Laser beam identification device and method

Abstract

This invention discloses a laser beam identification device and method for identifying whether a test beam is a first laser beam or a second laser beam, wherein the spectral widths of the first and second laser beams are different. The laser beam identification device includes a beam expander, an aperture, and a detector. The beam expander allows the output beam formed after the test beam passes through to be incident on a first and a second slit in the aperture. The output light from the first and second slits interferes. The detector is located on the light-emitting side of the aperture and is used to detect the light intensity at at least two positions, which are different positions along the direction of the interference fringes. Based on the light intensity at these at least two positions, the detector determines whether the light field distribution at these positions is a fringe distribution or a uniform field distribution, thereby determining whether the test beam is the first or the second laser beam. This invention has low cost, relatively small size, and low power consumption.

Description

Technical Field

[0001] This invention relates to the field of optics, and in particular to a laser beam identification device and method. Background Technology

[0002] Currently, laser communication systems have permeated all aspects of the economy, society, and people's lives. The sheer number of laser communication devices makes their maintenance both urgent and demanding. In existing technologies, laser communication systems face a common practical problem in maintenance: the pump laser and the signal transmission laser operate alternately using time-division multiplexing, and both employ a coaxial optical path design. Therefore, maintenance requires measures to identify which laser is operating at a given moment in order to quickly and accurately diagnose system faults.

[0003] The existing identification method involves using a first optical path 1, which is a coaxial transmission optical path for both lasers. A beam splitter 2 is inserted into the first optical path 1, for example, at an insertion angle of 45 degrees, with a splitting power ratio of approximately 1 / 10. This results in a low-power split beam transmitted along the second optical path 3. The spectral width of the split beam can then be observed using a spectrometer. The different spectral widths of the laser beams produced by the two lasers allow for identification of the laser type. However, spectrometers are expensive, bulky, heavy, and power-consuming, making them unsuitable for on-site maintenance. Summary of the Invention

[0004] The purpose of this invention is to provide a laser beam identification device and method that is lower in cost, smaller in size, and consumes less power compared to using a spectrometer.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A laser beam identification device is used to identify whether a beam to be tested is a first laser beam or a second laser beam, wherein the spectral width of the first laser beam is different from the spectral width of the second laser beam.

[0007] The laser beam identification device includes a beam expander, an aperture, and a detector. The aperture is disposed on the light-emitting side of the beam expander. The aperture has a first slit and a second slit arranged side by side. The beam expander is used to allow the beam to be tested to pass through the beam expander, and the resulting outgoing beam is incident on the first slit and the second slit, so that the outgoing beam passes through the first slit and the second slit, and the outgoing light from the first slit interferes with the outgoing light from the second slit.

[0008] The detection unit is disposed on the light-emitting side of the aperture. When the beam to be tested is the first laser beam, the optical path difference at the location of the detection unit is less than the maximum optical path difference of the first laser beam. When the beam to be tested is the second laser beam, the optical path difference at the location of the detection unit is greater than the maximum optical path difference of the second laser beam. The detection unit is used to detect the light intensity at at least two locations, which are different locations along the direction of interference fringe arrangement. Based on the light intensity at the at least two locations, the light field distribution at the at least two locations is determined to be either a fringe distribution or a uniform field distribution, thereby determining whether the beam to be tested is the first laser beam or the second laser beam.

[0009] Optionally, the at least two positions include a first position and a second position, wherein the distance between the first position and the second position is 2m+1 times half the period, where m is an integer greater than or equal to zero, the period refers to the distance between adjacent bright fringe centers or adjacent dark fringe centers in the interference-formed fringe light field, and half the period refers to half of the period.

[0010] The detection unit includes a first detection element and a second detection element, wherein the first detection element is disposed at the first position and the second detection element is disposed at the second position.

[0011] Optionally, the at least two positions include a first position, a second position, a third position, and a fourth position arranged sequentially along the direction of the interference fringes. The interval between the first position and the second position is 2m+1 times half the period, the interval between the third position and the fourth position is 2n+1 times half the period, and the interval between the second position and the third position is 2h+1.5 times half the period. m, n, and h are all integers greater than or equal to zero. The period refers to the interval between adjacent bright fringe centers or adjacent dark fringe centers in the interference-formed fringe light field, and half the period refers to half of the period.

[0012] The detection unit includes a first detection element, a second detection element, a third detection element, and a fourth detection element. The first detection element is disposed at the first position, the second detection element is disposed at the second position, the third detection element is disposed at the third position, and the fourth detection element is disposed at the fourth position.

[0013] Optionally, it also includes a preset detection element disposed at the observation center, the preset detection element being used to detect light intensity, the observation center being the position of the center of the interval between the first slit and the second slit corresponding to the plane where the detection part is located.

[0014] Optionally, the detection unit includes multiple detection elements, and the detection elements are disposed at any of the at least two positions. The incident cavity surface width of the detection element is less than half a period. The period refers to the interval distance between adjacent bright fringe centers or adjacent dark fringe centers in the interference-formed fringe light field, and half a period refers to half of the period.

[0015] Optionally, it also includes a mounting base and an insertion part. The beam expander, the aperture, and the detector are disposed on the mounting base, and the insertion part is disposed on one end of the mounting base. The insertion part is connected to the circuit board to mount the laser beam identification device on the circuit board.

[0016] A laser beam identification method is used to identify whether a beam under test is a first laser beam or a second laser beam, wherein the spectral width of the first laser beam is different from that of the second laser beam.

[0017] The laser beam identification device includes a beam expander, an aperture, and a detector. The aperture is disposed on the light-emitting side of the beam expander. The aperture has a first slit and a second slit arranged side by side. The beam expander is used to allow the beam to be tested to pass through the beam expander, and the resulting outgoing beam is incident on the first slit and the second slit, so that the outgoing beam passes through the first slit and the second slit, and the outgoing light from the first slit interferes with the outgoing light from the second slit.

