CN110702230B

CN110702230B - Fourier transform spectrometer

Info

Publication number: CN110702230B
Application number: CN201911253978.8A
Authority: CN
Inventors: 尹志军; 吴冰; 张虞; 许志城
Original assignee: Nanjing Nanzhi Institute Of Advanced Optoelectronic Integration
Current assignee: Nanjing Nanzhi Institute Of Advanced Optoelectronic Integration
Priority date: 2019-12-10
Filing date: 2019-12-10
Publication date: 2020-03-20
Anticipated expiration: 2039-12-10
Also published as: CN110702230A

Abstract

The application discloses Fourier transform spectrometer includes: the beam splitter is used for splitting linearly polarized light formed by a spectrum to be measured into a first light beam and a second light beam with equal energy; the first light beam enters the electro-optic crystal single crystal optical fiber; a voltage driver; the second light beam enters the optical fiber ring and generates phase delay; a beam combiner; the photoelectric detector detects the first light beam and the second light beam which generate the combined beam interference to form a combined beam interference detection signal; and the signal processor collects the beam combination interference detection signals, collects voltage driving information of the voltage driver, and calculates a target spectrum based on a preset processing strategy. The structure design of the spectrometer can improve the maximum optical path difference of the two arms on one hand, and can keep the structure compact and the working stability on the other hand.

Description

Fourier transform spectrometer

Technical Field

The application relates to the technical field of spectrometers, in particular to a Fourier transform spectrometer.

Background

The infrared spectrum has wide applicability to samples, can be applied to solid, liquid or gaseous samples, and can detect inorganic, organic and high molecular compounds. In addition, the infrared spectrum has the characteristics of rapid test, convenient operation, good repeatability, high sensitivity, small sample consumption, simple instrument structure and the like, so that the infrared spectrum becomes the most common and indispensable tool for modern structural chemistry and analytical chemistry. In addition, the infrared spectrum also has wide application in the research of the conformation and mechanical properties of the high polymer and the fields of physics, astronomy, meteorology, remote sensing, biology, medicine and the like. The infrared spectrometer is an instrument for analyzing infrared spectrum and is mainly divided into the following two types according to the working principle:

1. dispersive, essentially comprising prisms and grating spectrometers

The dispersive element device of the dispersive spectrometer is a prism grating, which belongs to single-channel measurement, namely only one narrow-band spectral element is measured at a time. The spectral distribution of the light source can be measured by rotating the prism or the grating and changing the orientation point by point. With the development of information technology and electronic computers, a new infrared spectrometer featuring multi-channel measurement has emerged, i.e. in one measurement, the detector can measure the information of each spectral element in the light source at the same time, e.g. in hadamard transform spectrometer, the input or output slit is replaced by a coding template on the basis of a grating spectrometer, and then the signal measured by the detector is processed by a computer. The signal-to-noise ratio of a hadamard transform spectrometer is higher compared to a grating spectrometer.

2. The interference type mainly comprises Fourier transform infrared spectrometer (FTIR, the same below)

It is non-dispersive, and the core part is a double-beam interferometer, commonly a Michelson interferometer. When the movable mirror moves, the optical path difference between two beams of coherent light passing through the interferometer changes, and the light intensity measured by the detector also changes, so that an interference pattern is obtained. The core principle of the Fourier transform spectrometer is that a Michelson interferometer is adopted to perform interference sampling on incident spectrum information. Two arms of the Michelson interferometer generate relative phase difference in a mode of moving the reflecting mirror, and the size and sampling precision of the relative phase difference determine the spectral measurement precision and the measurement range of the FTIR.

After the mathematical operation of Fourier transform, the spectrum of the incident light can be obtained.

