communications markets (long haul, fiber to the home, metro networks, etc.). Shorthaul requirements continue to grow and are expected to exceed the capacity of simple single mode fiber transmission. Spatial multiplexing is a new technique in fiber communications allowing fiber capacity to grow in another dimension by carrying signals on orthogonal modes of light. The short length and high capacity requirements for data center and fronthaul links make them well suited for exploitation of orbital angular momentum (OAM) of light in spatial multiplexing. We report experiments using commercial transceivers for OOK at 10 Gb/s on three channels (30 Gb/s total on fundamental and two OAM modes), and 10 Gb/s OOK on fundamental and DP-QPSK at 100 Gb/s on two OAM modes. OOK transmission was error free (< 10-12), while DP-QPSK had error below 10-7.