CN113739917B - A Spectral Measurement System Based on Spinning Fiber - Google Patents

Abstract

The invention belongs to the related technical field of spectrometers, and discloses a spectral measurement system based on a spinning optical fiber. The measuring system comprises an optical filter, a polarizer, a rotary optical fiber, an analyzer and a power meter, wherein the optical filter enables light with a specific frequency spectrum in the light to be measured to pass through; the light passing through the optical filter is changed into linearly polarized light under the action of the polarizer, the optical fiber is arranged behind the optical filter, the linearly polarized light enters the optical fiber and is dispersed on the cross section of the optical fiber according to the polarization azimuth angle of the optical fiber, namely, the monochromatic light of each frequency component is dispersed and distributed along the circumferential direction in space; the analyzer is arranged behind the rotary optical fiber, rotates at a preset step angle, and couples light energy into a power meter arranged behind the analyzer, the power meter is used for measuring total optical power at each rotation angle, and the optical power meter is used for obtaining the spectrum of the light to be measured. The invention solves the problems of low measurement resolution and large size of the existing spectrometer.

Description

A Spectral Measurement System Based on Spinning Fiber

technical field

The invention belongs to the related technical field of spectrometers, and more particularly, relates to a spectrum measurement system based on a spinning optical fiber.

Background technique

Spectrometer is an optical instrument that qualitatively and quantitatively analyzes the composition and content of substances through optical principles. As an indispensable tool for spectral analysis, spectrometers are used in biosensing, medical analysis, gas sensing, environmental Analysis, oil exploration and food quality testing and many other fields. Existing spectrometers can be divided into three types: visible light type, infrared type, and ultraviolet type spectrometers according to the wavelength range of the light waves they measure. type, etc. The spectrometer based on prism spectrometer mainly uses the different refractive indices of different wavelengths of light in the prism material to achieve dispersion, and its resolution is limited by the refractive index and diffraction limit of the material. The spectrometer based on grating spectrometer uses grating as the dispersive element, and its resolution is the same Limited by grating line density and diffraction limit. Compared with prism dispersion spectrometers and grating dispersion spectrometers, Fourier spectrometers have the advantages of high luminous flux, high spectral resolution, and infinite theoretical resolution, so they have been widely used in many fields.

However, in order to achieve high resolution, Fourier spectrometers require a long moving distance, which makes them usually large in size and contains moving components, making it difficult to meet the requirements of high spectral resolution and compact structure at the same time. Spectroscopic measurement techniques and spectrometers with the advantages of high spectral resolution and miniaturization.

SUMMARY OF THE INVENTION

In view of the above defects or improvement requirements of the prior art, the present invention provides a spectrum measurement system based on a spinning optical fiber, which solves the problems of low measurement resolution and large size of the existing spectrometer.

In order to achieve the above object, according to the present invention, a spectroscopic measurement system based on a swirl fiber is provided, and the measurement system includes an optical filter, a polarizer, a swirl fiber, an analyzer and a power meter, wherein,

The optical filter is used to receive the light to be measured and pass the light of a specific spectrum in the light to be measured; the polarizer is arranged behind the optical filter, and the light passing through the optical filter passes through the polarizer. Under the action, it becomes linearly polarized light, the swirl fiber is arranged behind the filter, the linearly polarized light enters the swivel fiber, and is dispersed according to its polarization azimuth on the cross section of the swirl fiber, that is, In space, the monochromatic light of each frequency component is dispersed and distributed along the circumferential direction; the analyzer is arranged behind the rotating fiber, the analyzer rotates at a preset step angle, and couples the light energy to the rear of the analyzer. In the power meter, the power meter is used to measure the total optical power at each rotation angle, and the spectrum of the light to be measured is obtained by calculating the optical power.

Further preferably, the optical filter, polarizer, spin fiber, analyzer and power meter are coaxially distributed.

Further preferably, the optical power of the light collected in the power meter is calculated according to the following relational formula:

Among them, θ _i is the total rotation angle after the rotating device rotates i times, g(θ _i ) is the optical power under the total rotation angle θ _i , λ is the wavelength in the measured spectral range, and λ ₁ is the measured spectral range The left boundary wavelength, λ _m is the right boundary wavelength of the measured spectrum, k(λ)z is the rotation angle of the polarization azimuth angle of the monochromatic light of different wavelengths after the action of the rotating fiber of length z, k(λ) is the rotation angle. The dispersion coefficient of the fiber, θ ₀ is the angle between the polarization direction of the complex light and the transmission axis of the analyzer when it is incident.

