Optical receiver, optical semiconductor apparatus, and optical communication system utilizing the same

An optical communication system comprising:

• (a) a semiconductor laser for supplying a modulated signal light;
• (b) an optical fiber for transmitting the signal light therethrough;
• and
• (c) an optical receiver for directly detecting the signal light, said optical receiver comprising:
• an optical semiconductor apparatus comprising (i):
• beam splitting means and (ii) a plurality of optical filters, a plurality of light components split by said beam splitting means being coupled to said plurality of optical filters, respectively, and said plurality of optical filters being arranged such that a tuned transmission wavelength for a first transverse mode light component in one of said plurality of optical filters is set equal to that for a second transverse mode light component in the other of said plurality of optical filters;
• and
• an opto-electric converter, said opto-electric converter being arranged to receive light components passing through said optical filters to convert the light components to an electric signal,
• wherein said first transverse mode is a TE mode and said second transverse mode is a TM mode.

An optical communication system comprising:

• (a) a semiconductor laser for supplying a modulated signal light;
• (b) an optical fiber for transmitting the signal light therethrough;
• and
• (c) an optical semiconductor apparatus for directly detecting the signal light, said optical semiconductor apparatus comprising:
• beam splitting means;
• and
• a plurality of optical filters, a plurality of light components split by said beam splitting means being coupled to said plurality of optical filters, respectively, and said plurality of optical filters being arranged such that a tuned transmission wavelength for a first transverse mode light component in one of said plurality of optical filters is set equal to that for a second transverse mode light component in the other of said plurality of optical filters.

An optical receiver comprising:

• an optical input waveguide means for receiving light from outside;
• and
• a filter waveguide means connected to said input waveguide means, said optical filter waveguide means having a distributed feedback portion constituted by a diffraction grating, and being constituted so that (i) propagation constants for mutually orthogonal polarization modes having different transverse mode orders are equal to each other and (ii) such that an effective refractive index for a 0th order TM mode light component is equal to an effective refractive index for a higher order TE mode light component,
• wherein said optical input waveguide means and said filter waveguide means are constituted such that light propagated through said optical input waveguide means is coupled to 0th and first order modes of said filter waveguide means with the same coupling coefficient.

An optical receiver comprising:

• an optical input waveguide means for receiving light from outside;
• a TE-TM mode splitter for splitting light from said input waveguide means into TE and TM light components;
• and
• first and second waveguide type optical filters, each of said optical filters has a waveguide having a distributed feedback portion constituted by a diffraction grating, the TE mode light component split by said mode splitter being coupled to a first order mode of said first optical filter and the TM mode light component split by said mode splitter being coupled to a 0th order mode of said second optical filter.

An optical semiconductor apparatus comprising:

• an optical input waveguide means for receiving light from outside;
• a mode splitter for splitting light from said input waveguide means into first and second mode light components;
• and
• first and second waveguide type optical filters, the first mode light component split by said mode splitter being coupled to a first order mode of said first optical filter and the second mode light component split by said mode splitter being coupled to a 0th order mode of said second optical filter.