A GFF filter and a coating method and a preparation method thereof

Abstract

The application relates to the technical field of optical communication, and discloses a GFF filter and a film coating method and a preparation method thereof. The film coating method comprises the following steps: scanning a last film layer of current film coating to obtain an actual test spectrum curve of the last film layer; simulating and analyzing the actual test spectrum curve of the last film layer and a theoretical spectrum curve of the last film layer to obtain an actual thickness of the last film layer; simulating the actual thickness of the last film layer and a theoretical spectrum curve of a current film layer to obtain an optimal thickness value of the current film layer; obtaining an actual light intensity change curve of a next film layer according to the optimal thickness value of the current film layer obtained through simulation analysis, obtaining a light control curve through laser direct light control, setting a pause point at the optimal thickness value of the film layer, and completing preparation of the film layer. The unique preparation scheme is used, so that specific film layer limitation does not need to be considered in design, the design difficulty is greatly reduced, the number of film layers and the thickness of the film layers are greatly reduced, and the processing difficulty requirement is also reduced.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to a GFF filter and its coating and preparation methods. Background Technology

[0002] In optical fiber communication, optical signals are transmitted by being loaded onto light waves. Different wavelengths of light can transmit corresponding data independently, resulting in a huge transmission bandwidth. However, signal loss still exists in long-distance optical transmission. To compensate for the signal loss of optical fibers, erbium-doped fiber amplifiers (EDBFAs) are used to amplify the light intensity signal to ensure reliable information transmission. However, EDBFAs have the inherent drawbacks of fiber optic amplifiers. They transmit and amplify light waves within a wavelength bandwidth of tens of nanometers around the 1.55-micrometer band. Since the gain of EDBFAs is not constant within this range, after multiple amplification stages, adjacent optical frequencies exhibit significant changes in intensity, a problem known as gain unevenness. When the gain unevenness of EDBFAs exceeds the acceptable value for the communication system, the gain unevenness after cascading multiple EDBFAs can lead to the accumulation of gain deviations in different channels at different wavelengths, resulting in signal degradation.

[0003] One solution is to couple the erbium-doped fiber amplifier (EDBFA) to a device that has the reverse characteristics of an EDBFA. Such a device can flatten the output gain of the EDBFA across its wavelength bandwidth. A gain flattening filter (GFF) is then used at the output of the EDBFA to flatten the signal. The quality of the GFF is typically described by the peak-to-peak error function.

[0004] To achieve this good peak-to-peak error function value, the entire processing and preparation process requires extremely high precision. Through the design and analysis of the film system, the systematic error control precision of the film layer needs to be controlled below 0.03% in order to achieve the corresponding spectral characteristic requirements.

[0005] Therefore, existing technologies all consider using single-point laser direct optical control for fabrication. In order to achieve precision control and error compensation during the processing, it is necessary to set a certain range for the thickness of the film layer to ensure that the laser wavelength of the corresponding film layer can be controlled to an extreme value within the spectral range. This results in extremely high requirements for the film layer in the design. On the other hand, to achieve the required peak-to-peak error function value, more film layers need to be designed, resulting in an extremely thick film layer. From the perspective of the fabrication process, this places higher demands on the precision of the processing technology. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a GFF filter and its coating and preparation methods, which effectively solves the problems of excessive number and thickness of gain-flat filter films, limited film thickness, and high processing difficulty.

[0007] To achieve the objectives of this invention, the following technical solution is adopted:

[0008] A coating method for a GFF filter includes the following steps:

[0009] Scan the previous film layer of the current coating to obtain the actual test spectrum curve of the previous film layer;

[0010] The actual thickness of the previous film layer is obtained by simulating and analyzing the actual test spectral curve and the theoretical spectral curve of the previous film layer.

[0011] Simulate the actual thickness of the previous film layer and the theoretical spectral curve of the current film layer to obtain the optimal thickness value of the current film layer;

[0012] Based on the optimal thickness value of the current film layer obtained from the simulation analysis, the actual light intensity change curve of the next film layer is obtained. The light control curve is obtained by direct laser light control. The stop point of the optimal thickness value of the film layer is set to complete the preparation of the film layer.

