Method of adjusting power for a wavelength-division multiplexed optical transmission system

1. A method of adjusting power for a WDM optical transmission system comprising emitter means, an optical transmission line, and receiver means, comprising adjusting for each wavelength channel, the power emitted for said channel by the emitter means as a function of the optical powers received for said channel at the inlet to the first amplifier, wherein for each channel a reference power is continuously determined as a function of the optical powers received for said channel at the inlet to the first amplifier, said reference power being the power that ought to be received for said channel at the inlet to the first amplifier, and the emitter means are controlled so as to servo-control the power at said inlet on said reference power, wherein for each channel i, a parameter f i is determined which is a function of the powers received at the inlet to the first amplifier, and in that the reference power is modified by replacing its preceding value with a reference value that is a function of said preceding value and also of the parameter f i , wherein the parameter f i is such that:

f

i

=

∑

j

=

l

,

m

⁢

⁢

P

ij

-

1

where P ij represents the power at the jth point of the transmission line for channel i and where m is the number of points of said line.

2. A method according to claim 1 , wherein the new reference power is the product of the preceding reference power and a function of the parameter f i .

3. A method according to claim 1 , wherein the parameter f i is related to the mean {overscore (f)} of the parameters f i as determined for the various channels.

4. A method of adjusting power for a WDM optical transmission system comprising emitter means, an optical transmission line, and receiver means, comprising adjusting for each wavelength channel, the power emitted for said channel by the emitter means as a function of the optical powers received for said channel at the inlet to the first amplifier, wherein for each channel a reference power is continuously determined as a function of the optical powers received for said channel at the inlet to the first amplifier, said reference power being the power that ought to be received for said channel at the inlet to the first amplifier, and the emitter means are controlled so as to servo-control the power at said inlet on said reference power, wherein for each channel i, a parameter f i is determined which is a function of the powers received at the inlet to the first amplifier, and in that the reference power is modified by replacing its preceding value with a reference value that is a function of said preceding value and also of the parameter f i , characterized in that the parameter f i is such that:

f i =1/( P i1 ·P im ) 1/2

wherein,

P i1 is the power of the i th channel at the 1 st amplifier and

P im is the power of the i th channel at the m th amplifier.

5. A method according to claim 4 , wherein the new reference power is the product of the preceding reference power and a function of the parameter f i .

6. A method according to claim 4 , wherein the parameter f i is related to the mean {overscore (f)} of the parameters f i as determined for the various channels.

7. A method of adjusting power for a WDM optical transmission system comprising emitter means, an optical transmission line, and receiver means, comprising adjusting for each wavelength channel, the power emitted for said channel by the emitter means as a function of the optical powers received for said channel at the inlet to the first amplifier, wherein for each channel a reference power is continuously determined as a function of the optical powers received for said channel at the inlet to the first amplifier, said reference power being the power that ought to be received for said channel at the inlet to the first amplifier, and the emitter means are controlled so as to servo-control the power at said inlet on said reference power, wherein for each channel i, a parameter f i is determined which is a function of the powers received at the inlet to the first amplifier, and in that the reference power is modified by replacing its preceding value with a reference value that is a function of said preceding value and also of the parameter f i , wherein the new reference power is the product of the preceding reference value and a function of f i , wherein the function is a product η·f i , η being a weighting factor selected so that the total power received by the first amplifier is constant.

8. A method according to claim 7 , wherein the new reference power is the product of the preceding reference power and a function of the parameter f i .

9. A method according to claim 7 , wherein the parameter f i is related to the mean {overscore (f)} of the parameters f i as determined for the various channels.