JP3444958B2 - Optical comb generator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention
Many optical spectral lines required for the wavelength reference of the light source are constant
Are arranged at optical frequency intervals, and the optical frequency of each spectrum is
Optical comb generator for generating stable optical spectrums
In particular, the improvement of the intensity of this optical spectrum group, and
Increasing the number of optical spectrum lines that compose the optical spectrum group
Large, that is, the wavelength range in which the optical comb signal is generated (optical comb
Optical comb generator with expanded signal generation wavelength band)
About. 2. Description of the Related Art A conventional optical comb generator is shown in FIG.
Shown in The conventional optical comb generator includes an optical resonator 1 and its
The fleece of the optical resonator 1 shown in FIG.
Position of light at frequency fm in the μ-wave band corresponding to the spectrum range
Optical phase modulator 2 for performing phase modulation and modulation on optical phase modulator 2
It is composed of a modulation oscillator 3 for giving a signal. Next, the operation of the optical comb generator will be described.
You. Stabilizing the optical frequency near the resonance frequency of the optical resonator 1
Laser beam emitted from the stabilized wavelength light source
It enters the nerator. This incident laser light is
The free spectral lens of the optical resonator 1 is controlled by the phase modulator 2.
Phase modulation at the frequency fm corresponding to the
Several side modules are provided on both sides of the laser beam at an optical frequency interval of fm.
The light of the mode is generated [FIG. 8 (c)]. This side mode
Of the optical resonator 1 conforms to the resonance conditions of the optical resonator 1,
Is repeated by the reflecting mirrors 1a and 1b constituting
You. By repeating this reflection, the laser light is
2 further undergoes phase modulation, so each side mode
The light of the
This produces light in the mode (FIG. 8D). [0004] These side-mode lights are transmitted between optical frequencies.
Since the gap is fixed at fm, the overlap strength is increased.
[FIG. 8 (e)]. FIGS. 8C and 8D show the results shown in FIG.
To explain the state up to the normal state, as an example
One round trip and two round trips. As shown in FIGS.
As shown in the figure, the incident laser light of wavelength λ0
The level dropped during repeated round trips in
The level of the light in the id mode increases. Like this
The group of side mode light generated by
Due to the imperfect reflectivity of the resulting reflecting mirrors 1a and 1b
Transmitted to the outside and this transmitted light enters the optical comb generator
With the optical frequency interval of fm around the optical frequency of the laser light
An optical comb signal consisting of hundreds of optical spectrum lines
You. [0005] However, the prior art
In optical comb generators, the wavelength
The power of the emitted laser light is limited,
That the power of the modulated signal that can be applied to the
The wavelength range of the optical comb signal is limited to 20-40 nm.
waiting. On the other hand, a high
Accuracy broadband wavelength swept light source is used for spectroscopy and
A wavelength sweep range of 100 nm or more is required for evaluation
In order to realize that, 100nm or more
Optical comb generator that can generate comb signals in a wide wavelength range
Is required. An object of the present invention is to provide a wide wavelength range.
It is an optical comb signal, and the intensity of each spectral line is
Optical comb generator that can generate a large optical comb signal
Is to provide a lator. [0006] In order to solve the above problems,
In addition, the optical comb generator of the present invention is a wavelength stabilized light source.
Only light of a single wavelength is incident on the optical resonator.
Instead of the amplified optical comb signal,
) Are also configured to be incident light to the optical resonator. Sand
An optical resonator comprising a pair of optical resonator mirrors;
In order to change the optical path length between the mirrors.
An optical phase modulator disposed between a vibrator mirror and the optical phase modulator;
Providing a modulator with a modulation signal for changing the optical path length.
A modulation oscillator, and an output resonated and transmitted by the optical resonator.
Light that receives at least part of light and amplifies its optical power
An amplifier and at least a part of the light amplified by the optical amplifier
Optical feedback means for causing the optical resonator to enter the optical resonator again.
