Symbol spaced adaptive MIMO equalization for ultrahigh bit rate metro coherent optical links

A novel approach to symbol spaced adaptive multiple-input-multiple-output (MIMO) equalization is proposed. Different functionalities are defined for static versus adaptive equalizers, to minimize noise enhancement. Static equalizers are used for anti-aliasing filtering and bulk CD compensation, and a newly proposed modified-LMS-based adaptive MIMO equalizer is used to compensate for fiber random impairments such as residual CD and PMD. In addition, the proposed technique enables the use of low-cost reduced bandwidth components in both transmit and receive sides, and supports aggressive in-line optical filtering in the existing WDM network. Moreover, the proposed technique perfectly suits coherent metro applications, allowing significant power savings in application specific integrated circuit implementation.