Magneto-optic fiber-coupled tuneable optical attenuation

Tuneable, variable, optical attenuation through an optical circulator with a broad, linear attenuation range of Δ<i>α</i> ∼ (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 Δ<i>α</i> > 30 dB, a resolution of Δ<i>α</i> ∼ 0.02 dB, a response time of <i>t</i> < 2 ms, and a temperature dependence over <i>T</i> = 25-70°C of Δ<i>α</i> / Δ<i>T</i> = -8 × 10^-4 dB/°C. At <i>λ</i> = 1550 nm, the calculated Faraday material effective Verdet constant is (1/A)<i>V</i> _eff = 109 × 10³ dB/(T.m).