The main advantages of fourier transform spectrometers are:

(1) the measuring speed is high. The time of one-time scanning of the movable mirror is about 1s, namely, the scanning in the set spectral range can be completed within 1s, the computer immediately performs Fourier transform to form an FTIR spectrum, and the measuring speed of the computer is hundreds of times faster than that of a dispersive or grating infrared spectrometer. The method can monitor samples separated by the chromatograph on line, enables the combination of the chromatograph and the infrared spectrum to be possible, can effectively track rapid in-situ chemical reaction and the like, and can not be realized by a dispersive or grating infrared spectrometer.

(2) The resolution is high. According to the working principle of the FTIR instrument, the resolution of FTIR is approximately equal to the reciprocal of the maximum optical path difference, that is, the reciprocal of 2 times of the moving effective distance of the moving mirror, theoretically, the higher resolution can be obtained as long as the moving effective distance of the moving mirror is longer, while the resolution of the dispersive or grating infrared spectrometer is inversely proportional to the width of the spectrum slit, but the narrower the width of the spectrum slit is, the smaller the luminous flux is, and as a result, the sensitivity and the signal-to-noise ratio of the spectrum are sacrificed, so that the resolution of the dispersive or grating infrared spectrometer cannot be very high.

(3) The signal-to-noise ratio is good. The original data measured by the FTIR instrument is an interference pattern of a whole beam of mixed light, and the interference pattern does not pass through a spectrum slit, so that the signal intensity is high, and the signal-to-noise ratio is excellent.

(4) The wave number accuracy and repeatability are good. The accurate calibration of the FTIR instrument to the peak position is completed by the built-in laser, the single wavelength light emitted by the laser is very stable, and the position of the interferometer moving mirror monitored and determined by the laser is very accurate, so that the data obtained by the laser is very accurate to determine the frequency of the infrared light emitted by the light source, and the measurement results are the same at different times, so that the wave number accuracy and the repeatability are good.

(5) The measuring range is wide. Many FTIR instruments can measure spectra in the near, mid and far entire infrared regions simply by replacing appropriate beam splitters, light sources, detectors.

However, the michelson interferometer is a very precise device and is easily affected by external environmental disturbances, such as changes in vibration, temperature, and the like. The adoption of the mode of moving the lens to adjust the phases of the two arms inevitably introduces various noises caused by the movement of the lens, so that the mechanical moving mirror type FTIR generally has larger volume and is placed on an optical platform for vibration isolation for use. In order to reduce environmental interference and reduce the size of the instrument, various methods are adopted, for example, patent CN109405973A discloses an interferometer for a fourier transform spectrometer, which adopts two symmetrical angle mirrors to form an interference movable arm; patent CN108180997A discloses a fourier transform spectrometer based on DLP technology, which uses DLP as a micro-motion element to generate phase modulation.

A more efficient approach is to avoid introducing moving parts in the FTIR, changing the phase modulating element to a static type element. For example, patent CN109738066A discloses a micro-step mirror for static fourier transform spectroscopy, which generates phase modulation by micro-steps; patent CN108593110A proposes an all-fiber fourier transform spectrometer based on PZT phase modulation, which generates phase modulation through PZT; patent CN103884425B proposes a Herriott type multiple reflection photoelastic modulation interferometer, which generates phase modulation by the Herriott type photoelastic modulation interferometer. Research on an electro-optical modulation type static Fourier spectrometer and software development thereof (doctor's paper, university of North and Central province, Yang Min) have studied the modulation effect in FTIR by using an electro-optical crystal light modulator. Micro FTIR using electro-optic crystal waveguides was studied in the Integrated optical waveguide static Fourier transform Microspectrometer resolution multiplication method (Lijinyo et al, Physics, vol64, No.11,2015).

However, the main problem of the static-type FTIR described above is the low resolution. This is because the resolution of FTIR is determined by the maximum optical path difference of the two arms, and the larger the optical path difference, the higher the resolution. Static FTIR is constrained by the size of the device due to the photoelastic effect or the electro-optical effect, and cannot generate a large enough optical path difference. Electro-optic modulators such as those reported in integrated optical waveguide static fourier transform micro-spectrometer resolution multiplication methods, despite the enhanced two-pass approach, have a resolution of over a hundred nanometers (115 nm) at 1550nm, which has not achieved effective results in many spectroscopic applications.

