Abstract: Provided is an optical transmission module which can generate PAM4 optical modulation signals without converting a plurality of binary electric signals to a multi-level electric signal. An optical transmission module (200) comprising: a light source (60) for emitting continuous waveform (CW) light; optical modulators (51,52,53) arranged in series with a path of the CW light configured to modulate the CW light by switching relatively large absorption and relatively small absorption of the optical modulators in response to a modulation signal applied to the respective optical modulators; and an arithmetic logic circuit (100) configured to receive a plurality of binary electrical signals, and then to perform logic operation on the plurality of binary electrical signals for generating a new plurality of binary electrical signals, wherein each of the new plurality of binary electrical signals is applied to the respective optical modulators as the modulation signal.

Abstract: Provided is an optical transmission module which can generate PAM4 optical modulation signals without converting a plurality of binary electric signals to a multi-level electric signal. An optical transmission module (200) comprising: a light source (60) for emitting continuous waveform (CW) light; optical modulators (51,52,53) arranged in series with a path of the CW light configured to modulate the CW light by switching relatively large absorption and relatively small absorption of the optical modulators in response to a modulation signal applied to the respective optical modulators; and an arithmetic logic circuit (100) configured to receive a plurality of binary electrical signals, and then to perform logic operation on the plurality of binary electrical signals for generating a new plurality of binary electrical signals, wherein each of the new plurality of binary electrical signals is applied to the respective optical modulators as the modulation signal.

Abstract: Provided is an optical transmission module in which noise is further reduced. The optical transmission module includes a first semiconductor layer having a first electrode arranged thereon, an active layer with a stripe shape formed on the first semiconductor layer, and a second semiconductor layer with a stripe shape formed on the active layer. The second semiconductor layer has a second electrode arranged thereon and includes a diffraction grating arranged along an extending direction of the active layer. The active layer includes a first portion having first stripe width, a second portion having a second stripe width smaller than the first stripe width, and a connection portion having a varying stripe width so as to connect the first portion and the second portion to each other. The diffraction grating overlaps with the first portion and does not overlap with the second portion in planar view.

Abstract: Multilevel optical intensity modulation high in accuracy is performed using electro-absorption optical modulators. There is provided a plurality of EA modulators connected in series in a path of an optical signal from a light source, and a multilevel-coded modulated optical signal is generated by modulating an intensity of an input optical signal from the light source based on a modulation signal using the EA modulators. Each of the EA modulators is switched between an ON state and an OFF state of optical absorption in accordance with the modulation signal. Regarding an extinction ratio of the ON state to the OFF state in each of the EA modulators, the EA modulators have respective values difference from each other, and are arranged in ascending order of the extinction ratio from the light source side.

Abstract: Provided is an optical transmission module in which noise is further reduced. The optical transmission module includes a first semiconductor layer having a first electrode arranged thereon, an active layer with a stripe shape formed on the first semiconductor layer, and a second semiconductor layer with a stripe shape formed on the active layer. The second semiconductor layer has a second electrode arranged thereon and includes a diffraction grating arranged along an extending direction of the active layer. The active layer includes a first portion having first stripe width, a second portion having a second stripe width smaller than the first stripe width, and a connection portion having a varying stripe width so as to connect the first portion and the second portion to each other. The diffraction grating overlaps with the first portion and does not overlap with the second portion in planar view.

Abstract: Multilevel optical intensity modulation high in accuracy is performed using electro-absorption optical modulators. There is provided a plurality of EA modulators connected in series in a path of an optical signal from a light source, and a multilevel-coded modulated optical signal is generated by modulating an intensity of an input optical signal from the light source based on a modulation signal using the EA modulators. Each of the EA modulators is switched between an ON state and an OFF state of optical absorption in accordance with the modulation signal. Regarding an extinction ratio of the ON state to the OFF state in each of the EA modulators, the EA modulators have respective values difference from each other, and are arranged in ascending order of the extinction ratio from the light source side.

Abstract: In order to prevent non-uniformity in emission wavelength among different sites along an optical axis direction, provided is a resonator portion including: a waveguide which includes at least two areas where an effective refraction index varies in the optical axis direction; and diffraction gratings formed along the optical axis direction of the waveguide. The diffraction grating that is formed in one of the at least two areas of the waveguide where the effective refraction index is large has a pitch narrower than a pitch of the diffraction grating that is formed in another of the at least two areas of the waveguide where the effective refraction index is small.

Abstract: In order to prevent non-uniformity in emission wavelength among different sites along an optical axis direction, provided is a resonator portion including: a waveguide which includes at least two areas where an effective refraction index varies in the optical axis direction; and diffraction gratings formed along the optical axis direction of the waveguide. The diffraction grating that is formed in one of the at least two areas of the waveguide where the effective refraction index is large has a pitch narrower than a pitch of the diffraction grating that is formed in another of the at least two areas of the waveguide where the effective refraction index is small.