Testing fiber tapers for use in the SDSS-V focal plane system

We present measurements of 40 fiber tapers created as a possible approach to feed the BOSS spectrographs for SDSS-V in the Southern hemisphere at Las Campanas observatory. The fibers are designed with 180µm core at the input (telescope feed) end, and tapering to a 120µm core at the output (spectrograph) end. The taper is located in close proximity to the output end and is protected by metal strain relief held in place by the ferrule. We find the fiber tapers to provide adequate throughput but to underperform related to standard (untapered) fibers when it comes to FRD. We present here measurements from three different test bench setups, located at the University of Washington, Yale University, and SSL at the University of California, Berkeley. We find that although the overall throughput is high, the FRD is poor in the tapers. The current fiber taper performance is not adequate for the SDSS-V fiber requirements.