Further preferably, the length of the twisted optical fiber is adjusted according to the required dispersion of the monochromatic light on the circumference.

Further preferably, the light to be measured is narrow-band polychromatic light.

Further preferably, the analyzer is placed on a rotating mechanism, and the analyzer is driven to rotate by the rotation of the rotating mechanism.

Further preferably, the filter is a bandpass filter.

Further preferably, the length of the spiral line is selected according to actual needs, and the shape of the required spiral fiber is linear or curved, so as to ensure that light enters from one end of the spiral fiber to the other end and outputs.

In general, compared with the prior art, the above technical solutions conceived by the present invention have the following beneficial effects:

1. The dispersive element used in the spectral measurement system provided in the present invention is a spun highly birefringent optical fiber, which utilizes the polarization mode dispersion effect of the spun fiber to ignore polarization-related losses, transmission power losses, nonlinear effects and other physical properties. After the effect, its theoretical resolution is almost infinite, and more importantly, its spectral resolution can be continuously improved by increasing the length of the swirl fiber, and increasing the length of the swirl fiber is very easy to achieve in the fabrication of the actual spectrometer; therefore, Compared with the existing spectrometer, the spectrum measurement system of the present invention not only has high measurement accuracy, but also the measurement accuracy can be adjusted by adjusting the length of the spinning optical fiber;

2. In the present invention, when the required length of the twisted fiber is very long, the middle of the twisted fiber can be bent, and it is only necessary to ensure that the light enters the other end from one end of the twisted fiber and is output. Therefore, even for the required long twisted fiber , the space occupied by the entire measurement system is also very small, and its space size is greatly reduced compared to the Fourier spectrometer;

3. Each component used in the present invention has a simple structure, does not require a large moving element, and does not require a long moving distance during the measurement process. Therefore, compared with the existing Fourier spectrometer, the The structure is more compact and the size is smaller.

Description of drawings

1 is a schematic structural diagram of a spectrum measurement system based on a swirl fiber constructed according to a preferred embodiment of the present invention;

FIG. 2 is a schematic diagram of the action of the swirl fiber constructed according to the preferred embodiment of the present invention to the polychromatic light.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as there is no conflict with each other.

As shown in Figure 1, a spectroscopic measurement system based on Spun highly birefringent optical fiber. The narrow-band polychromatic light source measured for the first time passes through a band-pass filter to allow light of a specific spectrum to pass. After being coupled into the swirl fiber, the monochromatic component of the polychromatic light is distributed in a space circle on the cross section of the output end of the swirl fiber through the dispersion effect of the swirl fiber. Then, the dispersed polychromatic light passes through an analyzer, which is placed on a fixed rotating device, and the rotating device drives the analyzer to rotate at equal intervals at a certain step angle. Finally, the optical energy after the action of the analyzer is coupled to the optical power meter, and the total optical power at each rotation angle is measured. After mathematical solution, the spectral details of the incident light source can be obtained.

The optical fiber-based spectrometer and the spectral measurement method proposed by the present invention can realize the high-resolution measurement of the spectrum in a compact structure, and theoretically have almost infinite resolution, and are especially suitable for the measurement of the narrow-band spectrum.

When the rotating device rotates with the analyzer at a fixed step angle at equal intervals, and the step angle is set as Δθrad, the polarization azimuth angle of the polarized light after the dispersion of the spinning fiber changes relative to the analyzer, resulting in Finally, the optical power detected by the optical power meter changes. Assuming that the spectral function of the incident light source is f(λ), and the spectral function after the optical fiber dispersion is g(λ), the output light power after the action of the analyzer, the spectral function of the incident light source and the step angle are as follows: Functional relationship:

Among them, θ ₀ is the angle between the polarization direction of the polychromatic light and the light transmission axis of the analyzer when it is incident, and θ _i is the total rotation angle after the rotating device rotates i times, that is, θ _i =iΔθ. k(λ)z is the rotation angle of the polarization azimuth angle of the monochromatic light of different wavelengths after the action of the swirl fiber of length z, k(λ) is the dispersion coefficient of the swirl fiber, and its size is determined by the characteristic parameters of the swirl fiber and the light wave. The wavelength λ of is determined by k(λ)=k ₀ +aλ in a very narrow spectral width. When the rotating device rotates once, the total optical power data, that is, the number of sampling points, is n=2π/Δθ.

