A novel mode add/drop multiplexer based on two parallel combinative long period fiber gratings

摘要

The pair of parallel combinative long-period fiber gratings can be used to add and drop higher-order core modes, serving as a key device in mode-division multiplexing (MDM) transmission. For higher-order modes EH_(2m) multiplexing, the grating written in SMF need to be tilted, but the grating tilt is unnecessary in FMF. To minimize coupling interferences, the modes should be multiplexed in order from low to high and be demultiplexed in order from high to low in MDM transmission.