Small-size flat-top optical filter and use method thereof

Abstract

The invention relates to the technical field of optical communication, in particular to a small-size flat-top optical filter and a using method thereof, and the small-size flat-top optical filter comprises an optical input and output assembly, a beam expanding assembly, a rotatable reflecting mirror, a beam shaping assembly, a grating assembly and a light reflecting micromirror. A rotatable reflector is arranged in the optical filter, the tunable function of the optical filter is realized, an optical signal reflected by a light reflection micromirror can be an optical signal with a preset wavelength by rotating the rotatable reflector, the optical signal is filtered by a grating assembly for four times, the output spectrum rectangularity is optimized, and the out-of-band isolation is also remarkably improved; compared with an optical fiber mode field difference technology and a diaphragm technology in the prior art, the technical scheme provided by the invention has the advantages that the scene adaptability is higher, the requirements on the control precision and the manufacturing process in the debugging process are lower, and the production cycle and the cost of the optical filter are favorably reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of optical communications, and in particular to a small-sized flat-top optical filter and a method for using the same. Background Art

[0002] With the development of optical communication technology, optical transport networks have put forward more stringent requirements on signal rate, channel capacity, and channel width. Improving the single-wavelength rate is one of the important ways to increase the single-fiber transmission capacity of the optical transport network. At the same time, in order to achieve long-distance transmission of single-wavelength high-speed, coherent modulators have become a key influencing factor.

[0003] As a core component in optical communication systems, the performance of coherent modulators directly determines the modulation quality and transmission performance of signals. In coherent optical communication systems, coherent modulators enable precise modulation of optical signals, efficiently loading digital information onto optical carriers. However, in practical applications, the transmitter end of coherent optical modules generates a certain amount of out-of-band noise, which mixes into the modulated signal and seriously affects signal quality. The presence of out-of-band noise not only reduces the system's optical signal-to-noise ratio (OSNR) but also increases the signal's bit error rate (BER), thereby limiting the signal's ability to transmit over long distances.

[0004] To effectively improve the system's optical signal-to-noise ratio (OSNR) and extend signal transmission distance, using optical filters to filter the signals at the transmitter end of coherent optical modules has become an effective solution. Bandpass filters allow signals within a specific frequency range to pass while filtering out signals outside that range. Therefore, bandpass filters are also called flat-top filters.

[0005] The common flat-top optical filters currently on the market have numerous technical limitations. Some utilize mode field differentiation between the input and output fibers. While this technology achieves filtering to a certain extent, it places extremely high demands on mode field matching between the input and output fibers. Any deviation in mode field matching can lead to a sharp decline in filtering performance. This technology also places stringent demands on fiber manufacturing processes and coupling accuracy, increasing production costs and making system debugging more difficult. Other flat-top optical filters utilize an aperture to limit the propagation range of the light beam, thereby achieving a filtering effect. However, this technology requires extremely high precision in the size, position, and shape of the aperture. Any slight deviation can affect filter performance. Furthermore, in practical applications, the aperture setting can introduce additional optical loss, reducing the overall transmission efficiency of the system.

[0006] In view of this, overcoming the defects of the prior art is an urgent problem to be solved in this technical field. Summary of the Invention

[0007] The technical problem to be solved by the present invention is that the existing flat-top optical filters have high requirements in terms of adaptability to application scenarios, control accuracy and manufacturing process.

[0008] The present invention adopts the following technical solutions: In a first aspect, the present invention provides a small-sized flat-top optical filter, comprising: an optical input and output component 1, a beam expander component 2, a rotatable reflector 3, a beam shaping component 4, a grating component 5, and a light-reflecting micromirror 6; the optical input and output component 1 is used to transmit a signal light beam and receive a returned optical signal of a predetermined wavelength. The signal light beam passes through the beam expander component 2, is reflected by the rotatable reflector 3 to the beam shaping component 4, and then passes through the grating component 5. The grating component 5 reflects the signal light beam to the beam shaping component 4. The beam shaping component 4 reflects the optical signal of the predetermined wavelength to the light-reflecting micromirror 6. The light-reflecting micromirror 6 reflects the optical signal of the predetermined wavelength back to the optical input and output component 1 along the original path. The optical signal of the predetermined wavelength is determined by the rotation angle of the rotatable reflector 3 .

