Gain equalization system and method

Abstract

A power equalization system and method for use in an optical transmission system are provided. The power equalization system includes an optical line including at least one transmission channel and a management line. The transmission system further includes a plurality of amplifiers, a plurality of Optical spectrum analyzers and a plurality of equalizers. The plurality of amplifiers are coupled to the optical line, spaced periodically throughout the optical transmission system. As information is sent through the optical transmission system, the plurality of amplifiers boost the power of each channel of the optical signal. A plurality of optical spectrum analyzers are also coupled to the optical lien and are spaced periodically throughout the optical transmission system and are co-located with a first portion of the amplifiers coupled to the optical line. A plurality of equalizers are also coupled to the optical line and are spaced periodically throughout the optical transmission system and equalize the power on each channel of the optical line. The plurality of equalizers are co-located with a second portion of the plurality of amplifiers and at least one of the plurality of Optical spectrum analyzers is not co-located with one of the plurality of equalizers. As optical information is transmitted over the optical transmission system, the Optical spectrum analyzers provide analysis data via the management line to the non co-located equalizers for use by the equalizers in equalizing the power of the channels of the optical line at that point. The analysis data generated by the Optical spectrum analyzer identifies the analysis data at the point of the Optical spectrum analyzer which is not co-located with the equalizer.

1. A power equalization system for use in an optical transmission system, the system comprising:
 an optical line, wherein the optical line includes at least one transmission channel;  
 a plurality of amplifiers coupled to the optical line, wherein the amplifiers are spaced periodically throughout  along the optical line;  
 a plurality of Optical  optical spectrum analyzers coupled to the optical line, wherein the Optical  optical spectrum analyzers are spaced periodically throughout  along the optical line and wherein the Optical  optical spectrum analyzers generate analysis data; and  
 a plurality of equalizers coupled to the optical line, wherein the equalizers are spaced periodically throughout  along the optical line and wherein the equalizers equalize the power on the channels;  
 a management line  channel for transmitting management data coupled to the pluralities of amplifiers, Optical  optical spectrum analyzers and equalizers;  
 wherein the plurality of Optical  optical spectrum analyzers are collocated  co- located  with a portion of the plurality of amplifiers and wherein the plurality of equalizers are collocated  co- located  with a second portion of the plurality of amplifiers and wherein at least one of the plurality of Optical  optical spectrum analyzers is not collocated  co- located  with the plurality of equalizers; and  
 wherebywherein analysis data generated by the Opticaloptical spectrum analyzers is transmitted via the management channel to the equalizers for use by the equalizers in equalizing the power of the channels of the optical line.  
 
     
     
       2. The system of  claim 1 , wherein the amplifiers are spaced periodically along the optical line and include in-line amplifiers. 
     
     
       3. The system of  claim 1 , wherein the equalizers are spaced periodically along the optical line and are configured to equalize the power of each channel individually. 
     
     
       4. The system of  claim 1 , wherein the equalizers are spaced periodically along the optical line and include dynamic gain equalizers. 
     
     
       5. The system of  claim 1 , wherein the analysis data transmitted by the Optical  optical spectrum analyzer is transmitted upstream. 
     
     
       6. The system of  claim 1 , wherein the plurality of amplifiers include:
 a plurality of erbium-doped fiber amplifiers coupled to the optical line and the management line  channel, wherein the erbium-doped fiber amplifiers adjust the power of the optical line to counteract gain tilt;  
 wherebywherein the erbium-doped fiber amplifiers counteract gain tilt through the adjustment of the power of all channels collectively at the amplifiers.  
 
     
     
       7. The system of  claim 6 , wherein the plurality of erbium-doped fiber amplifiers adjust the power of the optical line to counteract the gain tilt from Stimulated Raman Scattering. 
     
     
       8. The system of  claim 6 , wherein the plurality of erbium-doped fiber amplifiers adjust the power of the optical line to counteract the gain tilt from non-uniform fiber loss. 
     
     
       9. The system of  claim 6 , wherein the plurality of erbium-doped fiber amplifiers adjust the power of the optical line to counter act  counteract the gain tilt based upon the analysis data transmitted via the management line. 
     
