Dual-polarization bidirectional optical devices

An optical transceiver comprising:

• a light source configured to output light having a first wavelength;
• a transmission unit configured to output a first modulated input signal and a second modulated input signal;
• a polarization beamsplitter rotator configured to cause the first modulated input signal and the second modulated input signal to have different polarizations;
• a first optical element configured to (i) receive the first modulated input signal from the transmission unit, (ii) provide and receive optical signals to and from the polarization beamsplitter rotator, and (iii) provide a first optical signal from the polarization beamsplitter rotator to a receiving unit, wherein the first optical element is wavelength selective;
• a second optical element configured to (i) receive the second modulated input signal from the transmission unit, (ii) provide and receive optical signals to and from the polarization beamsplitter rotator, and (iii) provide a second optical signal from the polarization beamsplitter rotator to the receiving unit, wherein the second optical element is wavelength selective;
• and
• the receiving unit, wherein the receiving unit is configured to (i) receive the first optical signal and the second optical signal, (ii) perform polarization-demultiplexing on the first optical signal and the second optical signal to output two polarization-demultiplexed optical signals, and (iii) detect intensities of the two polarization-demultiplexed optical signals.