[0009] Preferably, the beam shaping assembly 4 includes a biconvex cylindrical mirror 40, a plane reflector 41, and a concave reflector 42, wherein the plane reflector 41 is disposed between the biconvex cylindrical mirror 40 and the concave reflector 42, and the biconvex cylindrical mirror 40 is located between the rotatable reflector 3 and the plane reflector 41. The plane reflector 41 is used to reflect the optical signal transmitted by the biconvex cylindrical mirror 40 to the concave reflector 42, and the concave reflector 42 is used to reflect the optical signal into the grating assembly 5; The light reflecting micromirror 6 is disposed at the rear focus of the concave reflecting mirror 42 .

[0010] Preferably, the biconvex cylindrical mirror 40 includes a first cylindrical surface 400 and a second cylindrical surface 401, and the first cylindrical surface 400 and the second cylindrical surface 401 are used to amplify the size of the optical signal on the plane reflector 41; The first cylindrical surface 400 and the second cylindrical surface 401 are coated with an anti-reflection film.

[0011] Preferably, the grating assembly 5 includes a plano-convex cylindrical mirror 50 and a grating unit 51. The plano-convex cylindrical mirror 50 is located between the grating unit 51 and the concave reflector 42. The plano-convex cylindrical mirror 50 is used to adjust the divergence angle of the signal light beam. After passing through the grating unit 51, the signal light beam is dispersed, and light of different wavelengths is separated at different angles. The light is then transmitted through the plano-convex cylindrical mirror 50 to the concave reflector 42, and then reflected by the concave reflector 42 to the light reflecting micromirror 6.

[0012] Preferably, the grating unit 51 is a diffraction grating, and one of the surfaces of the diffraction grating is a reflective surface; Alternatively, the grating unit 51 includes a transmissive diffraction grating 510 and a second right-angle prism 511 , and a right-angle side of the second right-angle prism 511 is disposed close to the transmissive diffraction grating 510 .

[0013] Preferably, the optical input and output assembly 1 includes an optical input and output unit 10 and a collimating lens unit 11, and the collimating lens unit 11 is arranged between the optical input and output unit 10 and the beam expanding assembly 2; The optical input and output unit 10 includes an optical input pin 100 and an optical output pin 101, and the collimating lens unit 11 includes a first collimating lens 110 and a second collimating lens 111. The first collimating lens 110 is arranged corresponding to the optical input pin 100, and the second collimating lens 111 is arranged corresponding to the optical output pin 101. Alternatively, the optical input and output unit 10 includes a circulator and a dual-core pin, the collimating lens unit 11 is a single lens, the circulator and the dual-core pin are optically connected, and the collimating lens unit 11 is arranged corresponding to the dual-core pin.

[0014] Preferably, the beam expansion component 2 includes at least one first right-angle prism 20 , and the at least one first right-angle prism 20 is used to expand the signal light beam of the optical input and output component 1 .

[0015] Preferably, the rotatable reflector 3 is a MEMS reflector, the angle of the rotatable reflector 3 can be rotated by ±2.2°, and the wavelength can be tuned by 40nm±1nm.

[0016] Preferably, the light reflecting micromirror 6 has a length of 1 mm ± 0.01 mm and a width of 50 um ± 0.01 um.

[0017] In a second aspect, the present invention provides a method for using a small-sized flat-top optical filter based on the first aspect, which is applicable to the small-sized flat-top optical filter described in the first aspect, comprising: The optical input and output component 1 outputs the signal light beam, and after the signal light beam passes through the grating component 5, it is reflected back as an optical signal of a predetermined wavelength on the light reflecting micromirror 6, and the optical signal of the predetermined wavelength returns to the optical input and output component 1 along the original optical path; The wavelength of the optical signal of the predetermined wavelength is measured at the output end of the optical input and output component 1 , and the angle of the rotatable reflector 3 is adjusted until the expected spectrum is obtained. The rotatable reflector 3 is locked, and the next step of the filter operation can be carried out.

