Method and apparatus for providing chromatic dispersion compensation in a wavelength division multiplexed optical transmission system

Abstract

A WDM optical communication system is provided that includes a transmitter and a receiver. An optical fiber transmission path couples the transmitter to the receiver. The transmission path includes at least one repeater having an optical amplifier located therein. A dispersion compensator is disposed at an intermediate point along the transmission path. The intermediate point is located outside of the repeater. The compensator includes a wavelength routing device for dividing a signal having a prescribed bandwidth into a plurality of distinct sub-bands. A plurality of output paths is provided for respectively receiving the plurality of distinct sub-bands. The dispersion compensator also includes a dispersion compensating optical element coupled to each of the output paths. Each dispersion compensating optical element substantially compensates for dispersion at a prescribed wavelength within the bandpass of its respective sub-band. A coupler recombining the distinct sub-bands and couples them back onto the optical fiber transmission path.

1 . A WDM optical communication system, comprising: 
 a transmitter and a receiver;    an optical fiber transmission path coupling said transmitter to said receiver, said transmission path including at least one repeater having an optical amplifier located therein;    a dispersion compensator disposed at an intermediate point along said transmission path outside of the repeater, said compensator including: 
 a wavelength routing device for dividing a signal having a prescribed bandwidth into a plurality of distinct sub-bands;  
 a plurality of output paths for respectively receiving said plurality of distinct sub-bands;  
 a dispersion compensating optical element coupled to each of the output paths, said dispersion compensating optical elements each substantially compensating for dispersion at a prescribed wavelength within the bandpass of its respective sub-band;  
 a coupler for recombining said distinct sub-bands and coupling said recombined distinct sub-bands onto said optical fiber transmission path.  
   
     
     
         2 . The system of    claim 2    wherein said transmission path comprises at least one optical fiber and a cable supporting said optical fiber, said cable having a prescribed portion in which said dispersion compensator is located.  
     
     
         3 . The system of  1  wherein said plurality of distinct sub-bands comprises two distinct sub-bands corresponding to upper and lower bands.  
     
     
         4 . The system of    claim 3    wherein said lower band includes a first dispersion equalizing fiber having a positive dispersion.  
     
     
         5 . The system of    claim 4    wherein the dispersion of said first dispersion equalizing fiber is approximately equal to 19 ps/km-nm.  
     
     
         6 . The system of    claim 4    wherein said upper band includes a second dispersion equalizing fiber having a negative dispersion.  
     
     
         7 . The system of    claim 6    wherein the dispersion of the second dispersion equalizing fiber is within a range of about −80 to −100 ps/km-nm.  
     
     
         8 . The system of    claim 7    wherein said optical fiber transmission path has a path average dispersion of −2.5 ps/km-nm.  
     
     
         9 . The system of    claim 8    wherein said first dispersion equalizing fiber has a length providing a total dispersion of approximately 817 ps/nm.  
     
     
         10 . The system of    claim 9    wherein said second dispersion equalizing fiber has a length providing a total dispersion of approximately −1387 ps/nm.  
     
     
         11 . The system of    claim 6    wherein said first and second dispersion equalizing fibers have first and second lengths, respectively, that provide gain equalization between said upper and lower bands.  
     
     
         12 . The system of    claim 6    wherein said lower band further comprises a loss element to provide gain equalization between said upper and lower bands.  
     
     
         13 . The system of    claim 6    wherein said upper band further comprises a third dispersion equalizing fiber having a negative dispersion with a magnitude less than the magnitude of the second dispersion equalizing fiber.  
     
     
         14 . The system of    claim 13    wherein the dispersion of the third dispersion equalizing fiber is approximately equal to −2 ps/km-nm.