Abstract: A metal stem includes a cylindrical portion in which an FPC inserting portion is formed, and a base standing upright from one plane of the cylindrical portion. A tubular lens cap with one open end is fixed to a peripheral portion of the one plane of the cylindrical portion, and has a lens mounted on a bottomed portion. A substrate mounted on one plane of the base includes a signal wiring layer and a ground wiring layer. An optical semiconductor element is mounted on the substrate and has a signal terminal connected to the signal wiring layer of the substrate, and a ground terminal connected to the ground wiring layer of the substrate. An FPC substrate is disposed so as to pass through the FPC inserting portion and to face the one plane of the base. The FPC substrate includes a signal wiring layer connected to the signal wiring layer of the substrate with a metal wire.

Abstract: A metal stem includes a cylindrical portion in which an FPC inserting portion is formed, and a base standing upright from one plane of the cylindrical portion. A tubular lens cap with one open end is fixed to a peripheral portion of the one plane of the cylindrical portion, and has a lens mounted on a bottomed portion. A substrate mounted on one plane of the base includes a signal wiring layer and a ground wiring layer. An optical semiconductor element is mounted on the substrate and has a signal terminal connected to the signal wiring layer of the substrate, and a ground terminal connected to the ground wiring layer of the substrate. An FPC substrate is disposed so as to pass through the FPC inserting portion and to face the one plane of the base. The FPC substrate includes a signal wiring layer connected to the signal wiring layer of the substrate with a metal wire.

Abstract: An optical receiver to receive a multilevel modulation signal in which a value of transmission data is assigned to plural signal levels, the optical receiver including a clock generator to generate a recovered clock signal from the multilevel modulation signal when the clock generator detects that a signal level of the multilevel modulation signal transitions between two median levels of the signal levels, and a data identifier to identify a value of the transmission data by using the generated recovered clock signal and the multilevel modulation signal.

Abstract: A dummy-light generating device includes a continuous wave (CW) light source that outputs CW light, a modulated-light generating unit that generates, using the CW light, first intensity-modulated light subjected to intensity modulation and second intensity-modulated light delayed by a half time of a modulation cycle of the first intensity-modulated light with respect to the first intensity-modulated light and having a polarization state e different from a polarization state e of the first intensity-modulated light, and a polarization combiner that performs polarization combination of the first intensity-modulated light and second intensity-modulated light and outputs light after the polarization combination as dummy light.

Abstract: A dummy-light generating device includes a continuous wave (CW) light source that outputs CW light, a modulated-light generating unit that generates, using the CW light, first intensity-modulated light subjected to intensity modulation and second intensity-modulated light delayed by a half time of a modulation cycle of the first intensity-modulated light with respect to the first intensity-modulated light and having a polarization state e different from a polarization state e of the first intensity-modulated light, and a polarization combiner that performs polarization combination of the first intensity-modulated light and second intensity-modulated light and outputs light after the polarization combination as dummy light.

Abstract: A dummy-light generating device includes a continuous wave (CW) light source that outputs CW light, a modulated-light generating unit that generates, using the CW light, first intensity-modulated light subjected to intensity modulation and second intensity-modulated light delayed by a half time of a modulation cycle of the first intensity-modulated light with respect to the first intensity-modulated light and having a polarization state e different from a polarization state e of the first intensity-modulated light, and a polarization combiner that performs polarization combination of the first intensity-modulated light and second intensity-modulated light and outputs light after the polarization combination as dummy light.