Waveguide-type coupler/splitter

Abstract

A 2-input/2-output directional coupler is arranged as an element coupler/splitter for a first stage, and 1-input/2-output coupler/splitters are used as element coupler/splitters for a second stage and subsequent stages. Output ports of these element coupler/splitters are concatenated with input ports of other element coupler/splitters to form a 2-input/multi-output coupler/splitter. An optical signal can be inputted through one input port of the first-stage 2-input/2-output directional coupler, and an optical signal for optical line monitoring can be inputted through the other input port. It is unnecessary, therefore, to use an optical wavelength division multiplexer/demultiplexer or other optical part which conventionally is connected at the time of optical line monitoring.

Dependencies are inferred from the claim text.