A semi-automatic optimization method for CWDM4 phase compensation length

Abstract

This invention discloses a semi-automatic optimization method for the phase compensation length of a CWDM4. The method uses estimated values ​​to obtain the ideal values ​​of the compensation length and in stage 1. When , the method scans near the ideal values ​​to obtain the ideal optimal value of the transmittance image in dB that satisfies certain conditions. When , the method uses a dual-pointer hash statistical method to obtain and filter out the values ​​of and that satisfy the conditions, and then checks to obtain the optimal transmittance image and the corresponding optimal values ​​of and . Finally, the method scans the actual Stage 1 of the CWDM4 to obtain the actual optimal value of the compensation length.

Description

Technical Field

[0001] This invention relates to the field of silicon photonics chip technology, and in particular to a semi-automatic optimization method for CWDM4 phase compensation length. Background Technology

[0002] Coarse wavelength division multiplexing (CWDM) is an important technique for increasing optical bandwidth in high-density interconnects. A CWDM4 demultiplexer can demultiplex a 100Gb / s optical input into four channels of CWDM optical signals. For a CWDM4 20 nm device, the center wavelengths of the four optical channels are 1271 nm, 1291 nm, 1311 nm, and 1331 nm. Conversely, a CWDM4 multiplexer can perform the reverse process.

[0003] Figure 1 is a schematic diagram of the standard stage structure in the CWDM4 device. As can be clearly seen from the figure, the stage structure consists of six arc-shaped waveguides (arcs) with PTC values ​​of 0.50, 0.20, 0.20, and 0.04, respectively. The lengths of the six arcs are respectively... , , , , and These six lengths are referred to as delay lengths or compensation lengths. The top left corner is defined as port 2, the bottom left corner as port 1, the top right corner as port 4, and the bottom right corner as port 3.

[0004] A commonly used CWDM4 device contains a three-stage structure, which are designated as stage1, stage2a, and stage2b, respectively. Their connection method is as follows: Figure 2 As shown. The relevant physical quantities are defined as follows:

[0005] : Figure 1 The phase compensation length shown is a generalized representation of the corresponding lengths of the three stages;

[0006] : Figure 2 The phase compensation length corresponding to the stage 1 structure shown;

[0007] : Figure 2 The phase compensation length corresponding to the stage 2a structure shown;

[0008] : Figure 2 The phase compensation length corresponding to the stage 2b structure shown;

[0009] To ensure optimal performance of the CWDM4 device, the phase compensation lengths in Stage 1, Stage 2a, and Stage 2b are particularly crucial. Based on the preset relationships of the CWDM4 Stage phase compensation lengths, we can obtain:

[0010]

[0011] As can be seen from the formula above, if the optimal phase compensation length is obtained... And thus, one can obtain at the same time and The value of the phase compensation length. Formulas can be used Make an estimate:

[0012]

[0013] in:

[0014] The design wavelength of CWDM4 is the center wavelength of the four channels. ;

[0015] The desired wavelength spacing is equal to the center wavelength spacing of the designed channels. ;

[0016] The group refractive index of a waveguide is usually obtained from simulation results or calculated from experimental measurements.

[0017] From the formula Know, It is inversely proportional to ΔL (estimated phase compensation length), that is... , and The longer the length, the smaller the spacing between the center wavelengths of each channel in the CWDM4.

[0018] If a directional coupler (DC) is used instead Figure 1 The PTC structure in, such as Figure 3 As shown, then according to the formula The calculated estimated value is then manually adjusted near the estimated value. , and The value is adjusted, and the transmittance image is observed with the human eye to select an appropriate value. and Then adjust manually. , and The value of is used to obtain the transmittance image of the overall CWDM4 structure. This is the existing method of manually adjusting to obtain the optimal performance of the CWDM4 structure, but this method has three drawbacks:

[0019] First, it is time-consuming and labor-intensive, and it is difficult to achieve the required precision. Scale. If you want to Use step size within the range Perform a scan to determine and The value must be at least This is the first manual operation to determine. , and The value must be at least This single operation involves a huge workload; however, the number of comparisons required when two combinations are very close has not yet been included. Adding this case would further increase the workload. For example, to achieve an accuracy of... , i.e., step size value If at this time To perform a scan on the interval, it is necessary to This operation incurs a significant time cost.

