| 摘要 |
An optical waveguide has a wavelength division multiplexing (WDM) filter, a first core, a second core and a cladding portion. A reception-light signal having a 1.5 mum wavelength band transmits through the second core and the WDM filter, and the reception-light signal transmits through an optical fiber and is detected by a photodiode. In contrast, a transmission-light signal having a 1.3 mum wavelength band transmits through the first core, and a major portion of the transmission-light signal is reflected to the second core by the WDM filter and is output to an outside. The remaining portion of the transmission-light signal undesirably transmits through the WDM filter. Also, stray light derived from the transmission-light signal transmits through the cladding portion of the optical waveguide and the WDM filter. Because a direction of a prolonged line of the first core extending toward the WDM filter differs from an extending direction of the optical fiber, either the remaining portion of the transmission-light signal or the stray light does not transmit through the optical fiber, so that either the transmission-light signal or the stray light is not detected by the photodiode. Accordingly, a cross-talk can be prevented, and an optical communication can be performed at a high quality.
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