A method for producing a low-noise RF signal based on optical regenerative oscillation from optical nonlinearity in an optical whispering gallery mode resonator, comprising: coupling laser light at an optical pump frequency into an optical whispering gallery mode resonator that supports whispering gallery modes and exhibits optical nonlinearity to cause both nonlinear optical mixing and parametric amplification by taking energy from the laser light at the optical pump frequency to generate light at a plurality of new optical frequencies different from the optical pump frequency; operating a modulation device that causes a modulation in the laser light based on a radio frequency signal containing an RF frequency and a plurality of RF harmonics of the RF frequency and being applied to the modulation device to produce modulated laser light having modulation bands correspond to the RF frequency and the plurality of RF harmonics inside the optical whispering gallery mode resonator and to cause nonlinear optical mixing of light in the optical whispering gallery mode resonator at the optical pump frequency and the modulation bands to transfer power from the optical pump frequency to the modulation bands; coupling light out of the optical whispering gallery mode resonator into a photodetector to produce an RF detector output at the RF frequency and the plurality of RF harmonics of the RF frequency based on demodulation at the photodetector of light at the optical pump frequency and the modulation bands; directing the RF detector output into an RF circuit that processes the RF signal based on the RF detector output, wherein the RF circuit comprises an RF filter interposed between the photodetector and an RF amplifier; operating the optical whispering gallery mode resonator, the modulation device, the photodetector and the RF circuit to form an active opto-electronic oscillator loop to sustain an opto-electronic oscillation to sustain the RF signal containing at least some of the RF frequency and the plurality of RF harmonics of the RF frequency in the RF circuit and to reduce a phase noise in the RF signal via the nonlinear optical mixing and filtering by the optical whispering gallery mode resonator; and configuring the RF circuit in the active opto-electronic oscillator loop to effectuate an RF passband that selects the some of the RF frequency and the plurality of RF harmonics of the RF frequency while eliminating other RF frequencies. coupling laser light at an optical pump frequency into an optical whispering gallery mode resonator that supports whispering gallery modes and exhibits optical nonlinearity to cause both nonlinear optical mixing and parametric amplification by taking energy from the laser light at the optical pump frequency to generate light at a plurality of new optical frequencies different from the optical pump frequency; operating a modulation device that causes a modulation in the laser light based on a radio frequency signal containing an RF frequency and a plurality of RF harmonics of the RF frequency and being applied to the modulation device to produce modulated laser light having modulation bands correspond to the RF frequency and the plurality of RF harmonics inside the optical whispering gallery mode resonator and to cause nonlinear optical mixing of light in the optical whispering gallery mode resonator at the optical pump frequency and the modulation bands to transfer power from the optical pump frequency to the modulation bands; coupling light out of the optical whispering gallery mode resonator into a photodetector to produce an RF detector output at the RF frequency and the plurality of RF harmonics of the RF frequency based on demodulation at the photodetector of light at the optical pump frequency and the modulation bands; directing the RF detector output into an RF circuit that processes the RF signal based on the RF detector output, wherein the RF circuit comprises an RF filter interposed between the photodetector and an RF amplifier; operating the optical whispering gallery mode resonator, the modulation device, the photodetector and the RF circuit to form an active opto-electronic oscillator loop to sustain an opto-electronic oscillation to sustain the RF signal containing at least some of the RF frequency and the plurality of RF harmonics of the RF frequency in the RF circuit and to reduce a phase noise in the RF signal via the nonlinear optical mixing and filtering by the optical whispering gallery mode resonator; and configuring the RF circuit in the active opto-electronic oscillator loop to effectuate an RF passband that selects the some of the RF frequency and the plurality of RF harmonics of the RF frequency while eliminating other RF frequencies.