[0020] Secondly, due to the lack of evaluation standards, it is difficult to ensure that the sum of the offsets of the center wavelengths of the four channels is minimized.

[0021] Third , and value pairs , and There are minor effects, and it is very difficult to obtain the best results by manual operation alone.

[0022] To address the aforementioned problems, this invention proposes a semi-automatic optimization method for the phase compensation length of CWDM4. This method significantly reduces the manual and time costs of obtaining the optimal performance CWDM4 structure. Furthermore, it can accurately optimize the phase compensation length to... This scale significantly improves the performance of integrated optical paths. Summary of the Invention

[0023] A semi-automatic optimization method for CWDM4 phase compensation length includes the following steps:

[0024] Step 1: Replace the process tolerance coupler (PTC) in the CWDM4 structure with a directional coupler (DC), and calculate the estimated value ΔL of the phase compensation length in the ideal CWDM4 structure when using DC;

[0025] Step 2: Use the ΔL calculated in Step 1 as the compensation length for stage 1 in CWDM4. The ideal value is calculated using the following formula to obtain the compensation length. Ideal value:

[0026]

[0027] Step 3: Let Scan the region near the ideal compensation length obtained in step 2. The length of the image is used to obtain a transmittance image in dB that satisfies the following condition, thus obtaining... Ideal optimal value:

[0028]

[0029] in, The full spectrum wavelength of the input light wave, The center wavelengths corresponding to the parts of the image with a transmittance loss of less than 3dB for the input light wave, expressed in dB. To design the channel center wavelength, the center wavelengths of the CWDM4 device correspond to respectively The corresponding value of i is ; This is the phase compensation length corresponding to the stage 1 structure; Transmittance is expressed in dB.

[0030] Step 4: Using the ideal structure CWDM4 obtained in Step 3... The ideal optimal value setting in the actual CWDM4 Stage1 structure The value; let The two-pointer hash statistics method is used to obtain and Various possible combinations, filter out those that satisfy of , The combination, in the selected , Multiple images are plotted simultaneously around the combined value, and the optimal transmittance image is obtained by visual inspection. The image corresponding to the optimal transmittance image is then selected. , The optimal value;

[0031] Step 5: Based on the information obtained in Step 4 , To obtain the optimal value, the entire actual Stage 1 structure of CWDM4 is scanned using the method in step 3 to obtain the compensation length. The actual optimal value;

[0032] Step 6: Adjust the compensation lengths of Stage 2a and Stage 2b in CWDM4. and Compensation length of the corresponding Stage1 structure , Maintain consistency, compensate length By slightly less The optimal value is selected from the vicinity of the given value through manual adjustment and visual observation.

[0033] Preferably, the transmittance in step 3 The calculation formula is:

[0034]

[0035] in, To output optical power, This refers to the input optical power.

[0036] Preferably, the two-pointer hash statistics method in step 4 is as follows:

[0037] Step 4.1: Create an empty dictionary object dict1; dict1 will be used to store... Value and initial value and Key-value pairs consisting of a string representing the terminating value as the key and the length of the temporary list lst as the value; the temporary list lst is used to store the current... When the value remains unchanged, it satisfies the condition that two adjacent values ​​are equal. All consecutive values ​​when the difference is less than the threshold value;

[0038] Step 4.2: Set the threshold value (threshold_value), which is the threshold value between two adjacent values. The maximum allowed difference between values;

[0039] Step 4.3: Set the left pointer `left_index` to index 0;

[0040] Step 4.4: The left pointer `left_index` is looped in a while loop until the index it points to is not less than the length of list `lst_WGD2` minus 1; `lst_WGD2` is used to store the values ​​that meet the condition. All of the obtained combinations A list of components;

[0041] Step 4.5: Reset the temporary list object lst to null;

[0042] Step 4.6: Use a for loop to iterate from the index pointed to by the left pointer `left_index` to the length of the list `lst_WGD2`.

