Meander coupler-type filters for dense wavelength-division multiplex systems

A novel wavelength-division multiplexer/demultiplexer, called a meander coupler, was presented recently. It is a strongly asymmetric codirectional coupler with periodic variation of the coupling constant κ made in GaInAsP/InP.1 The original device is particularly suited for bidirectional communication, but meander couplers are also capable of separating various optical channels, if an appropriate number of devices is cascaded. Under such circumstances it is desirable to suppress the sidelobes of the sinc2-type transmission characteristics and reduce the filter halfwidth considerably below the 10-15 nm originally reported.1 Experimental results corresponding to the former and theoretical investigations with respect to the latter task are presented.