Seeded Raman amplifier in a linear configuration for generating a 1240 nm laser

A third-order Stokes wavelength seed signal at the desired output wavelength of 1240 nm and a zeroth-order Stokes wavelength signal at 1066 nm are input into a Raman amplifier comprised of two Raman resonators in a linear configuration. The first resonator converts the zeroth-order Stokes wavelength signal at 1066 nm into a first-order Stokes wavelength signal at 1118 nm, and also outputs the third-order Stokes wavelength seed signal at 1240 nm. The second resonator then converts the 1118 nm output from the first resonator into a second-order Stokes wavelength signal at 1176 nm, which amplifies the 1240 nm seed signal power level. Each Raman resonator includes a photosensitive Raman fiber communicating with a plurality of high-reflector Bragg gratings. The linewidths of the second and third Stokes orders are controlled by adjusting the resonant bandwidth of the second Raman resonator by offsetting the respective center wavelengths of the high-reflector Bragg gratings.