[0043] Step 4.7: Determine if the left pointer `left_index` is equal to the right pointer `right_index`;

[0044] Step 4.8: If the condition in Step 4.7 is met, add the corresponding value of the right pointer `right_index` in `lst_WGD3` to the temporary list `lst`, and continue the `for` loop in Step 4.6; `lst_WGD3` is used to store the values ​​that meet the condition. The obtained All in the combination A list of components;

[0045] Step 4.9: If the judgment condition in Step 4.7 is not met, determine whether the value in the lst_WGD2 list corresponding to the left pointer left_index is consistent with the value in the lst_WGD2 list corresponding to the right pointer right_index, and whether the difference between the value in the lst_WGD3 list corresponding to the left pointer left_index and the value in the lst_WGD3 list corresponding to the right pointer right_index is less than the threshold.

[0046] Step 4.10: If the conditions in step 4.9 are met, add the corresponding value of the right pointer right_index in lst_WGD3 to the temporary list lst, and set the left pointer left_index to the index value currently pointed to by the right pointer right_index;

[0047] Step 4.11: Further determine whether the current right pointer right_index is equal to the length of the lst_WGD2 list minus 1. If it is, store the string formed by concatenating the number of elements in the list lst with the minimum and maximum values ​​in the list lst as the key in dict1, interrupt the for loop, and enter the next while loop.

[0048] Step 4.12: If the condition in step 4.9 is not met, store the number of elements in list lst as the value and the string formed by concatenating the minimum and maximum values ​​in list lst as the key in dict1, interrupt the for loop, and enter the next while loop. Attached Figure Description

[0049] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0050] Figure 1 A schematic diagram of the CWDM4 device Stage;

[0051] Figure 2 This is a schematic diagram showing the relationship between the Stage structures of the CWDM4 device;

[0052] Figure 3 A schematic diagram of the Stage structure constructed using an ideal directional coupler for CWDM4;

[0053] Figure 4 To calculate the optimal compensation length for the CWDM4 device Flowchart;

[0054] Figure 5 To calculate the optimal compensation length for the CWDM4 device Flowchart;

[0055] Figure 6 for Figure 5 The method uses a two-pointer hash statistical calculation method to obtain some results;

[0056] Figure 7 The percentage of CWDM4 transmittance image obtained using the method of the present invention;

[0057] Figure 8 The image shows the CWDM4 transmittance in dB, obtained using the method of the present invention.

[0058] Figure 9 This represents the percentage of the CWDM4 transmittance image obtained through manual adjustment in existing methods.

[0059] Figure 10 This is a CWDM4 transmittance image displayed in dB, obtained by manual adjustment using existing methods. Detailed Implementation

[0060] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following detailed description, in conjunction with the accompanying drawings and preferred embodiments, provides a waveguide cross structure made of different materials according to the present invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable manner.

[0061] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships, such as A and / or B. Specifically, it can mean that A and B can be included at the same time, A can exist alone, or B can exist alone, and any of the above three situations can be met.

[0062] The traditional formula for calculating insertion loss is:

[0063]

[0064] For a more intuitive image display, transmittance is defined in dB. The calculation formula is:

[0065]

[0066] Reference Figure 1-3 The structure makes In the calculated Nearby area scan The length of the image, and the transmittance image obtained after scanning in dB, must meet the following conditions:

[0067]

[0068] in,

[0069] The full spectrum wavelength of the input light wave

[0070] The center wavelengths of the input light wave, expressed in dB, are the transmittance of the image. The transmittance loss is less than 3 dB for each part.

[0071] Design the channel center wavelength; for the CWDM4 device, the center wavelengths correspond to... The corresponding value of i is .

[0072] Figure 4 is a flowchart corresponding to the specific implementation process described above. Following the flowchart in Figure 4, according to the formula... This allows us to initially determine the optimal configuration of the structure shown in Figure 3 when using an ideal DC structure. Length. Figure 4 As can be seen from the process, since the wavelength range of the target port outlet is a given 1271 nm - 1331 nm, the part outside this wavelength can be deleted by image processing methods, otherwise it may affect the application of formula (6).

[0073] Next, scan Figure 1In the actual Stage1 structure The length. First, according to the previously obtained data when using the ideal DC structure. The optimal length setting in the actual Stage 1 structure The value of. Secondly, from Figure 1 It's not hard to see that two PTC 0.20 units were used, therefore, .scanning and Various possible combinations are selected to satisfy the formula. Combine and record.

