DWDM filter and preparation method thereof
By introducing negative thermal expansion materials and aperiodic membrane stack design, the signal quality problems of DWDM filters under high channel density and temperature changes are solved, and a temperature adaptive and low crosstalk DWDM filter is realized, supporting smaller channel spacing and higher signal transmission capacity.
Patent Information
- Application Number
- CN202510551237.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-29
- Publication Date
- 2025-07-11
AI Technical Summary
The existing DWDM filters have problems with high channel density and temperature changes, resulting in a decrease in signal quality and an increase in energy consumption. The traditional filter coating process increases crosstalk when the channel interval is less than 0.4nm, and the wavelength drift caused by temperature changes requires additional temperature control devices.
The temperature compensation layer and aperiodic film stack structure are designed using negative thermal expansion materials, combined with doped materials, offset the wavelength drift caused by temperature changes, and reduce signal crosstalk through aperiodic thickness arrangement design.
The temperature adaptation and ultra-dense channel spacing of the DWDM filter are realized, which reduces signal crosstalk, improves channel density, and meets the needs of high-capacity communication in the future.
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Figure CN120294915A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of optical fiber communication, and particularly relates to a DWDM filter and a preparation method thereof. Background Art
[0002] DWDM (Dense Wavelength Division Multiplexing) technology is one of the core technologies of modern optical fiber communication. It multiplexes optical signals of different wavelengths onto a single optical fiber for transmission, greatly improving the transmission capacity of the optical fiber. In a DWDM system, a filter is one of the key devices, which is used to select or separate optical signals of specific wavelengths. Currently, devices based on thin film interference filters (TFFs) are widely used due to their simple structure and low cost.
[0003] With the development of optical fiber communication, DWDM (dense wavelength division multiplexer) systems need to provide more channel numbers. Channel spacings of 0.8 nm and 0.4 nm can no longer meet the signal transmission requirements of optical communication. To obtain a larger communication capacity, DWDM systems require a higher channel density. However, when the channel spacing is less than 0.4 nm in the filter coating process using a traditional symmetric film stack, crosstalk will increase significantly, affecting the isolation of the device and resulting in a decline in signal quality. On the other hand, traditional filter plates are very sensitive to temperature changes. Temperature changes will cause the film layer to expand or contract, thereby causing a drift in the filtering wavelength of the DWDM (dense wavelength division multiplexer) (about 0.02 nm / °C). To operate stably, an additional temperature control device is usually required, which not only increases the cost but also improves the energy consumption. Summary of the Invention
[0004] An object of the present invention is to solve at least to some extent one of the technical problems existing in the prior art.
[0005] For this reason, an object of an embodiment of the present invention is to provide a DWDM filter. By introducing a negative thermal expansion material to design a temperature compensation layer and a non-periodic film stack design, temperature self-adaptation and ultra-dense channel spacing of the DWDM filter are achieved, offsetting the wavelength drift caused by temperature changes while meeting the future high-capacity communication requirements.
[0006] The first technical solution adopted by the present invention is:
[0007] A DWDM filter, characterized in that it comprises: a first inner sleeve, a second inner sleeve, an outer sleeve, a first pigtail, a second pigtail, a first lens, a second lens and a filter film. The first inner sleeve and the second inner sleeve are respectively sleeved at both ends of the outer sleeve. The first pigtail is sleeved from outside to inside in the first inner sleeve. The outer end of the first lens is connected to the inner end of the first pigtail, and the inner end of the first lens is connected to the filter film. The second pigtail is sleeved from outside to inside in the second inner sleeve. The outer end of the second lens is connected to the inner end of the second pigtail. The filter film comprises a base layer, a film stack and a temperature compensation layer. The film stack is located above the base layer. The film stack is composed of a plurality of high refractive index material layers and a plurality of low refractive index material layers arranged alternately. The thickness sorting of each high refractive index material layer and each low refractive index material layer is a preset non-periodic sequence. The temperature compensation layer is composed of a negative thermal expansion material and a doping material.
[0008] Further, the first inner sleeve, the second inner sleeve and the outer sleeve are all glass tubes, and the base layer is a silicon substrate.
[0009] Further, the first lens is a self-focusing lens, and the second lens is a spherical lens.
