A photonic integrated circuit comprising: a polarizer comprising a polarizer waveguide and having a first polarizer port and a second polarizer port, the polarizer configured to have, within a range of operational wavelengths of the PIC, a propagation extinction ratio of at least 75dB and a birefringence of at least 0.012; a source Y-junction having a source base waveguide coupled to the first polarizer port, a source first branch waveguide coupled to a source connector configured to be connected to a light source and a source second branch waveguide coupled to a detector connector configured to be connected to a photodetector, wherein the source base waveguide and branch waveguides (i) are polarization maintaining, and (ii) are configured to support a single transverse mode of light; and an interferometric Y-junction having an interferometric base waveguide coupled to the second polarizer port, an interferometric first branch waveguide coupled to a first fiber coil connector configured to be connected to a first port of a fiber coil, and an interferometric second branch waveguide coupled to a second fiber coil connector configured to be connected to a second port of the fiber coil, wherein the interferometric base waveguide and branch waveguides (i) are polarization maintaining, (ii) have a predetermined length difference with respect to one another, and (iii) are configured to support a single transverse mode of light, wherein the polarizer is substantially aligned with the interferometric Y-junction, with a single mode waveguide filter in between; wherein the polarizer waveguide comprises three 180-degree curves, consecutively coupled to one another to form an m-shape; wherein a waveguide length difference between the interferometric first branch waveguide and the interferometric second branch waveguide is greater than a depolarization length of the interferometric first branch waveguide and the interferometric second branch waveguide. a polarizer comprising a polarizer waveguide and having a first polarizer port and a second polarizer port, the polarizer configured to have, within a range of operational wavelengths of the PIC, a propagation extinction ratio of at least 75dB and a birefringence of at least 0.012; a source Y-junction having a source base waveguide coupled to the first polarizer port, a source first branch waveguide coupled to a source connector configured to be connected to a light source and a source second branch waveguide coupled to a detector connector configured to be connected to a photodetector, wherein the source base waveguide and branch waveguides (i) are polarization maintaining, and (ii) are configured to support a single transverse mode of light; and an interferometric Y-junction having an interferometric base waveguide coupled to the second polarizer port, an interferometric first branch waveguide coupled to a first fiber coil connector configured to be connected to a first port of a fiber coil, and an interferometric second branch waveguide coupled to a second fiber coil connector configured to be connected to a second port of the fiber coil, wherein the interferometric base waveguide and branch waveguides (i) are polarization maintaining, (ii) have a predetermined length difference with respect to one another, and (iii) are configured to support a single transverse mode of light, wherein the polarizer is substantially aligned with the interferometric Y-junction, with a single mode waveguide filter in between; wherein the polarizer waveguide comprises three 180-degree curves, consecutively coupled to one another to form an m-shape; wherein a waveguide length difference between the interferometric first branch waveguide and the interferometric second branch waveguide is greater than a depolarization length of the interferometric first branch waveguide and the interferometric second branch waveguide.