Disclosure of Invention

The technical problem that this application will be solved is for providing a Fourier transform spectrometer, and the structural design of this spectrometer can make the biggest optical path difference of two arms obtain promoting on the one hand, and on the other hand can keep compact structure and job stabilization nature.

In order to solve the above technical problem, the present application provides a fourier transform spectrometer, comprising:

the beam splitter is used for splitting linearly polarized light formed by a spectrum to be measured into a first light beam and a second light beam with equal energy;

the first light beam enters the electro-optic crystal single crystal optical fiber;

the voltage driver drives the refractive index of the electro-optic crystal single crystal fiber to change so that the optical path of the first light beam changes;

the second light beam enters the optical fiber ring and generates phase delay;

the beam combiner is used for carrying out beam combination interference on a first light beam emitted by the electro-optic crystal single crystal optical fiber and a second light beam emitted by the optical fiber ring;

the photoelectric detector detects the first light beam and the second light beam which generate the combined beam interference to form a combined beam interference detection signal;

and the signal processor collects the beam combination interference detection signals, collects voltage driving information of the voltage driver, and calculates a target spectrum based on a preset processing strategy.

Optionally, the electro-optic crystal single crystal fiber is an annular member formed by the electro-optic crystal single crystal fiber.

Optionally, the voltage driver comprises a positive electrode and a negative electrode, the positive electrode being a ring-shaped electrode disposed outside and concentric with the ring-shaped member; the negative electrode is a ring-shaped electrode disposed inside and concentric with the ring-shaped member.

Optionally, the voltage driver includes a positive electrode and a negative electrode, the positive electrode is disposed above a horizontal plane of the annular member, and the negative electrode is disposed below the horizontal plane of the annular member.

Optionally, the voltage driver comprises a positive electrode and a negative electrode; the peripheral outer wall of the electro-optic crystal single crystal optical fiber is provided with a metal coating, the upper ring layer of the metal coating forms the positive electrode, and the lower ring layer of the metal coating forms the negative electrode; an isolation cutting seam is arranged between the upper ring layer and the lower ring layer.

Optionally, the annular member comprises concentric rings of unequal radii.

Optionally, the concentric rings are spirally wound to form a multi-layer spiral concentric ring structure.

Optionally, the voltage driver comprises a positive electrode and a negative electrode; the positive electrode and the negative electrode are both of a multilayer spiral structure, one of which extends along the inner winding of the multilayer spiral concentric ring structure, and the other of which extends along the outer winding of the multilayer spiral concentric ring structure.

In addition, in order to solve the above technical problem, the present application further provides a fourier transform spectrometer, including:

the spectrum collector is used for inputting a spectrum signal;

the spectrum signal input by the spectrum collector passes through the optical fiber beam splitter and is divided into a first light beam and a second light beam with equal energy;

a first ring of electro-optic fibers into which the first beam of light enters;

a first voltage driver for applying a forward electric field to the first crystallized optical fiber ring;

a second ring of electro-optic fibers into which the second beam of light enters;

the second voltage driver is used for applying a negative electric field to the second crystal optical fiber ring;

the first crystal optical fiber loop reflector is arranged at the output end of the first crystal optical fiber loop and used for reflecting the output first light beam to return along the original path;

the second crystal optical fiber loop reflector is arranged at the output end of the second crystal optical fiber loop and used for reflecting the output second light beam to return along the original path;

the beam combiner is used for receiving the first light beam and the second light beam returned along the original path and enabling the first light beam and the second light beam to generate beam combining interference;

the photoelectric detector is arranged at the output end of the beam combiner and used for detecting the first light beam and the second light beam which generate the beam combination interference and sending out a beam combination interference detection signal;

Optionally, the beam splitter and the beam combiner are the same optical element with beam splitting and combining functions.

