Raman optical fiber amplifier using erbium doped fiber

A Raman optical fiber amplifier using an erbium doped fiber for a wavelength division multiplexing optical communication system having an optical transmitter for transmitting wavelength division multiplexed optical signals through an optical fiber and an optical receiver for receiving the optical signals through the optical fiber, comprising:

• at least one erbium doped fiber having a light absorption rate of less than 1.0 dB/km in wavelength range of 1,425 nm to 1,520 nm that Raman-amplifies and outputs optical signals in the wavelength range of 1,525 nm to 1,620 nm inputted through a first end of the erbium doped fiber connected with the optical fiber;
• at least one first pumping source providing pump light in the wavelength range of 1,425 nm to 1,520 nm so as to forward Raman-pump the erbium-doped fiber;
• at least one first wavelength selective coupler for providing the pump light emitted from the first pumping source to be introduced into the erbium doped fiber;
• at least one second pumping source providing pump light in the wavelength range of 1,425 nm to 1,520 nm so as to backward Raman-pump the erbium-doped fiber;
• and,
• at least one second wavelength selective coupler for providing the pump light emitted from the second pumping source to be introduced into the erbium doped fiber.