All-fiber Faraday rotator made by a multiturn figure-of-eight coil with matched birefringence

With a figure-of-eight winding of monomode fiber, we have been able to build multiturn (>100) coils which can be easily trimmed to match the condition of exactly one wavelength-per-turn birefringence. As an example, we report a 45 degrees Faraday rotator intended for an all-fiber optical isolator at lambda = 1300 nm.