     
       10. The system of  claim 1 , wherein the plurality of equalizers are spaced periodically along the optical line and are configured to equalize the power on the channels so the average power over a periodic spacing is zero. 
     
     
       11. The system of  claim 1 , wherein the management line  channel includes an optical supervisory channel. 
     
     
       12. The system of  claim 11 , wherein the optical supervisory channel includes one of the transmission channels of the optical line. 
     
     
       13. The system of  claim 1 , wherein the management channel includes a public telephone network. 
     
     
       14. The system of  claim 1 , wherein the management channel includes the Internet. 
     
     
       15. A method of gain equalization of an optical transmission system, the method comprising the steps of:
 transmitting an optical signal over at least one optical channel of the optical transmission system;  
 transmitting a management signal over a management line  channel of the optical transmission system;  
 amplifying the optical signal at predetermined  amplifying positions in the optical transmission system;  
 analyzing the optical signal at a first portion of the predetermined  amplifying positions;  
 determining an optical spectrum gain from the optical signal analysis;  
 transmitting an optical spectrum gain signal including the optical spectrum gain to an equalizer; and  
 equalizing the optical signal based upon the received optical spectrum gain at a second portion of the predetermined  amplifying positions;  
 wherein at least one position of the first portion of predetermined  amplifying positions is not collocated  co- located  with a predetermined amplifying  position of the second portion.  
 
     
     
       16. The method of  claim 15 , wherein the step of transmitting an optical signal over at least one optical channel includes transmitting optical signals over a plurality of optical channels. 
     
     
       17. The method of  claim 16 , wherein the steps of analyzing the optical signal and determining the optical spectrum gain includes analyzing each optical signal channel and determining the optical spectrum gain for each optical signal channel. 
     
     
       18. The method of  claim 17 , wherein the step of equalizing the optical signal includes equalizing each channel of the optical signal based upon the optical spectrum gain of each channel. 
     
     
       19. The method of  claim 15 , wherein the optical spectrum gain average over a predetermined span is zero. 
     
     
       20. The method of  claim 15 , wherein the equalizing of the optical signal includes dynamic gain equalization. 
     
     
       21. The method of  claim 15 , wherein the transmission of the optical spectrum gain signal is upstream. 
     
     
       22. The method of  claim 15  further comprising:
 determining an amount of gain tilt in the optical signal based upon the optical signal analysis;  
 transmitting a gain tilt signal including the amount of gain tilt of the optical signal to an  one or more erbium-doped fiber amplifiers;  
 adjusting the power of the optical signal with the erbium-doped fiber amplifiers based upon the amount of gain tilt, wherein the erbium-doped fiber amplifiers counteract gain tilt through the adjustment of the power of all channels collectively at the amplifiers.  
 
     
     
       23. An optical transmission system, comprising:
   a plurality of optical transmission channels coupled at a first end to a first terminal and at a second end to a second terminal;        an optical spectrum analyzer coupled to the optical transmission channels at a first intermediate location between the first end and the second end;        an equalizer coupled to the optical transmission channels at a second intermediate location between the first end and the second end, wherein the equalizer is spaced apart from the optical spectrum analyzer;        wherein the system is configured to transmit analysis data generated by the optical spectrum analyzer to the equalizer for use by the equalizer in reducing power differences in the optical transmission channels.      
     
     
       24. An optical transmission system as recited in  claim 23 , further comprising a management channel, wherein said management channel is configured to carry said analysis data from the optical spectrum analyzer to the equalizer.  
     
     
       25. An optical transmission system as recited in  claim 23 , further comprising a first amplifier co- located with the optical spectrum analyzer and a second amplifier co - located with the equalizer, the first and second amplifiers being coupled to the optical transmission channels and configured to amplify optical signals in said channels.    
     
     
       26. An optical transmission system as recited in  claim 23 , further comprising a management channel, wherein said management channel is coupled to said first and second amplifiers such that commands from said optical spectrum analyzer are communicable via said management channel to said first and second amplifiers.  
     
     
       27. The optical transmission system of  claim 23 , further comprising an amplification location, wherein the first and second intermediate locations are not co- located with the amplification location.    
     
     
       28. The optical transmission system of  claim 27 , wherein the amplification location is between the first intermediate location and the second intermediate location.  
     