[0013] Furthermore, the steps also include:

[0014] The film layer adopts a standard Fabry-Perot cavity basic structure ((HL)^m(LH)^m L)^n, where m>0, n>=6 and n<=12, where H is a high refractive index film layer with a center wavelength optical thickness of one-quarter, L is a low refractive index film layer with a center wavelength optical thickness of one-quarter, m is an array of alternating sequences of HL and LH, and n is an array of alternating sequences of ((HL)^m(LH)^m) and L.

[0015] Furthermore, the steps also include:

[0016] The high refractive index film is made of at least one of Ta2O5, Nb2O5, and TiO2, and the refractive index of the high refractive index film is in the range of 1.85 to 2.5 at 1550 nm.

[0017] Furthermore, the steps also include:

[0018] The material of the low refractive index film is at least one of SiO2, Al2O3, and MgF2, and the refractive index of the low refractive index film is in the range of 1.38 to 1.6 at 1550 nm.

[0019] A method for preparing a GFF filter includes the following steps:

[0020] Prepare a substrate having a film system consisting of alternating high-refractive-index and low-refractive-index layers; the film system adopts a standard Fabry-Perot cavity basic structure;

[0021] Scan the previous film layer of the current coating to obtain the actual test spectrum curve of the previous film layer; simulate and analyze the actual test spectrum curve of the previous film layer and the theoretical spectrum curve of the previous film layer to obtain the actual thickness of the previous film layer; simulate the actual thickness of the previous film layer and the theoretical spectrum curve of the current film layer to obtain the optimal thickness value of the current film layer; based on the optimal thickness value of the current film layer obtained from the simulation analysis, obtain the actual light intensity change curve of the next film layer; obtain the light control curve through direct laser light control; set the stopping point at the optimal thickness value of the film layer to complete the preparation of the film layer;

[0022] Repeat the previous step to complete the preparation of all film layers and obtain the filter;

[0023] The spectral characteristic curve of the filter after coating is tested to see if it meets the spectral characteristic requirements of GFF filter.

[0024] Furthermore, the number of cavities in the Fabry-Paro cavity ranges from 6 to 12.

[0025] Furthermore, the substrate is formed from silicon dioxide or silicon material.

[0026] Furthermore, the step of detecting whether the spectral characteristic curve of the filter after coating meets the spectral characteristic requirements of the GFF filter specifically includes:

[0027] The peak-to-peak error function between the final spectral characteristic curve after the coating is completed and the target spectral curve is measured, and the error is satisfied to be less than 0.03% of 0.45dB.

[0028] Furthermore, the step of detecting whether the spectral characteristic curve of the filter after coating meets the spectral characteristic requirements of the GFF filter specifically includes:

[0029] By comparing the final spectral characteristic curve with the target spectral curve, the peak-to-peak error function is calculated. If the peak-to-peak error function value meets the requirement of being less than 0.45 dB, the fabrication of the GFF filter is complete. The specific calculation method of the peak-to-peak error function is as follows:

[0030] EF(i)[dB]=Ttarget(i)[dB]-Tmeasured(i)[dB]

[0031] Wherein, FE is the difference function, and the EF value represents the difference between the target transmittance Ttarget and the test transmittance Tmeasured within the spectral range;

[0032] PPEF[dB]=EFmax[dB]-EFmin[dB]

[0033] PPEF is the peak-to-peak error function. The PPEF value represents the difference between the maximum value of the difference function EFma and the minimum value of the difference function EFmin within the spectral range.

