| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical branching transmitter uniformizing the S/N obtained at each branching end in the multi-drop optical transmission system where plural optical branching devices are connected in cascade. SOLUTION: Plural optical branching devices 2a-2d are connected in series on an optical transmission line 4 from an electricoptic converter 1 for optical transmission. From the optical branching devices 2a-2d, opticelectric converters 3a-3e for optical reception are in multi-drop connection for plural ways of branching. A transmission signal level at the branch end branched from the string of series connection of the optical branching devices 2a-2d is set higher in the parting order from the start so that the signal level at the start is equal. Furthermore, the branching ratio is set so that a relation of P2 <2> =P1 <2> (1+N2 /N) is established, where P1 , P2 are optical reception levels at a branch point and a succeeding branch remote from the start point branched by the optical branching devices 2a-2d, N is an entire object noise, and N2 is noise generated from each of the optical branching devices 2a-2d to a succeeding branch point. |