Was. The optical frequency is stabilized near the resonance frequency of the optical resonator.
Laser light emitted from the wavelength stabilized light source
Incident on. This incident laser light is transmitted by the phase modulator.
Frequency corresponding to the free spectral range of the optical resonator.
Because it is subjected to phase modulation at several fm,
Several side-mode lights are generated at an optical frequency interval of fm
You. This side mode light meets the resonance conditions of the optical resonator
Reflected by the optical resonator mirror that constitutes the optical resonator
repeat. Due to the repetition of this reflection, the laser light
Each side receives additional phase modulation by the phase modulator.
Mode light exposes itself as fundamental mode light.
To produce side mode light. These side modes
Of light is fixed because the optical frequency interval is fixed at fm.
Strengthen the bonding strength. Rhinos created in this way
Of light in the cavity mode
The light is transmitted to the outside due to imperfect reflectivity.
Fm light centered on the optical frequency of the laser light incident on the resonator
An optical core consisting of hundreds of optical spectral lines arranged at frequency intervals
Signal. The generated optical comb signal is amplified by an optical amplifier.
Then, the light is returned to the optical resonator by the optical feedback means. Incident again
Of each spectrum of the divided light (incident spectrum group)
The spectral frequency matches the resonance frequency of the optical resonator
Therefore, each spectrum becomes light in the fundamental mode.
Each generate a group of spectra. Again incident
Light (incident spectrum group) is amplified by an optical amplifier.
Moreover, each spectrum becomes light in the fundamental mode.
Therefore, each generates a group of spectra,
The wavelength range of the signal is wider and each spectral line is
Increase strength by combining. An embodiment of the present invention will be described below with reference to the drawings.
You. Figure 1 shows an optical fiber amplifier (fiber amplifier)
1 shows a schematic configuration of a first embodiment of the present invention used as a width device.
FIG. In the first embodiment, a pair of optical resonator mirrors 1
a and 1b, an oscillator 3 for modulation,
The mirror is disposed between the pair of optical resonator mirrors 1a and 1b.
Optical phase modulator driven by a modulation signal from tuning oscillator 3
2 and a first for splitting the output signal from the optical resonator 1 into two.
And the output of the first fiber coupler 6.
An optical fiber connected to one of the force ends by an optical fiber 8
A buffer amplifier 4 and an optical fiber 8
The optical isolator 9 to be connected and the optical isolator 9
A second one of the input ends connected by an optical fiber 8
Fiber coupler 7 and the other of the second fiber coupler 7
Of light located between the input end of the
Phase shifter 10, optical phase shifter 10 and second fiber
The other input end of the plastic 7, the output of the second fiber coupler 7
End and Optical Resonator 1, Optical Resonator 1 and First Fiber Coupler 6
, 22, 23 disposed between each of
And a control system for controlling the optical phase shifter 10.
Have been. Here, the first fiber coupler 6, the second
The fiber coupler 7 and the optical fiber 8 constitute optical feedback means.
Has formed. The control system includes the first fiber coupler 6
Beam splitter that splits the output light from the other output end of the
Of the light split by the beam splitter 26
Receiver 27 and the output terminal of the receiver 27
Connected to the output terminal of the amplifier 28
Phase detector 29, and the input terminal is the output of the phase detector 29.
And an output terminal for controlling the optical phase shifter 10.
An optical phase shifter controller 30 connected to the input end;
The modulation signal is supplied to the phase detector 29 and the optical phase shifter controller 30.
And a modulation signal source 31 for an optical phase shifter.
I have. Here, the optical resonator 1 and the optical phase modulator 2,
In addition, the optical phase shifter 10 will be described a little.
Optical resonator 1 and optical phase modulator used in the above embodiment
2 can be applied in any type.
A μ-wave resonator is used as the vibrator 1 and the phase modulator 2 is connected to the μ-wave resonator.
Formed by mounting dielectric bulk crystal inside the resonator
Or a traveling wave type waveguide on an optical waveguide formed on a dielectric substrate.
