Raman fiber amplifier communication systems

Abstract

The specification describes an improved optical fiber design in which the criteria for high performance in a Raman amplified optical system, such as moderate effective area, moderate dispersion, low dispersion slope, and selected zero dispersion wavelength, are simultaneously optimized. In preferred embodiments of the invention, the dispersion characteristics are deliberately made selectively dependent on the core radius. This allows manufacturing variability in the dispersion properties, introduced in the core-making process, to be mitigated during subsequent processing steps.

1 . An optical WDM system using Raman amplification comprising: 
 a. a length of optical fiber,    b. lightwave signal means for introducing a lightwave signal into the optical fiber, the lightwave signal comprising at least three wavelength division multiplexed (WDM) wavelengths,    c. optical pump means for introducing lightwave pump energy into the core of the glass fiber, whereby the lightwave pump energy interacts with the lightwave signal to produce Raman amplification of the lightwave signal,    the invention characterized in that the optical fiber comprises sequential regions of: 
 i. a core region extending from the center of the optical fiber, with essentially all of the core region having a positive Δ,  
 ii. a trench region, with essentially all of the trench region having a negative Δ,  
 iii. a ring region having a positive Δ,  
   and the optical fiber is characterized by: 
 Dispersion at 1550 nm: 5-8.5 ps/nm-km  
 Dispersion slope at 1550 nm: <0.045 ps/nm 2 -km  
 Effective area at 1550 nm: >50 μm 2    
   Cable cutoff wavelength: <1410 nm    Macrobend loss (32 mm) at 1625 nm: <5×10 3  dB/km    Zero dispersion wavelength: <1400 nm.    
   
   
       2 . The system of  claim 1  wherein the signal means includes wavelengths above 1510 nm, and includes 1550 nm.  
   
   
       3 . The system of  claim 2  wherein: 
 Dispersion at 1550 nm=7.3±2 ps/nm-km    
   
   
       4 . The system of  claim 2  wherein: 
 Effective area at 1550 nm=54-62 μm 2      
   
   
       5 . The system of  claim 2  wherein: 
 Dispersion slope at 1550 nm: <0.042 ps/nm 2 -km    
   
   
       6 . The system of  claim 2  wherein: 
 Dispersion at 1550 nm=7.3±2 ps/nm-km    Effective area at 1550 nm=54-58 μm 2      Dispersion slope at 1550 nm: <0.042 ps/nm 2 -km    
   
   
       7 . The system of  claim 1  wherein the system includes at least one erbium-doped fiber amplifier.  
   
   
       8 . The system of  claim 1  wherein the at least three wavelength division multiplexed (WDM) wavelengths operate over the S-, L- or extended L-bands.  
   
   
       9 . The system of  claim 1  wherein the lightwave signal means operates at 40 Gb/s.  
   
   
       10 . The system of  claim 1  further including means for dispersion slope compensation.  
   
   
       11 . An optical WDM system comprising: 
 a. a length of optical fiber,    b. lightwave signal means for introducing a lightwave signal into the optical fiber, the lightwave signal comprising at least three wavelength division multiplexed (WDM) wavelengths,    c. means for dispersion slope compensation having a relative dispersion slope, defined as dispersion slope divided by dispersion at a given wavelength matched to the optical fiber, of: 
 0.0064 to 0.0082 per nm at a wavelength of approximately 1510 nm (S-band application)  
 0.0046 to 0.0058 per nm at a wavelength of approximately 1550 nm (C-band application)  
 00.42 to 00.54 per nm at a wavelength of approximately 1570 nm (C+L band compensation with combined module)  
 0.0038 to 0.0048 per nm at a wavelength of approximately 1590 nm (L-band application)  
   the invention characterized in that the optical fiber comprises sequential regions of: 
 i. a core region extending from the center of the optical fiber, with essentially all of the core region having a positive Δ,  
 ii. a trench region, with essentially all of the trench region having a negative Δ,  
 iii. a ring region having a positive Δ,  
   and the optical fiber is characterized by: 
 Dispersion at 1550 nm: 5-8.5 ps/nm-km  
 Dispersion slope at 1550 nm: <0.045 ps/nm 2 -km  
 Effective area at 1550 nm: >50 μm 2    
 Cable cutoff wavelength: <1410 nm  
 Macrobend loss (32 mm) at 1625 nm: <5×10 3  dB/km  
 Zero dispersion wavelength: <1400 nm.  
   
   
   
       12 . The system of  claim 11  wherein the C-band and L-band compensation is achieved with a single means having an RDS of 00.42 to 00.54 per nm at a wavelength of approximately 1570 nm.