Angular division multiplexer for fiber communication using graded-index rod lenses

An angular division multiplexer which uses graded-index (GRIN) rod lenses and a spatial modal filter (SMF) is described. Angular division multiplexing (ADM) uses selective excitation of mode groups " to multiplex signals in a transmission fiber. The GRIN-rod lenses collimate the input beams from two input fibers. The SMF selects particular mode groups from each input to be imaged on the transmission fiber. Design and construction of the device are described. Experimental results show that each signal is well confined to its designated mode groups. Crosstalk results are adequate for digital data transmission.