Multi-wavelength Raman laser

A multi-wavelength Raman laser, comprising:

• an optical ring laser loop having a single mode optical fiber with its two ends coupled nearby in an optical fiber ring;
• a Raman optical fiber coil disposed in the optical loop, the Raman optical fiber having multiple modes over a pump wavelength to a plurality of signal wavelengths;
• a frequency shifter disposed in said optical loop and shifting optical radiation by a frequency shift;
• a source of optical pump power having the pump wavelength for pumping the Raman optical fiber at the pump wavelength to obtain a plurality of optical signals, wherein gain is provided by Raman amplification over at least one Stokes order corresponding to the pump wavelength in response to a Raman interaction of the optical pump power and a phonon spectrum of the Raman optical fiber such that said Raman optical fiber transfers optical power between an optical signal at said pump wavelength and the plurality of optical signals at least approximately at the at least one Stokes order including a plurality of signal wavelengths;
• a periodic filter disposed in said optical loop, the periodic filter having a filter spectrum placed approximately at the at least one Stokes order, the filter spectrum including the plurality of signal wavelength having pass bands separated by a fixed wavelength spacing, the periodic filter filtering the plurality of optical signals to filter out a plurality of filtered optical signals having the plurality of signal wavelengths with fixed spacings therebetween and selectively passing a plurality of signal wavelengths separated by a fixed spacing to provide a multi-wavelength signal;
• and
• a wavelength division multiplexer disposed between the two ends of the optical fiber ring in said optical loop, the multiplexer coupling a first optical fiber to a second optical fiber included in said loop, the multiplexer having a transmission coefficient between said first and second optical fibers that is greater for said pump wavelength than for said signal wavelengths, said optical pump power being coupled into said loop through a first end of said first optical fiber for receiving the source of optical pump power and the multi-wavelength signal being coupled out of said loop through a second end of said first optical fiber.

A multi-wavelength Raman laser test signal source, comprising:

• an optical ring laser loop having a single mode optical fiber with its two ends coupled nearby in an optical fiber ring;
• a Raman optical disposed in the optical loop, the having a Raman optical fiber coil having multiple modes over a pump wavelength to a plurality of signal wavelengths and a source of optical pump power having the pump wavelength for pumping the Raman optical fiber coil at the pump wavelength to obtain a plurality of optical signals, wherein gain is provided by Raman amplification over at least one Stokes order corresponding to the pump wavelength in response to Raman interaction of the optical pump power and a phonon spectrum of the Raman optical fiber coil such that the Raman optical fiber coil transfers optical power between an optical signal at said pump wavelength and the plurality of optical signals at least approximately at the at least one Stokes order including a plurality of signal wavelengths;
• a frequency shifter disposed in said optical loop and shifting optical radiation by a frequency shift for reducing mode competition to allow for broad band lasing;
• a periodic filter disposed in said optical loop, the periodic filter having a filter spectrum placed approximately at the at least one Stokes order, the filter spectrum including the plurality of signal wavelength having pass bands separated by a fixed wavelength spacing, the periodic filter filtering the plurality of optical signals to filter out a plurality of filtered optical signals having the plurality of signal wavelengths with fixed spacings therebetween and selectively passing a plurality of signal wavelengths separated by a fixed spacing to provide a multi-wavelength signal;
• and
• a coupler disposed between the two ends of the optical fiber ring in said optical loop, the coupler coupling out of the loop a fraction of optical power of the multi-wavelength signal.