[0018] Compared with the prior art, the present invention has the following advantages: a rotatable reflector 3 is provided in the optical filter to realize the tunable function of the optical filter; by rotating the rotatable reflector 3, the optical signal reflected back by the light-reflecting micromirror 6 can be an optical signal of a predetermined wavelength; and, after the signal light beam passes through the beam expansion component 2, the rotatable reflector 3 and the beam shaping component 4 in sequence from the signal output end of the optical input and output component 1, it enters the grating component 5, is reflected from the grating component 5, is reflected by the beam shaping component 4 to the light-reflecting micromirror 6, and the light-reflecting micromirror 6 reflects the optical signal of the predetermined wavelength back to the beam shaping component 4, and the optical signal of the predetermined wavelength is again The optical signal of a predetermined wavelength is reflected by the beam shaping component 4 into the grating component 5 and finally reflected from the grating component 5. The optical signal passes through the beam shaping component 4, the rotatable reflector 3, the beam expanding component 2 and the optical input and output component 1 in sequence and is output from the output end of the optical input and output component 1. Therefore, the optical signal is filtered by the grating component 5 four times, which optimizes the output spectrum rectangularity and significantly improves the out-of-band isolation. In addition, compared with the fiber mode field difference technology and aperture technology in the prior art, the technical solution provided by the present invention has higher scenario adaptability, lower control accuracy and manufacturing process requirements during the debugging process, and is conducive to reducing the production cycle and cost of the optical filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0020] Figure 1 This is a schematic diagram of the overall structure of a small-sized flat-top optical filter provided by an embodiment of the present invention; Figure 2 Schematic diagram of an optical input and output assembly of a small-sized flat-top optical filter provided by an embodiment of the present invention; Figure 3 Schematic diagram of a beam expansion component of a small-sized flat-top optical filter provided by an embodiment of the present invention; Figure 4 Schematic diagram of a grating assembly of a small-sized flat-top optical filter provided by an embodiment of the present invention; Figure 5 This is a schematic diagram of a specific form of a grating component of a small-sized flat-top optical filter provided by an embodiment of the present invention; Figure 6 Schematic diagram of a grating assembly of a small-sized flat-top optical filter provided by an embodiment of the present invention; Figure 7Schematic diagram of a transmissive diffraction grating of a small-sized flat-top optical filter provided by an embodiment of the present invention; Figure 8 Schematic diagram of a light-reflecting micromirror of a small-sized flat-top optical filter provided by an embodiment of the present invention; Figure 9 Schematic diagram of an output spectrum of a small-sized flat-top optical filter provided by an embodiment of the present invention; Figure 10 The figure is a schematic diagram of the use process of a small-sized flat-top optical filter provided by an embodiment of the present invention.

[0021] Wherein, the accompanying drawings are marked as follows: 1- Optical input and output assembly, 10- Optical input and output unit, 100- Optical input pin, 101- Optical output pin, 11- Collimating lens unit, 110- First collimating lens, 111- Second collimating lens, 2- Beam expansion assembly, 20- First right-angle prism, 3- Rotatable reflector, 4- Beam shaping assembly, 40- Double convex cylindrical mirror, 400- First cylinder, 401- Second cylinder, 41- Plane reflector, 42- Concave reflector, 5- Grating assembly, 50- Plano-convex cylindrical mirror, 51- Grating unit, 510- Transmission diffraction grating, 511- Second right-angle prism, 6- Light reflecting micromirror. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, 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 and are not intended to limit the present invention.

[0023] Unless the context requires otherwise, throughout the specification and claims, the term "including" is to be interpreted as meaning open inclusion, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific example" or "some examples" and the like are intended to indicate that the specific features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner, that is, although they may be carried in the embodiments or examples of the above terms due to reasons such as the order and position of appearance, it is not limited to that they can be carried in combination by one embodiment or example.

[0024] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present disclosure.

