MINNEAPOLIS, April 18 -- APA Optics Inc. has received orders from a US systems developer and a European systems developer for four units and one unit, respectively, of the company's new multi-mode fiber multiplexer/demultiplexer. All units have been shipped, and APA said that both buyers, whose names were not disclosed, plan to conduct performance tests on the product and analyze its application to integrated products currently in development.According to APA, the multi-mode dense wavelength division multiplexing (WDM) devices are intended for applications that use multi-mode fiber, such as local-area networks, campus and wide area networks. The multi-mode Mux/Demux unit is based upon APA's proprietary bulk diffraction grating technology, and is a 16-channel 200-GHz dense WDM unit able to add/drop from one to eight channels. The company asserted that multi-mode dense WDM is growing in significance with the widespread implementation of high-speed -- i.e., multi-Gigabit -- private data networks.