CN202853879U - Optical resonant frequency difference accurate measuring device - Google Patents
Optical resonant frequency difference accurate measuring device Download PDFInfo
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- CN202853879U CN202853879U CN 201220382289 CN201220382289U CN202853879U CN 202853879 U CN202853879 U CN 202853879U CN 201220382289 CN201220382289 CN 201220382289 CN 201220382289 U CN201220382289 U CN 201220382289U CN 202853879 U CN202853879 U CN 202853879U
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Abstract
The present utility model discloses an optical resonant frequency difference accurate measuring device. The device comprises a laser, a signal generator, an intensity modulator, a split light beam device, a pair of resonators, an luminous intensity signal conversion device and a phase demodulator; laser generated by the laser is subjected to intensity modulation by the intensity modulator according to signals of the signal generator, a pair of optical sideband signals are generated through the split light beam device and respectively pass into the pair of resonators, reflected light of the resonators are converted into intensity signals through the luminous intensity signal conversion device, then the signals are demodulated by the phase demodulator. In an optical resonant frequency difference accurate measuring method, the sideband modulation technology is adopted to accurately measure and compare resonant frequency of the resonators, sidebands are generated by the intensity modulator, each group of sidebands are provided with three components with fixed phase and intensity relation, and two groups of sidebands are respectively used for detecting resonant frequency of the different resonators, and the phase demodulator is used for demodulating. High precision and wide range measuring of resonant frequency difference of the resonators can be realized at the same time.
Description
Technical field
The utility model relates to a kind of poor accurate measuring technique of resonance frequency of different optical resonator.
Background technology
Optical resonantor comprises Fabry-Perot interferometer and optic fiber ring-shaped cavity etc., is the basic structure of multiple optical gauge.Take Fabry-Perot interferometer as example, the resonance frequency f of interferometer
kSatisfy:
f
k＝kc/(2nl)
Wherein, l is the length of interferometer, and n is the refractive index in the interferometer, and c is the light velocity, and k is any positive integer.By following formula as seen, by measuring the resonance frequency of resonator, can obtain the information of length and refractive index, and then realize the sensing of the many kinds of parameters such as distance, temperature, strain, refractive index, the precision of its sensing depends on the measuring accuracy of optical resonantor frequency.To quasi-static signal, and based on the measurement of the signal of difference such as shear strain etc., need accurately the relatively resonance frequency of two different resonators.
The method that present high precision resonance frequency measuring technique adopts the light position to modulate mutually.Modulate mutually by laser is carried out the position, make the instantaneous frequency of laser be sinusoidal rule variation with frequency omega; Then measure its reflection (or transmission, lower with) light intensity.When the centre frequency off-resonance frequency of laser, comprise the item that frequency is Ω in the frequency spectrum of catoptrical light intensity.When the centre frequency of laser is consistent with resonance frequency, because the symmetry of reflectance curve will not comprise the composition that frequency is Ω in the reflective light intensity.Intensity by Ω item in the demodulation reflective light intensity and position are mutually, can accurately detect the difference (R.W.P.Drever between the resonance frequency of laser center frequency and resonator cavity, et al., " Laser Phase and Frequency Stabilization Using an Optical-Resonator; " Applied Physics B-Photophysics and Laser Chemistry, vol.31, pp.97-105,1983.).Compare with the light intensity reflectivity of direct-detection resonator cavity, this method is insensitive to the intensity noise that light source, optical receiver and light path Distributed reflection cause, thereby can obtain high freuqency accuracy.But the restituted signal that this technology obtains only is being not more than the FWHM(Full width at half maximum of resonator spectral line width, full width at half maximum) in the scope, its restituted signal is just linear with the difference on the frequency of laser resonant cavity.In order to measure the difference of two resonance frequencies, current a kind of method is to use with a branch of laser to survey simultaneously this two resonance frequencies, and the size (J.H.Chow of its restituted signal of comparison, et al., " Demonstration of a passive subpicostrain fiber strain sensor, " Optics Letters, vol.30, pp.1923-1925,2005).The measurement range of this method is not more than the FWHM of resonator, if increase FWHM, then can reduce sensitivity and the precision of measurement.It is to use tunable laser that current another kind is measured the poor method of resonance frequency, frequency by scan laser, obtain respectively the frequency of two resonators laser when realizing resonance, subtract each other the difference (Q.Liu that just can obtain two resonance frequencies, et al., " Ultra-high-resolution large-dynamic-range optical fiber static strain sensor using Pound-Drever-Hall technique; " Opt.Lett., vol.36, pp.4044-4046,2011.).In this method, non-linear in carrying out large frequency range scanning process of laser limited the precision that resonance frequency is measured, and along with the increase of resonance frequency difference, the laser frequency sweep limit also will increase, and the precision that difference on the frequency is measured can descend thereupon.