[0074]

[0075] Figure 5 shows the flowchart of the two-pointer hash statistics algorithm on the right. The meanings of the variables used in the algorithm are as follows:

[0076] left_index: Left pointer (the left pointer points to the index value);

[0077] right_index: The right pointer (the right pointer points to the index value);

[0078] lst_WGD2: Used to store expressions that satisfy the decision conditions. The obtained All in the combination A list of components;

[0079] lst_WGD3: Used to store expressions that satisfy the decision conditions. The obtained All in the combination A list of components;

[0080] threshold_value: Threshold, two adjacent... The maximum allowed difference between values;

[0081] lst: A temporary list used to store current... When the value remains unchanged, it satisfies the condition that two adjacent values ​​are equal. All consecutive values ​​when the difference is less than the threshold value;

[0082] dict1: Used to store Value and initial value and The key-value pairs consist of a string of terminating values ​​as keys and the length of a temporary list lst as values.

[0083] Figure 5 The operation steps corresponding to the numbers in each step are as follows:

[0084] 1: Create an empty dictionary object dict1

[0085] 2: Set threshold_value=0.05 (the threshold can be adjusted according to needs)

[0086] 3: Set left_index to point to index 0

[0087] 4: The left_index loop iterates through the list until the index it points to is not less than the length of the list lst_WGD2 minus 1.

[0088] 5: Reset the temporary list object lst to empty.

[0089] 6: Use a for loop to iterate through the list from the index pointed to by left_index to the length of list lst_WGD2.

[0090] 7: Determine if left_index is equal to right_index.

[0091] 8: If the judgment condition mentioned in step 7 is met, add the corresponding value of right_index in lst_WGD3 to the temporary list lst, and continue with the for loop in step 6.

[0092] 9: If the judgment condition in step 7 is not met, determine whether the value in the lst_WGD2 list corresponding to left_index is consistent with the value in the lst_WGD2 list corresponding to right_index, and whether the difference between the value in the lst_WGD3 list corresponding to left_index and the value in the lst_WGD3 list corresponding to right_index is less than the threshold.

[0093] 10: If the conditions mentioned in step 9 are met, add the corresponding value of right_index in lst_WGD3 to the temporary list lst, and set left_index to the index value currently pointed to by right_index.

[0094] 11: Further check if the current right_index is equal to the length of the lst_WGD2 list minus 1. If it is, store the string formed by concatenating the number of elements in list lst with the minimum and maximum values ​​in list lst as the key in dict1. Interrupt the for loop and enter the next while loop.

[0095] 12: If the condition in step 9 is not met, store the string formed by concatenating the number of elements in list lst as the value and the minimum and maximum values ​​in list lst as the key in dict1. Interrupt the for loop and begin the next while loop.

[0096] After using the above algorithm, the output data (partial) shown in Figure 6 is obtained. The first column of data corresponds to... The value, the data in the second column corresponds to The starting value that satisfies the threshold determination condition in step 9 of the hash statistics algorithm, the third column of data corresponds to The termination value that satisfies the threshold determination condition in step 9 of the hash statistics algorithm. The value represents the value when... When a value is given, in initial value and How many satisfying expressions are there within the interval of the termination value? The combination of judgment conditions. The larger the Value, the better and more stable the transmittance image is around that combination value. Next, find the combination corresponding to the maximum Value; obviously, here it is... Furthermore, it's easy to see from Figure 6 that other combinations of values ​​near this range are also quite good, meaning the optimal compensation value is likely near this range. Finally, in Multiple images are plotted simultaneously around this set of interval values ​​and examined visually to obtain the optimal transmittance image. The flowchart on the left side of Figure 5 corresponds to the specific implementation process.

[0097] Finally, using the entire process shown in Figure 4 again, based on the obtained... The optimal compensation length is obtained by scanning the entire actual Stage 1 structure of CWDM4. Compensation length.

[0098] For Stage 2a and Stage 2b, their corresponding The compensation length is consistent with the Stage1 structure, while The compensation length can be achieved by using a length slightly smaller than The optimal value was selected near the compensation length through manual adjustment and visual observation.

