Optimization of telescope focal ratios for MLA-fiber coupled integral field units

We have developed an analytic model for generic image transfer using microlens-coupled fibers to determine the telescope input beam speed that optimizes the lenslet clear aperture and minimizes fiber focal-ratio degradation. Assuming fibers are fed at f/3.5 by the lenslets, our study shows that f/11 is the optimum telescope beam speed to feed a lenslet coupled to a fiber with a 100um diameter core. These considerations are relevant for design of high-efficiency dedicated survey telescopes that employ lenslet-coupled fiber systems.