Low relative phase noise optical comb generation device
A purpose of the present invention is to provide a low relative phase noise optical comb generation device in which a repetitive frequency of an interference signal of an optical comb is stabilized by reducing a relative phase noise of driving signals with different frequencies for driving multiple optical comb generators in an optical comb distance meter. A low relative phase noise optical comb generation device, comprising: at least three oscillators 13, 13 A, 13 B for generating frequency signals with mutually different frequencies phase locked to a reference frequency signal F REF given by a reference oscillator 11 ; and at least two frequency converters 14 A, 14 B to which a frequency signal obtained by one oscillator 13 of the at least three oscillators and respective frequency signals obtained by respective oscillators 13 A, 13 B other than the one oscillator are input; wherein the at least two frequency converters 14 A, 14 B supply the at least two types of modulation signals, in which a relative phase noise is reduced respectively as a sum frequency signal or a difference frequency signal of the frequency signal by the one oscillator and a frequency signal by other oscillator with a lower phase noise, to at least two optical comb generators 15 A, 15 B as driving signals.
1. A low relative phase noise optical comb generation device, comprising:
at least three oscillators for generating frequency signals with mutually different frequencies;
at least two frequency converters to which a frequency signal obtained by one oscillator of the at least three oscillators and respective frequency signals obtained by respective oscillators other than the one oscillator are input; and
at least two optical comb generators to which at least two types of modulation signals with mutually different frequencies converted by the at least two frequency converters are supplied,
wherein the at least two frequency converters supply the at least two types of modulation signals, in which a relative phase noise is reduced respectively as a sum frequency signal or a difference frequency signal of the frequency signal by the one oscillator and a frequency signal by other oscillator, to the at least two optical comb generators as driving signals.
2. The low relative phase noise optical comb generation device according to claim 1 , wherein the respective oscillators other than the one oscillator of the at least three oscillators are having a phase noise lower than a phase noise of the one oscillator.
3. The low relative phase noise optical comb generation device according to claim 1 , wherein the at least three oscillators generate frequency signals with mutually different frequencies phase locked to a reference frequency signal given by a reference oscillator.
4. The low relative phase noise optical comb generation device according to claim 1 , wherein the at least two frequency converters are respectively a frequency mixer.
5. The low relative phase noise optical comb generation device according to claim 1 , wherein the at least two frequency converters are respectively composed of a frequency mixer, a phase comparator, and a voltage-controlled oscillator.
6. The low relative phase noise optical comb generation device according to claim 1 , wherein the modulation signals are supplied as driving signals from the at least two frequency converters to the at least two optical comb generators respectively via a band pass filter.
7. The low relative phase noise optical comb generation device according to claim 1 , wherein the frequency signal obtained by the one oscillator is input to the at least two frequency converters respectively via an isolator.
8. The low relative phase noise optical comb generation device according to claim 1 , wherein the at least three oscillators generate at least three types of frequency signals respectively in a state that a frequency is fixed to a frequency phase locked to the reference frequency signal by a PLL circuit.
9. The low relative phase noise optical comb generation device according to claim 3 , wherein the respective oscillators other than the one oscillator of the at least three oscillators are respective direct digital synthesizer (DDS) oscillators driven by a clock phase locked to the reference frequency signal.
10. The low relative phase noise optical comb generation device according to claim 3 , comprising: three oscillators for generating frequency signals with mutually different frequencies phase locked to the reference frequency signal; two frequency converters; and two optical comb generators,
wherein two types of modulation signals with reduced relative phase noise obtained by the two frequency converters are supplied to the two optical comb generators as driving signals.
11. The low relative phase noise optical comb generation device according to claim 3 , comprising: (X+Y) oscillators for generating frequency signals with mutually different frequencies phase locked to the reference frequency signal; XY frequency converters; and Y optical comb generators, wherein X is an integer of 1 or more and Y is an integer of two or more,
wherein a basic structure composed of (Y+1) oscillators, Y frequency converters, and Y optical comb generators is multiplexed by X.