[0018] The detection unit is disposed on the light-emitting side of the aperture. When the beam to be tested is the first laser beam, the optical path difference at the location of the detection unit is less than the maximum optical path difference of the first laser beam. When the beam to be tested is the second laser beam, the optical path difference at the location of the detection unit is greater than the maximum optical path difference of the second laser beam. The detection unit is used to detect the light intensity at at least two locations, which are different locations along the direction of interference fringe arrangement.

[0019] The laser beam identification method includes:

[0020] The beam to be tested is incident on the beam expander of the laser beam discrimination device. The beam to be tested passes through the beam expander and the aperture in sequence, causing the light emitted from the first slit to interfere with the light emitted from the second slit, and causing the detector to detect the light intensity at the at least two positions.

[0021] Based on the light intensity at the at least two locations, it is determined whether the light field distribution at the at least two locations is a striped distribution or a uniform distribution. If the light field distribution at the at least two locations is a striped distribution, then the light beam to be tested is determined to be the first laser beam. If the light field distribution at the at least two locations is a uniform distribution, then the light beam to be tested is determined to be the second laser beam.

[0022] Optionally, the at least two positions include a first position and a second position, wherein the distance between the first position and the second position is 2m+1 times half the period, where m is an integer greater than or equal to zero, the period refers to the distance between adjacent bright fringe centers or adjacent dark fringe centers in the interference-formed fringe light field, and half the period refers to half of the period.

[0023] Determining whether the light field distribution at the at least two locations is a striped distribution or a uniform distribution based on the light intensity at the at least two locations includes:

[0024] If MAX(I1, I2) > 0, and |I1 - I2| > I th If so, the light field distribution at the at least two locations is determined to be a striped distribution;

[0025] If MAX(I1, I2) > 0, and |I1-I2| th If so, the light field distribution at the at least two locations is determined to be a uniform field distribution;

[0026] Where I1 represents the light intensity at the first position, I2 represents the light intensity at the second position, and I th This represents the threshold.

[0027] Optionally, the at least two positions include a first position, a second position, a third position, and a fourth position arranged sequentially along the direction of the interference fringes. The interval between the first position and the second position is 2m+1 times half the period, the interval between the third position and the fourth position is 2n+1 times half the period, and the interval between the second position and the third position is 2h+1.5 times half the period. m, n, and h are all integers greater than or equal to zero. The period refers to the interval between adjacent bright fringe centers or adjacent dark fringe centers in the interference-formed fringe light field, and half the period refers to half of the period.

[0028] Determining whether the light field distribution at the at least two locations is a striped distribution or a uniform distribution based on the light intensity at the at least two locations includes:

[0029] If MAX(I1, I2, I3, I4) > 0, and |I1 - I2| + |I3 - I4| > I th If so, the light field distribution at the at least two locations is determined to be a striped distribution;

[0030] If MAX(I1, I2, I3, I4) > 0, and |I1 - I2| + |I3 - I4| < I th If so, the light field distribution at the at least two locations is determined to be a uniform field distribution;

[0031] ​Wherein, I1 represents the light intensity at the first position, I2 represents the light intensity at the second position, I3 represents the light intensity at the third position, and I4 represents the light intensity at the fourth position. th This represents the threshold.

[0032] Optionally, it also includes:

[0033] The light intensity at the observation center is detected. If I0=0, it is determined that there is no light beam input to be tested. If I0>0, it is determined that there is light beam input to be tested. I0 represents the light intensity at the observation center, which is the position of the center of the gap between the first slit and the second slit on the plane where the detection unit is located.

[0034] As can be seen from the above technical solution, the laser beam identification device and method provided by the present invention are used to identify whether the beam to be tested is a first laser beam or a second laser beam, wherein the spectral width of the first laser beam is different from that of the second laser beam. The laser beam identification device includes a beam expander, an aperture, and a detector. The aperture is disposed on the light-emitting side of the beam expander and has a first slit and a second slit arranged side-by-side. The beam expander is used to allow the beam to be tested to pass through it, and the resulting outgoing beam is incident on the first and second slits, causing interference between the outgoing light from the first slit and the outgoing light from the second slit. The detector is disposed on the light-emitting side of the aperture. When the beam to be tested is the first laser beam, the optical path difference at the location of the detector is less than the maximum optical path difference of the first laser beam; when the beam to be tested is the second laser beam, the optical path difference at the location of the detector is greater than the maximum optical path difference of the second laser beam. The detection unit is used to detect the light intensity at at least two locations, which are different positions along the direction of the interference fringes. Based on the light intensity at these at least two locations, it can determine whether the light field distribution at these locations is a fringe distribution or a uniform field distribution, thereby identifying whether the beam under test is a first laser beam or a second laser beam. The first laser beam and the second laser beam can be laser beams generated by two different lasers, and the lasers can be identified by identifying the laser beams.

[0035] The laser beam identification device and method of the present invention cause the test beam to interfere through a double slit. Within the interference light field, a detector detects whether the light field distribution at the detector is a fringe distribution or a uniform distribution, thereby determining whether the test beam is a first laser beam or a second laser beam. Compared with using a spectrometer, the laser beam identification device of the present invention has lower cost, smaller size, and lower power consumption. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the optical path of an existing identification laser beam;

[0038] Figure 2 This is a schematic diagram illustrating the principle of Young's double-slit interference.

[0039] Figure 3 This is a schematic diagram of a laser beam identification device provided in an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram showing the arrangement of various detection elements in the detection section of a laser beam discrimination device according to an embodiment of the present invention;

[0041] Figure 5 This is a flowchart of a laser beam identification method provided in an embodiment of the present invention.

