Multi-channel electro-optic receiver with polarization diversity and timing-skew management

An electro-optic receiver, comprising:

• a polarization splitter and rotator having an optical input optically connected to receive incoming light, the polarization splitter and rotator having a first optical output and a second optical output, the polarization splitter and rotator configured to direct a first portion of the incoming light having a first polarization through the first optical output, the polarization splitter and rotator configured to rotate a polarization of a second portion of the incoming light from a second polarization to the first polarization so that the second portion of the incoming light is a polarization-rotated second portion of the incoming light, the polarization splitter and rotator configured to direct the polarization-rotated second portion of the incoming light through the second optical output;
• an optical waveguide having a first end optically to the first optical output of the polarization splitter and rotator, the optical waveguide having a second end optically connected to the second optical output of the polarization splitter and rotator, such that the first portion of the incoming light travels from the first optical output of the polarization splitter and rotator through the optical waveguide in a first direction, and such that the polarization-rotated second portion of the incoming light travels from the second optical output of the polarization splitter and rotator through the optical waveguide in a second direction opposite the first direction;
• a plurality of ring resonators positioned alongside the optical waveguide and within an evanescent optical coupling distance of the optical waveguide, each of the plurality of ring resonators configured to operate at a respective resonant wavelength, such that the first portion of the incoming light having a wavelength substantially equal to the respective resonant wavelength of a given one of the plurality of ring resonators optically couples into the given one of the plurality of ring resonators in a first propagation direction, and such that the polarization-rotated second portion of the incoming light having a wavelength substantially equal to the respective resonant wavelength of the given one of the plurality of ring resonators optically couples into the given one of the plurality of ring resonators in a second propagation direction opposite the first propagation direction;
• a plurality of photodetectors respectively associated with the plurality of ring resonators;
• a plurality of output optical waveguides respectively optically coupled to the plurality of ring resonators, each of the plurality of output optical waveguides including a coupling section, a short section, and a long section, the coupling section positioned to evanescently couple light from a corresponding one of the plurality of ring resonators, the short section extending from a first end of the coupling section to a corresponding one of the plurality of photodetectors, the long section extending from a second end of the coupling section to the corresponding one of the plurality of photodetectors;
• and
• a variable optical attenuator optically coupled to the optical waveguide, the variable optical attenuator configured to attenuate an optical power of light propagating within the optical waveguide to a level where light returning through the optical waveguide to the polarization splitter and rotator is non-disruptive to a source of the incoming light while simultaneously enabling frequency tuning and locking of the plurality of ring resonators to the light propagating within the optical waveguide.