     
       29. A method for use in an optical transmission system, comprising:
   amplifying an optical signal at one or more amplifying positions in the optical transmission system;        analyzing the optical signal at a first position and determining an optical spectrum gain;        transmitting an optical spectrum gain signal to an equalizer at a second position spaced apart from said first position; and        reducing spectral component power differences in the optical signal at said first second position based upon the received optical spectrum gain.      
     
     
       30. A method as recited in  claim 29 , wherein said spectrum gain signal is transmitted over a management channel to said equalizer.  
     
     
       31. A method as recited in  claim 30 , further comprising transmitting a command signal over the management channel to control one or more amplifiers.  
     
     
       32. A method as recited in  claim 29 , wherein said second position corresponds to one of said amplifying positions.  
     
     
       33. A method as recited in  claim 32 , wherein the optical signal is amplified at first and second amplifying positions, said first position corresponds to one of said amplifying positions, and said second position corresponds to a different one of said amplifying positions.  
     
     
       34. A system for use in an optical transmission system, comprising:
   at least one amplifier configured to amplify an optical signal at one or more amplifying positions in the optical transmission system;        at least one equalizer;        an analyzer configured to analyze the optical signal at a first position, to determine a spectrum gain, and to transmit a spectrum gain signal to said equalizer;        wherein said equalizer is located at a second position spaced apart from said first position, and is configured to reduce channel - to - channel power differences in the optical signal at said first second position based upon the received spectrum gain.      
     
     
       35. A system as recited in  claim 34 , wherein said gain signal is transmittable over a channel to said equalizer.  
     
     
       36. A system as recited in  claim 35 , wherein said at least one amplifier is configured to be controlled via a command signal received over said channel.  
     
     
       37. A system as recited in  claim 34 , wherein said second position corresponds to one of said amplifying positions.  
     
     
       38. A system as recited in  claim 37 , wherein the optical signal is amplifiable at first and second amplifying positions, said first position corresponds to one of said amplifying positions, and said second position corresponds to a different one of said amplifying positions.  
     
     
       39. A system as recited in  claim 34 , comprising a plurality of equalizers spaced periodically along an optical line of said system.  
     
     
       40. A system as recited in  claim 34 , wherein said equalizer comprises a dynamic gain equalizer.  
     
     
       41. An optical transmission system, comprising:
   an optical channel;        a management channel;        at least one amplifier stationed at an amplifying position along said optical channel;        at least one equalizer stationed at an equalizing position along said optical channel;        an amplifier stationed at an analyzing position along said optical channel and configured to generate a spectrum gain signal and to transmit said spectrum gain signal via said management channel to said at least one equalizer.      
     
     
       42. A system as recited in  claim 41 , further comprising at least one equalizer, wherein said equalizer is located at an equalizing position spaced apart from said analyzing position, and is configured to reduce channel- to - channel power difference in an optical signal at said equalizing position based upon the spectrum gain signal.    
     
     
       43. A system as recited in  claim 42 , wherein said equalizing position corresponds top said amplifying position.  
     
     
       44. A system as recited in  claim 43 , wherein said equalizer comprises a dynamic gain equalizer.  
     
     
       45. A method for use in an optical transmission system, comprising:
   amplifying an optical signal at one or more amplifying positions in the optical transmission system;        analyzing the optical signal at a first position and determining an optical spectrum gain;        transmitting an optical spectrum gain signal via a management channel to a remote location.      
     
     
       46. A method as recited in  claim 45 , wherein said spectrum gain signal is transmitted over said management channel to an equalizer at a second position spaced apart from said first position.  
     
     
       47. A method as recited in  claim 46 , further comprising reducing spectral component power differences in the optical signal said second position based upon the optical spectrum gain.  
     
     
       48. A method as recited in  claim 25 , further comprising transmitting a command signal over the management channel to control one or more amplifiers.  
     
     
       49. A method as recited in  claim 46 , wherein said second position corresponds to one of said amplifying positions.  
     
     
       50. A method as recited in  claim 46 , wherein the optical signal is amplified at first and second amplifying positions, said first position corresponds to one of said amplifying positions, and said second position corresponds to a different one of said amplifying positions.