[0025] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "multiple" means two or more. In addition, for example, the description may also use the method of adding "A" and "B" at the end to describe the same type of nouns as two independent individuals. In this case, the corresponding features defined as "A" and "B" are only used to distinguish the description purposes of the same type of individuals, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0026] When describing some embodiments, the expressions “coupled”, “coupled” and “connected” and their derivatives may be used. For example, when describing some embodiments, the term “connected” may be used to indicate that two or more components are in direct physical or electrical contact with each other. For another example, when describing some embodiments, the term “coupled” may be used to indicate that two or more components are in direct physical or electrical contact. However, the term “connected” or “coupled” may also mean that two or more components are not in direct contact with each other, but still cooperate or interact with each other, such as “optical coupling”, “wireless connection”, etc. The embodiments disclosed herein are not necessarily limited to the contents of the present invention.

[0027] In the description of the present invention, the expression "A and / or B" (where A and B are used to formally represent specific characteristic contents) is involved, and the corresponding expressions include the following three combinations: only A, only B, and a combination of A and B.

[0028] As used herein, "about," "substantially," or "approximately" includes the stated value and an average value that is within an acceptable range of deviation from the particular value as determined by one of ordinary skill in the art taking into account the measurements in question and errors associated with measurement of the particular quantity (i.e., limitations of the measurement system).

[0029] 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 they do not conflict with each other.

[0030] Embodiment 1: Embodiment 1 of the present invention provides a small-sized flat-top optical filter, such as Figure 1 As shown, it includes: an optical input and output component 1, a beam expanding component 2, a rotatable reflector 3, a beam shaping component 4, a grating component 5 and a light reflecting micromirror 6; the optical input and output component 1 is used to transmit a signal light beam and receive a returned optical signal of a predetermined wavelength. The signal light beam passes through the beam expanding component 2, is reflected by the rotatable reflector 3 to the beam shaping component 4, and then passes through the grating component 5. The grating component 5 reflects the signal light beam to the beam shaping component 4. The beam shaping component 4 reflects the optical signal of the predetermined wavelength to the light reflecting micromirror 6. The light reflecting micromirror 6 reflects the optical signal of the predetermined wavelength back to the optical input and output component 1 along the original path; wherein the optical signal of the predetermined wavelength is determined by the rotation angle of the rotatable reflector 3.

[0031] In one embodiment, the rotatable reflector 3 is driven to rotate by a micro motor, and the rotation angle of the micro motor is controlled by a control circuit. The rotatable reflector 3 is an optical micro-electro-mechanical system (MEMS) reflector. The angle of the rotatable reflector 3 can rotate by ±2.2°, and the wavelength can be tuned by 40nm±1nm.

[0032] In order to reflect back the light signal of the predetermined wavelength as much as possible and avoid the light signal of other wavelengths from being reflected, in one embodiment, the length of the light reflecting micromirror 6 is 1mm±0.01mm and the width is 50um±0.01um. Figure 8 As shown, the X direction is the length direction of the light reflecting micromirror 6, and the Y direction is the width direction.

[0033] In the above-described scheme, in the return optical path of the optical signal of the predetermined wavelength passing through the light-reflecting micromirror 6, it should be noted that only the optical signal perpendicularly incident on the light-reflecting micromirror 6 can be output from the optical input / output assembly 1 along the original optical path. Since the optical signal diverges after reflection from the grating assembly 5, light of different wavelengths is separated by different angles. Due to the narrow width of the light-reflecting micromirror 6, except for the optical signal of the predetermined wavelength perpendicularly incident on the light-reflecting micromirror 6, optical signals of other wavelengths cannot be incident on the light-reflecting micromirror 6, resulting in rapid attenuation. Ultimately, the light beam output from the output end of the optical input / output assembly 1 is a bandpass filtered spectrum with a flat top.

