An optimization procedure for spatial mode multiplexing from individual single mode fibers into a few mode fiber based on a spatial aperture sampling concept has been developed. By placing space-variant imaging elements between the single mode and few mode fibers, each beam aperture can be shaped for lower loss coupling and low mode dependent losses. The optimization achieves a record theoretical −1.5 dB insertion loss for a three mode fiber (improving on the previous theoretical −2 dB record), and an insertion loss of −1.59 dB for a six mode fiber.