CN202547780U - Broadband reference light source optical frequency domain vernier method spectrograph - Google Patents
Broadband reference light source optical frequency domain vernier method spectrograph Download PDFInfo
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- CN202547780U CN202547780U CN2012201069903U CN201220106990U CN202547780U CN 202547780 U CN202547780 U CN 202547780U CN 2012201069903 U CN2012201069903 U CN 2012201069903U CN 201220106990 U CN201220106990 U CN 201220106990U CN 202547780 U CN202547780 U CN 202547780U
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Abstract
The utility model discloses a broadband reference light source optical frequency domain vernier method spectrograph. The spectrograph comprises an incident collimating lens; a broadband light source; an amplitude modulator for modulating frequency-stabilized reference light wave into an amplitude modulation light wave; an optical fiber coupler for superposing the amplitude modulation light wave with the incident light to be measured from the incident collimating lens; a tunable F-P (Fabry-Perot) interferometer for selecting one monochromatic light wave from the light waves from the optical fiber coupler through tuning the cavity length to pass; an F-P (Fabry-Perot) etalon for extracting light wave having a specific frequency from the tunable F-P interferometer; a low pass filter for extracting an electrical signal generated by the light waves to be measured of an photoelectric signal; a band-pass filter for extracting an electrical signal generated by the broadband light source of the photoelectric signal; a power measurement module; and a wavelength demodulation module. The broadband reference light source optical frequency domain vernier method spectrograph provided by the utility model realizes selection of light frequency; can tune the cavity length of a resonant cavity within a narrow range, and avoid technical problems caused by movable parts.
Description
Technical field
The utility model relates to reference light source optical frequency territory, a kind of broadband vernier method spectrometer, belongs to the spectrographic detection field, can be applied to the fields such as mensuration, optical communication and Fibre Optical Sensor of the absorption spectrum of material.
Background technology
The prior art of measuring spectrum mainly contains two types at present.One type is that light wave with different wave length is distributed on the different direction in spaces, and wherein common beam splitter is prism and grating.Another kind of is that light wave with different wave length separates in time, and wherein Fourier transform spectrometer, commonly can utilize Michelson interferometer or Mach-Zehnder interferometer to realize.
One of formerly technological; Utilize grating that the light wave of different wave length is distributed to different direction in spaces; Utilize linear detector array or linear image sensor (like CCD or cmos image sensor) to survey the power of different wave length light wave, obtain spectrum to be measured thus.The advantage of this method is: response speed is fast, and wavelength resolution also can be very high.Shortcoming mainly is to need bigger distance between detector and the grating, thereby causes the machining difficulty, the equipment heavy, and cost an arm and a leg.
Formerly two of technology, light wave is imported a Michelson-or Mach-Zehnder interferometer, the light wave of output is the coherent light of the light wave that transmits in two arms, its power is the function of wavelength and phase differential.Through regulating the length of a light arm, change phase differential, can obtain luminous power with the long variation in chamber.And the relation of spectrum and this signal just in time is the cosine Fourier transform, therefore, through finding the solution inverse Fourier transform, can obtain spectrum to be measured.The advantage of this method is that spectrographic detection scope and wavelength resolution are all very high.Shortcoming is: expend time in very much, can not measure and change spectrum faster; Have moving component, also very high to the requirement of machining; Equipment is also huge and expensive.Therefore how to overcome above-mentioned technical matters in the prior art, become the direction that those of ordinary skills make great efforts.
Summary of the invention
The utility model purpose provides reference light source optical frequency territory, a kind of broadband vernier method spectrometer, and it has avoided using bigger Michelson interferometer and the grating-image sensor architecture of volume, and realizes the light frequency selection; And can be on very little amplitude the chamber of tuned resonating cavity long, avoided adopting the technical matters that movable part produced.
For achieving the above object, the technical scheme that the utility model adopts is: a kind of optical frequency territory vernier method spectrometer that is used for the frequency selection comprises:
The incident collimation lens is used for incident light to be measured is coupled into optical fiber;
Electro-Optical Sensor Set is used for light wave is converted into electric signal;
Pre-amplifying module is used for the electric signal from said Electro-Optical Sensor Set is carried out processing and amplifying;
Wideband light source is used to provide a frequency stabilization benchmark light wave;
Amplitude modulator will be modulated to an amplitude modulation(PAM) light wave from the frequency stabilization benchmark light wave of said wideband light source;
Fiber coupler, will from said amplitude modulator amplitude modulation(PAM) light wave be superimposed from the incident light to be measured of said incident collimation lens;
Tunable F-P interferometer, it selects a series of monochromatic optical wave to pass through in from said fiber coupler light wave through tuning cavity length;
The F-P etalon is used for extracting the light wave from said tunable F-P interferometer CF;
Low-pass filter is used for extracting the electric signal that photosignal light wave to be measured is produced;
BPF., the centre frequency of the passband of BPF. equals the frequency of said amplitude modulator, is used for extracting the electric signal that the photosignal wideband light source is produced;
Power measurement module according to calculating luminous power from said low-pass filter electric signal, is measured and is write down the light wave of different frequency in the light wave to be measured successively and store the luminous power data;
The Wavelength demodulation module according to the signal from said BPF., is used to analyze the frequency of current measured light wave.