[0034] A GFF filter is prepared according to the above-described method for preparing a GFF filter.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] This invention employs a unique preparation scheme. During the processing, the optimal film thickness is analyzed by simulating the scanning spectral curve. This eliminates the need for compensation coating through extreme value control during processing, and eliminates the need to consider specific film layer limitations in the design. On the one hand, the design difficulty is greatly reduced, and on the other hand, the number of film layers and the film thickness are also significantly reduced, which also reduces the requirements for processing difficulty. Attached Figure Description

[0037] Figure 1 This is a step-by-step diagram of a GFF filter coating process;

[0038] Figure 2 This is a step-by-step diagram of a GFF filter fabrication method;

[0039] Figure 3 This is a schematic diagram of the initial structure-spectral performance of specific embodiment 1;

[0040] Figure 4 This is a schematic diagram of the initial spectral performance of the Fabry-Paro cavity in specific embodiment 1;

[0041] Figure 5 This is a schematic diagram of the design spectral performance and the target curve of specific embodiment 1;

[0042] Figure 6 This is the first layer spectral performance curve of specific embodiment 1;

[0043] Figure 7 These are the second-layer theoretical spectral performance curves and the performance curves without error compensation in specific embodiment 1;

[0044] Figure 8 These are the actual spectral performance curves and the target curve of specific embodiment 1;

[0045] Figure 9 This is a schematic diagram of the initial structure-spectral performance of specific embodiment 2;

[0046] Figure 10This is a schematic diagram of the initial structure spectral performance of the Fabry-Perot cavity in specific embodiment 2.

[0047] Figure 11 This is a schematic diagram of the design spectral performance and the target curve of specific embodiment 2;

[0048] Figure 12 This is the first layer spectral performance curve of specific embodiment 2;

[0049] Figure 13 These are the second-layer theoretical spectral performance curves and the performance curves without error compensation in specific embodiment 2;

[0050] Figure 14 These are the spectral performance curves and target curves actually tested in Specific Embodiment 2; Detailed Implementation

[0051] like Figure 1 As shown, the present invention provides a coating method for a GFF filter, comprising:

[0052] S11: Scan the previous film layer of the current coating to obtain the actual test spectrum curve of the previous film layer;

[0053] S12: Simulate and analyze the actual test spectral curve and the theoretical spectral curve of the previous film layer to obtain the actual thickness of the previous film layer;

[0054] S13: Simulate the actual test spectrum curve of the previous film layer and the theoretical spectrum curve of the current film layer to obtain the optimal thickness value of the current film layer;

[0055] S14: Based on the optimal thickness value of the current film layer obtained from the simulation analysis, obtain the actual light intensity change curve of the next film layer, obtain the light control curve through direct laser light control, set the stopping point at the optimal thickness value of the film layer, and complete the preparation of the film layer.

[0056] Specifically, the film adopts the standard Fabry-Perot cavity basic structure ((HL)^m(LH)^m L)^n, where m>0, n>=6 and n<=12, where H is a high refractive index film with a one-quarter center wavelength optical thickness, L is a low refractive index film with a one-quarter center wavelength optical thickness, m is an array of alternating sequences of HL and LH, and n is an array of alternating sequences of ((HL)^m(LH)^m) and L.

[0057] The material of the high refractive index film is at least one of Ta2O5, Nb2O5, and TiO2, and the refractive index of the high refractive index film is in the range of 1.85 to 2.5 at 1550 nm.

[0058] The material of the low refractive index film is at least one of SiO2, Al2O3, and MgF2, and the refractive index of the low refractive index film is in the range of 1.38 to 1.6 at 1550 nm.

[0059] like Figure 2 As shown, the present invention provides a method for preparing a GFF filter, comprising:

[0060] S21: Prepare a substrate with a film system consisting of alternating high-refractive-index and low-refractive-index films; the film system adopts a standard Fabry-Perot cavity basic structure;

[0061] S22: Scan the previous film layer of the current coating to obtain the actual test spectrum curve of the previous film layer; simulate and analyze the actual test spectrum curve of the previous film layer and the theoretical spectrum curve of the previous film layer to obtain the actual thickness of the previous film layer; simulate the actual thickness of the previous film layer and the theoretical spectrum curve of the current film layer to obtain the optimal thickness value of the current film layer; based on the optimal thickness value of the current film layer obtained from the simulation analysis, obtain the actual light intensity change curve of the next film layer, obtain the light control curve through direct laser light control, set the stopping point at the optimal thickness value of the film layer, and complete the preparation of the film layer;

[0062] S23: Repeat the above steps to complete the preparation of all film layers and obtain the filter;

[0063] S24: Check whether the spectral characteristic curve of the filter after coating meets the spectral characteristic requirements of GFF filter.

