In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths (i. Ginzton Laboratory, Stanford University, Stanford, CA 94305, USA †gahn@stanford. edu Abstract. Wavelength division multiplexers are fundamental to the functioning and performance of integrated photonic circuits, with applications ranging from optical interconnects to sensing and quantum technologies. To begin with, we assume that we have the element.