Because the technique scheme utilization, the utility model compared with prior art has advantage and effect:
1, the utility model utilizes the very little resonator cavity of two volumes to realize the function that light frequency is selected, avoided using the bigger Michelson interferometer of volume, or the free space propagation distance of growing in grating-image sensor architecture.
2, the utility model only needs a photodetector, has avoided using the imageing sensor of expensive instrument level.
3, the utility model only need be on very little amplitude in the process of scan light frequency the chamber of tuned resonating cavity long.Therefore can adopt means such as electrooptical modulation, avoid adopting the problem that movable part caused.
4, the spectral resolution of the utility model can reach high resolving accuracy at an easy rate by the Free Spectral Range decision of etalon.
Description of drawings
Fig. 1 is the structure of the utility model;
Fig. 2 is the power transmission spectrum of resonator cavity;
Fig. 3 is the power transmission spectrum of F-P etalon and tunable F-P interferometer;
Fig. 4 is for realizing frequency sweeping through tuning tunable F-P interferometer;
Fig. 5 is the voltage signal of tuned resonance cavity length.
In the above accompanying drawing: 1, incident collimation lens; 2, tunable F-P interferometer; 3, F-P etalon; 4, Electro-Optical Sensor Set; 5, pre-amplifying module; 6, fiber coupler; 7, wideband light source; 8, amplitude modulator; 9, low-pass filter; 10, BPF.; 11, power measurement module; 12, Wavelength demodulation module; 13, fibre optic isolater.
Embodiment
Below in conjunction with accompanying drawing and embodiment the utility model is further described:
Embodiment: a kind of optical frequency territory vernier method spectrometer that is used for the frequency selection shown in accompanying drawing, comprising:
Electro-Optical Sensor Set 4 is used for light wave is converted into electric signal;
Pre-amplifying module 5 is used for the electric signal from said Electro-Optical Sensor Set 4 is carried out processing and amplifying;
Wideband light source 7 is used to provide a frequency stabilization benchmark light wave;
Fiber coupler 6, will from said amplitude modulator 8 amplitude modulation(PAM) light waves be superimposed from the incident light to be measured of said incident collimation lens 1;
Low-pass filter 9 is used for extracting the electric signal that photosignal light wave to be measured is produced;
BPF. 10, the centre frequency of the passband of BPF. 9 equals the frequency of said amplitude modulator 8, is used for extracting the electric signal that the photosignal wideband light source is produced;
Be provided with a fibre optic isolater 13 between above-mentioned F-P etalon 3 and the tunable F-P interferometer 2, be used to isolate reflected light.
Foregoing is further set forth as follows.
According to the knowledge of multiple-beam interference, the power transmission spectrum of resonator cavity presents pectination, and is as shown in Figure 2.Wherein Free Spectral Range (chamber longitudinal mode spacing) is inversely proportional to the interior light path (it is long to abbreviate the chamber as) of resonator cavity.The width of chamber longitudinal mode, just the width of transmitted spectrum is determined by fineness.Fineness is high more, and the shape of longitudinal mode is sharp-pointed more, and the longitudinal mode width D is narrow more.
Have the resonator cavity of two serial connections in the utility model, i.e. long variable tunable F-P interferometer in chamber and the long fixing F-P etalon in chamber.Both Free Spectral Ranges have a small difference.As shown in Figure 3, Fig. 3 (a) is the transmission spectrum of F-P etalon, and Fig. 3 (b) is the transmission spectrum of tunable F-P interferometer, and both transmitted spectrums are at light frequency v
iThe place overlaps, and does not overlap at other any wavelength, and therefore, light wave to be measured passes after two resonator cavitys, and only remaining frequency is v
iMonochromatic optical wave.
According to the relevant knowledge of resonator cavity, its longitudinal mode frequency does
Wherein C is the light velocity, and L is a light path in the chamber, and n is a positive integer, is the sequence number of longitudinal mode.
