Design of a Seven-core All-fiber Mode Coupler Demultiplexer for Weakly Coupled Mode Division Multiplexing Systems

In order to increase the throughput of a single-wavelength-carrier optical-interconnect connection, researchers have focused on spatial-division multiplexing technology. It is widely agreed that the most innovative and successful approach to satisfying the capacity need of the expanding information traffic is to make more use of spatial multiplexing of data in optical communication. Mode-division multiplexing is a sub set of spatial division multiplexing. As there are numerous modes involved in a mode multiplexing transmission system, the functional components are quite different from the standard one. To further boost the data throughput of optical communications, MDM systems are an interesting avenue to explore. However, the success of mode division multiplexing transmission relies on four basic components namely, few-mode fiber, mode multiplexer/de-multiplexer, few-mode fiber amplifiers and mode selectors. This article gives a brief review of recent progress in mode multiplexer/de-multiplexer. Lastly, a seven-core all fiber micro-structured coupler has been proposed for mode de-multiplexing. The structure satisfies the self-symmetry property and able to separate six modes namely, LP
01
, LP
11
, LP
21
, LP
02
, LP
31
and LP
12
. Seven-core micro-structured optical fibre has a few-mode core that supports six linearly polarized modes at 1550 nm. The few-mode core is in the middle, and six single-mode cores surround it in a hexagonal pattern. The LP
01
mode in each single-mode core couples to the corresponding six LP modes in the few-mode core are based on avoid-crossing effect. The proposed multi-core coupler can be used as both multiplexer and de-multiplexer for next-generation mode division multiplexing systems.