2x2 Fiber-optic Rotary Joint optically connects two optical fibers on its stationary side with their counterparts on the rotating side. Two optical channels follow separate paths and have low loss, small-signal variations during rotation, and no crosstalk. The fixed side has standard FC receptacles, while the rotating side has M3 receptacles.

There is an Achromatic Doublet (AD) and High NA Aspheric (AH) option for the lenses inside the rotary joint. AD configuration uses 0.22 NA achromatic doublet lenses that ensure consistent performance over the entire visible range from 450 to 650 nm. Achromatic doublets are intended for use with a low NA fiber-coupled laser light. AH configuration has high NA aspheric lenses that fit high NA optical fibers used with LED or Ce:YAG light sources. Aspheric lenses are optimized for 530 nm but work reasonably well for other wavelengths.

This passive rotary joint is intended for optogenetics experiments involving independent activation or silencing of two different brain sites/regions of the larger tethered behaving animals like rats.