Method to transport a reference clock signal

摘要

The present application describes a method to transport a reference clock signal (GPS) from a central office (CO) to a line terminal (LT1) in a communication system wherein the central office (CO) communicates with the line terminal (LT1) in a carrier unit (DLC) via an optical link (PON). The method comprises a) retrieving the reference clock signal (GPS) by the central office (CO);b) synchronizing a first counter into the central office (CO) with the reference clock signal (GPS); c) regularly transferring counter values of the first counter as part of physical layer operation and maintenance (PLOAM) cells over the optical link (PON); d) adjusting a counter value of a second counter of the carrier unit (DLC) when a counter value is received as part of a the physical layer operation and maintenance cell (PLOAM); e) deriving clock signals from the second counter for the line terminal (LT1). Furthermore, the method comprises in order to realize the step c) assigning a predefined value to a predefined message identifier field (MESS-ID) of the physical layer operation and maintenance cell (PLOAM) and comprising the counter values of the first counter in a plurality of predefined message fields (MESS-FLD1, MESS-FLD2, ..., MESS_FLD6) of the physical layer operation and maintenance cell (PLOAM) and being associated to the predefined message identifier field; and in order to realize the step d) recognizing the predefined value of the predefined message identifier field (MESS-ID) and upon a recognition extracting the counter value from the plurality of predefined message fields (MESS-FLD1, MESS-FLD2, ..., MESS-FLD6). <IMAGE>