Reconfigurable wavelength add-drop filtering based on a Banyan network topology and ferroelectric liquid crystal fiber-optic switches

This paper presents a modular optical implementation of a Banyan network by using the physical flexibility of the optical fiber to form the interconnections between compact switching stages based on bulk polarization optics. Specifically, these switching stages use total internal reflection (TIR) prisms with ferroelectric liquid crystal (FLC) polarization rotators to form compact modules. Using this Banyan network implementation, a reconfigurable multiwavelength add-drop filter for wavelength division multiplexed (WDM) applications is proposed. Experimental results for our fiber connected 2 in-2 out FLC-based bulk-optic switching stage gives a ~6.7 dB optical insertion loss and a ~-40 dB optical interchannel crosstalk level. A low 2 dB optical insertion loss design number is expected with optimized components, realizing high (e.g., 35 μs) switching speed and low crosstalk switching networks