PURPOSE: To implement the installation work easily and comparatively inexpensively by deciding the standard optical length S properly and selecting and using an optical tap having a proper branching ratio in response to the distance between optical taps among optical taps manufactured while taking a specific kmax as the maximum branching ratio, taking a specific La as the distance and varying the branch ratio.
CONSTITUTION: Optical taps 11-1 to 11-n having a maximum insertion loss Lt [dB] are inserted to an optical fiber 13 with a loss of Lf [dB/m] per unit length extended to downstream while using a master equipment 12 at the uppermost stream. The branch ratio Ki of each optical tap 11-i is selected from those of plural optical taps of plural kinds manufactured by varying the branch ratio while the value La calculated by equation of La=Lt+Lf×S [dB], where S is the standard optical length in meter. Then the optical tap having the branch ratio Ki calculated by equation of Ki=Ki-1-N×La [dB], where N is the quantized number of a distance li with an optical tap 11-i-1 whose branch ratio is Ki-1 adjacent to an optical tap 11-i toward the upperstream by the standard optical length S. Thus, simple structure, comparatively low cost and ease of installation are attained.
TODA MASATOSHI
KAGAMI MANABU
SAKAI YOICHI
