Broadband optical fiber

Abstract

Provided is an optical fiber that is in particular suitable for Raman amplification. An effective area at a wavelength of 1570 nm is in a range of 35 μm 2 to 45 μm 2 , an absolute value of a dispersion slope at the wavelength is equal to or less than 0.04 ps/nm 2 /km, and a dispersion value at the wavelength is in a range of 5 ps/nm/km to 10 ps/nm/km. It is desirable that a refractive index profile contains at least one annular region between a center core and a cladding region.

What is claimed is:  
     
         1 . An optical fiber comprising a core and cladding and having characteristics in that: 
 an effective area A eff  at a wavelength of 1570 nm is not less than 35 μm 2 ;    an absolute value of a dispersion slope at the wavelength is equal to or less than 0.04 ps/nm 2 /km;    a dispersion value at the wavelength is in a range of 5 ps/nm/km to 10 ps/nm/km;    a dispersion of the optical fiber is no less than 2 ps/nm/km over a wavelength range between 1430 nm and 1625 nm;    a zero-dispersion wavelength of the optical fiber is out of a wavelength range between 1400 nm and 1650 nm; and    a cutoff wavelength of the optical fiber is shorter than 1430 nm.    
     
     
         2 . An optical transmission system of wavelength division multiplex (WDM) comprising an optical signal transmitter, optical signal receiver, optical transmission line, pumping light source and optical multiplexer for introducing a pumping light from the source into the optical transmission line to Raman-amplify an optical signal on the optical transmission line, wherein at least part of the optical transmission line comprises one type of the optical fiber as recited in  claim 1 .  
     
     
         3 . The optical transmission system of WDM according to  claim 2 , wherein the optical transmission line further comprises another type of optical fiber.  
     
     
         4 . The optical transmission system of WDM according to  claim 2 , wherein the length of the optical transmission line is less than or equal to 100 km.