[0034] A rotatable reflector 3 is provided in the optical filter to realize the tunable function of the optical filter. By rotating the rotatable reflector 3, the optical signal reflected back by the light-reflecting micromirror 6 can be an optical signal of a predetermined wavelength. In addition, after the signal light beam passes through the beam expansion component 2, the rotatable reflector 3 and the beam shaping component 4 in sequence from the signal output end of the optical input and output component 1, it enters the grating component 5, is reflected from the grating component 5, is reflected by the beam shaping component 4 to the light-reflecting micromirror 6, and the light-reflecting micromirror 6 reflects the optical signal of the predetermined wavelength back to the beam shaping component 4. The optical signal of the predetermined wavelength is reflected again by the beam shaping component 4. The optical signal is emitted into the grating component 5 and finally reflected from the grating component 5. The optical signal of the predetermined wavelength passes through the beam shaping component 4, the rotatable reflector 3, the beam expanding component 2 and the optical input and output component 1 in sequence and is output from the output end of the optical input and output component 1. Therefore, the optical signal is filtered by the grating component 5 four times, which optimizes the output spectrum rectangularity and significantly improves the out-of-band isolation. Compared with the fiber mode field difference technology and the aperture technology in the prior art, the technical solution provided by the present invention has higher scenario adaptability, lower control accuracy and manufacturing process requirements during the debugging process, and is conducive to reducing the production cycle and cost of the optical filter.

[0035] In addition, in the above scheme, by repeatedly using the optical path of the rotatable reflector 3, the beam shaping component 4 and the grating component 5, the packaging size of the device can be effectively reduced compared to the existing technology that mostly uses independent input optical paths and output optical paths.

[0036] According to the small-sized flat-top optical filter provided in the above solution, the structural details of the optical filter are further described in detail below.

[0037] The optical input and output component 1 is used to transmit signal beams and receive optical signals of predetermined wavelengths. After being emitted from the output end of the optical input and output component 1, the signal beam needs to be collimated to be transmitted to the beam expansion component 2. Before the optical signal of predetermined wavelength is transmitted from the beam expansion component 2 to the input end of the optical input and output component 1, it needs to be converged to reduce optical loss. Based on this, Figure 1 As shown, the optical input and output assembly 1 includes an optical input and output unit 10 and a collimating lens unit 11 , and the collimating lens unit 11 is disposed between the optical input and output unit 10 and the beam expanding assembly 2 .

[0038] In actual application scenarios, the optical transmission channel and the optical receiving channel can be two independent channels or the same channel. For the above two methods, the first method is as follows Figure 2As shown, the optical input and output unit 10 includes an optical input pin 100 and an optical output pin 101. The collimating lens unit 11 includes a first collimating lens 110 and a second collimating lens 111. The first collimating lens 110 is positioned corresponding to the optical input pin 100, and the second collimating lens 111 is positioned corresponding to the optical output pin 101. After the optical input pin 100 outputs a signal beam, it passes through the collimating lens and becomes parallel light, which then travels through the subsequent optical path. The reflected optical signal of a predetermined wavelength enters the collimating lens and is then output from the optical output pin 101. The port of the optical input pin 100 is positioned at the focal point of the first collimating lens 110, and the port of the optical output pin 101 is positioned at the focal point of the second collimating lens 111. Both the optical input pin 100 and the optical output pin 101 are dual-core pins. In the second embodiment, the optical input and output unit 10 includes a circulator (not shown in the figure) and a dual-core pin (not shown in the figure), the collimating lens unit 11 is a single lens, the circulator and the dual-core pin are optically connected, and the collimating lens unit 11 is arranged corresponding to the dual-core pin.

[0039] For the beam expander 2, if Figure 3 As shown, the beam expansion assembly 2 includes at least one first right-angle prism 20, which is used to expand the signal light beam of the optical input and output assembly 1. In actual application scenarios, the number of the first right-angle prism 20 can be one or more, and the specific number can be increased or decreased according to the bandwidth requirements of the spectrum and the mirror diameter of the rotatable reflector 3. After passing through the first right-angle prism 20, the parallel light from the collimating lens unit 11 is expanded in the Y-axis direction (with the first right-angle prism 20 as the first right-angle prism). Figure 3 The diameter of the light spot in the X direction does not change, and the magnification β of the light spot in the Y direction is determined by the refractive index n and the vertex angle θ of the first right-angle prism 20, specifically: After the amplified signal light beam passes through the first right-angle prism 20, the Y-axis direction light spot continues to be amplified. However, it is worth noting that the diameter of the amplified light spot must be smaller than the mirror diameter of the rotatable reflector 3 to ensure that the light beam can be effectively received by the mirror surface of the rotatable reflector 3.