[0042] The reference numerals in the accompanying drawings include:

[0043] 1-First optical path, 2-Beam splitter, 3-Second optical path, 4-Observation screen, 101-Beam expander, 102-Aperture, 103-Detector, 104-Preset detector element, 105-Mounting base, 106-Insertment, 201-First detector element, 202-Second detector element, 203-Third detector element, 204-Fourth detector element. Detailed Implementation

[0044] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0045] This embodiment provides a laser beam identification device for identifying whether the beam to be tested is a first laser beam or a second laser beam, wherein the spectral width of the first laser beam is different from that of the second laser beam;

[0046] The laser beam identification device includes a beam expander, an aperture, and a detector. The aperture is disposed on the light-emitting side of the beam expander. The aperture has a first slit and a second slit arranged side by side. The beam expander is used to allow the beam to be tested to pass through the beam expander, and the resulting outgoing beam is incident on the first slit and the second slit, so that the outgoing beam passes through the first slit and the second slit, and the outgoing light from the first slit interferes with the outgoing light from the second slit.

[0047] The detection unit is disposed on the light-emitting side of the aperture. When the beam to be tested is the first laser beam, the optical path difference at the location of the detection unit is less than the maximum optical path difference of the first laser beam. When the beam to be tested is the second laser beam, the optical path difference at the location of the detection unit is greater than the maximum optical path difference of the second laser beam. The detection unit is used to detect the light intensity at at least two locations, which are different locations along the direction of interference fringe arrangement. Based on the light intensity at the at least two locations, the light field distribution at the at least two locations is determined to be either a fringe distribution or a uniform field distribution, thereby determining whether the beam to be tested is the first laser beam or the second laser beam.

[0048] The beam to be tested is subjected to interference by passing through the beam expander and the aperture, which are located at the first and second slits. The detector is positioned on the light-emitting side of the aperture and is situated within the interference light field.

[0049] The maximum optical path difference of a laser beam refers to the following: Since real-world laser beams have a spectral distribution with a certain width (spectral width), theoretical derivation shows that the amplitude of the peaks and valleys of the intensity distribution in the interference fringes gradually decreases as the optical path difference increases, modulated by a monotonically decreasing function returning to zero. This decreases until it reaches zero at the zero point of the monotonically decreasing function, at which point the interference fringes almost disappear, becoming a uniformly distributed light field. The optical path difference corresponding to the zero point of the monotonically decreasing function is the maximum optical path difference. The maximum optical path difference of a laser beam is related to the spectral width of the laser beam.

[0050] In this embodiment, the spectral width of the first laser beam is different from that of the second laser beam, and the maximum optical path difference of the first laser beam is different from that of the second laser beam.

[0051] When the beam under test is the first laser beam, the optical path difference at the location of the detector is less than the maximum optical path difference of the first laser beam. Therefore, an interference-generated fringe-distributed optical field exists at the location of the detector. When the beam under test is the second laser beam, the optical path difference at the location of the detector is greater than the maximum optical path difference of the second laser beam, and a uniform optical field has formed at the location of the detector. Based on this, by detecting whether the optical field distribution at the location of the detector is a fringe distribution or a uniform field distribution, it can be determined whether the beam under test is the first laser beam or the second laser beam.

[0052] The first laser beam and the second laser beam can be laser beams generated by two different lasers. This laser beam identification device identifies the laser by identifying the laser beam. The laser beam identification device in this embodiment includes a beam expander, an aperture, and a detector. The components can be arranged according to the optical path requirements. Compared with using a spectrometer, it has lower cost, smaller size, and lower power consumption.

[0053] For reference Figure 2 , Figure 2 This is a schematic diagram illustrating the principle of Young's double-slit interference, as shown below. Figure 2 As shown, the interval between the double slits s1 and s2 is d, the distance between the observation screen 4 and the double slits is D, and the center between the double slits is O. O corresponds to position O' on the observation screen 4. An x-axis is established on the observation screen 4 with O' as the origin, along the direction of the interference fringes. The fringe spacing is Δx, that is, the center-to-center spacing between two adjacent bright fringes is Δx or the center-to-center spacing between two adjacent dark fringes is Δx. The coordinate of the observation position P on the observation screen 4 is x, and the optical path difference corresponding to position P is ΔL.

[0054] The light source has a center wavelength of λ and a spectral width of Δλ. Assuming the light source is an ideal monochromatic source (the spectral distribution of an ideal monochromatic source is an infinitely narrow single spectral line), at the observation position P, due to the optical path difference with the double slits s1 and s2, the following interference criteria apply: When the optical path difference ΔL is an even multiple of half the wavelength (2m, where m is a positive or negative integer), a constructive interference maximum occurs, meaning the observation position P is the center of the bright fringe; when the optical path difference ΔL is an odd multiple of half the wavelength (2m+1, where m is a positive or negative integer), a destructive interference minimum occurs, meaning the observation position P is the center of the dark fringe. Bright and dark fringes alternate along the x-axis. The strict formula for calculating the optical path difference is as follows:

[0055] ; (1)

[0056] According to formula (1), when x=0, the optical path difference ΔL=0; when x=∞, ΔL=d. This means that as the observation position P moves from the origin O' to infinity, the optical path difference ΔL gradually increases from the minimum value of 0 to the maximum value of d.