The utility model content
In order to solve the precision measured in two resonant frequency processes and the contradiction of measurement range size, the utility model provides a kind of New measuring technique, this technology can realize the accurate comparison of two resonator cavity frequencies, and its measurement range is not subjected to the restriction of resonator cavity FWHM, and only depends on the frequency of electronic radio-frequency modulation signal.
The utility model adopts following technical scheme for achieving the above object:
A kind of optical resonance difference on the frequency device for accurately measuring is characterized in that: comprise laser instrument, signal generator, intensity modulator, divided beams device, a pair of resonator, light intensity signal conversion equipment and phase demodulation device; The laser that described laser instrument produces according to the signal of signal generator after the intensity modulator intensity modulated, produce a pair of optics sideband signals through the divided beams device again, enter respectively a pair of resonator, the reflected light of described resonator converts strength signal to through the light intensity signal conversion equipment, again by the demodulation of phase demodulation device.
Preferably: described resonator is Fabry-Perot interferometer.Described phase demodulation device is I/Q quadrature demodulation chip.
A kind of optical resonance difference on the frequency accurate measurement method, adopt the sideband modulation technology accurately to measure and compare the resonance frequency of resonator, it is characterized in that: sideband is produced by intensity modulator, each group sideband has three compositions with fixed bit phase and strength relationship, two groups of sidebands are respectively applied to survey the resonance frequency of different resonators, and with the demodulation of phase demodulation device.
The utility model can be realized high precision and the large range measuring poor to the resonance frequency of resonator simultaneously.
Description of drawings
Fig. 1 is the utility model apparatus structure synoptic diagram;
Laser is laser instrument among the figure, and IM is intensity modulator, and FG1 and FG2 are signal generators, CP is beam splitter, and CIR is the light gyroscope, and FPI 1 and FPI 2 are a pair of Fabry-Perot interferometers, PD is photodiode, and PDM is I/Q phase demodulation device, and Computer is computer;
Fig. 2 is frequency and the phase relation figure of sideband;
Fig. 3 is phase demodulation device structural representation;
IQ Demodulator is I/Q phase demodulation device among the figure, and PHASE SPLITTER is phase-splitter, and DAQ is data acquisition, and LPF is low-pass filter; Program is program;
Fig. 4 is the signal waveforms that demodulates.
Embodiment
A kind of optical resonance difference on the frequency device for accurately measuring comprises laser instrument, signal generator, intensity modulator, divided beams device, a pair of resonator, light intensity signal conversion equipment and phase demodulation device as shown in Figure 1; The laser that described laser instrument produces according to the signal of signal generator after the intensity modulator intensity modulated, produce a pair of optics sideband signals through the divided beams device again, enter respectively a pair of resonator, the reflected light of described resonator converts strength signal to through the light intensity signal conversion equipment, again by the demodulation of phase demodulation device.
Laser is Ω by the centre frequency of particular design
SRadiofrequency signal carry out intensity modulated, produce a pair of optics sideband signals.The centre frequency of two pairs of sideband signals has difference 2 Ω
S, thereby can to survey respectively simultaneously two centre frequency differences be 2 Ω
S2 resonators; Simultaneously, for each roadside band signal, its instantaneous frequency is all with frequency omega
MBe sinusoidal rule and change, the reflective light intensity medium frequency is Ω
MComposition intensity with the position mutually can be by the demodulation of phase demodulation device out.
Laser after the intensity modulated is divided into two-way, and two sidebands are used to respectively survey the resonance frequency of 2 different resonators, by adjusting centre wavelength and the modulating frequency Ω of laser instrument
S, so that the two-way sideband signals lays respectively on the resonance frequency of resonator cavity to be measured.By the wavelength of scanned laser, demodulate the difference on the frequency of signal from 2 resonator reflective light intensities, add 2 Ω
SBe the actual frequency difference of two resonators.Ω in this measurement scheme
SFrequency determined measurement range, irrelevant with the FWHM of optical resonantor.
Below in conjunction with drawings and Examples the utility model is further specified.
Among Fig. 1, Laser is laser instrument, and IM is intensity modulator, and FG1 and FG2 are signal generators, and its signal that produces is as follows:
FG1＝sin(Ω
Mt)，FG2＝sin(Ω
St)+2sin(Ω
St+Ω
Mt)-sin(Ω
St-Ω
Mt)
CP is beam splitter, and CIR is the light gyroscope, and FPI 1 and FPI 2 are a pair of Fabry-Perot interferometers to be measured, and PD is photodiode.PDM is I/Q phase demodulation device.
