Abstract
A wideband 1.3/1.55 µm wavelength division multiplexer (WDM) is demonstrated. It is composed of point-symmetrically connected Mach-Zehnder interferometers (MZIs) and fabricated using silica-based waveguides with relative index differences of 0.45% and 7 × 7 µm2 cores. The passband and stopband are successfully widened by factors of ~1.5 and 2, respectively, compared with an ordinary MZI-type WDM.