Alternatively, the phase modulator 2 is formed by forming a resonance type electrode.
Optical resonator with mirror coating on both end surfaces of the dielectric substrate
1 may be formed. The optical phase shifter 10 is generated in the optical resonator 1.
The standing wave of the laser light from the wavelength-stabilized light source 20
Of the fundamental mode of the optical comb signal re-entered into the resonator 1
The phase relationship of standing waves caused by light is matched, and the electric field
Laser from wavelength stabilized light source 20 to add width
Constant phase adjustment for light or re-entered optical comb signal light
Is applied. By doing so, in the optical resonator
Optical power loss can be prevented. Therefore, the optical comb generator
Of each optical element and the wavelength stabilizing light source 20 constituting the
If the relationship can be fixed to the point that phase adjustment is not required
The optical phase shifter 10 according to the first embodiment and its control
You don't need a system (just one guide for alignment)
Then, when the half wavelength is 0.7 μm, from the best positional relationship
If it is shifted by 0.7μm, the peaks and valleys of both standing waves will be exactly
The loss of the overlapping optical power is the largest). Also, the position
If the fluctuation of the relationship can be ignored,
By inserting a medium such as glass or optical fiber, an effective optical
Optical phase shifter that changes the optical distance by a fixed amount
A lid may be used. In the first embodiment, the wavelength stabilized light
The laser light from the light source 20 is subjected to phase adjustment,
Considering the fluctuation of the positional relationship during operation of the
Control of optical components or applying an electric field to a dielectric
An active optical phase shifter that changes the refractive index was used. Further, as in this embodiment, a fiber amplifier is used.
The problem with using a fiber is that it has a large noise figure.
When using an amplifier, the spontaneous emission light from the fiber amplifier
The reflection is repeated by the optical resonator mirror that constitutes the optical resonator,
And since it is amplified by the fiber amplifier, the optical comb signal
A phenomenon in which the S / N is degraded occurs. This
In this case, as in this embodiment, the light is emitted from the fiber amplifier 4.
The generated spontaneous emission light is reflected by the optical resonator mirrors 1a and 1b.
Optical isolator to prevent amplification by fiber amplifier 4
9 into the optical feedback system and fix the optical feedback direction.
No. In this way, the generated spontaneous emission light is
If it does not pass through the shaker 1, it is amplified by the fiber amplifier 4
Absent. Since the optical resonator 1 has the characteristics of an optical filter,
Spontaneous emission noise at optical frequencies not involved in vibration is removed here
Is done. For this reason, the spontaneous emission noise is band-limited and the intensity is
Attenuated and good S / N can be secured. The operation of the first embodiment will be described. External waves
A wavelength-stabilized light source 20 whose wavelength has been stabilized by a length criterion
The phase of the laser light emitted from the laser is adjusted by the optical phase shifter 10.
After that, the light is condensed by the condensing lens 21 and
It is guided to one input terminal of the baccoupler 7. The second file
The laser light emitted from the iva coupler 7 is a collimator lens
The light is collimated by 22 and is incident on the optical resonator 1. Light position
Modulating oscillator that is a high-frequency signal source for driving phase modulator 2
Reference numeral 3 denotes a circumference corresponding to the free spectral range of the optical resonator 1.
It outputs an AC signal of wave number fm, so
The laser light incident on the device undergoes phase modulation at the frequency of fm.
You. The frequency of the incident laser light is
Since the laser light matches the resonant optical frequency, the laser light
The optical phase modulation operation of the optical phase modulator 2 is performed every time the optical modulator 1 reciprocates in the optical disk 1.
The side mode light with the incident laser light as the fundamental wave
appear. The generated side mode light has an optical frequency of fm.
This optical frequency position is shared by the optical resonator 1.
Laser light belonging to each mode
Reciprocating in the optical resonator 1 ten to several hundred times,
Increasing the number of generated light. As a result, the free spectrum of the optical resonator 1 is obtained.