The following explains the technical effects of the technical scheme provided by the application:

the spectrum to be measured can firstly enter a polarization selector after being converged and collimated by an optical collecting device, linearly polarized light is selected, and then the spectrum enters a beam splitter which is a 50% beam splitter, so that the spectrum to be measured is divided into two beams of light with equal energy: a first light beam and a second light beam. Wherein the first light beam enters the electro-optic crystal single crystal fiber and the second light beam enters the corresponding fiber ring. The purpose of the fiber loop is to create a phase delay, which equalizes the phase difference between the two arms of the FTIR. Under the drive of voltage driver, the single crystal fiber of electro-optical crystal generates the refractive index change caused by electro-optical effect to change the optical path length of the path. Then two beams of light emitted by the optical fiber ring and the electro-optic crystal single crystal optical fiber are subjected to beam combination interference and are detected by a photoelectric detector. The detected signal is input to a signal processor. While the signal processor obtains voltage drive information. And taking the collected signal of the photoelectric detector as an amplitude (ordinate) and the voltage driving signal as an abscissa, performing Fourier transform, and calculating a target spectrum.

Therefore, the structural design of the spectrometer can improve the maximum optical path difference of the two arms on one hand, and can keep compact structure and working stability on the other hand.

Drawings

FIG. 1 is a functional block diagram of a Fourier transform spectrometer as shown in an exemplary embodiment of the present application;

FIG. 2 is a schematic structural diagram of an electro-optic crystal single crystal fiber of the Fourier transform spectrometer of FIG. 1;

FIG. 3 is a schematic diagram of the electro-optic crystal single crystal fiber of FIG. 2 after an electric field is applied;

FIG. 4 is a schematic diagram of the electro-optic single crystal fiber of FIG. 2 formed as a ring-shaped member and applied with a first electric field;

FIG. 5 is a schematic diagram of the electro-optic single crystal fiber of FIG. 2 formed as a ring-shaped member and applied with a second electric field;

FIG. 6 is a schematic diagram of the electro-optic single crystal fiber of FIG. 2 formed as a ring-shaped member and applied with a third electric field;

FIG. 7 is a schematic structural diagram of the electro-optic crystal of FIG. 2 in which single crystal optical fibers are wound to form a plurality of spiral concentric rings;

FIG. 8 is a schematic diagram of a Fourier transform spectrometer as shown in another exemplary embodiment of the present application;

fig. 9 is a schematic structural diagram of the first and second crystal fiber rings of the fourier transform spectrometer shown in fig. 8.

Wherein, the corresponding relationship between the component names and the reference numbers in fig. 1 to 9 is:

a beam splitter 101; an electro-optic crystal single crystal optical fiber 102; a core layer 1021; a cladding layer 1022; a voltage driver 103; a positive electrode 1031; a negative electrode 1032; a fiber ring 104; a beam combiner 105; a photodetector 106; a signal acquisition module 107; a Fourier transform module 108; a multi-layer helical concentric ring structure 109;

a spectrum collector 201; a first crystal fiber ring 202; a first voltage driver; a second ring of crystallized optical fibers 204; a second voltage driver; a first crystal fiber loop reflector 206; a second crystal fiber loop reflector 207; an optical fiber splitter-combiner 208.

Detailed Description

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following examples do not represent all embodiments consistent with the present application. But merely as exemplifications of systems and methods consistent with certain aspects of the application, as recited in the claims.

Referring to FIG. 1, FIG. 1 is a schematic block diagram of a Fourier transform spectrometer according to an exemplary embodiment of the present application.

