Nonlinear fiber amplifiers used for a 1430-1530nm low-loss window in optical fibers

A broadband nonlinear polarization amplifier comprising:

• an input port for inputting an optical signal having a wavelength .lambda.;
• an optical fiber for receiving said optical signal and amplifying and spectrally broadening said optical signal therein through nonlinear polarization, said optical fiber having zero-dispersion at wavelength .lambda..sub.0 and a cut-off wavelength less than 1240 nm;
• a pumping means operated at wavelength 1240 nm for generating a pumping light to pump said optical fiber;
• and
• an output port for outputting said amplified and spectrally broadened optical signal,
• wherein .lambda..gtoreq..lambda..sub.0 .gtoreq.1240 nm, and
• said pumping light cascades through said optical fiber a plurality of Raman orders including an intermediate order having a wavelength .lambda..sub.r at a close proximity to said zero-dispersion wavelength .lambda..sub.0 to phase match four-wave mixing (if r .lambda..sub.r <.lambda..sub.0) or parametric amplification (if .lambda..sub.r >.lambda..sub.0).

A broadband nonlinear polarization amplifier comprising:

• an input port for inputting an optical signal having a wavelength between about 1430 nm and 1530 nm;
• a Sagnac Raman cavity comprising
• a broadband mirror, and
• a loop mirror comprising a Raman gain fiber and an optical coupler connected thereto, said fiber receiving said optical signal and amplifying and spectrally broadening said optical signal therein through nonlinear polarization, said fiber having zero-dispersion at wavelength .lambda..sub.0 and a cut-off wavelength .lambda..sub.CO ;
• a pumping means operated at a wavelength .lambda..sub.p for generating a pumping light to pump said fiber through a coupling means;
• and
• an output port for outputting said amplified and spectrally broadened optical signal,
• wherein 1430 nm.gtoreq..lambda..sub.0 .gtoreq..lambda..sub.p, and
• said pumping light cascades through said distributed gain medium a plurality of Raman orders including an intermediate order having a wavelength .lambda..sub.r at a close proximity to said zero-dispersion wavelength .lambda..sub.0 to phase match four-wave mixing (if .lambda..sub.r <.lambda..sub.0) or parametric amplification (if .lambda..sub.r >.lambda..sub.0).

A method of producing an amplified broadband optical signal, said method comprising:

• providing a Sagnac Raman cavity comprising a broadband mirror, and a loop mirror comprising of a Raman gain fiber and an optical coupler connected thereto, said fiber having a zero-dispersion wavelength .lambda..sub.0 and a cut-off wavelength .lambda..sub.CO ;
• inputting an optical signal having a wavelength .lambda. between about 1430 nm and 1530 nm to said gain fiber;
• generating a pumping light from a pumping means operated at a wavelength .lambda..sub.p ;
• pumping said gain fiber with said pumping light for amplifying said optical signal;
• cascading said pumping light through said gain fiber a plurality of Raman orders, the wavelength .lambda..sub.p being such that an intermediate Raman order has a wavelength .lambda..sub.r at a close proximity to said zero-dispersion wavelength .lambda..sub.0 ;
• phase matching said intermediate Raman order with four-wave mixing (if .lambda..sub.r <.lambda..sub.0) or parametric amplification (if .lambda..sub.r >.lambda..sub.0) for spectral broadening;
• and
• outputting said amplified and spectrally broadened optical signal, wherein .lambda..gtoreq..lambda..sub.0 .gtoreq..lambda..sub.p.