Magneto-optic fiber-coupled tuneable optical attenuation

Tuneable, variable, optical attenuation through an optical circulator with a broad, linear attenuation range of Δα ∼ (30-40) dB is demonstrated using non-reciprocal Faraday rotation in a double-pass configuration with a combination of permanent magnets and an electromagnet. A fiber-coupled magneto-optical variable optical attenuator (MVOA) operates over the near IR with an attenuation tuning range of Δα > 30 dB, a resolution of Δα ∼ 0.02 dB, a response time of t < 2 ms, and a temperature dependence over T = 25-70°C of Δα / ΔT = -8 × 10^-4 dB/°C. At λ = 1550 nm, the calculated Faraday material effective Verdet constant is (1/A)V _eff = 109 × 10³ dB/(T.m).