Patent ID: 7339723

Claim:
An optical transmission system, comprising: an optical fiber transmission line; one or more optical repeating apparatuses; an optical receiving apparatus; and a transferring means for transferring a supervisory signal, based on a quality deterioration of an optical signal detected by said optical receiving apparatus, to said optical repeating apparatus from said optical receiving apparatus, wherein at least one of said optical repeating apparatuses comprises: an optical level variation detecting unit configured to detect a level variation of an optical signal; a supervisory and control unit configured to supervise level variation and transmit it as the level variation information; and a level variation storing unit configured to store information based on the level variation; said optical receiving apparatus comprises: a quality deterioration detecting unit configured to detect a quality deterioration of an optical signal, and wherein said supervisory and control unit comprises: circuitry configured to make said level variation storing unit sequentially discard the information of the level variation having passed a predetermined period while storing the information of the level variation in a constant interval; and circuitry configured to make said level variation storing unit hold storage of the information of the level variation from a time when said level variation storing unit has stored the information of the level variation based on a particular optical signal detected by said optical level variation storing unit until a time when said level variation storing unit is controlled by the supervisory signal transferred by said transferring means.