Patent ID: 6898221

Claim:
An apparatus for frequency tuning and locking for use with an optical source tunable over an optical frequency range and producing an output beam of light having a frequency comprising a first reference element having an output power that varies monotonically with input frequency over the operating frequency range and being adapted to receive at least a portion of the output beam of light, the first reference element producing a first reference beam of light, a second reference element having an output power that is frequency dependent and being adapted to receive at least a portion of the output beam of light, the second reference element producing a second reference beam of light, a first optical detector for measuring the power of the first reference beam of light and producing a first reference signal, a second optical detector for measuring the power of the second reference beam of light and producing a second reference signal and electronic circuitry coupled to the first and second optical detectors for receiving the first and second reference signals and producing a coarse error signal for permitting coarse adjustment of the frequency of the output beam of light and a fine error signal for permitting fine adjustment of the frequency of the output beam of light.