The gain medium of Distributed Raman Amplifier is Single Mode Fiber (SMF) of at least  25km in length. 50 km works better. That is to say, the signal is amplified all along the transmission fiber.

 In OSNR calculation, the Equivalent Noise Figure of distributed backward pump Raman Amplifier is 0dB, and typical value may be as low  -2dB, which improves  system OSNR and transmission distance. By lowering the amount of light at the input of the fiber non-linearity effect (SBS) is decreased .

A typical application you would input 13 dB into your transmission fiber and go 60 km where the signal would be 0dBm at the input of the Ramon amplifier when it was turned off.  When the Ramon was turned on the effective signal at the input would increase to 8 dB providing more than adequate light to drive a EDFA for distribution or to extend another 60 km.

4Cable TV's  distributed Raman Amplifier is a series of products, with different Raman Gain and Gain bandwidth to meet differential needs. The unit adopts Japanese Fitel Raman pump laser, build-in laser APC, AGC, ATC closed-looped circuit ensuring long life and stable operation of the pump laser.

Product feature

Perfect laser APC, AGC, ATC closed-looped circuit ensuring long life and stable operation of the pump laser.

Low noise figure and flat gain.

Adopts famous Fitel Raman pump laser.

Different Gain bandwidth option:
           RFA4000: CATV.
           RFA5000: C-Band.
           RFA6000: L-Band.
           RFA7000: C & L-Band.

Differential gain suits for different network.

Main application

Fiber CATV system, super-long trunk inconvenient for building relay station.
          Relay distance > 60Km.
          Single span distance > 80Km.

DWDM, CATV super-long trunk optical transmission system.

Submarine optical transmission system.