[0057] For non-monochromatic light sources in the real world, due to their spectral distribution with a certain width (i.e., spectral width), theoretical derivation shows that the amplitude of the peaks and valleys of the light intensity distribution in the interference fringes gradually decreases as the optical path difference increases, modulated by a monotonically decreasing function returning to zero, until it shrinks to zero at the zero point of this monotonically decreasing function. At this point, the interference fringes almost disappear, becoming a uniformly distributed light field. Therefore, the zero point of the monotonically decreasing function corresponds to a maximum optical path difference ΔL. M The calculation formula is as follows:

[0058] ; (2)

[0059] Based on the above analysis, the actual maximum optical path difference in Young's double-slit interference is d. Therefore, when d ≤ ΔL M In theory, the interference fringes can extend to infinity along the observation screen 4, and the contrast between the bright and dark fringes will gradually decrease, but the fringes will not disappear; when d > ΔL M At this time, the observation position can be gradually moved further away to the maximum optical path difference ΔL. M The corresponding observation position, whose coordinates can be represented as x. M When the actual observed coordinates are greater than x M When this occurs, the interference fringes can be considered to disappear.

[0060] According to formula (2), the maximum optical path difference is related to the spectral width of light. Based on this, the laser beam identification device utilizes the difference in spectral width between the first laser beam and the second laser beam, and the difference in the maximum optical path difference between the first laser beam and the second laser beam. By detecting whether the light field is fringe distribution or uniform field distribution at the same observation position, it can identify whether the beam to be tested is the first laser beam or the second laser beam.

[0061] For example, refer to Figure 3 , Figure 3 This is a schematic diagram of a laser beam identification device according to one embodiment. As shown in the figure, the laser beam identification device includes a beam expander 101, an aperture 102, and a detector 103. After the beam to be tested passes through the beam expander 101, the resulting outgoing beam simultaneously enters the first slit and the second slit of the aperture 102. The detector 103 is disposed on the light-emitting side of the aperture 102. The solid lines with arrows in the figure indicate the direction of light propagation.

[0062] In some embodiments, the at least two positions include a first position and a second position, the distance between the first position and the second position being 2m+1 times half the period, where m is an integer greater than or equal to zero. The detection unit 103 includes a first detection element and a second detection element, the first detection element being disposed at the first position and the second detection element being disposed at the second position. The period refers to the distance between adjacent bright fringe centers or adjacent dark fringe centers in the interference-formed fringe light field; the period is also called the fringe interval Δx, and half the period refers to half of the period. Thus, if the light field where the detection unit 103 is located is a fringe distribution, assuming the bright fringe center moves to the first position, since the distance between the first position and the second position is 2m+1 times half the period, i.e., an odd multiple of half the period, a certain dark fringe center will exactly move to the second position. At this time, the difference between the light intensity at the first position and the light intensity at the second position is the largest. If the light field where the detection unit 103 is located is a uniform field distribution, the difference between the light intensity at the first position and the light intensity at the second position changes very little and is relatively constant. Based on this, the light field distribution is determined to be either a fringe distribution or a uniform field distribution based on the light intensity at the first position and the second position. When the wavelengths of the first laser beam and the second laser beam are known, the first position and the second position can be determined based on the wavelength of the first laser beam, such that when the beam to be tested is the first laser beam, the first position corresponds to the center of bright fringe / dark fringe, and the second position corresponds to the center of dark fringe / bright fringe. Thus, based on the light intensity at the first position and the second position, and based on the contrast between the brightness at the first position and the second position, it can be determined whether the light field distribution is a striped distribution or a uniform distribution.

[0063] The period, or stripe spacing Δx, can be calculated based on the allowable wavelength range specified by the optical signaling standard protocol for the lasers that generate the first and second laser beams. The period can be calculated by selecting a certain wavelength value from the specified allowable wavelength range, such as the center wavelength of the allowable wavelength range.

[0064] In some embodiments, the at least two positions include a first position, a second position, a third position, and a fourth position arranged sequentially along the direction of the interference fringe arrangement. The interval between the first position and the second position is 2m+1 times half a period, the interval between the third position and the fourth position is 2n+1 times half a period, and the interval between the second position and the third position is 2h+1.5 times half a period, where m, n, and h are all integers greater than or equal to zero. The detection unit 103 includes a first detection element, a second detection element, a third detection element, and a fourth detection element. The first detection element is disposed at the first position, the second detection element is disposed at the second position, the third detection element is disposed at the third position, and the fourth detection element is disposed at the fourth position.

[0065] The period refers to the distance between adjacent bright fringe centers or adjacent dark fringe centers in the interference fringe light field. The period is also called the fringe spacing Δx, and half-period refers to half the period. The first or second laser beam is a laser beam generated by a laser. The wavelength of the laser beam generated by the actual laser is within the allowable wavelength range specified in the laser's design. However, in actual identification, the wavelength of the actual laser beam generated by the laser is uncertain. Assuming the allowable wavelength range specified in the laser's design is expressed as [lower limit wavelength, upper limit wavelength], when the laser beam changes from the lower limit wavelength to the upper limit wavelength, at a certain observation position, the interference fringes will sweep across multiple fringes away from the origin. This phenomenon, where the position of the interference fringes shifts laterally for different wavelengths of laser beams, makes it difficult to detect the contrast between bright and dark fringes.

