Method of performing target Raman gain locking and Raman fiber amplifier

A method of performing target Raman gain locking, comprising:

• step 1 of extracting an optical signal from an output side of a splitting coupler (1) of a Raman fiber amplifier (9);
• step 2 of performing a first-level-bandpass filtering on the optical signal extracted in the step 1, splitting a composite out-of-band optical signal and a composite in-band optical signal with respect to a filtering operation band;
• step 3 of performing a second-level-bandpass filtering on the composite out-of-band optical signal split in step 2, to filter out a monitoring optical signal therein and extract an out-of-band ASE optical signal;
• step 4 of detecting a power of the out-of-band ASE optical signal extracted in the step 3;
• step 5 of determining a mathematical relation between a target gain value and the power of the out-of-band ASE optical signal generated from a Raman gain itself;
• step 6 of determining a standard power the of out-of-band ASE optical signal to remove interference;
• and
• step 7 of adjusting power of a pump laser of the Raman fiber amplifier (9) by a control unit (15) of the Raman fiber amplifier (9), to make the power of the out-of-band ASE optical signal detected in the step 4 be equal to and locked to the standard power of the out-of-band ASE optical signal,
• wherein the step 6 further comprising substeps as follows:
• step 6-1 of in case that the Raman fiber amplifier is powered ON and the pump laser thereof is powered OFF, performing the steps 1 to 4, obtaining the power of the out-of-band ASE optical signal, and at same time, detecting power Pin of the split composite in-band optical signal;
• step 6-2 of comparing the power Pin of the composite in-band optical signal and a signal light loss threshold value of the Raman fiber amplifier, and controlling the OFF and ON of the pump laser of the Raman fiber amplifier (9) by the control unit of the Raman fiber amplifier, wherein when the power Pin of the composite in-band optical signal is smaller than the signal light loss threshold value of the Raman fiber amplifier (9), the pump laser remaining OFF state, otherwise the pump laser is powered ON;
• step 6-3 of determining mathematical correspondence relation between target gain value of the Raman fiber amplifier (9) and an average out-of-band gain value;
• step 6-4 of determining the average out-of-band gain value corresponding to the target gain value according to the mathematical correspondence relation determined in step 6-3, and multiplying it by the power of the out-of-band ASE optical signal obtained in the step 6-1, thus obtaining a first amendment value;
• step 6-5 of determining a mathematical correspondence relation between the power Pin of the composite in-band optical signal obtained in the step 6-1 and in-band/out-of-band isolation degree i;
• step 6-6 of obtaining a second amendment value
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• according to the mathematical correspondence relation determined in step 6-5;
• and
• step 6-7 of adding the first amendment value obtained in the step 6-4, the second amendment value obtained in the step 6-6 and the power of the out-of-band ASE optical signal corresponding to the target gain value obtained from the mathematical relation determined in the step 5, thus obtaining the standard power of the out-of-band ASE optical signal.