Patent ID: 7251072

Claim:
An optical transmission system which transports optical signals over an optical transmission line, comprising: (a) an optical transmitter, comprising: optical amplifying means for amplifying main signals, and optical amplifying control means for starting up said optical amplifying means, waiting a first predetermined time to raise output power of said optical amplifying means up to a desired level, in order to prevent an OSC signal from experiencing abrupt power variations; and (b) an optical receiver, comprising: pump light emitting means for producing a pump light for injection to the optical transmission line so as to make the optical transmission line serve as an amplifying medium, and pump light emitting control means for starting up said pump light emitting means, waiting a second predetermined time to raise the pump light to a desired power level, in order to prevent the OSC signal from experiencing abrupt power variations; wherein said pump light emitting control means comprises a timer with a predetermined time constant that is enabled when the optical transmission system starts to operate; and said pump light emitting control means starts to raise the pump light in a stepwise fashion after said timer has expired, whereby said pump light emitting means starts up later than said optical amplifying means.