There are two kinds of Faraday Rotator: one is crystal(e.g., TGG) which has a Verdat Constant and the rotation is the integration of v*B*dl. Another kind is magnetic Garnet, there is a critical value of magnetic field for saturation and the rotation depends on the thickness.
Flux: As faraday introduced, the Faraday Glass is another Faraday rotator, but I’’m not sure the Vendat cons is big enough at 1550nm. I’’ll need to discuss the spec of this kind od glass with faraday.