A number of side modules arranged at optical frequency intervals corresponding to the range
An optical comb signal composed of a group of light beams is generated. Outbreak
A part of the optical comb signal obtained is an optical resonator constituting the optical resonator 1.
The light passes through the mirror 1b. Optical output from optical resonator 1
System signal is condensed by the condensing lens 23 and the first fiber camera
It is branched by the plastic 6. One of the split lights is a fiber
Amplified by the amplifier 4 and passed through the optical isolator 9 to the second
Phase adjusted by optical phase shifter 10 by fiber coupler 7
The laser light from the wavelength stabilized light source 20 is multiplexed with
Optical cavity again as incident light whose optical frequency is arranged at fm intervals
1 is incident. The incident light reciprocates in the optical resonator 1.
Each time the light is included in the incident light by the optical phase modulation action of the optical phase modulator 2.
The light of all the modes that come in
It generates light in the mode. The generated side mode light is
fm at the optical frequency interval, and this optical frequency position is
In order to satisfy the resonance condition of the optical resonator 1, it belongs to each mode.
Laser light reciprocates tens to hundreds of times in the optical resonator
The number of light generated in the id mode is increased. As a result, the wavelength stabilized light source 2
When only laser light from 0 is incident on the optical resonator 1,
In addition, the free spectrum of the optical resonator 1 over a wide frequency range
Numerous sensors arranged at optical frequency intervals corresponding to the
An optical comb signal composed of a group of light in the id mode is generated.
You. Part of the generated optical comb signal constitutes the optical resonator 1
After passing through the optical resonator mirror 1b, the first
The light is branched by the fiber coupler 6 and one of the lights is amplified and combined.
The wave is then incident on the optical resonator 1 again. The other split light is a beam splitter.
It is branched again at 26, one is taken out as output light,
The other is used as light for controlling the optical phase shifter 10.
The light for controlling the optical phase shifter 10 has a light intensity of
7 is detected. This detection signal includes a change for the optical phase shifter.
Wave through the optical phase shifter controller 30 by the tone signal source 31
Optical phase modulation is applied to the laser light of the long stabilizing light source 20.
Therefore, it is amplified by the fiber amplifier 4 and again
Determination of the fundamental wave mode of the optical comb signal incident on 1
Standing by standing wave and laser light from wavelength stabilized light source 20
The phase shift between the waves is caused by the modulation signal source 31 for the optical phase shifter.
Since it occurs at a cycle corresponding to the output frequency,
A fluctuating intensity modulated signal is included. This signal is phase
Modulated signal source 31 for optical phase shifter which is input to detector 29
Is synchronously detected by the signal of. From the phase detector 29,
Signal strength is maximum, that is, both standing in the optical resonator 1
When the phases of the waves match, the level becomes 0, and the phase is delayed.
Only the + and-signals correspond to only the phase, dispersion type for the phase
Is obtained. Using this output signal, the optical phase
Negative feedback control to the optical phase shifter 10 through the shifter controller 30
Give it to you. By controlling in this way, the intensity of the optical comb signal
Can be stabilized in the maximum state. In this example
Is used to control the optical phase shifter 10 by branching the output light.
However, it is used by branching from the amplification feedback loop of the optical comb signal.
You may. In addition, such a phase control system will be described later.
Can also be used for examples. With such a configuration, several tens n
The optical comb signal itself spread over the wavelength range of m to the optical resonator 1
Of each mode forming the optical comb signal
The Hikari produces more optical comb signals, resulting in
Optical comb signal generation wavelength range compared to the optical comb signal
Are enlarged, and the power of each mode light is increased. FIG. 2 shows a conventional optical comb generator and the present invention.
The envelope of each optical comb signal of the optical comb generator
Show characteristics. In the figure, the vertical axis is an arbitrary scale. Figure
As can be seen from the optical comb generator of the present invention,
Optical comb signals are generated in a wider wavelength range than conventional ones.
