A rigorous technique for the design of postdetection filters, previously applied to low-bit-rate systems, is extended to allow for practical implementation for very high bit rates. This has been accomplished by realising the filters as microstrip structures. Two alternative optimisation techniques are explored, one based on the optimisation of an ideal-transmission-line structure followed by the application of CAD tools, and the other based on the direct optimisation of microstrip lines. Owing to the shortcomings of the public domain microstrip models, the approach based on ideal transmission lines is identified as most appropriate. Simulated system results are presented to illustrate the performance benefits that this approach can offer to very high-bit-rate optical communication systems.