[0010] Further, both the first pigtail and the second pigtail are single-fiber pigtails.
[0011] Further, the temperature compensation layer is located between the base layer and the film stack, or the temperature compensation layer is located above the film stack.
[0012] Further, the negative thermal expansion material is one of ZrW2O8, HfW2O8 and Sc2(WO4)3.
[0013] Further, the doping material is Al2O3.
[0014] Further, the non-periodic sequence is one of the Fibonacci sequence, the Tribonacci sequence and the Padovan sequence.
[0015] Further, the high refractive index material layer is composed of Ta2O5, and the low refractive index material layer is composed of SiO2.
[0016] The second technical solution adopted by the present invention is:
[0017] A preparation method of a DWDM filter, which is realized by the above-mentioned DWDM filter, and comprises:
[0018] Determine the first reference thickness of the high refractive index material layer and the second reference thickness of the low refractive index material layer according to the target wavelength, the first refractive index of the high refractive index material layer, and the second refractive index of the low refractive index material layer;
[0019] Determine the first material thickness of each high refractive index material layer and the second material thickness of each low refractive index material layer according to the first reference thickness, the second reference thickness, and a preset aperiodic sequence;
[0020] Determine the thickness of the temperature compensation layer according to the thermal expansion coefficient of the film stack, the thickness of the film stack, and the thermal expansion coefficient of the negative thermal expansion material;
[0021] Set the temperature compensation layer and the film stack on the substrate layer according to the thickness of the temperature compensation layer, the first material thickness, and the second material thickness to obtain a filter;
[0022] Assemble according to the structure of the DWDM filter according to any one of claims 1 to 9.
[0023] The beneficial effects of the present invention are as follows: By introducing a negative thermal expansion material to design the temperature compensation layer, the wavelength drift caused by the temperature change of the film stack is offset, and the remaining temperature drift is further suppressed by doping materials, realizing the temperature self-adaptation of the DWDM filter; By designing the high and low refractive index material layers with an aperiodic thickness arrangement, the interference law is disrupted, and the interference energy is dispersed, thereby significantly reducing signal crosstalk, thus supporting a smaller interval between DWDM filters and improving the channel density of DWDM devices. Description of the Drawings
[0024] Figure 1 It is a schematic structural diagram of a DWDM filter provided by an embodiment of the present invention;
[0025] Figure 2 It is a schematic structural diagram of a traditional filter provided by an embodiment of the present invention;
[0026] Figure 3 It is a schematic structural diagram of a filter of a DWDM filter provided by an embodiment of the present invention;
[0027] Figure 4 It is a schematic diagram of the steps of a preparation method of a DWDM filter provided by an embodiment of the present invention;
[0028] Reference numerals: 1: small glass tube; 2: single-fiber pigtail; 3: self-focusing lens; 4: filter; 5: spherical lens; 6: large glass tube; 7: single-fiber pigtail; 8: small glass tube. Detailed Embodiments
[0029] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as limiting the present invention. For the step numbers in the following embodiments, they are only set for the convenience of explanation and illustration, and no limitation is imposed on the order between the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.
[0030] In the description of the present invention, the meaning of "a plurality" is two or more. If the first and second are described, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence of the indicated technical features. In addition, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this technology belongs.
[0031] Figure 1 The following is a schematic structural diagram of a DWDM filter provided by an embodiment of the present invention. Refer to Figure 1 , An embodiment of the present invention provides a DWDM filter, including: a first inner sleeve, a second inner sleeve, an outer sleeve, a first pigtail, a second pigtail, a first lens, a second lens, and a filter film. The first inner sleeve and the second inner sleeve are respectively sleeved at both ends of the outer sleeve. The first pigtail is sleeved from the outside to the inside in the first inner sleeve. The outer end of the first lens is connected to the inner end of the first pigtail, and the inner end of the first lens is connected to the filter film. The second pigtail is sleeved from the outside to the inside in the second inner sleeve. The outer end of the second lens is connected to the inner end of the second pigtail. The filter film includes a base layer, a film stack, and a temperature compensation layer. The film stack is located on the base layer. The film stack is composed of a plurality of high refractive index material layers and a plurality of low refractive index material layers arranged alternately. The thickness sorting of each high refractive index material layer and each low refractive index material layer is a preset non-periodic sequence. The temperature compensation layer is composed of a negative thermal expansion material and a doping material.