In one embodiment of the present application, a fourier transform spectrometer is provided comprising: the beam splitter 101 is used for splitting linearly polarized light formed by a spectrum to be measured into a first light beam and a second light beam with equal energy through the beam splitter 101; an electro-optic crystal single crystal fiber 102 into which the first light beam enters; a voltage driver 103, wherein the voltage driver 103 drives the refractive index of the electro-optic crystal single crystal fiber 102 to change, so that the optical path of the first light beam changes; the optical fiber loop 104, the second light beam enters the optical fiber loop 104, and the phase delay occurs; a beam combiner 105, in which a first light beam emitted from the electro-optic crystal single crystal optical fiber 102 and a second light beam emitted from the optical fiber ring 104 are combined and interfered; the photoelectric detector 106 detects the first light beam and the second light beam which generate the combined beam interference to form a combined beam interference detection signal; and a signal processor which collects the beam interference detection signal, collects voltage driving information of the voltage driver 103, and calculates a target spectrum based on a predetermined processing strategy.

As shown in fig. 1, a spectrum to be measured may first enter a polarization selector after being converged and collimated by an optical collection device, select linearly polarized light, and then enter a beam splitter 101, where the beam splitter 101 is a 50% beam splitter 101, so as to split the spectrum into two beams of light with equal energy: a first light beam and a second light beam. Wherein a first light beam enters the electro-optic crystal single crystal fiber 102 and a second light beam enters the corresponding fiber loop 104. The purpose of the fiber optic ring 104 is to create a phase delay that equalizes the phase difference between the two arms of the FTIR. The electro-optic crystal single crystal fiber 102 is driven by a voltage driver 103 to generate refractive index conversion by an electro-optic effect, and change the optical path length of the path. Then, the two beams of light emitted from the optical fiber ring 104 and the electro-optic crystal single crystal optical fiber 102 are subjected to beam combination interference and detected by the photodetector 106. The detected signal is input to a signal processor. While the signal processor obtains voltage drive information. The acquired signal of the photodetector 106 is taken as an amplitude (ordinate) and the voltage drive signal is taken as abscissa, fourier transform is performed, and the target spectrum is calculated.

In the above embodiment, it should be noted that the signal processor may include a signal acquisition module 107 and a fourier transform module 108, the combined interference detection signal sent by the photodetector 106 is sent to the signal acquisition module 107, meanwhile, the signal acquisition module 107 receives voltage driving information of the voltage driver 103, then sends the two data to the fourier transform module 108, and the fourier transform module 108 takes the acquisition signal of the photodetector 106 as an amplitude (ordinate) and the voltage driving signal as an abscissa, performs fourier transform, and calculates the target spectrum.

It should be noted that the optical fiber ring 104 mentioned in the above embodiments is not driven by applying an electro-optical signal, i.e., a voltage. The function is as follows: a phase delay is generated so that the electro-optic crystal single crystal fiber 102 has no phase difference with the fiber loop 104 when no voltage is applied. Therefore, when the electro-optic crystal single crystal fiber 102 is applied with voltage, the first light beam and the second light beam pass through the beam combiner 105 and have phase difference.

The structure of the electro-optic crystal single crystal fiber 102 and the principle of the electro-optic effect will be described below. Specifically, referring to fig. 2 and fig. 3, fig. 2 is a schematic structural diagram of an electro-optic crystal single crystal fiber 102 of the fourier transform spectrometer of fig. 1; fig. 3 is a schematic diagram of the electro-optic crystal single crystal fiber 102 in fig. 2 after an electric field is applied.

The invention adopts the electro-optic crystal single crystal optical fiber 102 to form the phase delayer. Single crystal optical fibers, also known as fiber monocrystals or crystal fibers, are single crystals of crystalline material grown into fibers with diameters ranging from a few microns to hundreds of microns. Single crystal fibers can be grown from a variety of different crystalline materials, each with different functions, where the single crystal fiber with the electrooptic effect is referred to as an electrooptic crystal single crystal fiber 102. As shown in fig. 1, the electro-optic crystal single crystal optical fiber 102 has a two-layer structure of a clad layer 1022 and a core layer 1021, similar to a general optical fiber. The light transmission direction is the a-axis direction, and the crystal axis of the single crystal is the c-axis. The refractive index of the core layer 1021 is along the c-axis and the b-axis according to the polarization direction

And

(ii) a The refractive index in cladding 1022 is also defined as

And

. According to the electro-optic effect, when a direct current electric field is applied in the c-axis direction of the crystal, the change of the refractive index is:

the formula I is as follows:

wherein, △

A refractive index representing the change of light along the c-axis polarization direction of the core layer 1021;

core 1021 refractive index representing the polarization direction of light along the c-axis;

representing the linear electro-optic coefficient of the crystal along the c-axis.

