Multi-stable variable optical attenuator based on a liquid crystal gel-filled photonic crystal fiber

This work demonstrates a multi-stable variable optical attenuator (VOA) that is fabricated by infiltrating a photonic crystal fiber (PCF) with a liquid crystal (LC) gel. Varying the cooling rate or biasing the electric field during gelation yields various degrees of scattering. Therefore, LC gel-filled PCFs with various transmittances can be realized. At a wavelength of 1550 nm, an attenuation rate of -33.4  dB/cm is obtained at a cooling rate of 30°C/min and a biasing voltage of 400 V during gelation. The proposed all-in-fiber VOA exhibits tunable attenuation and multiple stable states at room temperature.