[0040] For the beam shaping component 4, after the signal beam passes through the beam shaping component 4, the diameter of the signal beam spot in one direction becomes significantly larger, and the overall area of the spot appears to be enlarged. The specific method is as follows: Figure 4As shown, the beam shaping assembly 4 includes a biconvex cylindrical mirror 40, a plane reflector 41, and a concave reflector 42. The plane reflector 41 is disposed between the biconvex cylindrical mirror 40 and the concave reflector 42. The biconvex cylindrical mirror 40 is located between the rotatable reflector 3 and the plane reflector 41. The plane reflector 41 is located between the biconvex cylindrical mirror 40 and the focal point of the biconvex cylindrical mirror 40. The light reflecting micromirror 6 is disposed at the back focal point of the concave reflector 42. In one embodiment, the curvature radius of the concave reflector 42 can be 9 mm ± 0.1 mm, and the reflective surface of the concave reflector 42 is coated with a reflective film. During the actual test, the focus of the double convex cylindrical mirror 40 is located at point A in the figure. A plane reflector 41 is set between point A and the double convex cylindrical mirror 40, so that the light signal originally converged at point A is reflected to converge at point A'. Point A and point A' are symmetrical with respect to the plane reflector 41 as the axis. The light signal converges at point A' and then diverges, thereby expanding the overall area of the light spot.

[0041] Among them, such as Figure 5 As shown, the biconvex cylindrical mirror 40 includes a first cylindrical surface 400 and a second cylindrical surface 401. The first cylindrical surface 400 and the second cylindrical surface 401 are used to amplify the size of the light signal on the plane reflector 41. The first cylindrical surface 400 and the second cylindrical surface 401 are coated with an anti-reflection film. Specifically, with the light transmission direction as the Z direction as a reference, the axis of the first cylindrical surface 400 is as follows: Figure 5 The axis of the second cylindrical surface 401 is in the Y direction. After the signal beam passes through the first cylindrical surface 400 and the second cylindrical surface 401, the area of the light spot in the Y direction is significantly increased, and the area in the X direction is also increased to a smaller extent, thereby achieving signal beam shaping.

[0042] After being reflected by the concave reflector 42, the signal light beam enters the grating component 5. After being reflected in the grating component 5, the signal light beam diverges, thereby achieving the screening of light wavelengths. The grating component 5 can be specifically as follows: Figure 6As shown, the grating assembly 5 includes a plano-convex cylindrical mirror 50 and a grating unit 51. The plano-convex cylindrical mirror 50 is located between the grating unit 51 and the concave reflector 42. The plano-convex cylindrical mirror 50 is used to adjust the divergence angle of the signal light beam. After passing through the grating unit 51, the signal light beam is dispersed. Light of different wavelengths is separated at different angles. The light is then transmitted through the plano-convex cylindrical mirror 50 to the concave reflector 42, and is reflected by the concave reflector 42 to the light reflecting micromirror 6. The longitudinal rotation radius of the cylinder of the plano-convex cylindrical mirror 50 can be 15.8mm±0.1mm. The plano-convex cylindrical mirror 50 is used to adjust the divergence angle of the signal light beam so that the signal light beam is incident on the diffraction grating in a more regular form. With respect to the grating unit 51, in one embodiment, the grating unit 51 is a diffraction grating, and one of the surfaces of the diffraction grating is a reflective surface; the diffraction grating can be a reflective grating with 1400 lines. In another embodiment, as Figure 7 As shown, the grating unit 51 includes a transmissive diffraction grating 510 and a second right-angle prism 511 , and a right-angle side of the second right-angle prism 511 is arranged close to the transmissive diffraction grating 510 .

