| 摘要 |
PURPOSE:To keep a stable optical frequency interval by generating a 2nd beat signal with a frequency of a beat signal caused between two carrier optical frequencies and a frequency of a reference frequency oscillator, using the signal frequency as an error sign and feeding back the result to a light source of one carrier optical frequency. CONSTITUTION:An electric beat signal SR (1st beat signal) of a frequency corresponding to the optical frequency interval of signal lights L1,L2 radiated from a reference light source 1 and a reference light source 2 is obtained as an output of a photodetector 7. Moreover, a mixer 8 synthesizes the electric beat signal SR of the photodetctor 7 with an output of a reference frequency oscillator 9 oscillating the frequency of the reference electric signal to extract a 2nd beat signal SR0. Then an optical frequency control circuit 10 changes the low frequency electric beat signal SR0 being an error signal into a DC signal S1, which is superimposed onto a bias voltage (current) to apply feedback control to the reference light source 2. Thus, the relatively stable optical frequency interval is controlled. |
