Asymmetrical interleavers and deinterleavers. In one example embodiment, an asymmetrical deinterleaver includes first, second, third, fourth, and fifth filter cells interleaved with first, second, third, and fourth waveplates and followed by a fifth waveplate. The filter cells are configured to filter optical signals propagating on first and second legs of an optical loop. The asymmetrical deinterleaver also includes a retro reflector optically coupled with the filter cells and waveplates. The retro reflector is configured to reflect the optical signals between the first leg and the second leg to form the optical loop. The asymmetrical deinterleaver further includes a single-fiber collimator optically coupled to the first leg of the optical loop and a dual-fiber collimator optically coupled to the second leg of the optical loop.