Method and device for stabilization of optical power and spectral line of radiation by mode locked ultra-short pulse fiber laser

A mode locked broadband ultrashort light pulse fiber oscillator based on a nonlinear polarization rotation (NPR) of light comprising:

• a unidirectional fiber ring resonator operative to generate a train of ultrashort light pulses each having a broad range of frequencies, the fiber ring resonator including at least one light polarization controller unit;
• and
• an optoelectronic control feedback loop receiving a portion of light, which is tapped off from the ring resonator, and having at least first, second and one or more third control channels, the first control channel receiving a first unfiltered fraction of the tapped portion with the broad range of frequencies, the second control channel receiving a second filtered fraction of the tapped portion with a narrow range of frequencies which is filtered from within the broad range, the control feedback loop being configured to evaluate the received first unfiltered and second filtered fractions and output a control signal if a predetermined criterion is not met, wherein the one polarization controller unit receives the control signal and, in response thereto, is operative to change a state of polarization of the ultrashort light pulses circulating within the fiber ring resonator so that the criterion is met,
• the one third control channel receiving a third unfiltered fraction of the tapped portion in parallel to the first and second controlled channels, the third channel including an optical spectrum analyzer operative to process the received third fraction and determine relative strengths of respective DC and high frequency components in the third unfiltered fraction, with the high frequency component corresponding to a pulse repetition rate and indicative of a mode-locked regime.