A photonic integrated circuit is provided having a plurality of light paths each configured to branch light received from at least one light receiving input to a first light path section and a second light path section, to turn the polarization of at least a portion of the light received at the receiving input into light of a first linear polarization and light of a second linear polarization that is orthogonal to the first polarization; wherein the first light path section is configured to emit light of the first linear polarization to the outside; wherein the second light path section is configured to determine an interference signal using the light having the second linear polarization of the first light path and light having the second received from the outside.