Optical transmission system

An optical transmission system which transports optical signals between upstream and downstream stations over an optical transmission line, each station comprising:

• optical amplifying means for amplifying main signals;
• optical amplifying control means for starting up said optical transmitter, 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;
• a 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
• a 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 in the downstream station starts up later than said optical amplifying means in the upstream station.

A method of suppressing optical supervisory signal errors, comprising:

• raising output power of an optical amplifier up to a desired level in a stepwise fashion, the optical amplifier being disposed in an optical transmitter to amplify main optical signals for transport over a downstream optical transmission line;
• raising a pump light to a desired power level in a stepwise fashion, the pump lights being produced by a pump light source disposed in an optical receiver for injection to the downstream optical transmission line so as to cause Raman amplification;
• monitoring power levels of at least one of an incoming main optical signal and an incoming optical supervisory signal that the optical receiver receives;
• transmitting the result of said monitoring from the optical receiver to the optical transmitter by using an optical supervisory signal over an upstream optic transmission line;
• and
• determining the number and interval of steps in said stepwise raising of the output power of the optical amplifier, based on the result of said monitoring,
• enabling a first timer having a predetermined time constant, when the optical transmitter starts to operate;
• starting an optical amplifier controller raising the output power of said optical amplifier in a stepwise fashion after said first timer has expired;
• and
• enabling a second timer having a predetermined time constant, when the optical transmitter starts to operate;
• starting a pump light source controller raising the pump light in a stepwise fashion after said second timer has expired, whereby said pump light source starts up later than said optical amplifier.

A method of suppressing optical supervisory signal errors, comprising:

• raising output power of an optical amplifier up to a desired level in a stepwise fashion, the optical amplifier being disposed in an optical transmitter to amplify main optical signals for transport over downstream fiber-optic transmission line;
• raising a pump beam to a desired power level in a stepwise fashion, the pump beams being produced by a pump light source disposed in an optical receiver for injection to the downstream fiber-optic transmission line so as to cause Raman amplification;
• monitoring power levels of at least one of an incoming main optical signal and an incoming optical supervisory signal that the optical receiver receives;
• and
• determining the number and interval of steps in said stepwise raising of the pump beam, based on the result of said monitoring.

A method of suppressing optical supervisory signal errors, comprising:

• raising output power of an optical amplifier up to a desired level in a stepwise fashion, the optical amplifier being disposed in an optical transmitter to amplify main optical signals for transport over a downstream optical transmission line;
• raising a pump light to a desired power level in a stepwise fashion, the pump lights being produced by a pump light source disposed in an optical receiver for injection to the downstream optical transmission line so as to cause Raman amplification;
• monitoring power levels of at least one of an incoming main optical signal and an incoming optical supervisory signal that the optical receiver receives;
• notifying the optical transmitter of completion of said stepwise raising of the pump light by sending an optical supervisory signal over an upstream -optic transmission line;
• and
• determining the number and interval of steps in said stepwise raising of the output power of the optical amplifier and in said stepwise raising of the pump light, based on the result of said monitoring;
• enabling a first timer having a predetermined time constant, when the optical transmitter starts to operate;
• starting an optical amplifier controller raising the output power of said optical amplifier in a stepwise fashion after said first timer has expired;
• and
• enabling a second timer having a predetermined time constant, when the optical transmitter starts to operate;
• starting a pump light source controller raising the pump light in a stepwise fashion after said second timer has expired, whereby said pump light source starts up later than said optical amplifier.

A method of suppressing optical supervisory signal errors, comprising:

• raising output power of an optical amplifier up to a desired level in a stepwise fashion, the optical amplifier being disposed in an optical transmitter to amplify main optical signals for transport over a downstream optical transmission line;
• raising a pump light to a desired power level in a stepwise fashion, the pump lights being produced by a pump light source disposed in an optical receiver for injection to the downstream optical transmission line so as to cause Raman amplification;
• monitoring power levels of at least one of an incoming main optical signal and an incoming main optical supervisory signal that the optical receiver receives;
• transmitting the result of said monitoring from the optical receiver to the optical transmitter by using an optical supervisory signal over an upstream optical transmission line;
• and
• determining the number and interval of steps in said stepwise raising of the output power of the optical amplifier and in said stepwise raising of the pump light, based on the result of said monitoring;
• enabling a first timer having a predetermined time constant, when the optical transmitter starts to operate;
• starting an optical amplifier controller raising the output power of said optical amplifier in a stepwise fashion after said first timer has expired;
• and
• enabling a second timer having a predetermined time constant, when the optical transmitter starts to operate;
• starting a pump light source controller raising the pump light in a stepwise fashion after said second timer has expired, whereby said pump light source starts up later than said optical amplifier;
• wherein the sending end and receiving end perform said stepwise raising of the output power and pump beam, respectively, while exchanging each other's ongoing process status by sending optical supervisory signals back and forth over the upstream and downstream optical transmission lines.