[0032] Specifically, refer to Figure 1 , The two inner sleeves and the outer sleeve are of a straight tube structure. The two inner sleeves are respectively sleeved inside both ends of the outer sleeve. The inner layers of the two inner sleeves are respectively sleeved on the capillaries of the two pigtails. The inner ends of the two pigtails are respectively fixedly connected to the two lenses. Among them, the inner end of the first lens is also connected to the filter film. The filter film is used to select optical signals of specific wavelengths.
[0033] In the traditional filter film design method, the filter film is mainly composed of a silicon substrate and a film stack. Figure 2 The following is a schematic structural diagram of a traditional filter film. Refer to Figure 2, where the silicon substrate mainly serves as a mechanical support, and the film stack is mainly obtained by alternately depositing high- and low-refractive-index materials on the silicon substrate. The optical thickness of the high- and low-refractive-index materials in each layer is taken as λ / 4 (1 / 4 of the target wavelength), and they are arranged periodically. Taking λ / 4 is to achieve filtering through interference. When the phase difference of light of a certain specific wavelength satisfies the interference condition, the light of that wavelength will be enhanced and transmitted, while the light of other wavelengths will be weakened or completely reflected, so that it is a passband for a certain wavelength range and a stopband for another wavelength range.
[0034] The high-refractive-index material usually uses Ta2O5, and its refractive index n H is 2.1, and the low-refractive-index material generally uses SiO2, and its refractive index n L is 1.45. The material thickness of each refractive layer is the ratio of the optical thickness to the refractive index, and the material thickness formula is:
[0035] d = λ / (4n)
[0036] where d is the film thickness and n is the refractive index. Calculated with the target wavelength of 1550 nm, the thickness d H of each high-refractive-index material is 184 nm, and the thickness d L of the low-refractive-index material is 267 nm. Table 1 is the layer sequence arrangement table of the traditional filter.
[0037] Table 1
[0038]
[0039] The traditional thin-film filter made of the above traditional filter has the following problems:
[0040] 1) The temperature drift of the filter is about 0.02 - 0.03 nm / °C, and an external temperature control device is required, resulting in a power consumption increase of more than 30%;
[0041] 2) When the channel spacing of the traditional symmetric film stack ≤ 0.4 nm, the sidelobe crosstalk (channel isolation) > 20 dB, which cannot meet the requirements of ultra-dense wavelength division multiplexing;
[0042] In this embodiment, mainly based on the production of the traditional filter, the filter is improved from the following two aspects to solve the above problems:
[0043] 1) Introduce a negative thermal expansion material to design a temperature compensation layer, such as ZrW2O8 (zirconium tungstate oxide) to offset the wavelength drift caused by the temperature change of the film stack, and further suppress the remaining temperature drift through doping materials such as alumina (Al2O3) to achieve temperature self-adaptation of the DWDM filter.
[0044] The principle of temperature compensation is as follows: The wavelength drift of the DWDM filter is mainly caused by the thermal expansion of the material. The core of temperature compensation is to offset the wavelength shift caused by the expansion of the film stack through the contraction of the negative thermal expansion material.
[0045] Assume that the total thickness of the film stack is about 10 μm, the thermal expansion coefficient of the film stack is 4.5x10^-6 / °C, and ZrW2O8 is used as the negative thermal expansion material with a thermal expansion coefficient of 8.7x10^-6 / °C. When the external temperature changes, the following formula needs to be satisfied:
[0046] ΔL 总 = ΔL 膜堆 + ΔL 补偿层 = 0
[0047] Where:
[0048] ΔL 膜堆 = α 膜堆 ·L 膜堆 ·ΔT
[0049] ΔL 补偿层 = α 补偿层 ·L 补偿层 ·ΔT
[0050] L 补偿层 = α 膜堆 ·L 膜堆 / α 补偿层
[0051] In the above formula, ΔL 总 is the total deformation of the film stack and the compensation layer, ΔL 膜堆 is the deformation of the film stack, ΔL 补偿层 is the deformation of the compensation layer, ΔT is the temperature change value, α 膜堆 is the thermal expansion coefficient of the film stack, α 补偿层 is the thermal expansion coefficient of the negative thermal expansion material, L 补偿层 is the designed thickness of the compensation layer, L 膜堆 is the initial thickness of the film stack. Substituting the values for calculation, L 补偿层 = 5.17 μm (the compensation layer material here is ZrW2O8).
