| 摘要 |
An optical point-to-multipoint connection arrangement comprises a number of ONUs connected via an optical distribution network (ODN) to an OLT containing a main CTF (CTFA) and one or more redunctant CTFs (CTFR). The CTF (CTFA) carries out ranging on at least one of the ONUs (ONUA), then CTFR requests ONUA to transmit at a given time a signal burst which it expects to receive, taking ranging into account, at time t0, but receives instead at a time t0+ delta , delta being positive or negative. CTFR then alters its own time-reference in the same direction as the delta , i.e. where delta is positive, delaying its time-reference by that amount and where delta is negative, advancing its time-reference by the same amount. The result is that, when operation is switched from the main to the redundant path, a major interruption in service is avoided. |