The formula II is as follows:

wherein, △

A refractive index representing the change of light along the b-axis polarization direction of the core layer 1021;

core 1021 refractive index representing the polarization direction of light along the b-axis;

representing the linear electro-optic coefficient of the crystal along the b-axis.

As shown in FIG. 3, two electrodes are arranged along the c-axis direction of the single crystal fiber, with the distance d between the electrodes, and respectively applied with positive voltage

And a negative voltage

The inside of the single crystal fiber will have an electric field

. Electric field

The size of (A) is as follows:

the polarization state of the incident light direction is parallel to the c-axis or b-axis direction. When the polarization direction of the incident light is parallel to the c-axis direction, the refractive index changes according to the form of formula 1; when the polarization direction of the incident light is parallel to the b-axis, the refractive index will vary according to equation 2.

In the above embodiments, further design can be made of the shape of the electro-optic crystal single crystal fiber 102 and its applied electric field. For example, referring to fig. 4, 5 and 6, fig. 4 is a schematic structural view of the electro-optic crystal single crystal fiber of fig. 2 forming a ring-shaped member and applying a first electric field; FIG. 5 is a schematic diagram of the electro-optic single crystal fiber of FIG. 2 formed as a ring-shaped member and applied with a second electric field; FIG. 6 is a schematic diagram of the structure of the electro-optic crystal single crystal fiber of FIG. 2 in which a ring-shaped member is formed and a third electric field is applied.

For example, as shown in fig. 4, the electro-optic crystal single crystal optical fiber 102 is a ring-shaped member formed of one electro-optic crystal single crystal optical fiber 102. On this basis, the voltage driver 103 includes a positive electrode 1031 and a negative electrode 1032, the positive electrode 1031 being a ring-shaped electrode disposed outside the ring-shaped member and concentric with the ring-shaped member; the negative electrode 1032 is a ring-shaped electrode disposed inside and concentric with the ring-shaped member.

In the above structure, the bent winding of the single crystal optical fiber is called a loop shape, and the length can be increased as shown in fig. 3. The positive electrode 1031 and the negative electrode 1032 are respectively arranged on the inner side and the outer side of the annular single crystal optical fiber to form a radial electric field, and the a axis of the crystal is parallel to the annular axial direction.

In addition, another electric field application may be devised, as shown in fig. 5. The positive electrode 1031 is disposed above the horizontal plane of the ring-shaped member, and the negative electrode 1032 is disposed below the horizontal plane of the ring-shaped member.

Of course, an electric field applying mechanism may be designed, as shown in fig. 6, the peripheral outer wall of the electro-optic crystal single crystal optical fiber 102 has a metal coating, an upper ring layer of the metal coating forms a positive electrode 1031, and a lower ring layer of the metal coating forms a negative electrode 1032; an isolation cutting seam is arranged between the upper ring layer and the lower ring layer.

Furthermore, the ring-shaped member formed by the single crystal optical fiber can be improved. Referring to fig. 7, fig. 7 is a schematic structural diagram of a multi-layer spiral concentric ring formed by winding the single crystal electro-optic fiber 102 in fig. 2.

In this configuration, the annular members comprise concentric rings of unequal radii and concentricity, as shown in FIG. 7. And the concentric rings are spirally wound to form a multi-layer spiral concentric ring structure 109. In this configuration, the number of concentric ring fibers and the number of corresponding ring electrodes can be increased to form a multi-layered arrangement, further increasing the length of the fibers. The number of layers of the annular optical fiber arranged up and down can be increased to form the spiral optical fiber, and meanwhile, the electrode also has a multilayer structure, so that the length of the optical fiber is further increased. The two arrangement methods can be combined to form an optical fiber shape with a plurality of concentric spiral shapes and a plurality of layers. On the basis, the optical path difference of the two arms can be further improved, and the resolution ratio is improved.

