In order to realize flexible bandwidth allocation in access networks with bit rates of 10Gb/s or more, transmitting data by parallel streams with different wavelengths is an attractive approach. In such systems, the timing skew induced by fiber dispersion is the critical problem. This paper proposes a skew compensation LSI for an optical access system based on power splitter based wavelength division multiplexing passive optical network (PS-WDM-PON). The LSI can compensate timing skew of more than 9.6ns with 82ps resolution; experiments show that transmission distance of 24km are possible if the bit rate of each wavelength is 2.5Gbit/s and all wavelengths lie within 20nm.