Is expanded, and the signal is
Is increasing in strength. To the signal strength of each spectral line
In other words, from the relationship with the amplification factor of the optical amplifier, the fundamental wave
The rate of increase in the intensity of side mode light is greater than that of mode light.
No. FIG. 3 shows a semiconductor laser amplifier (traveling wave type or
Is a Fabry-Perot type) as an optical amplifier.
It is a figure showing the schematic structure of the 2nd example. Second embodiment
Consists of a small optical element for the feedback system of the optical comb signal
It is intended to be low-priced, but as in the first embodiment
A feedback system using a fiber coupler can also be used. In the second embodiment, a pair of optical resonator mirrors 1 is used.
a and 1b, an oscillator 3 for modulation,
The mirror is disposed between the pair of optical resonator mirrors 1a and 1b.
Optical phase modulator driven by a modulation signal from tuning oscillator 3
2 and a first for splitting the output signal from the optical resonator 1 into two.
Beam splitter 16 and the first beam splitter
Reflection that changes the optical path of one of the lights split at 16
And a mirror for receiving light reflected by the reflection mirror.
Semiconductor laser amplifier 14 and semiconductor laser amplifier 14
A reflection mirror 18 for changing the optical path of the light amplified by
Optical isolator 9 for receiving light reflected by reflection mirror 18
Receiving the laser beam from the wavelength stabilizing light source 20
Optical phase shifter 10 for shifting the phase, and optical phase shifter 1
0 and the light from the optical isolator 9 are multiplexed.
And a second beam splitter for outputting to the optical resonator 1.
17, the reflection mirror 18, and the input of the semiconductor laser amplifier 14.
And the output side 14b of the semiconductor laser amplifier 14
Condensing lens disposed between each of the reflecting mirrors 18
24 and a collimator lens 25.
The optical feedback means 5 includes a first beam splitter 16 and a second beam splitter 16.
It is composed of a beam splitter 17 and reflection mirrors 18, 18.
Has formed. The operation of the second embodiment will be described. Wavelength stable
The laser light emitted from the light source 20 is
After the phase is adjusted by the second beam splitter 17,
Through the optical resonator 1. Optical resonator 1, modulation source
The vibrator 3 and the optical phase modulator 2 are the same as in the first embodiment.
Operates and corresponds to the free spectral range of the optical resonator 1.
Group of side mode lights arranged at different optical frequency intervals
A configured optical comb signal is generated. Optical comb signal generated
Is partially transmitted through the optical resonator mirror 1b constituting the optical resonator 1.
Spend. The optical comb signal output from the optical resonator 1 is the first
The beam is split by the beam splitter 16. One of the branches
The light is reflected by the reflection mirror 18 and collected by the condenser lens 24.
The light is incident on the semiconductor laser amplifier 14. semiconductor
The light amplified by the laser amplifier 14 is the collimator lens 2
5, the light is collimated, reflected by the reflecting mirror 18, and
The second beam splitter 17 is provided via the
The wavelength stabilized light source whose phase has been adjusted by the optical phase shifter 10
It is combined with the laser light from 20. The multiplexed light is
The light is again shared as incident light with several optical frequencies arranged at fm intervals.
It is incident on the shaker 1. Hereinafter, a laser beam from the wavelength stabilizing light source 20 will be described.
Only when it is incident on the optical resonator 1 in a wider frequency range.
Over the free spectral range of the optical resonator 1
Of multiple side-mode lights arranged at corresponding optical frequency intervals
Operation up to generation of optical comb signal composed of groups is first
This is the same as the embodiment. One of the generated optical comb signals
The part transmits through the optical resonator mirror 1b constituting the optical resonator 1.
Then, as described above, the first beam splitter 16 branches.
And one of the lights is amplified and multiplexed, and the optical resonator 1
Incident on. The other split light is taken as output light.
Will be issued. The second embodiment is the same as the first embodiment.
