Patent ID: 7180343

Claim:
An apparatus for synchronizing a clock using a source synchronous clock in an optical transmission system, the apparatus comprising: a first and a second source synchronous channel receiving means for receiving a source synchronous channel inputted from an external device; a first and a second clock dividing means for dividing the source synchronous clock received from the first and the second source synchronous channel receiving means to a low frequency clock to be used to synchronize a clock; a first and a second reference clock selecting means for selecting one of the divided source synchronous clock from the first clock dividing means, the divided source synchronous clock from the second clock dividing means and a system clock as a reference clock; a first and a second phase detecting means for receiving the reference clock from the first and the second reference clock selecting means, receiving a supplementary clock from a third and a fourth clock dividing means, wherein the supplementary clock is generated at the third and the fourth clock dividing means by receiving a returned clock (TXSRCCLK) received from an external optical transmission system and dividing the returned clock, comparing the reference clock and the supplementary clock, and generating a phase difference signal according to the comparison result; a first and a second phase difference signal selecting means for selecting a phase difference signal from the first and the second phase detecting means and a phase difference signal generated by comparing a phase in an internal logic; and a first and a second voltage oscillating means for generating a predetermined synchronous frequency according to the selected phase difference signal, and transmitting a clock synchronized to a source synchronous channel to the external optical transmission system.