The driving signal FG2 of intensity modulator IM comprises three frequency contents with fixed bit phase and strength relationship.By laser is carried out intensity modulated, two groups of sidebands about laser center frequency symmetry have been produced, as shown in Figure 2.Each group sideband all has the frequency identical with FG2 and phase relation, and the result of this combination is that its instantaneous frequency is with frequency omega
MBeing sinusoidal rule changes.The centre frequency of two groups of sidebands differs 2 Ω
SBy adjusting centre wavelength and the Ω of laser instrument
SSize, these two groups of sideband signals can be adjusted to that the resonance frequency with a resonator is consistent respectively.
After the light signal that is reflected back from FPI is converted to strength signal by PD, by phase demodulation device PDM demodulation out.The structure of PDM as shown in Figure 3, reference signal g (Ω t) produces the orthogonal signal that 2 tunnel frequencies are identical, the position differs pi/2, signal f to be demodulated (t) is then adjusted through the position mutually by the respectively demodulation of these two-way orthogonal signal, at last synthetic one road signal.Compare with existing phase demodulation device, this detuner utilizes program to carry out the position and adjusts mutually, do not need analog shifter circuit (J.H.Chow, et al., " Demonstration of a passive subpicostrain fiber strain sensor, " Optics Letters, vol.30, pp.1923-1925,2005), conveniently be applied to automatic measurement system.
By the centre frequency of tuned laser, each group sideband all scans in corresponding resonance frequency, and the signal that demodulates as shown in Figure 4, and is identical with the restituted signal of current position phase modulation scheme, all has the insensitive characteristics of intensity noise.By calculating the difference of two resonance frequencies in the restituted signal, add 2 Ω
S, namely obtain the actual frequency difference of two resonator cavitys.In the experiment, the measuring accuracy of the difference of two resonance frequencies that calculate from restituted signal is better than 100kHz.Ω
SProduced by electronic device, its frequency accuracy is better than 1Hz.Therefore, the measuring accuracy of the difference of two resonance frequencies is better than 100kHz. by means of the effect of moving of sideband, and the measurement range of this system only depends on Ω
SFrequency Of Signal Generator, be not subjected to the restriction of resonator FWHM, thereby can realize large measurement range.Obtain the measurement range greater than 2GHz in the experiment, only be subject to Ω
SThe frequency range of signal generator.
Claims (3)
1. an optical resonance difference on the frequency device for accurately measuring is characterized in that: comprise laser instrument, signal generator, intensity modulator, divided beams device, a pair of resonator, light intensity signal conversion equipment and phase demodulation device; The laser that described laser instrument produces according to the signal of signal generator after the intensity modulator intensity modulated, produce a pair of optics sideband signals through the divided beams device again, enter respectively a pair of resonator, the reflected light of described resonator converts strength signal to through the light intensity signal conversion equipment, again by the demodulation of phase demodulation device.
2. a kind of optical resonance difference on the frequency device for accurately measuring according to claim 1, it is characterized in that: described resonator is Fabry-Perot interferometer.
3. a kind of optical resonance difference on the frequency device for accurately measuring according to claim 1, it is characterized in that: described phase demodulation device is I/Q quadrature demodulation chip.
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| CN 201220382289 CN202853879U (en) | 2012-08-03 | 2012-08-03 | Optical resonant frequency difference accurate measuring device |
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| CN 201220382289 CN202853879U (en) | 2012-08-03 | 2012-08-03 | Optical resonant frequency difference accurate measuring device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102818695A (en) * | 2012-08-03 | 2012-12-12 | 无锡联河光子技术有限公司 | Accurate measurement device for optical resonance frequency difference and method thereof |
| CN104048617B (en) * | 2014-07-09 | 2017-02-01 | 中国科学院半导体研究所 | Sensing modulating method for high-precision fiber bragg grating insensitive to polarization state changes |
-
2012
- 2012-08-03 CN CN 201220382289 patent/CN202853879U/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102818695A (en) * | 2012-08-03 | 2012-12-12 | 无锡联河光子技术有限公司 | Accurate measurement device for optical resonance frequency difference and method thereof |
| CN104048617B (en) * | 2014-07-09 | 2017-02-01 | 中国科学院半导体研究所 | Sensing modulating method for high-precision fiber bragg grating insensitive to polarization state changes |
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|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CX01 | Expiry of patent term |
Granted publication date: 20130403 |
|
| CX01 | Expiry of patent term |