[0064] Specifically, in S21, the number of Fabry-Paro cavities ranges from 6 to 12.

[0065] The substrate is made of silicon dioxide or silicon material, such as D263T, WMS-15, BK7, FS, Si, etc.

[0066] Specifically, the peak-to-peak error function between the final spectral characteristic curve after the coating is completed and the target spectral curve is measured, and the error is satisfied to be less than 0.03% of 0.45dB.

[0067] By comparing the final spectral characteristic curve with the target spectral curve, the peak-to-peak error function is calculated. If the peak-to-peak error function value meets the requirement of being less than 0.45 dB, the fabrication of the GFF filter is complete. The specific calculation method of the peak-to-peak error function is as follows:

[0068] EF(i)[dB]=Ttarget(i)[dB]-Tmeasured(i)[dB]

[0069] Wherein, FE is the difference function, and the EF value represents the difference between the target transmittance Ttarget and the test transmittance Tmeasured within the spectral range;

[0070] PPEF[dB]=EFmax[dB]-EFmin[dB]

[0071] Wherein, PPEF is the peak-to-peak error function, and the PPEF value represents the difference between the maximum value of the difference function EFmax and the minimum value of the difference function EFmin within the spectral range.

[0072] A GFF filter is prepared according to steps S21 to S24 to finally obtain a GFF filter.

[0073] The specific implementation method is as follows:

[0074] This first embodiment is one example of a GFF filter, such as... Figure 3 As shown, under an incident angle of 3 degrees, the spectral curve in the range of 1524 nm to 1573 nm is close to the target curve, and the peak-to-peak error function is less than 0.45 dB.

[0075] The fabrication process of the GFF filter described above in this embodiment is as follows:

[0076] (1) The basic structure using the Fabry-Perot cavity is shown in the following spectral characteristic curve. Figure 4 As shown, the specific initial results are as follows:

[0077] HLH2LHLHL

[0078] HLH2LHLHL

[0079] HLH2LHLHL

[0080] HLHLH2LHLHLHL

[0081] HLHLH2LHLHLHL

[0082] HLHLH2LHLHLHL

[0083] HLHLH2LHLHLHL

[0084] HLHLH2LHLHLHL

[0085] HLH2LHLHL

[0086] HLH2LHLHL

[0087] HLH2LHLHL

[0088] It consists of 11 Fabry-Perot cavities, where H represents a high emissivity material film with a thickness of 1 / 4 wavelength. The material is Ta2O5, and its refractive index is 2.094 near 1550 nm.

[0089] L represents a low emissivity material film with a thickness of 1 / 4 wavelength, the material being SiO2, and the refractive index being 1.471 near 1550 nm;

[0090] (2) Remove the limiting conditions set for the film layers, and obtain a spectral characteristic curve consistent with the target curve by optimizing the thickness of all film layers, such as... Figure 5 As shown in Table 1 below, the optimized film thickness is as follows:

[0091] Table 1: Materials and Thicknesses of Example 1

[0092]

[0093]

[0094]

[0095]

[0096] The implementation method of the GFF filter using the above-described technical solution in this embodiment is as follows:

[0097] 1) When realizing the first film layer, the spectral curves in the 1520-1580nm wavelength range were compared with the theoretical spectral curves in the same range to simulate and analyze the actual thickness of the first film layer. The theoretical spectral curves corresponding to the first film layer in the 1520-1580nm wavelength range and the actual measured spectral curves are shown in the figure. Figure 6 Through simulation analysis, the theoretical film thickness is 176.96 nm, while the actual film thickness is 171.96 nm.

