Abstract: An optical circuit board which is mounted with a loop-back circuit for returning aligning light to the fiber array in the vicinity of the fiber array connection end. Since an aligning loop-back circuit can be formed in an optical waveguide pattern, a production cost does not increase in comparison to an optical circuit board of the related art. The aligning light combined from the optical fiber to the aligning port of the optical circuit board is returned to the optical fiber around the loop-back circuit. Therefore, it is possible to perform alignment using the returned light. That is, alignment can be performed while being mounted on a package without installing a light-reflecting film or mirror.

Abstract: A simple optical waveband multiplexer/demultiplexer operable to separate a wavelength-division multiplexed light beam WDM consisting of a plurality of wavebands WB each including a plurality of optical channels, into a predetermined plurality of wavebands WB, and output the separated plurality of wavebands WB from a plurality of output ports, wherein the wavelength-division multiplexed light beam WDM is transmitted through two array waveguides each capable of performing a demultiplexing function with a resolution corresponding to wavelengths of the optical channels, and a characteristic of sequentially shifting the output ports by one position with shifting of input ports by one position, whereby the wavelength-division multiplexed light beam WDM is separated into a plurality of wavebands WB each including the mutually different optical channels selected from the optical channels included in the wavelength-division multiplexed light beam WDM, and the separated wavebands WB are outputted from the plurality of