In addition, in the above embodiments of the present application, the polarization selector may employ a birefringent prism, a polarizing plate, a polarization-coated lens, or the like, so that the polarization direction of light becomes linearly polarized and parallel to the a-axis of the electro-optic crystal single crystal fiber 102. The 50% splitter 101 may employ a coated polarizer or a fiber splitter 101.

In addition, the optical fiber ring 104 can also selectively adopt the electro-optic crystal single crystal optical fiber 102, forms a mirror symmetry form with the other optical fiber, and applies voltage signals with the same sequence, but the voltage directions of the two are opposite, so that the refractive index of one optical fiber is increased, the refractive index of the other optical fiber is reduced, and push-pull type delay is formed, thereby increasing the equivalent optical path difference. This solution is another embodiment of the present application to be described next. Referring to fig. 8 and 9, fig. 8 is a schematic diagram of a fourier transform spectrometer according to another exemplary embodiment of the present application; fig. 9 is a schematic structural diagram of the first and second crystal fiber rings of the fourier transform spectrometer shown in fig. 8.

In the alternative embodiment, as shown in FIG. 8, the Fourier transform spectrometer comprises

A spectrum collector 201 for inputting a spectrum signal;

the spectrum signal input by the spectrum collector 201 passes through the optical fiber beam splitter 101 and is divided into a first light beam and a second light beam with equal energy;

a first crystal fiber ring 202, the first light beam entering the first crystal fiber ring 202;

a first voltage driver for applying a forward electric field to the first crystallized fiber loop 202;

a second ring of electro-optic fibers 204, the second beam entering the second ring of electro-optic fibers 204;

a second voltage driver for applying a negative electric field to the second crystallized fiber loop 204;

a first fiber loop reflector 206, disposed at the output end of the first fiber loop 202, for reflecting the output first light beam and returning the reflected light beam along the original path;

a second crystal fiber loop reflector 207, disposed at the output end of the second crystal fiber loop 204, for reflecting the output second light beam and returning the second light beam along the original path;

a beam combiner 105, configured to receive the first light beam and the second light beam returned along the original path, and cause the first light beam and the second light beam to generate beam combining interference;

the photoelectric detector 106 is arranged at the output end of the beam combiner 105 and used for detecting the first light beam and the second light beam which generate the combined beam interference and sending out a combined beam interference detection signal;

and a signal processor which collects the beam interference detection signal, collects voltage driving information of the voltage driver 103, and calculates a target spectrum based on a predetermined processing strategy.

Further, as shown in fig. 8, the beam splitter and the beam combiner may be the same optical element having the functions of splitting and combining, and the optical element may be positioned as the fiber optic splitter-combiner 208.

The Fourier transform spectrometer of the all-fiber electro-optic crystal single crystal fiber 102 adopts a complete mirror image mode to form two interference arms of FTIR, and two completely consistent rings of the electro-optic crystal single crystal fiber 102 form a phase delayer, wherein one of the phase delayers increases the optical path and the other phase delayer reduces the optical path to form a push-pull type structure. The ring of electro-optic crystal single crystal optical fibers 102 has two ports, one of which is an input and output port, and the other of which is connected to a fiber ring 104 path mirror to return the light in the fiber ring 104. Two light beams returning from the fiber ring 104 enter the photodetector through the beam combiner 105. The FTIR formed in the mode has a complete mirror image structure, and two arms of the mirror image FTIR have consistent influence on the phase of light when influenced by environments such as vibration, thermal disturbance and the like, so that the final output result is not influenced, and the working stability of the FTIR is ensured to the maximum extent.