[0098] 2) By simulating the actual thickness of the first film layer and the theoretical spectral curve of the second layer, the optimal thickness solution for the second layer was obtained as 163.949 nm. Through compensation for the thickness of the second layer, the spectral characteristic curve of the actual fabrication can be made consistent with the theoretically designed spectral curve, thus achieving consistency between the spectral characteristics of the first two layers and the theoretical design. The corresponding spectral characteristic curves are as follows: Figure 7 As shown;

[0099] 3) Following the same procedure as in step 2), the compensation thickness of each subsequent film layer is obtained, and the film is prepared based on the compensation thickness to ultimately achieve the corresponding spectral characteristic curve, such as... Figure 8 As shown, the corresponding PPEF value is 0.234 dB;

[0100] The GFF filter in this embodiment achieves a gain-flat filter with a ModulationDepth close to 7dB through the design and implementation method of the present invention, and its corresponding PPEF meets the requirement of less than 0.45dB.

[0101] The specific implementation method 2 is as follows:

[0102] This embodiment is one example of a GFF filter, such as... Figure 9 As shown, under an incident angle of 3 degrees, the spectral curve in the range of 1524 nm to 1573 nm is close to the target curve, and the peak-to-peak error function is less than 0.45 dB.

[0103] The fabrication process of the GFF filter described above in this embodiment is as follows:

[0104] (1) The basic structure using the Fabry-Perot cavity is shown in the following spectral characteristic curve. Figure 10 As shown, the specific initial results are as follows:

[0105] HLHL2HLHLHL

[0106] HLHL2HLHLHL

[0107] HLHL2HLHLHL

[0108] HLHL2HLHLHL

[0109] HLHLHL2HLHLHLHL

[0110] HLHLHL2HLHLHLHL

[0111] HLHL2HLHLHL

[0112] HLHL2HLHLHL

[0113] HLHL2HLHLHL

[0114] HLHL2HLHLHL

[0115] It consists of 11 Fabry-Perot cavities, where H represents a high emissivity material film with a thickness of 1 / 4 wavelength. The material is Ta2O5, and the refractive index is 2.094 near 1549.2 nm.

[0116] L represents a low emissivity material film with a thickness of 1 / 4 wavelength, the material being SiO2, and the refractive index being 1.471 near 1549.2 nm;

[0117] (2) Remove the limiting conditions set for the film layers, and obtain a spectral characteristic curve consistent with the target curve by optimizing the thickness of all film layers, such as... Figure 11 As shown in Table 2 below, the optimized film thickness is as follows:

[0118] Table 2: Materials and Thicknesses in Example 2

[0119]

[0120]

[0121]

[0122] The implementation method of the GFF filter using the above-described technical solution in this embodiment is as follows:

[0123] 1) When realizing the first film layer, the spectral curves in the 1520-1580nm wavelength range were compared with the theoretical spectral curves in the same range to simulate and analyze the actual thickness of the first film layer. The theoretical spectral curves corresponding to the first film layer in the 1520-1580nm wavelength range and the actual measured spectral curves are shown in the figure. Figure 12 Through simulation analysis, the theoretical film thickness is 182.97 nm, while the actual film thickness is 184.97 nm.

[0124] 2) By simulating the actual thickness of the first film layer and the theoretical spectral curve of the second layer, the optimal thickness solution for the second layer was obtained as 249.984 nm (the theoretical value is 251.51 nm). Through compensation for the thickness of the second layer, the spectral characteristic curve of the actual fabrication can be made consistent with the theoretically designed spectral curve, thus achieving consistency between the spectral characteristics of the first two layers and the theoretical design. The corresponding spectral characteristic curves are as follows: Figure 13 As shown;

[0125] 3) Following the same procedure as in step 2), the compensation thickness of each subsequent film layer is obtained, and the film is prepared based on the compensation thickness to ultimately achieve the corresponding spectral characteristic curve, such as... Figure 14 As shown, the corresponding PPEF = 0.332dB;

[0126] The GFF filter in this embodiment achieves a gain-flat filter with a ModulationDepth close to 12dB through the design and implementation method of the present invention, and its corresponding PPEF meets the requirement of 0.45dB.

[0127] Finally, it should be noted that the above embodiments only illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These are all equivalent modifications and variations made to the above embodiments based on the essential technology of the present invention, and all of these fall within the protection scope of the present invention.