[0066] To address this, in this embodiment, by sequentially setting the first, second, third, and fourth positions along the direction of the interference fringes, and with the spacing between each position as described above, assuming the center of a bright fringe moves to the first position, since the spacing between the first and second positions is 2m+1 times half the period (an odd multiple of half the period), the center of a dark fringe will exactly move to the second position. At this point, the difference in light intensity between the first and second positions is the largest. At this point, the third position is exactly in the middle of adjacent bright and dark fringes, and the fourth position is exactly in the middle of adjacent bright and dark fringes, with the smallest difference in light intensity between the third and fourth positions. When the interference fringes shift laterally by 1 / 4 of the period, the situation is exactly the opposite. At this point, the first position is exactly in the middle of adjacent bright and dark fringes, and the second position also corresponds exactly to the middle of adjacent bright and dark fringes, with the smallest difference in light intensity between the first and second positions. Meanwhile, the third position is at the center of a bright fringe / dark fringe, and the fourth position is at the center of a dark fringe / bright fringe, with the largest difference in light intensity between the third and fourth positions. Similarly, when the interference fringes move laterally between these two cases, the difference between the light intensity at the first position and the light intensity at the second position is between the maximum and minimum values ​​of the difference, and the difference between the light intensity at the third position and the light intensity at the fourth position is between the maximum and minimum values ​​of the difference. In this embodiment, determining whether the light field is fringe or uniform based on the light intensity at each of the first to fourth positions improves the accuracy of the determination.

[0067] In some embodiments, the laser beam identification device further includes a preset detection element 104 disposed at the observation center. The preset detection element 104 is used to detect light intensity. The observation center is the position of the center of the gap between the first slit and the second slit, corresponding to the position on the plane where the detection part 103 is located. The preset detection element 104 can detect whether there is a light field on the light-emitting side of the aperture part 102, and can detect whether there is a beam to be tested input.

[0068] In some embodiments, the detection unit 103 includes a plurality of detection elements, which are disposed at any of the at least two locations. The incident cavity surface width of the detection element is less than half a period. The period refers to the distance between the centers of adjacent bright fringes or the centers of adjacent dark fringes in the interference-formed fringe light field, and half a period refers to half of the period. Half a period is also the distance between the centers of adjacent bright and dark fringes. Having an incident cavity surface width less than half a period is more advantageous for detecting the brightness contrast of the interference fringes. The detection elements may be, but are not limited to, narrow-ridge waveguide edge-emitting devices.

[0069] In this embodiment, the structure of the beam expander 101 is not limited. It is sufficient that the beam to be measured, after passing through the beam expander 101, forms an outgoing beam that enters the first slit and the second slit, and the outgoing light from the first slit interferes with the outgoing light from the second slit. The beam expander 101 expands the incident fine beam, making the size of the expanded beam larger than the double-slit interval. In some embodiments, the beam expander 101 may include, but is not limited to, a convex lens or a concave lens. (See reference...) Figure 3 ,exist Figure 3 The beam expander 101 in the device shown includes a concave lens, and the beam expander 101 can be referred to as a beam expander.

[0070] In some embodiments, the laser beam identification device further includes a mounting base 105 and an insertion part 106. The beam expander 101, the aperture 102, and the detector 103 are disposed on the mounting base 105, and the insertion part 106 is disposed on one end of the mounting base 105. The laser beam identification device is mounted on the circuit board by connecting to the circuit board through the insertion part 106. The components of this laser beam identification device can be small in size and have a small spacing, so that they can be packaged with the circuit board. The insertion part 106 can also be referred to as a pin. This laser beam identification device can adopt a TO package, and can adopt a multi-pin TO package, in which each detection element can share a common ground lead.

[0071] In a specific example, the first laser beam is generated by a distributed feedback laser diode (DFB-LD), and the second laser beam is generated by a Fabry-Perot laser diode (FP-LD).

[0072] According to the optical communication standard protocol, the allowed wavelength range of DFB-LD is 1310nm±20nm, its spectral width Δλ=0.001nm, and its monochromaticity is good. ΔL is calculated according to formula (2). M,DFB =1716.1mm±52mm. According to the optical communication standard protocol, the allowed wavelength range of FP-LD is 1310nm±50nm, its spectral width Δλ=2nm, and its monochromaticity is poor. ΔL is calculated according to formula (2). M, FP =0.86mm±0.07mm.

[0073] In this example, the double-slit spacing d is taken as 1.35mm, since d << ΔL M,DFB Therefore, the observation range of interference fringes in DFB-LD can be extended to infinity; and since d > ΔL M, FP Therefore, the interference fringes of FP-LD have a maximum observation coordinate x. M In this example, the distance D between the virtual observation screen (i.e., the plane where the detection unit 103 is located) and the aperture unit 102 is 1.5mm, which is beneficial for achieving a compact spatial layout of the various components of this device.

[0074] In this example, the detection unit 103 includes a first detection element 201, a second detection element 202, a third detection element 203, and a fourth detection element 204 arranged sequentially along the direction of the interference fringes. (See reference...) Figure 4 As shown, Figure 4 This is a schematic diagram of the arrangement of various detection elements in the detection section of a laser beam discrimination device according to an embodiment. The center-to-center distance d1 between the first detection element 201 and the second detection element 202 is 2m+1 times half a period; the center-to-center distance d2 between the third detection element 203 and the fourth detection element 204 is 2n+1 times half a period; and the center-to-center distance d3 between the second detection element 202 and the third detection element 203 is 2h+1.5 times half a period. Where m, n, and h are not specifically limited. The center observation coordinate x of the linear array formed by the first detection element 201 to the fourth detection element 204 is 1.65 mm. According to formula (1), the optical path difference ΔL at this position is approximately 0.98 mm, which is greater than ΔL. M, FP The maximum value is 0.93 mm, therefore the interference fringes of the FP-LD have disappeared and the light field is uniformly distributed.

[0075] If the bright interference fringes of DFB-LD are numbered, starting from the observation coordinate x=0 and numbered 0, 1, 2, 3..., then the formula for calculating the interference fringe number N at the observation coordinate x is as follows:

[0076] ; (3)

[0077] The square brackets in the formula indicate rounding to the nearest integer. By combining formulas (1) and (3), for the lower limit wavelength of DFB-LD of 1290nm, the interference fringe number corresponding to the observation coordinate x=1.65mm is 758; for the upper limit wavelength of DFB-LD of 1330nm, the interference fringe number corresponding to the observation coordinate x=1.65mm is 735.

