Patent ID: 8331784

Claim:
A network system comprising: a first OLT (Optical Line Terminal) and a second OLT; a first ONU (Optical Network Unit) and a second ONU; and a clock synchronization control unit connected to the first OLT and the second OLT to supply a common clock timing, wherein the first ONU and the second ONU are connected to each other through an optical fiber shared by the first OLT and the second OLT such that data is transmitted between the first OLT and the first ONU and between the second OLT and the second ONU, wherein each of the first OLT and the second OLT includes: a clock oscillator which generates a clock signal; a clock receiving unit that receives the common clock timing from the clock synchronization control unit; and a clock detecting unit that synchronizes the clock signal generated from the clock oscillator with the common clock timing received by the clock receiving unit, and wherein the first OLT and the second OLT supply the clock signal to the first ONU and the second ONU, respectively, at the common clock timing.