[0052] Actually, 500 nm (1 / 10 of the theoretical value) is selected. Through simulation optimization, it is found that 500 nm thick ZrW2O8 can offset 80% of the temperature drift, and the remaining temperature drift is further suppressed by the doped material alumina (Al2O3). During actual production, attention should be paid to the process limitations. When it exceeds 800 nm, the film layer stress will be greater than 1.2 GPa, resulting in substrate cracking. Tests show that in the range of 40 - 85 °C, the wavelength drift <0.04 nm, and the temperature drift decreases from 0.00304 nm / °C (traditional design) to 0.000072 nm / °C (this embodiment), with a reduction of 98%.
[0053] 2) Instead of using the traditional periodic arrangement, by arranging the high and low refractive index materials with non-periodic thickness, such as the Fibonacci sequence, to prepare the high and low refractive index material layers, disrupting the interference pattern and dispersing the interfering energy, thereby significantly reducing signal crosstalk, thus supporting a smaller interval between DWDM filters and increasing the channel density of DWDM devices.
[0054] The principle of introducing non-periodic thickness arrangement is as follows: the phase difference of the reflected light of the traditional periodic film stack where n is the refractive index of the material of this layer, d is the thickness of the material of this layer, and λ is the wavelength of the incident light. The periodic phase difference causes the side lobes to concentrate. The non-periodic thickness arrangement design (taking the Fibonacci sequence as an example) introduces a phase difference where F i is the i-th term of the Fibonacci sequence, and the non-periodic phase difference disperses the side lobe energy into a wide frequency band; secondly, the increasing (or non-decreasing) of the film layer thickness is equivalent to introducing frequency modulation, broadening the side lobe bandwidth, which is equivalent to the chirp signal in communication. The increasing of the film layer thickness causes the equivalent refractive index to gradually change, forming a "chirp grating" and diffusing the side lobe energy.
[0055] Tests have shown that the side lobe suppression ratio has been increased from 15 dB (traditional method) to 38 dB (this embodiment), the channel interval can be compressed to 0.1 nm effect (ITU-T G.694.1 standard), and the single-fiber transmission capacity has been greatly improved, meeting the requirements of 5G fronthaul and data center interconnection.
[0056] Based on the above two improvements, in this embodiment, the specific filter design method can be:
[0057] Figure 3 is a schematic diagram of the filter structure of a DWDM filter provided in this embodiment. Referring to Figure 3 , during manufacturing, first, a 500-nm-thick ZrW2O8 (zirconium tungsten oxide) layer is sputtered on a silicon substrate, and then Ta2O5 and SiO2 film layers are alternately grown by ion beam deposition, and the thickness is designed according to the Fibonacci sequence (1, 1, 2, 3, 5...). Tests show that within the range of 40 - 85 °C, the wavelength drift is <0.04 nm, and the adjacent crosstalk is <40 dB when the channel interval is 0.1 nm.
[0058] As can be seen from the foregoing, the reference thickness d of the high refractive index material H = 184 nm, and the reference thickness d of the low refractive index material L = 267 nm. The thickness of the high refractive index layer = d H ·F i , and the thickness of the low refractive index layer = d L ·F i , where Fi is the i-th term of the Fibonacci sequence, and the sequence is 1, 1, 2, 3, 5, 8, 13... (i = 1, 2, 3...). Table 2 is the layer sequence arrangement table of the filter plate of a DWDM filter provided in this embodiment. Referring to Table 2, the specific arrangement thickness is as follows:
[0059] Table 2
[0060] Sequence Material Type Thickness (nm) Function Description Fibonacci Coefficient 1 Silicon Substrate 500000 Mechanical Support / 2 <![CDATA[ZrW2O8]]> 500 Temperature Compensation / 3 <![CDATA[Ta2O5]]> 184 High Refractive Index Layer (1 * Reference Unit) 1 4 <![CDATA[SiO2]]> 267 Low Refractive Index Layer (1 * Reference Unit) 1 5 <![CDATA[Ta2O5]]> 368 High Refractive Index Layer (2 * Reference Units) 2 6 <![CDATA[SiO2]]> 801 Low Refractive Index Layer (3 * Reference Units) 3 7 <![CDATA[Ta2O5]]> 920 High Refractive Index Layer (5 * Reference Units) 5 8 <![CDATA[SiO2]]> 2136 Low Refractive Index Layer (8 * Reference Units) 8 ......