Can obtain the Free Spectral Range of resonator cavity from formula (1), just the difference on the frequency of adjacent longitudinal mode does
Can find out that from formula (1) and formula (2) when changing the long L in chamber, the light frequency v at Free Spectral Range and n longitudinal mode place can change.But, long like the change amount Δ L that fruit caving is long much smaller than the chamber, promptly have relationship delta L＜＜L, can find out that from formula (2) some subtle change on the denominator can be to Free Spectral Range Δ v generation remarkable influence, we can think that Δ v is constant.On the other hand, at the optical frequency wave band, the ordinal number n of chamber longitudinal mode is very big.Therefore, some subtle change of Free Spectral Range (longitudinal mode spacing) all can add up, and make the light frequency at n longitudinal mode place produce significant the variation.In sum, the effect of the fine setting long L in chamber just is equivalent to the transmitted spectrum of translation resonator cavity, and is as shown in Figure 4.For the ease of difference, the position of the transmitted spectrum of interferometer some have been moved down slightly among the figure.
Shown in accompanying drawing 4, wherein: v1: sampled light frequency 1, v2: sampled light frequency 2; V3: sampled light frequency 3, v4: sampled light frequency 4, V5: the spectrum of tunable F-P interferometer; The spectrum of V6:F-P etalon, d1: the skew of longitudinal mode, d2: the skew of sampled light frequency; Among Fig. 4 (a), when n longitudinal mode of m longitudinal mode of etalon 7 spectrum and interferometer 3 spectrum coincided, sampled light frequency v1 can pass through; Among Fig. 4 (b), m+1 longitudinal mode and n+1 longitudinal mode coincide, and sampled light frequency v2 can pass through; Among Fig. 4 (c), m+2 longitudinal mode and n+2 longitudinal mode coincide, and sampled light frequency v3 can pass through; Among Fig. 4 (d), m+3 longitudinal mode and n+3 longitudinal mode coincide, and sampled light frequency v4 can pass through.
We can find out from Fig. 4, the value d1 that the frequency of n longitudinal mode has only only been drifted about very little, and the sampled light frequency of system has just been crossed over very big scope d2.These characteristics have determined very little of the long tuning value in the needed chamber of the utility model, thereby can adopt technology such as electrooptical modulation, have avoided the use movable part.
Technical scheme is as shown in Figure 1.
Incident light to be measured is coupled into optical fiber by incident collimation lens 1; Through fiber coupler 6, get into tunable F-P interferometer 2; Tunable F-P interferometer 2 is optical filters of a pectination, and its transmitted spectrum is as shown in Figure 2.In the incident light wave to be measured, the light wave that has only the longitudinal mode of those frequencies and interferometer to coincide can pass through.
The light wave of interferometer output gets into etalon through fibre optic isolater 13.The purpose of between tunable F-P interferometer 2 and F-P etalon 3, inserting fiber coupler 6 is in order to isolate reflected light.
Can know from the explanation of Fig. 3, Fig. 4 and preamble, long through the chamber of tuning tunable F-P interferometer 2, can select finally to pass the frequency of the light wave of etalon artificially.That is to say, can from light wave to be measured, select a monochromatic optical wave.This function is the basis of realizing spectral measurement.
From the monochromatic optical wave of F-P etalon 3 outgoing, changed into electric signal and amplification by Electro-Optical Sensor Set 4 and pre-amplifying module 5, then through low-pass filter 9, ingoing power measurement module 11.Acting as of power measurement module 11: calculate luminous power from electric signal; Sampling also stores the luminous power data.
In the utility model, the chamber of tunable F-P interferometer 2 is long by tuning continuously, thereby its transmitted spectrum also moves continuously.Can know that from the explanation of Fig. 3, Fig. 4 and preamble in a tuning cycle, different frequency components is passed system in different time in the light wave to be measured, by power measurement module 11 measured and records.So, include the power information of the light wave of different wave length in the data that power measurement module 11 obtains.
For a spectrometric instrument, be not enough just only with the monochromatic optical wave separating and measuring in the spectrum to be measured, also must be able to judge the frequency of current measured light wave.See intuitively, can calculate the light frequency of the current light wave that passes through through the chamber length of stellar interferometer.But, because the variable quantity of chamber length is very little, can not obtain enough accurate the measurement, so the utility model provides a wideband light source as the means of judging current sampled light frequency.
The light wave that wideband light source sends becomes the light wave of an amplitude modulation(PAM) through the modulation of amplitude modulator.This light wave is superimposed with light wave to be measured through fiber coupler 6, through tunable F-P interferometer 2, fiber coupler 6, F-P etalon 3, arrives Electro-Optical Sensor Set 4 and pre-amplifying module 5.That is to say and same light path of light wave process to be measured, and surveyed by same detector.
