Equalization in Coherent Lightwave Systems Using Microwave Waveguides.

The maximum bit rate-distance product in recent single-frequency laser, direct detection, lightwave system experiments has been limited by dispersion. Here we consider an equalization technique, appropriate for coherent lightwave systems, that uses a microwave waveguide for overcoming the delay dispersion problem. Results show that small, low-loss waveguides can be used to greatly reduce dispersion. For example, an 8 GHz bandwidth signal transmitted over 68 km of fiber can be equalized by a waveguide with a cross-section of 6X3 mm and a length of only 15 cm. With the waveguide equalizer, the dispersion-limited maximum bit rate-distance product for a standard fiber system can be increased to that of a dispersion-shifted fiber system at 1.5microns, e.g., a 16-fold increase in maximum bit rate for 100 km transmission distances.