Patent ID: 7907843
Filing Date: 2011-03-15
Classification: H04J

Abstract:
1. A system having a plurality of subscriber terminals (STs) each being enabled to send a signal only within a time period enabled for the ST and a central terminal (CT) which is connected with one end of an optical fiber branched and connected to a plurality of said STs, the system comprising: a measurement unit, operative for each of a given series of time periods, to measure an optical reception level of an optical fiber signal in the time period; a table that at least stores said reception level of a received signal from each of said STs in association with the ST, said reception level being measured by said measurement unit in a normal state where signals from said STs are exclusively received; a decision unit, operative for each of said given series of time periods, to decide whether a signal from one of said STs associated with the time period is exclusively received with no collision with any other signal; and an identification unit, responsive to a decision that said signal from an ST associated with the time period is not exclusively received, to identify a defective one of said STs which causes signals from said STs to be received colliding with each other in said CT, based on a value obtained by subtracting said stored reception level from said measured optical reception level for the time period.