Performance of fractional tap-spacing equalizers for long-haul high-capacity digital fibre-optic communication systems

Abstract

It is known that for data transmission above 100 Mbits s⁻¹ multimode fibre systems, working at 1.3 μm wavelength, are more modal-dispersion-limited than loss-limited. Then some form of baseband equalization is highly desirable. Baseband equalizers are usually made in the form of a transverse filter with variable tap gains and tap spacing equal to the symbol spacingT. However, the performance of these equalizers depends critically on the timing phase. To overcome this difficulty, in this paper we analyse the performances of fractional tap-spacing equalizers that have a tap spacing smaller thanT. Results obtained show that this type of equalizer gives satisfactory performance for a broad continuous range of timing phase values. It allows the application of simple clock recovery schemes in the receiver.