Abstract: A coherent receiver comprising: a signal port receiving the signal light that has two polarization components at right angles each other; a polarization dependent beam splitter (PBS) that splits the signal light into two portions depending on the polarizations contained in the signal light; a beam splitter (BS) that splits the local light into two portions; a multi-mode interference (MMI) device that interferes between one of the two portions of the signal light and one of the two portions of the local light; optical components provided between the PBS and the MMI device; and wherein the PBS splitting a first wavelength range of the signal light and a second wavelength range outside the first wavelength range.

Abstract: A coherent receiver comprising: a signal port receiving the signal light that has two polarization components at right angles each other; a polarization dependent beam splitter (PBS) that splits the signal light into two portions depending on the polarizations contained in the signal light; a beam splitter (BS) that splits the local light into two portions; a multi-mode interference (MMI) device that interferes between one of the two portions of the signal light and one of the two portions of the local light; optical components provided between the PBS and the MMI device; and wherein the PBS splitting a first wavelength range of the signal light and a second wavelength range outside the first wavelength range.

Abstract: Methods of assembling and testing an optical coherent receiver are disclosed. The method includes steps of, preparing a test beam by combining a first test beam and a second test beam each having respective polarizations orthogonal to each other, entering the test beam accompanied with a third test beam, and aligning a polarization beam splitter (PBS) that splits the test beam depending on the polarizations thereof and a beam splitter (BS) that split the third test beam. A feature of the methods are that the alignment of the PBS and the BS and the monitor of outputs therefrom are concurrently carrier out for two multi-mode interference (MMI) devices.

Abstract: An optical device includes: a stem; a mount portion connected with the stem and having an upper face, a first face and a second face opposite to the first face, the first face and the second face constituting a side face with respect to the upper face; an optical element mounted on the upper face of the mount portion; an electronic components mounted on the first face and the second face of the mount portion respectively; a first lead that penetrates the stem and is extended to a side of the first face of the mount portion; and a second lead that penetrates the stem and is extended to a side of the second face of the mount portion.

Abstract: An optical device includes: a stem; a mount portion connected with the stem and having an upper face, a first face and a second face opposite to the first face, the first face and the second face constituting a side face with respect to the upper face; an optical element mounted on the upper face of the mount portion; an electronic components mounted on the first face and the second face of the mount portion respectively; a first lead that penetrates the stem and is extended to a side of the first face of the mount portion; and a second lead that penetrates the stem and is extended to a side of the second face of the mount portion.

Abstract: A light-receiving device including: a lens; and a light-receiving element optically coupled to the lens, a plurality of optical path divided by the lens crossing each other in a position of between the lens and the light-receiving element.

Abstract: An electronic module includes: a first-stage circuit producing a drive signal based on a first potential that is either a positive or negative potential; a second-stage circuit including a first element reversely driven between a second potential equal to the first potential and the drive signal, and a second element connected in a forward biasing direction toward the second potential; and a transmission line having a signal conductor over which the drive signal is transmitted to the first element, and a reference conductor maintained at a reference potential. A connection between the first potential of the first-stage circuit and the reference conductor of the transmission line and a connection between the second potential of the second-stage circuit and the reference conductor are at an equal potential.