[0078] Taking a wavelength of 1290nm as an example, through numerical calculation, when the interference fringe number N changes from 758 to 759 (or when N changes by 1.00 for non-integer values), the change in the observation coordinate x, Δx, can be obtained. This value is the fringe spacing (i.e., the period). According to this calculation method, within the allowable wavelength range of DFB-LD, the calculated fringe spacing Δx is 4.4-4.5μm. Therefore, the center-to-center distance between adjacent bright and dark fringes (i.e., the half-period) is 2.2-2.25μm. Thus, the incident cavity width of each detector element in the 103 linear array of the detector section should be approximately 2μm, which is more conducive to detecting the contrast between bright and dark interference fringes.

[0079] The calculations also show that when the DFB-LD changes from the lower wavelength to the upper wavelength, at the observation coordinate x=1.65mm, the interference fringes sweep away from the origin by 758-735=23 fringe intervals. This phenomenon, where the position of the interference fringes shifts laterally for different laser wavelengths, makes it difficult to detect the contrast between bright and dark fringes. Therefore, in this example, the detection unit 103 is provided with at least four detection elements. The center spacing of each detection element from the first detection element 201 to the fourth detection element 204 is set as described above. Then: assuming that the incident cavity surface of the first detection element 201 coincides with the center of a bright fringe, the second detection element 202 will necessarily coincide with the center of a dark fringe. At this time, the photoelectric signal difference between the first detection element 201 and the second detection element 202 is the largest. At the same time, the third detection element 203 and the fourth detection element 204 will similarly receive a combination of half bright fringes and half dark fringes, that is, the photoelectric signal difference between the third detection element 203 and the fourth detection element 204 is the smallest. When the interference fringes shift laterally by 1 / 4 of the fringe spacing, the situation is exactly the opposite. The photoelectric signal difference between the third detection element 203 and the fourth detection element 204 is the largest, while the photoelectric signal difference between the first detection element 201 and the second detection element 202 is the smallest. And so on. When the interference fringes move laterally between these two cases, the photoelectric signal difference between the first detection element 201 and the second detection element 202 and the photoelectric signal difference between the third detection element 203 and the fourth detection element 204 are also between their maximum and minimum values.

[0080] In some embodiments, the detection unit 103 may be connected to a processing device. The processing device determines, based on the light intensity obtained by the detection unit 103 at the at least two locations, whether the light field distribution at those locations is a fringe distribution or a uniform field distribution, thereby determining whether the beam to be tested is a first laser beam or a second laser beam. The processing device may include a data acquisition module for acquiring the electrical signals output by the detection unit 103, including but not limited to amplifying or performing analog-to-digital conversion on the electrical signals. The processing device may also include a data processing module for performing calculations based on the obtained light intensity data at the at least two locations and outputting a determination result. The data processing module may employ, but is not limited to, a microcontroller or a field-programmable gate array (FPGA).

[0081] This embodiment also provides a laser beam identification method for identifying whether the beam to be tested is a first laser beam or a second laser beam, wherein the spectral width of the first laser beam is different from the spectral width of the second laser beam;

[0082] The laser beam identification device includes a beam expander, an aperture, and a detector. The aperture is disposed on the light-emitting side of the beam expander. The aperture has a first slit and a second slit arranged side by side. The beam expander is used to allow the beam to be tested to pass through the beam expander, and the resulting outgoing beam is incident on the first slit and the second slit, so that the outgoing beam passes through the first slit and the second slit, and the outgoing light from the first slit interferes with the outgoing light from the second slit.

[0083] The detection unit is disposed on the light-emitting side of the aperture. When the beam to be tested is the first laser beam, the optical path difference at the location of the detection unit is less than the maximum optical path difference of the first laser beam. When the beam to be tested is the second laser beam, the optical path difference at the location of the detection unit is greater than the maximum optical path difference of the second laser beam. The detection unit is used to detect the light intensity at at least two locations, which are different locations along the direction of the interference fringes.

[0084] For reference Figure 5 , Figure 5 A flowchart of a laser beam identification method provided in one embodiment is shown in the figure. The laser beam identification method includes the following steps:

[0085] S11: The beam to be tested is incident on the beam expander of the laser beam identification device, and the beam to be tested passes through the beam expander and the aperture in sequence, so that the light emitted from the first slit and the light emitted from the second slit interfere, and the detection unit detects the light intensity at the at least two positions.

[0086] S12: Determine whether the light field distribution at the at least two locations is a striped distribution or a uniform distribution based on the light intensity at the at least two locations. If the light field distribution at the at least two locations is a striped distribution, then determine that the beam to be tested is the first laser beam. If the light field distribution at the at least two locations is a uniform distribution, then determine that the beam to be tested is the second laser beam.

[0087] The spectral widths of the first laser beam and the second laser beam are different, as are their maximum optical path differences. When the beam under test is the first laser beam, the optical path difference at the location of the detector 103 is less than the maximum optical path difference of the first laser beam; therefore, an interference-formed fringe distribution light field exists at the location of the detector 103. When the beam under test is the second laser beam, the optical path difference at the location of the detector 103 is greater than the maximum optical path difference of the second laser beam, and a uniform light field has formed at the location of the detector 103. Based on this, by detecting whether the light field distribution at the location of the detector 103 is a fringe distribution or a uniform field distribution, it can be determined whether the beam under test is the first laser beam or the second laser beam.

[0088] The first laser beam and the second laser beam can be laser beams generated by two different lasers. This laser beam identification method identifies the laser by identifying the laser beam. The laser beam identification device used in this embodiment includes a beam expander, an aperture, and a detector. The components can be arranged according to the optical path requirements. Compared with using a spectrometer, it has lower cost, smaller size, and lower power consumption.