[0061] It can be recognized that in this embodiment, by introducing a negative thermal expansion material to design a temperature compensation layer, the wavelength drift caused by the temperature change of the film stack is offset, and by doping the material, the remaining temperature drift is further suppressed, realizing the temperature self-adaptation of the DWDM filter; by designing the high and low refractive index material layers with non-periodic thickness arrangements, the interference law is disrupted, and the interference energy is dispersed, thereby significantly reducing signal crosstalk, thus supporting a smaller interval between DWDM filters and improving the channel density of the DWDM device; the wavelength drift can be <0.04 nm within the range of 40 - 85 °C, and the adjacent crosstalk is <40 dB when the channel interval is 0.1 nm.
[0062] In some alternative embodiments, the first inner sleeve, the second inner sleeve, and the outer sleeve are all glass tubes, and the base layer is a silicon substrate.
[0063] Specifically, in this embodiment, glass is mainly used as the material of the tube structure, and in some other embodiments, tube structures of other materials can be used.
[0064] In some alternative embodiments, the first lens is a self-focusing lens spherical lens, and the second lens is a spherical lens.
[0065] Specifically, in this embodiment, a self-focusing lens is used to achieve focusing, and a spherical lens is used to achieve collimation. In some other embodiments, other types of lenses can also be selected according to actual needs.
[0066] In some alternative embodiments, the first pigtail and the second pigtail are both single-fiber pigtails.
[0067] In some alternative embodiments, the temperature compensation layer is located between the base layer and the film stack, or the temperature compensation layer is located above the film stack.
[0068] Specifically, in this embodiment, the position of the temperature compensation layer can be located between the base layer and the film stack, or can also be located above the film stack.
[0069] In some alternative embodiments, the negative thermal expansion material is one of ZrW2O8, HfW2O8, and Sc2(WO4)3.
[0070] Specifically, in this embodiment, the negative thermal expansion material can be any one of ZrW2O8, HfW2O8, and Sc2(WO4)3. In some other embodiments, other materials with negative thermal expansion coefficients can also be selected according to actual requirements.
[0071] In some alternative embodiments, the doping material is Al2O3.
[0072] Specifically, in this embodiment, Al2O3 is selected as the doping material for further suppressing temperature drift. In some other embodiments, doping materials of other types can also be selected according to actual requirements.
[0073] In some alternative embodiments, the aperiodic sequence is one of the Fibonacci sequence, the Tribonacci sequence, and the Padovan sequence.
[0074] Specifically, in this embodiment, the aperiodic sequence can be any one of the Fibonacci sequence, the Tribonacci sequence, and the Padovan sequence. In some other embodiments, other aperiodic sequences can be used, or the high and low refractive index layers can be designed by mixing an aperiodic sequence and a periodic sequence (for example, the first N layers are aperiodic (Fibonacci), and the subsequent layers are periodically arranged).
[0075] In some alternative embodiments, the high refractive index material layer is composed of Ta2O5, and the low refractive index material layer is composed of SiO2.
[0076] Specifically, in this embodiment, the high refractive index material layer is composed of Ta2O5, and the low refractive index material layer is composed of SiO2. In some other embodiments, other high and low refractive index materials can also be selected according to actual requirements.
[0077] Referring to Figure 4 , an embodiment of the present invention provides a method for preparing a DWDM filter, including:
[0078] S101. Determine the first reference thickness of the high refractive index material layer and the second reference thickness of the low refractive index material layer according to the target wavelength, the first refractive index of the high refractive index material layer, and the second refractive index of the low refractive index material layer;
[0079] S102. Determine the first material thickness of each high refractive index material layer and the second material thickness of each low refractive index material layer according to the first reference thickness, the second reference thickness, and a preset aperiodic sequence;
[0080] S103. Determine the thickness of the temperature compensation layer according to the thermal expansion coefficient of the film stack, the thickness of the film stack, and the thermal expansion coefficient of the negative thermal expansion material;
[0081] S104. Set a temperature compensation layer and a film stack on the base layer according to the thickness of the temperature compensation layer, the thickness of the first material, and the thickness of the second material to obtain a filter;
[0082] S105. Assemble according to the structure of the DWDM filter of any one of claims 1 to 9.