As shown in fig. 9, a positive field may be applied to one of the rings and a negative field may be applied to one of the rings by applying opposing electrodes.

Specifically, the electro-optical crystal single crystal fiber is lithium niobate crystal (LiNbO 3), and other electro-optical crystals such as lithium tantalate can also be used. This example takes a lithium niobate crystal as an example. Firstly, growing a lithium niobate single crystal fiber by a process such as a mode-guiding method, a capillary solidification method or a laser heating pedestal method, and then obtaining a single crystal fiber cladding 1022 by a magnesium ion diffusion method, a proton exchange method or an ion implantation method. The diameter of the prepared single crystal optical fiber core is 5 μm, and the outer diameter of the cladding 1022 is 20 μm. The lithium niobate single crystal optical fiber is wound to form a multilayer spiral structure as shown in fig. 7, and has two ports. Electrodes are inserted between the multi-layer spiral structures as shown in fig. 9. FIG. 9 shows two mirror-image structures, in which a lithium niobate single crystal optical fiber is wound into a double helix structure of 10 upper and lower layers, in which the radius of the outer layer helix is 50mm, the radius of the inner layer helix is 40mm, the length of the single crystal optical fiber of one double helix structure is 5.6m, and the round-trip length is 11.2 m. The distance between the two layers of electrodes. Refractive index of lithium niobate crystal

Photoelectric coefficient of

According to the parameters and the formula I, the voltage of the lithium niobate single crystal optical fiber at the electrode is

Change of refractive index

. Formed by two lithium niobate single crystal optical fiber modulatorsThe maximum equivalent delay distance caused by the push-pull type delay period is

. Resolution equation according to FTIR (

In wave numbers):

the resolution of the device is

. In the 1.5 μm wave band, the resolution of the FTIR can reach 0.15 nm.

The embodiments provided in the present application are only a few examples of the general concept of the present application, and do not limit the scope of the present application. Any other embodiments extended according to the scheme of the present application without inventive efforts will be within the scope of protection of the present application for a person skilled in the art.

Claims

1. A fourier transform spectrometer, comprising:

the second light beam enters the optical fiber ring and generates phase delay;

the signal processor collects the beam combination interference detection signals, collects voltage driving information of the voltage driver, and calculates a target spectrum based on a preset processing strategy;

the electro-optic crystal single crystal optical fiber is an annular component formed by the electro-optic crystal single crystal optical fiber;

the annular member comprises concentric rings of unequal radii;

the concentric rings are spirally wound to form a multi-layer spiral concentric ring structure;

the voltage driver comprises a positive electrode and a negative electrode; the positive electrode and the negative electrode are both of a multilayer spiral structure, one of which extends along the inner winding of the multilayer spiral concentric ring structure, and the other of which extends along the outer winding of the multilayer spiral concentric ring structure.

2. The fourier transform spectrometer of claim 1, wherein the voltage driver comprises a positive electrode and a negative electrode, the positive electrode being an annular electrode disposed outside and concentric with the annular member; the negative electrode is a ring-shaped electrode disposed inside and concentric with the ring-shaped member.

3. The fourier transform spectrometer of claim 1, wherein the voltage driver comprises a positive electrode and a negative electrode; the peripheral outer wall of the electro-optic crystal single crystal optical fiber is provided with a metal coating, the upper ring layer of the metal coating forms the positive electrode, and the lower ring layer of the metal coating forms the negative electrode; an isolation cutting seam is arranged between the upper ring layer and the lower ring layer.

4. A fourier transform spectrometer, comprising:

the spectrum collector is used for inputting a spectrum signal;

the spectrum signal input by the spectrum collector passes through the beam splitter and is divided into a first light beam and a second light beam with equal energy;

a first ring of electro-optic fibers into which the first beam of light enters;

the signal processor collects the beam combination interference detection signals, collects voltage driving information of the voltage driver, and calculates a target spectrum based on a preset processing strategy; the beam splitter and the beam combiner are the same optical element with beam splitting and combining functions.