[0089] In some embodiments, the at least two positions include a first position and a second position, wherein the distance between the first position and the second position is 2m+1 times half a period, where m is an integer greater than or equal to zero. Determining whether the light field distribution at the at least two positions is a fringe distribution or a uniform distribution based on the light intensity at the at least two positions includes:

[0090] If MAX(I1, I2) > 0, and |I1 - I2| > I th If so, the light field distribution at the at least two locations is determined to be a striped distribution;

[0091] If MAX(I1, I2) > 0, and |I1-I2| th If so, the light field distribution at the at least two locations is determined to be a uniform field distribution;

[0092] Where I1 represents the light intensity at the first position, I2 represents the light intensity at the second position, and I th This represents the threshold.

[0093] ​If MAX(I1, I2) > 0, it indicates that there is a beam to be measured input. If MAX(I1, I2) = 0, it can be determined that there is no beam to be measured input.

[0094] In some embodiments, the at least two positions include a first position, a second position, a third position, and a fourth position arranged sequentially along the direction of the interference fringes. The interval between the first and second positions is 2m+1 times half a period, the interval between the third and fourth positions is 2n+1 times half a period, and the interval between the second and third positions is 2h+1.5 times half a period, where m, n, and h are all integers greater than or equal to zero. Determining whether the light field distribution at the at least two positions is a fringe distribution or a uniform distribution based on the light intensity at the at least two positions includes:

[0095] If MAX(I1, I2, I3, I4) > 0, and |I1 - I2| + |I3 - I4| > I th If so, the light field distribution at the at least two locations is determined to be a striped distribution;

[0096] If MAX(I1, I2, I3, I4) > 0, and |I1 - I2| + |I3 - I4| < I th If so, the light field distribution at the at least two locations is determined to be a uniform field distribution;

[0097] Wherein, I1 represents the light intensity at the first position, I2 represents the light intensity at the second position, I3 represents the light intensity at the third position, and I4 represents the light intensity at the fourth position. th This represents the threshold. MAX() represents the maximum value function, and || represents the absolute value function.

[0098] If MAX(I1, I2, I3, I4) > 0, it indicates that there is a beam to be tested input. If MAX(I1, I2, I3, I4) = 0, it can be determined that there is no beam to be tested input.

[0099] In some embodiments, the laser beam identification method further includes: detecting the light intensity at the observation center; if I0=0, it is determined that there is no beam input to be tested; if I0>0, it is determined that there is beam input to be tested. I0 represents the light intensity at the observation center, and the observation center is the position of the center of the gap between the first slit and the second slit on the plane where the detection unit is located.

[0100] In a specific instance, if MAX(I2, I3, I4, I5) = 0 or I0 = 0, then it is determined that there is no input beam to be measured. If MAX(I1, I2, I3, I4) > 0 or I0 > 0, and |I1 - I2| + |I3 - I4| > I thIf the light field distribution at the at least two positions is determined to be a fringe distribution, and the beam to be tested is the first laser beam; if MAX(I1, I2, I3, I4) > 0 or I0 > 0, and |I1-I2|+|I3-I4| < I th If the light field distribution at the at least two locations is determined to be a uniform field distribution, then the beam to be tested is the second laser beam.

[0101] The advantages of this laser beam identification device and method are as follows: 1. Based on Young's double-slit interference effect, the laser beam and laser type are identified by determining the presence of interference fringes through a clever geometric layout of optoelectronic devices; 2. This laser beam identification device is perfectly compatible with all permissible wavelength ranges specified in optical communication standard protocols; 3. The optoelectronic devices used in this laser beam identification device are of extremely low cost and easy to assemble, making them suitable for mass production; 4. This laser beam identification device is small in size, lightweight, and has low power consumption.

[0102] The laser beam identification device and method provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A laser beam identification device, characterized in that, Used to identify whether the beam under test is a first laser beam or a second laser beam, wherein the spectral width of the first laser beam is different from that of the second laser beam; The laser beam identification device includes a beam expander, an aperture, and a detector. The aperture is disposed on the light-emitting side of the beam expander. The aperture has a first slit and a second slit arranged side by side. The beam expander is used to allow the beam to be tested to pass through the beam expander, and the resulting outgoing beam is incident on the first slit and the second slit, so that the outgoing beam passes through the first slit and the second slit, and the outgoing light from the first slit interferes with the outgoing light from the second slit. The detection unit is disposed on the light-emitting side of the aperture. When the beam to be tested is the first laser beam, the optical path difference at the location of the detection unit is less than the maximum optical path difference of the first laser beam. When the beam to be tested is the second laser beam, the optical path difference at the location of the detection unit is greater than the maximum optical path difference of the second laser beam. The detection unit is used to detect the light intensity at at least two locations, which are different locations along the direction of interference fringe arrangement. Based on the light intensity at the at least two locations, the light field distribution at the at least two locations is determined to be either a fringe distribution or a uniform field distribution, thereby determining whether the beam to be tested is the first laser beam or the second laser beam.

2. The laser beam identification device according to claim 1, characterized in that, The at least two positions include a first position and a second position. The distance between the first position and the second position is 2m+1 times half the period, where m is an integer greater than or equal to zero. The period refers to the distance between the centers of adjacent bright fringes or the distance between the centers of adjacent dark fringes in the fringe light field formed by the interference. Half the period refers to half of the period. The detection unit includes a first detection element and a second detection element, wherein the first detection element is disposed at the first position and the second detection element is disposed at the second position.

