Single-source multiple-order raman amplifier for optical transmission systems

A single-source, multiple-order Raman pump source comprising:

• a cascaded Raman fiber laser comprising a single laser light source coupled into a multiple wavelength cascaded Raman resonator, said cascaded Raman resonator comprising an optical fiber, said optical fiber including a set of upstream reflective gratings, a set of downstream reflective gratings, a length of fiber between the upstream and downstream sets of gratings, and one or more adjustable reflectivity gratings for coupling output from the resonator, each grating having a center wavelength and a reflectivity at the center wavelength;
• wherein the center wavelengths of the grating are chosen to generate from the single light source a first optical output in a first wavelength range and a second optical output in a second wavelength range that provides Raman amplification of the first optical output;
• and
• wherein at least one of said downstream reflective gratings has a reflectivity of about 8% and at least one of said one or more adjustable reflectivity gratings has a reflectivity that is tunable from about 4% to about 12%.