| 摘要 |
In 1 to N communication based on code division multiplexing, ranging is performed by following the first to ninth steps. First step: all the optical network units are set to standby status. Second step: first and second optical network units are set to transmission enable status. Third step: the phase shift amount is set for the variable phase shifters of the first and second optical network units. Fourth step: reception of a fixed signal is attempted in the optical line terminal. Fifth step: if the fixed signal is not received, processing returns to the second step, and if received, the phase amount of the variable phase shifter is defined and fixed. In the sixth to ninth steps, an operation the same as the first to fifth steps is performed for the third to N-th optical network units. In these steps, the optical line terminal receives the i-th reply signal (i is an integer in the 1 to (n-1) range and in) sent from at least one i-th optical network unit out of the first to (n-1)th optical network units, and sequentially defines and fixes the phase shift amount of the variable phase shifter of the third to N-th optical network units.
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