The data rate in a single-mode fiber is approaching the capacity limit given by the Shannon theory. Mode division multiplexing, such as few modes, orbital angular momentum, and cylindrical vector beam (CVB) multiplexing, has shown great potential to further increase data capacity in both free-space and fiber communication. We propose and demonstrate high-order CVB multiplexing communication in an air-core photonics crystal fiber (PCF). The simulation results show that the 19-cell air-core PCF supports transmission of CVB modes from ±1 to ±4 orders. In the experiment, ±1- to ±4-orders CVBs are transmitted in 8.25-m-long air-core PCF with the mode purities higher than 76.5%. We demonstrate four coaxial CVB channel communication by multiplexing the ±2- and ±3-orders CVB modes. Each CVB channel carries 10-Gbit/s on–off keying signals and the measured bit error rates satisfy the forward error correction threshold. CVB communications based on air-core PCF can be used in short-distance optical communication with high capacity and low optical latency.
Mode division multiplexing provides mutually orthogonal communication channels to break the capacity-per-fiber limit given by the Shannon theorem. Cylindrical vector beams (CVBs) as a set of orthogonal eigen modes in optical fiber have the potential application in high capacity optical communication. However, there is still no efficient multiplexing/demultiplexing scheme for coaxial multiple CVBs generation and detection. In this work, we propose and demonstrate the efficient sorting of coaxial multiple CVBs based on the anisotropic geometric optical transformation approach using the Pancharatnam-Berry optical element (PBOE) device. The device is fabricated by the photo-alignment liquid crystal (LC) in a thin film with a total pixel number of 768×768 and a pixel size of 11.7 μm. Since the PBOE has the circular polarizations selective property, the device can independently modulate the left-handed circular polarized and right-handed circular polarized light components of CVB. The anisotropic geometric optical transformation is capable of transforming the ring-shape intensity distribution of CVB to two straight lines. Through the phase correction and fourier transform, the CVB is finally converted to a spot with a lateral displacement proportional to the input CVB orders. In the proof of concept experiment, we demonstrated CVB sorting with a large dynamic sorting range of 20 different orders of CVBs with efficiency up to 61.7%. The coaxial multiple CVBs with a minimal order interval of 3 are separated in the experiment. We also implement the CVB sorting approach in optical fiber communication system as a demultiplexer after 2.8 km signals transmission.