Patent ID: 8068744

Claim:
An optical transmitter comprising: a directly modulated laser; and a wavelength filter provided on a post-stage of the directly modulated laser, the wavelength filter including a first linear optical waveguide, a ring-shaped optical waveguide, and a second linear optical waveguide provided on the opposite side of the first linear optical waveguide sandwiching the ring-shaped optical waveguide, wherein one end of the first linear optical waveguide is a modulated light input port of the wavelength filter, the modulated light input port being coupled to the directly modulated laser so as to input modulated light output from the directly modulated laser, an other end of the first linear optical waveguide is a cutoff light output port of the wavelength filter, one end of the second linear optical waveguide is a transmitted light output port of the wavelength filter, and a peak of a filter transmission band of the wavelength filter is set on a shorter-wave side from a peak of a spectrum of modulated light output from the directly modulated laser.