An optical assembly may comprise an input fiber to provide a beam, a process fiber comprising a ring-shaped outer core surrounded by a cladding, and a first beam shifter arranged to receive the beam from the input fiber and to shift the beam spatially to illuminate the ring-shaped outer core of the process fiber. The optical assembly may further comprise a second beam shifter arranged to receive the beam from the first beam shifter and to add skew to the beam that is launched into the ring-shaped outer core of the process fiber.