[0043] After the signal beam is diverged by the grating unit 51, it is reflected on the concave reflector 42 to the light reflecting micromirror 6. As mentioned in the above scheme, the light reflecting micromirror 6 is set at the back focus of the concave reflector 42. In actual application scenarios, Figure 8 As shown, the light spot incident on the reflective surface of the light-reflecting micromirror 6 is an elliptical spot, and the light wavelengths λ1, λ2, ..., λn are distributed in the Y direction. By making the width in the Y direction narrow enough, only the wavelengths in the Y direction can be reflected back to the optical path output, obtaining a flat-top filtered spectrum. In addition, the width of the reflective surface of the light-reflecting micromirror 6 in the Y direction is in the μm range, which is much smaller than the width in the X direction in the mm range. The width in the Y direction can be designed according to the bandwidth requirements of the spectrum. Based on the above structure, as shown in FIG. Figure 9 As shown in the figure, from left to right, the flat-top filtering spectra of the conventional optical communication C-band with central wavelengths of short wave (1528nm), medium wave (1548nm), and long wave (1568nm) are respectively shown. The typical value of the 20dB bandwidth of the filtering spectrum is 600GHz.

[0044] In another embodiment, a glass slide 60 is further provided between the concave reflective mirrors 42 of the light reflecting micromirror 6 for collimating the optical signal.

[0045] In summary, the embodiment of the present invention further provides a method for using a small-sized flat-top optical filter, which is applicable to the small-sized flat-top optical filter described in the above solution, such as Figure 10 Shown, including: In step S1, the optical input and output component 1 outputs the signal light beam. After passing through the grating component 5, the signal light beam is reflected back as a light signal of a predetermined wavelength on the light reflecting micromirror 6. The light signal of the predetermined wavelength returns to the optical input and output component 1 along the original optical path.

[0046] Specifically, taking the optical input and output unit 10 including the optical input pin 100 and the optical output pin 101 as an example, the transmission path of the signal light beam is: optical input pin 100-collimating lens unit 11-first right-angle prism 20-rotatable reflector 3-double convex cylindrical mirror 40-plane reflector 41-concave reflector 42-plano-convex cylindrical mirror 50-grating unit 51-plano-convex cylindrical mirror 50-concave reflector 42-light reflecting micromirror 6; the return path of the optical signal of the predetermined wavelength is: light reflecting micromirror 6-concave reflector 42-plano-convex cylindrical mirror 50-grating unit 51-plano-convex cylindrical mirror 50-concave reflector 42-plane reflector 41-double convex cylindrical mirror 40-rotatable reflector 3-first right-angle prism 20-collimating lens unit 11-optical output pin 101.

[0047] In step S2, the wavelength of the optical signal of the predetermined wavelength is measured at the output end of the optical input and output component 1, and the angle of the rotatable reflector 3 is adjusted until the expected spectrum is obtained. The rotatable reflector 3 is locked, and the next operation of the filter can be carried out.

[0048] The next step operation may be a packaging operation, etc.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A small-sized flat-top optical filter, characterized in that: include: An optical input and output component (1), a beam expansion component (2), a rotatable reflector (3), a beam shaping component (4), a grating component (5) and a light reflecting micromirror (6); the optical input and output component (1) is used to transmit a signal light beam and receive a returned light signal of a predetermined wavelength, the signal light beam passes through the beam expansion component (2), is reflected by the rotatable reflector (3) to the beam shaping component (4), and then passes through the grating component (5), the grating component (5) reflects the signal light beam to the beam shaping component (4), the beam shaping component (4) reflects the light signal of the predetermined wavelength to the light reflecting micromirror (6), and the light reflecting micromirror (6) reflects the light signal of the predetermined wavelength back to the optical input and output component (1) along the original path; The optical signal of the predetermined wavelength is determined by the rotation angle of the rotatable reflector (3).

