The wavelength-division add/drop multiplexer is one of the key devices for wavelength-division multiplexing (WDM) transmission systems because of its ability to extract or add a certain wavelength at an intermediate node. Two types of optical add/drop multiplexers employing fiber gratings have prevously been demonstrated: a Mach-Zehnder inter-ferometer with Bragg gratings and two circulators combined with gratings.~1 These multiplexers, however, have some disadvantages such as instability and high cost. We present here a novel type of multiplexer based on the use of fiber gratings and polarization beam splitters (PBSs). Our multiplexer can potentially be constructed with low-cost elements, and yet shows high stability against perturbations.
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