Passive topologically biased Sagnac interferometer as a rotational sensor capable of sensing magnitude and direction of rotation

A tethered passively biased Sagnac interferometer comprising:

• a first optoelectronic box containing a light source and a photodetector;
• the output of said light source optically connected to the input of a first non-polarizing beam splitter/circulator residing in said first box;
• the reflected output of said first non-polarizing beam splitter/circulator optically connected to said photodetector;
• the transmitted output of said first non-polarizing beam splitter/circulator optically connected to a first input end of a fiber cable tethered outside of said first box;
• a second optics box optically connected to a second input end of said tethered fiber cable;
• residing in said second optics box:
• a linear polarizer;
• a second non-polarizing beam splitter;
• a depolarizer;
• a topological phase bias element;
• a non-polarization-maintaining single-mode fiber coil;
• the output of said linear polarizer optically connected to the input of said second non-polarizing beam splitter;
• the transmitted output of said second non-polarizing beam splitter optically connected to the input of said depolarizer;
• the output of said depolarizer optically connected to said topological phase bias element;
• the output of said topological phase bias element optically connected to a first input of said fiber coil;
• the reflected output of said second beam splitter optically connected to a second input of said fiber coil;
• wherein said topological phase bias element comprises:
• a first achromatic quarter-wave plate, optically connected to an achromatic half-wave plate with its optical axis oriented at 45 degrees relative to the axis of the first achromatic quarter-wave plate, further optically connected to a second achromatic quarter-wave plate with its optical axis oriented at 45 degrees relative to the axis of the achromatic half-wave plate.