To provide an upstream data clock so as to be speedily adaptive to various packets to come by selecting any one of sequences of phase signals most closely matched with a data packet and matching the phase of the data packet with that of selected sequence of phase signals.

A central station switch 2 is provided with plural clock recovery circuits CR 10, 12 and 14. The clock recovery circuit CR 10 is connected through a passive optical network PON 16 to a CPE unit CPE4, the cloak recovery circuit CR 12 is connected through a passive optical network PON 18 to a CPE unit CPE6, and the clock recovery circuit CR 14 is connected through a passive optical network PON 20 to a CPE unit CPE8. Upstream data are transmitted from the respective CPE units CPE4, 6 and 8 to the correspondent clock recovery circuits CR 10, 12 and 14, recovered by the central station switch 2 and processed.