The centre frequency of the passband of BPF. 10 equals the frequency of amplitude modulator 8, so the photosignal that wideband light source 7 produces can pass through BPF. 10, can not pass through low-pass filter 9; Otherwise the photosignal that light wave to be measured produces can pass through low-pass filter 9, can not pass through BPF. 10.
After process BPF. 10, the photosignal that wideband light source 7 produces gets into Wavelength demodulation module 12.Acting as of Wavelength demodulation module: demodulation obtains wavelength data from the luminous power data.The principle narration of demodulation as follows.
Do in the long tuning process in chamber at interferometer, its transmitted spectrum produces translation.When certain longitudinal mode of certain longitudinal mode of interferometer and etalon on time, have light wave can pass both; At other constantly, there is not light wave to pass.When having light wave to pass, can obtain photosignal; When not having light wave to pass, photosignal is 0.That is to say that in the long tuning process in chamber, photosignal is a series of pulses.The number of count pulse just can learn that current what pass through is the light wave of which wavelength.
The foregoing description only is the technical conceive and the characteristics of explanation the utility model, and its purpose is to let the personage who is familiar with this technology can understand content of the utility model and enforcement according to this, can not limit the protection domain of the utility model with this.All equivalences of being done according to the utility model spirit change or modify, and all should be encompassed within the protection domain of the utility model.
Claims (2)
1. reference light source optical frequency territory, broadband vernier method spectrometer is characterized in that: comprising:
Incident collimation lens (1) is used for incident light to be measured is coupled into optical fiber;
Electro-Optical Sensor Set (4) is used for light wave is converted into electric signal;
Pre-amplifying module (5) is used for the electric signal from said Electro-Optical Sensor Set (4) is carried out processing and amplifying;
Wideband light source (7) is used to provide a frequency stabilization benchmark light wave;
Amplitude modulator (8) will be modulated to an amplitude modulation(PAM) light wave from the frequency stabilization benchmark light wave of said wideband light source;
Fiber coupler (6) will be superimposed from the amplitude modulation(PAM) light wave of said amplitude modulator (8) and incident light to be measured from said incident collimation lens (1);
Tunable F-P interferometer (2), it selects a series of monochromatic optical wave to pass through in from said fiber coupler (6) light wave through tuning cavity length;
F-P etalon (3) is used for extracting the light wave from a series of light wave CFs of said tunable F-P interferometer (2);
Low-pass filter (9) is connected to said pre-amplifying module (5) output terminal, is used for extracting the electric signal that photosignal light wave to be measured is produced;
BPF. (10) is connected to said pre-amplifying module (5) output terminal, and the centre frequency of the passband of BPF. (9) equals the frequency of said amplitude modulator (8), is used for extracting the electric signal that the photosignal wideband light source is produced;
Power measurement module (11) according to calculating luminous power from said low-pass filter (9) electric signal, is measured and is write down the light wave of different frequency in the light wave to be measured successively and store the luminous power data;
Wavelength demodulation module (12) according to from said BPF. (10), is used to analyze the frequency of current measured light wave.
2. reference light source optical frequency territory, broadband according to claim 1 vernier method spectrometer is characterized in that: be provided with a fibre optic isolater (13) between said F-P etalon (3) and the tunable F-P interferometer (2), be used to isolate reflected light.
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| CN2012201069903U CN202547780U (en) | 2012-03-21 | 2012-03-21 | Broadband reference light source optical frequency domain vernier method spectrograph |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102607702A (en) * | 2012-03-21 | 2012-07-25 | 昆山煜肸传感器科技有限公司 | Optical-frequency-domain vernier-method spectrometer with broadband reference light source |
| CN107860405A (en) * | 2017-10-23 | 2018-03-30 | 华中科技大学 | A kind of spectrum demodulation method and its demodulating equipment based on cursor effect |
-
2012
- 2012-03-21 CN CN2012201069903U patent/CN202547780U/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102607702A (en) * | 2012-03-21 | 2012-07-25 | 昆山煜肸传感器科技有限公司 | Optical-frequency-domain vernier-method spectrometer with broadband reference light source |
| CN107860405A (en) * | 2017-10-23 | 2018-03-30 | 华中科技大学 | A kind of spectrum demodulation method and its demodulating equipment based on cursor effect |
| CN107860405B (en) * | 2017-10-23 | 2019-08-13 | 华中科技大学 | A kind of spectrum demodulation method and its demodulating equipment based on cursor effect |
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| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20121121 Termination date: 20140321 |