[0083] Specifically, in this embodiment, the optical thickness of each layer is determined according to the target wavelength and the refractive indices of the high- and low-refractive-index material layers respectively, and then the reference thicknesses of the high- and low-refractive-index material layers are determined according to the aforementioned material thickness formula. Then, according to the selected aperiodic sequence, the thicknesses of the high- and low-refractive-index material layers are determined, and finally a filter is prepared. Each component is assembled according to the aforementioned structure of the DWDM filter to obtain a DWDM filter.
[0084] The above is only a preferred embodiment of the present invention. The present invention is not limited to the above-mentioned implementation manners. As long as it achieves the technical effects of the present invention by the same means, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the scope of protection of the present invention. Within the scope of protection of the present invention, its technical solutions and / or implementation manners can have various different modifications and changes.
Claims
1. A DWDM filter, characterized in that, Comprising: A first inner sleeve, a second inner sleeve, an outer sleeve, a first pigtail, a second pigtail, a first lens, a second lens, and a filter film. The first inner sleeve and the second inner sleeve are respectively sleeved at two ends of the outer sleeve. The first pigtail is sleeved inside the first inner sleeve from outside to inside. The outer end of the first lens is connected to the inner end of the first pigtail, and the inner end of the first lens is connected to the filter film. The second pigtail is sleeved inside the second inner sleeve from outside to inside. The outer end of the second lens is connected to the inner end of the second pigtail. The filter film includes a base layer, a film stack, and a temperature compensation layer. The film stack is located on the base layer. The film stack is composed of a plurality of high refractive index material layers and a plurality of low refractive index material layers arranged alternately. The thickness sorting of each high refractive index material layer and each low refractive index material layer is a preset non-periodic sequence. The temperature compensation layer is composed of a negative thermal expansion material and a doping material.
2. The DWDM filter according to claim 1, wherein The first inner sleeve, the second inner sleeve, and the outer sleeve are all glass tubes, and the base layer is a silicon substrate.
3. A DWDM filter according to claim 1, characterized in that, The first lens is a self-focusing lens, and the second lens is a spherical lens.
4. A DWDM filter according to claim 1, characterized in that, Both the first pigtail and the second pigtail are single-fiber pigtails.
5. A DWDM filter according to claim 1, characterized in that, The temperature compensation layer is located between the base layer and the film stack, or the temperature compensation layer is located on the film stack.
6. A DWDM filter according to claim 1, characterized in that, The negative thermal expansion material is one of ZrW2O8, HfW2O8, and Sc2(WO4)3.
7. A DWDM filter according to claim 1, wherein The doping material is Al2O3.
8. A DWDM filter according to claim 1, characterized in that, The non-periodic sequence is one of the Fibonacci sequence, the Tribonacci sequence, and the Padovan sequence.
9. A DWDM filter according to claim 1, wherein, The high refractive index material layer is composed of Ta2O5, and the low refractive index material layer is composed of SiO2.
10. A method for preparing a DWDM filter, characterized in that, Comprising: Determining a first reference thickness of the high refractive index material layer and a second reference thickness of the low refractive index material layer according to the target wavelength, a first refractive index of the high refractive index material layer, and a second refractive index of the low refractive index material layer; Determining a first material thickness of each high refractive index material layer and a second material thickness of each low refractive index material layer according to the first reference thickness, the second reference thickness, and the preset non-periodic sequence; Determining the thickness of the temperature compensation layer according to the thermal expansion coefficient of the film stack, the thickness of the film stack, and the thermal expansion coefficient of the negative thermal expansion material; Arranging the temperature compensation layer and the film stack on the base layer according to the thickness of the temperature compensation layer, the first material thickness, and the second material thickness to obtain a filter film; Assembling according to the structure of the DWDM filter according to any one of claims 1 to 9.