Low-noise, switchable RF-lightwave synthesizer

A method of producing a local oscillator signal comprising the steps of:

• generating a reference frequency signal;
• generating a master optical signal based on the reference frequency signal, the master optical signal having multiple modes, each of the multiple modes having a different optical frequency;
• generating a primary slave optical signal having a primary slave signal frequency at or near a frequency of one of the multiple modes of the master optical signal;
• generating a secondary slave optical signal having a secondary slave signal frequency different than the primary slave signal frequency and at or near a frequency of one of the multiple modes of the master optical signal;
• coupling the primary slave optical signal and the secondary slave optical signal to produce a local oscillator optical signal;
• and
• combining the local oscillator optical signal and the reference frequency signal to produce a secondary slave correction signal to control the secondary slave signal frequency.

A frequency synthesizer having one or more local oscillator outputs, the frequency synthesizer comprising:

• an oscillator generating a reference signal at a reference frequency;
• a master laser receiving the reference signal and generating a master optical output having multiple optical modes, the multiple optical modes being at different mode frequencies and related to the reference frequency;
• means for generating a primary slave optical output;
• and
• at least one optical local oscillator output circuit, each optical local oscillator output circuit producing a local oscillator output of the one or more local oscillator outputs, each optical local oscillator circuit comprising;
• a secondary slave laser receiving the master optical output and being tuned to one of the multiple optical modes to generate a secondary slave optical output;
• an optical coupler receiving the primary slave optical output and the secondary slave optical output and producing the optical local oscillator output;
• and
• a switchable heterodyne phase-lock loop receiving the optical local oscillator output and the reference signal and producing a secondary feedback correction signal coupled to the secondary slave laser.

A frequency converter receiving an input electrical signal at a first frequency and producing an electrical carrier signal at a second frequency and a modulated electrical signal at the second frequency, the frequency converter comprising:

• a reference oscillator generating a reference signal at a reference frequency;
• a master laser coupled to the reference oscillator and generating a master optical output having multiple optical modes, the multiple optical modes being at different mode frequencies and related to the reference frequency;
• a primary slave laser receiving the master optical output and being tuned to one of the multiple optical modes to generate a primary slave optical output;
• a secondary slave laser receiving the master optical output and being tuned to a different one of the optical modes to generate a secondary slave optical output;
• an optical coupler receiving the primary slave optical output and the secondary slave optical output and producing an optical local oscillator output;
• a switchable heterodyne phase-lock loop receiving the optical local oscillator output and the reference frequency and producing a secondary feedback correction signal for the secondary slave laser
• a band-limited homodyne phase-lock loop receiving the primary slave optical output and the master optical output and producing a primary feedback correction signal coupled to the primary slave laser;
• a first photo-detector receiving the optical local oscillator output and producing the electrical carrier signal at the second frequency
• a lightwave modulator receiving the optical local oscillator output and the input electrical signal and producing a modulated optical output signal;
• and
• a second photo-detector receiving the modulated optical output signal and producing the a modulated electrical signal at the second frequency.