Abstract: The present invention is an optical transmission system comprising an optical source, a first lens and a second lens, a multimode optical waveguide, and a phase-only filter. The optical source generates an optical signal having a predetermined wavelength which is received by the first lens. The signal is then sent from the first lens through the phase-only filter and then to the second lens. The second lens then focuses the signal into the multimode optical waveguide. The multimode optical waveguide has predetermined dimensions and has multiple modes. The phase-only filter excites a plurality of modes in the optical waveguide to approximate equilibrium modal power distribution as the optical signal is received into the optical waveguide.