3. The laser beam identification device according to claim 1, characterized in that, The at least two positions include a first position, a second position, a third position, and a fourth position arranged sequentially along the direction of the interference fringes. The interval between the first position and the second position is 2m+1 times half the period, the interval between the third position and the fourth position is 2n+1 times half the period, and the interval between the second position and the third position is 2h+1.5 times half the period. m, n, and h are all integers greater than or equal to zero. The period refers to the interval between adjacent bright fringe centers or adjacent dark fringe centers in the interference-formed fringe light field, and half the period refers to half of the period. The detection unit includes a first detection element, a second detection element, a third detection element, and a fourth detection element. The first detection element is disposed at the first position, the second detection element is disposed at the second position, the third detection element is disposed at the third position, and the fourth detection element is disposed at the fourth position.

4. The laser beam identification device according to claim 1, characterized in that, It also includes a preset detection element set at the observation center, the preset detection element being used to detect light intensity, the observation center being the position of the center of the interval between the first slit and the second slit corresponding to the plane where the detection part is located.

5. The laser beam identification device according to claim 1, characterized in that, The detection unit includes multiple detection elements, and the detection elements are disposed at any of the at least two locations. The width of the incident cavity surface of the detection element is less than half a period. The period refers to the interval distance between adjacent bright fringe centers or adjacent dark fringe centers in the interference-formed fringe light field, and half a period refers to half of the period.

6. The laser beam identification device according to any one of claims 1 to 5, characterized in that, It also includes a mounting base and an insertion part. The beam expander, the aperture, and the detector are disposed on the mounting base, and the insertion part is disposed on one end of the mounting base. The insertion part is connected to the circuit board to mount the laser beam identification device on the circuit board.

7. A laser beam identification method, characterized in that, Used to identify whether the beam under test is a first laser beam or a second laser beam, wherein the spectral width of the first laser beam is different from that of the second laser beam; The laser beam identification device includes a beam expander, an aperture, and a detector. The aperture is disposed on the light-emitting side of the beam expander. The aperture has a first slit and a second slit arranged side by side. The beam expander is used to allow the beam to be tested to pass through the beam expander, and the resulting outgoing beam is incident on the first slit and the second slit, so that the outgoing beam passes through the first slit and the second slit, and the outgoing light from the first slit interferes with the outgoing light from the second slit. The detection unit is disposed on the light-emitting side of the aperture. When the beam to be tested is the first laser beam, the optical path difference at the location of the detection unit is less than the maximum optical path difference of the first laser beam. When the beam to be tested is the second laser beam, the optical path difference at the location of the detection unit is greater than the maximum optical path difference of the second laser beam. The detection unit is used to detect the light intensity at at least two locations, which are different locations along the direction of interference fringe arrangement. The laser beam identification method includes: The beam to be tested is incident on the beam expander of the laser beam discrimination device. The beam to be tested passes through the beam expander and the aperture in sequence, causing the light emitted from the first slit to interfere with the light emitted from the second slit, and causing the detector to detect the light intensity at the at least two positions. Based on the light intensity at the at least two locations, it is determined whether the light field distribution at the at least two locations is a striped distribution or a uniform distribution. If the light field distribution at the at least two locations is a striped distribution, then the light beam to be tested is determined to be the first laser beam. If the light field distribution at the at least two locations is a uniform distribution, then the light beam to be tested is determined to be the second laser beam.

8. The laser beam identification method according to claim 7, characterized in that, The at least two positions include a first position and a second position. The distance between the first position and the second position is 2m+1 times half the period, where m is an integer greater than or equal to zero. The period refers to the distance between the centers of adjacent bright fringes or the distance between the centers of adjacent dark fringes in the fringe light field formed by the interference. Half the period refers to half of the period. Determining whether the light field distribution at the at least two locations is a striped distribution or a uniform distribution based on the light intensity at the at least two locations includes: If MAX(I1, I2) > 0, and |I1 - I2| > I th If so, the light field distribution at the at least two locations is determined to be a striped distribution; If MAX(I1, I2) > 0, and |I1-I2| th If so, the light field distribution at the at least two locations is determined to be a uniform field distribution;​ Where I1 represents the light intensity at the first position, I2 represents the light intensity at the second position, and I th This represents the threshold.

9. The laser beam identification method according to claim 7, characterized in that, The at least two positions include a first position, a second position, a third position, and a fourth position arranged sequentially along the direction of the interference fringes. The interval between the first position and the second position is 2m+1 times half the period, the interval between the third position and the fourth position is 2n+1 times half the period, and the interval between the second position and the third position is 2h+1.5 times half the period. m, n, and h are all integers greater than or equal to zero. The period refers to the interval between adjacent bright fringe centers or adjacent dark fringe centers in the interference-formed fringe light field, and half the period refers to half of the period. Determining whether the light field distribution at the at least two locations is a striped distribution or a uniform distribution based on the light intensity at the at least two locations includes: If MAX(I1, I2, I3, I4) > 0, and |I1 - I2| + |I3 - I4| > I th If so, the light field distribution at the at least two locations is determined to be a striped distribution; If MAX(I1, I2, I3, I4) > 0, and |I1 - I2| + |I3 - I4| < I th If so, the light field distribution at the at least two locations is determined to be a uniform field distribution; Wherein, I1 represents the light intensity at the first position, I2 represents the light intensity at the second position, I3 represents the light intensity at the third position, and I4 represents the light intensity at the fourth position. th This represents the threshold.

10. The laser beam identification method according to any one of claims 7 to 9, characterized in that, Also includes: The light intensity at the observation center is detected. If I0=0, it is determined that there is no light beam input to be tested. If I0>0, it is determined that there is light beam input to be tested. I0 represents the light intensity at the observation center, which is the position of the center of the gap between the first slit and the second slit on the plane where the detection unit is located.

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