jats:pThe recent evolution of passive optical network standards and related research activities for physical layer solutions that achieve bit rates well above 10 Gbps per wavelength (jats:inline-formula <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> mml:miλ</mml:mi> </mml:math> </jats:inline-formula>) is discussed. We show that the advancement toward 50, 100, and jats:inline-formula <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mrow class="MJX-TeXAtom-ORD"> mml:mn200</mml:mn> </mml:mrow> </mml:mrow> <mml:mspace width="thickmathspace" /> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">G</mml:mi> <mml:mi mathvariant="normal">b</mml:mi> <mml:mi mathvariant="normal">p</mml:mi> <mml:mi mathvariant="normal">s</mml:mi> <mml:mrow class="MJX-TeXAtom-ORD"> mml:mo/</mml:mo> </mml:mrow> </mml:mrow> </mml:mrow> mml:miλ</mml:mi> </mml:math> </jats:inline-formula> will certainly require a strong introduction of advanced digital signal processing (DSP) technologies for linear, and maybe nonlinear, equalization and for forward error correction. We start by reviewing in detail the current standardization activities in the International Telecommunication Union and the Institute of Electrical and Electronics Engineers, and then we present a comparison of the DSP approaches for traditional direct detection solutions and for future coherent detection approaches.</jats:p>