Spontaneous emission light generated in the semiconductor laser amplifier 14
Is reflected by the optical resonator mirrors 1a and 1b, and the semiconductor laser
S / N degradation caused by amplification by the amplifier 14 was observed.
May be measured. To cope with this case, the optical feedback system
It is improved by inserting an isolator 9. The first and second embodiments described above.
Returns the amplified optical comb signal to the incident side of the optical resonator 1.
In this example, the optical comb signal is fed back to the output side of the optical resonator.
You can also. FIG. 4, FIG. 5, FIG.
6 and FIG. With such a configuration, an optical amplifier
And the optical feedback means are connected to the output port of a conventional optical comb generator.
The optical comb signal generation band can be expanded simply by attaching
Thus, an optical comb generator according to the present invention is obtained. Another perspective
Then, the optical amplifier 4 and the optical feedback means 5 are connected to the optical comb signal.
Can be used as an option to extend the bandwidth
It works. However, in such a configuration, spontaneous emission
S / N degradation of optical comb signal due to sound can be reduced.
Therefore, an optical amplifier with a low noise figure must be selected.
Must. FIG. 4 shows the optical fiber amplifier shown in FIG.
In a modification of the first embodiment used as an amplifier, an optical resonator
Configuration that re-enters the amplified optical comb signal from the output side of the
FIG. 9 is a diagram showing a schematic configuration of a third embodiment of the present invention. concrete
That is, the output of the optical resonator 1 is the first fiber cap.
The optical comb signal is branched into two by the
The signal is amplified by the fiber amplifier 4. Fiber Ann
The optical comb signal amplified and output from the loop 4 is
The light is further branched into two by the coupler 7, one of which is the output light.
Used as The other split optical comb signal is
The fiber 8 guides the first fiber coupler 6 to
Again from the output side of the optical resonator 1 via the coupler 6 of FIG.
It is. In addition, the other fiber branched by the first fiber coupler 6
The optical comb signal reverses the path of one of the optical comb signals described above.
Then, the light is again incident on the optical resonator 1 in the same manner. Also the waves
Laser light from long stabilizing light source 20 and re-entered optical comb
Phase matching with signal fundamental wave mode light
More taken. FIG. 5 is a diagram showing a schematic configuration of the fourth embodiment.
is there. As in the third embodiment shown in FIG.
The amplifier 4 amplifies the optical comb signal and outputs the amplified signal to the output side of the optical resonator 1.
This is a configuration in which light is re-incident from But in this case the output
The optical comb signal is amplified by the fiber amplifier 4 and
The light is branched into two by the coupler 6. Fiber coupler 6
Of the two output fibers 8, 8, one end face 8a
Has a mirror coating. For this reason, the branch
The other optical comb signal is used externally as an output signal,
The other optical comb signal is reflected by the reflection mirror on the fiber end face 8a.
Reflected by the fiber coupler 6 and the fiber amplifier 4
Via the output side of the optical resonator 1 again. FIGS. 6 and 7 show the second embodiment shown in FIG.
Laser diode amplifier (traveling wave type and Fabry-Perot)
Type) for the optical amplifier, and the optical
This is an example of the case where the
It is a figure showing a schematic structure of an example and a sixth example. The fifth embodiment shown in FIG. 6 is similar to that shown in FIG.
As in the third embodiment, an optical amplifier is provided on the output side of the optical resonator 1.
The optical feedback system included in the loop is configured. Third fruit
The difference from the embodiment is that the semiconductor laser amplifier 1 is used as an optical amplifier.
4 is used, and the components that make up the loop
Beam splitters 16 and 17 instead of
And the reflection mirrors 18, 18. The sixth embodiment shown in FIG. 7 is similar to that shown in FIG.
As in the fourth embodiment, the optical comb signal is
Configuration that branches and returns one signal to the optical resonator with a reflection mirror
It is. The difference from the fourth embodiment is that the semiconductor
Laser amplifier 14 and beeper as light feedback means.
