Mode Combining and -Splitting in Optical MIMO Transmission using Photonic Lanterns

Within the last years the multiple-input multiple-output (MIMO) technology has revolutionized the optical fibre community. Theoretically, the concept of MIMO is well understood and shows some similarities to wireless MIMO systems. However, practical implementations of optical components are in the focus of interest of substantial research. Optical couplers have long been used as passive optical components also being able to combine or split SISO (single-input single-output) data transmission. They have been proven to be well suited for the optical MIMO (multiple-input multiple-output) transmission despite their insertion losses and asymmetries. Nowadays, next to optical couplers, Photonic Lanterns (PLs) have attracted a lot of attention in the research community as they offer the benefit of a low loss transition from the input fibers to the modes supported by the waveguide at its output. Therefore they seem to be highly beneficial for optical MIMO communication. In this contribution mode coupling and splitting devices such as PLs and fusion couplers have been analysed in a testbed with regard to their respective MIMO suitability. Based on the obtained results, a simplified time-domain MIMO simulation model including PLs for mode-combining at the transmitter side as well as mode-splitting at the receiver side is elaborated. Our results obtained by the simulated bit-error rate (BER) performance show that PLs are well suited for the optical MIMO transmission.