Formula (1) can be expressed in matrix form as:

The step angle Δθ of the rotational transposition is given during the measurement process, and the unknowns in the above equation (2) are k(λ ₁ )z+θ ₀ -k(λ _m )z+θ ₀ , f(λ ₁ )-f(λ _m ), m determines the subdivision multiple of the incident light source spectrum, the total number of unknowns is 2m, and it only needs to satisfy the total number of rotations, that is, the total number of sampling n>2m, then the above equation is theoretically With the least squares solution, the m-fold subdivision of the light source spectrum is finally realized.

The effect of the swirl fiber on the polychromatic light is shown in Figure 2. The effect of the polarized polychromatic light passing through the swivel fiber will be dispersed according to its polarization azimuth on the cross section of the fiber, that is, the monochromatic light of each frequency component in space will be scattered along the The distribution is dispersed in the circumferential direction, and the longer the length of the spiral fiber, the more widely dispersed the spectrum of each frequency component, so even a spectrum with a very narrow spectral width can be dispersed by a long enough spiral fiber for detection.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (8)

1. The optical spectrum measuring system based on the spinning optical fiber is characterized by comprising an optical filter, a polarizer, the spinning optical fiber, an analyzer and a power meter, wherein,

the optical filter is used for receiving light to be measured and enabling light with a specific frequency spectrum in the light to be measured to pass through; the polarizer is arranged behind the optical filter, light passing through the optical filter is changed into linearly polarized light under the action of the polarizer, the optical fiber is arranged behind the optical filter, the linearly polarized light enters the optical fiber and is dispersed on the cross section of the optical fiber according to the polarization azimuth angle of the optical fiber, and the monochromatic light of each frequency component is dispersed and distributed along the circumferential direction in space; the analyzer is arranged behind the rotary optical fiber, rotates at a preset step angle, and couples light energy into a power meter arranged behind the analyzer, the power meter is used for measuring total optical power at each rotation angle, and the optical power meter is used for obtaining the spectrum of the light to be measured.

2. The optical rotary fiber-based spectrometry system of claim 1, wherein the optical filter, the polarizer, the optical rotary fiber, the analyzer and the power meter are coaxially disposed.

3. A spinning fiber based spectrometry system according to claim 1 or 2, wherein the optical power of the light collected in the power meter is calculated according to the following relationship:

wherein, theta _i Total angle of rotation, g (θ), after i rotations of the rotating device _i ) Is at the total rotation angle theta _i Optical power of lambda is the wavelength in the spectral range to be measured, lambda ₁ Is the wavelength, λ, of the left boundary of the measured spectrum _m Is the right end boundary wavelength of the measured spectrum, k (lambda) z is the rotation angle of the polarization azimuth angle of monochromatic light with different wavelengths after the action of the optical fiber with the length of z, k (lambda) is the dispersion coefficient of the optical fiber, theta ₀ The included angle between the polarization direction of the polychromatic light and the transmission axis of the analyzer.

4. A spinning-fiber based spectroscopic measurement system as set forth in claim 2 wherein the length of the spinning fiber is adjusted according to the desired degree of dispersion of the monochromatic light around the circumference.

5. The optical fiber spinning-based spectroscopic measurement system of claim 1 or 2 wherein the light to be measured is a narrowband polychromatic light.

6. The optical rotary fiber-based spectrometry system of claim 3, wherein the analyzer is disposed on a rotation mechanism, and the rotation of the rotation mechanism rotates the analyzer.

7. The optical rotary fiber-based spectrometry system of claim 3, wherein the filter is a bandpass filter.

8. The optical fiber spinning-based spectrum measuring system as claimed in claim 1 or 2, wherein the length of the spinning optical fiber is selected according to actual needs, and the required spinning optical fiber is in a linear or curved shape, so as to ensure that light enters from one end of the spinning optical fiber and is output from the other end of the spinning optical fiber.

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