A miniature WDM add/drop multiplexer and its manufacture is described. The
device has a plurality of wavelength-dependent filters in the form of
thin-film filters mounted to a core frame with the end sections of the
input/output optical fiber and other optical fibers associated with each
of the filters. The stresses associated with the filters are accounted
for. The core frame is sealed, together with the overall package
assembly, to provide for long-term reliability of the device. The
described device and method of manufacture is also generally applicable
to WDM multiplexers and demultiplexers.