| 摘要 |
<P>PROBLEM TO BE SOLVED: To automatically search for a noise source under switching control of a gate switch without interrupting an uplink signal by detecting reduction of uplink transmission quality caused by upward streamed noise appropriately from the degree of S/N reduction of an uplink port and a continuation situation. <P>SOLUTION: Gate switches 30-1 to 30-3 are capable of switching attenuation of an uplink signal and installed distributively in subscriber house side distribution lines and trunk line of a CATV transmission line in a tree structure with an optical node 26-1 continued to a head end 20 as an origin. An uplink transmission quality monitoring section 36 monitors an S/N of the uplink signal obtained from an uplink port 24 to which the head end 20 is connected, and detects reduction of uplink transmission quality from the degree of S/N reduction and the continuation situation. A noise source searching section 40 searches for a source of the upward streamed noise by sequentially switching and controlling, from upstream to downstream, the attenuation of the gate switches 30-1 to 30-3 provided in the CATV transmission line when the reduction of uplink transmission quality is detected by the uplink transmission quality monitoring section 36. <P>COPYRIGHT: (C)2009,JPO&INPIT |