The point that the splitter 16 and the reflection mirror 18 are used
You. The configuration as in the third to sixth embodiments can be adopted.
Also, as in the first and second embodiments, several tens of nm
The optical comb signal itself spread over the wavelength range becomes the incident light,
The laser light in each mode that forms the comb signal
To generate a signal, compared to a conventional optical comb signal
The wavelength range of optical comb signal generation is expanded,
Optical comb generator that generates an optical comb signal with increased power
Become According to the optical comb generator of the present invention,
Mode power is large, and generated wave of 100nm or more
Optical comb signal with long range can be obtained, so high accuracy and wide band
It can also be used as a wavelength reference for a swept wavelength light source,
The degree can be dramatically improved. As described above, the optical comb of the present invention can be used.
The light emitted from the optical resonator (spectrum
Optical amplifier for amplifying the group) and returning to the optical resonator after amplification
Optical feedback means for controlling
It is not possible to use only light with a wavelength of
Light (a spectrum group) that amplifies the generated optical comb signal
Is also made to be the incident light to the optical resonator.
Increase the number of wavelengths to have a wavelength range of 100 nm or more,
First, an optical comb signal with a large signal strength in each laser light mode
It can be output.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a schematic configuration of a first embodiment of the present invention. FIG. 2 is a diagram illustrating envelope characteristics of optical comb signals of a conventional optical comb generator and an optical comb generator of the present invention. FIG. 3 is a diagram showing a schematic configuration of a second embodiment of the present invention. FIG. 4 is a diagram showing a schematic configuration of a third embodiment of the present invention. FIG. 5 is a diagram showing a schematic configuration of a fourth embodiment of the present invention. FIG. 6 is a diagram showing a schematic configuration of a fifth embodiment of the present invention. FIG. 7 is a diagram showing a schematic configuration of a sixth embodiment of the present invention. 8A and 8B are diagrams illustrating an optical comb generator, FIG. 8A is a diagram illustrating a schematic configuration of a conventional optical comb generator, FIG. 8B is a diagram illustrating resonance characteristics of an optical resonator, and FIG. FIG. 4D is a diagram showing a laser spectrum when laser light makes one round trip in the chamber, FIG. 4D shows a laser spectrum when laser light makes two round trips in the optical resonator, and FIG. FIG. 3 is a diagram showing a laser spectrum when light reciprocates a large number of times and enters a steady state. [Description of Signs] 1 Optical resonators 1a, 1b Optical resonator mirror 2 Optical phase modulator 3 Modulating oscillator 4 Fiber amplifier (optical amplifier) 5 Optical feedback means 6 Fiber coupler (first fiber coupler) 7 Second Fiber coupler 8 Optical fiber 9 Optical isolator 10 Optical phase shifter 14 Semiconductor laser amplifier (optical amplifier) 16 Beam splitter (first beam splitter) 17 Second beam splitter 18 Reflection mirror 20 Wavelength stabilized light source 21 Lens (condensing lens) 22 lens (collimator lens) 23 lens (condenser lens, collimator lens) 24 lens (condenser lens) 25 lens (collimator lens) 26 beam splitter 27 light receiver 28 amplifier 29 phase detector 30 optical phase shifter controller 31 light Modulation signal source for phase shifter

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Claims (1)

(57) Claims 1. An optical comb generator for generating an optical comb signal by receiving a laser beam from a wavelength stabilized light source, comprising: a pair of optical resonator mirrors (1a, 1b). A resonator (1), an optical phase modulator (2) arranged between the pair of optical resonator mirrors for changing an optical path length between the optical resonator mirrors, and the optical phase modulator having the optical path length. A modulation oscillator (3) for providing a modulation signal to be changed, an optical amplifier (4) for receiving at least a part of the output light transmitted through the optical resonator and amplifying the optical power, and an amplification by the optical amplifier Optical feedback means (5) for returning at least a part of the obtained light to the optical resonator.