2. The small-sized flat-top optical filter according to claim 1, wherein The beam shaping assembly (4) comprises a biconvex cylindrical mirror (40), a plane reflector (41), and a concave reflector (42); the plane reflector (41) is arranged between the biconvex cylindrical mirror (40) and the concave reflector (42); the biconvex cylindrical mirror (40) is located between the rotatable reflector (3) and the plane reflector (41); and the plane reflector (41) is located between the biconvex cylindrical mirror (40) and a focus of the biconvex cylindrical mirror (40); The light reflecting micromirror (6) is arranged at the rear focus of the concave reflecting mirror (42).

3. The small-sized flat-top optical filter according to claim 2, wherein: The double convex cylindrical mirror (40) comprises a first cylindrical surface (400) and a second cylindrical surface (401), wherein the first cylindrical surface (400) and the second cylindrical surface (401) are used to amplify the size of the light signal on the plane reflector (41); The first cylindrical surface (400) and the second cylindrical surface (401) are coated with an anti-reflection film.

4. The small-sized flat-top optical filter according to claim 2, wherein: The grating assembly (5) includes a plano-convex cylindrical mirror (50) and a grating unit (51). The plano-convex cylindrical mirror (50) is located between the grating unit (51) and the concave reflector (42). The plano-convex cylindrical mirror (50) is used to adjust the divergence angle of the signal light beam. After passing through the grating unit (51), the signal light beam generates dispersion, and light of different wavelengths is separated at different angles. The light beam is then transmitted to the concave reflector (42) through the plano-convex cylindrical mirror (50), and then reflected to the light reflecting micromirror (6) by the concave reflector (42).

5. The small-sized flat-top optical filter according to claim 4, characterized in that: The grating unit (51) is a diffraction grating, and one of the surfaces of the diffraction grating is a reflection surface; Alternatively, the grating unit (51) comprises a transmission diffraction grating (510) and a second right-angle prism (511), and a right-angle side of the second right-angle prism (511) is arranged close to the transmission diffraction grating (510).

6. The small-sized flat-top optical filter according to any one of claims 1 to 5, characterized in that: The optical input and output assembly (1) comprises an optical input and output unit (10) and a collimating lens unit (11), wherein the collimating lens unit (11) is arranged between the optical input and output unit (10) and the beam expanding assembly (2); The optical input and output unit (10) comprises an optical input pin (100) and an optical output pin (101), and the collimating lens unit (11) comprises a first collimating lens (110) and a second collimating lens (111), wherein the first collimating lens (110) is arranged corresponding to the optical input pin (100), and the second collimating lens (111) is arranged corresponding to the optical output pin (101); Alternatively, the optical input and output unit (10) includes a circulator and a double-core pin, the collimating lens unit (11) is a single lens, the circulator and the double-core pin are optically connected, and the collimating lens unit (11) is arranged corresponding to the double-core pin.

7. The small-sized flat-top optical filter according to any one of claims 1 to 5, characterized in that: The beam expansion component (2) comprises at least one first right-angle prism (20), and the at least one first right-angle prism (20) is used to expand the signal light beam of the optical input and output component (1).

8. The small-sized flat-top optical filter according to any one of claims 1 to 5, characterized in that: The rotatable reflector (3) is a MEMS reflector, the angle of the rotatable reflector (3) is rotated by ±2.2°, and the wavelength is tuned by 40nm±1nm.

9. The small-sized flat-top optical filter according to any one of claims 1 to 5, characterized in that: The light reflecting micromirror (6) has a length of 1 mm ± 0.01 mm and a width of 50 μm ± 0.01 μm.

10. A method for using a small-sized flat-top optical filter, applicable to the small-sized flat-top optical filter according to any one of claims 1 to 9, characterized in that: include: The optical input and output component (1) outputs the signal light beam, and after the signal light beam passes through the grating component (5), it is reflected back on the light reflecting micromirror (6) as a light signal of a predetermined wavelength, and the light signal of the predetermined wavelength returns to the optical input and output component (1) along the original optical path; The wavelength value of the light signal of the predetermined wavelength is measured at the output end of the optical input and output component (1), and the angle of the rotatable reflector (3) is adjusted until the expected spectrum is obtained. The rotatable reflector (3) is locked, and the next step of the filter operation can be carried out.

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