Claims

1. A coating method for a GFF filter, characterized in that, Includes the following steps: Scan the previous film layer of the current coating to obtain the actual test spectrum curve of the previous film layer; The actual thickness of the previous film layer is obtained by simulating and analyzing the actual test spectral curve and the theoretical spectral curve of the previous film layer. Simulate the actual thickness of the previous film layer and the theoretical spectral curve of the current film layer to obtain the optimal thickness value of the current film layer; Based on the optimal thickness value of the current film layer obtained from the simulation analysis, the actual light intensity change curve of the next film layer is obtained. The light control curve is obtained by direct laser light control. The stop point of the optimal thickness value of the film layer is set to complete the preparation of the film layer. The film layer adopts a standard Fabry-Perot cavity basic structure ((HL)^m (LH)^m L)^n, where m>0, n>=6 and n<=12, where H is a high refractive index film layer with a center wavelength optical thickness of one-quarter, L is a low refractive index film layer with a center wavelength optical thickness of one-quarter, m is an array of alternating sequences of HL and LH, and n is an array of alternating sequences of ((HL)^m (LH)^m) and L.

2. The coating method for the GFF filter according to claim 1, characterized in that, The steps also include: The high refractive index film is made of at least one of Ta2O5, Nb2O5, and TiO2, and the refractive index of the high refractive index film is in the range of 1.85 to 2.5 at 1550 nm.

3. The coating method for the GFF filter according to claim 1, characterized in that, The steps also include: The material of the low refractive index film is at least one of SiO2, Al2O3, and MgF2, and the refractive index of the low refractive index film is in the range of 1.38 to 1.6 at 1550 nm.

4. A method for preparing a GFF filter, characterized in that, Includes the following steps: Prepare a substrate having a film system consisting of alternating high-refractive-index and low-refractive-index layers; the film system adopts a standard Fabry-Perot cavity basic structure; Scan the previous film layer of the current coating to obtain the actual test spectrum curve of the previous film layer; The actual thickness of the previous film layer is obtained by simulating and analyzing the actual test spectral curve and the theoretical spectral curve of the previous film layer. The actual thickness of the previous film layer and the theoretical spectral curve of the current film layer are simulated to obtain the optimal thickness value of the current film layer; based on the optimal thickness value of the current film layer obtained from the simulation analysis, the actual light intensity change curve of the next film layer is obtained; the light control curve is obtained by direct laser light control; the stop point of the optimal thickness value of the film layer is set to complete the preparation of the film layer. Repeat the previous step to complete the preparation of all film layers and obtain the filter; The spectral characteristic curve of the filter after coating is tested to see if it meets the spectral characteristic requirements of GFF filter. The number of cavities in the Fabry-Paro cavity ranges from 6 to 12.

5. The method for preparing the GFF filter according to claim 4, characterized in that, The substrate is formed from silicon dioxide or silicon material.

6. The method for preparing the GFF filter according to claim 4, characterized in that, The step of detecting whether the spectral characteristic curve of the filter after coating meets the spectral characteristic requirements of GFF filter specifically includes: The peak-to-peak error function between the final spectral characteristic curve after the coating is completed and the target spectral curve is measured, and the error is satisfied to be less than 0.03% of 0.45dB.

7. The method for preparing the GFF filter according to claim 6, characterized in that, The step of detecting whether the spectral characteristic curve of the filter after coating meets the spectral characteristic requirements of GFF filter further includes: By comparing the final spectral characteristic curve with the target spectral curve, the peak-to-peak error function is calculated. If the peak-to-peak error function value meets the requirement of being less than 0.45 dB, the fabrication of the GFF filter is complete. The specific calculation method of the peak-to-peak error function is as follows: EF(i)[dB]=Ttarget(i)[dB]-Tmeasured(i)[dB] Wherein, EF is the difference function, and the EF value represents the difference between the target transmittance Ttarget and the test transmittance Tmeasured within the spectral range; PPEF[dB]=EFmax[dB]-EFmin[dB] Wherein, PPEF is the peak-to-peak error function, and the PPEF value represents the difference between the maximum value of the difference function EFmax and the minimum value of the difference function EFmin within the spectral range.

8. A GFF filter, characterized in that, The GFF filter is prepared according to the preparation method of any one of claims 4-7.

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