[0099] Figure 7 shows the transmittance image of CWDM4 at the optimal compensation length, expressed as a percentage; Figure 8 shows the transmittance image of CWDM4 at the optimal compensation length, expressed in dB. From... Figure 8 As can be seen, the crosstalk values ​​of all channels are below -19dB, and the crosstalk suffered by the center wavelength of each channel is around -23dB.

[0100] Figure 9 and Figure 10 This is one of the better results obtained when adjusting manually, compared to Figure 7 The transmittance image obtained by manually adjusting the image, compared to the best optimization result obtained in Figure 8, is less than satisfactory.

[0101] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0102] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A semi-automatic optimization method for CWDM4 phase compensation length, comprising the following steps: Step 1: Replace the process tolerance coupler in the CWDM4 structure with a directional coupler, and calculate the estimated phase compensation length in the ideal CWDM4 structure when using DC. ΔL ; Step 2: Calculate the result in Step 1 ΔL As Compensation length of stage 1 in CWDM4 The ideal value is calculated using the following formula to obtain the compensation length. Ideal value: ； Step 3: Let Scan the region near the ideal compensation length obtained in step 2. The length of the image is used to obtain a transmittance image in dB that satisfies the following condition, thus obtaining... Ideal optimal value: ； in, The full spectrum wavelength of the input light wave, The center wavelengths corresponding to the parts of the image with a transmittance loss of less than 3dB for the input light wave, expressed in dB. To design the channel center wavelength, the center wavelengths of the CWDM4 device correspond to respectively Corresponding i The value is ; This is the phase compensation length corresponding to the stage 1 structure; Transmittance is expressed in dB. Step 4: Using the ideal structure CWDM4 obtained in Step 3... The ideal optimal value setting in the actual CWDM4 Stage1 structure The value; let The two-pointer hash statistics method is used to obtain and Various possible combinations, filter out those that satisfy of , The combination, in the selected , Multiple images are plotted simultaneously around the combined value, and the optimal transmittance image is obtained by visual inspection. The image corresponding to the optimal transmittance image is then selected. , The optimal value; Step 5: Based on the information obtained in Step 4 , To obtain the optimal value, the entire actual Stage 1 structure of CWDM4 is scanned using the method in step 3 to obtain the compensation length. The actual optimal value; Step 6: Adjust the compensation lengths of Stage 2a and Stage 2b in CWDM4. and Compensation length of the corresponding Stage1 structure , Maintain consistency, compensate length By slightly less The optimal value is selected from the vicinity of the given value through manual adjustment and visual observation.

2. The semi-automatic optimization method for CWDM4 phase compensation length according to claim 1, characterized in that: Transmittance in step 3 The calculation formula is: ； in, To output optical power, This refers to the input optical power.

3. The semi-automatic optimization method for CWDM4 phase compensation length according to claim 1, characterized in that, The two-pointer hash statistics method in step 4 is as follows: Step 4.1: Create an empty dictionary object dict1; dict1 is used to store Value and initial value and The key-value pairs consist of a string representing the terminating value as the key and the length of the temporary list lst as the value. The temporary list lst is used to store the current When the value remains unchanged, it satisfies the condition that two adjacent values ​​are equal. All consecutive values ​​when the difference is less than the threshold value; Step 4.2: Set the threshold value (threshold_value), which is the threshold value between two adjacent values. The maximum allowed difference between values; Step 4.3: Set the left pointer `left_index` to index 0; Step 4.4: The left pointer `left_index` is looped in a while loop until the index it points to is not less than the length of list `lst_WGD2` minus 1; `lst_WGD2` is used to store the values ​​that meet the condition. All of the obtained combinations A list of components; Step 4.5: Reset the temporary list object lst to null; Step 4.6: Use a for loop to iterate from the index pointed to by the left pointer `left_index` to the length of the list `lst_WGD2`. Step 4.7: Determine if the left pointer `left_index` is equal to the right pointer `right_index`; Step 4.8: If the condition in Step 4.7 is met, add the corresponding value of the right pointer `right_index` in `lst_WGD3` to the temporary list `lst`, and continue the `for` loop in Step 4.6; `lst_WGD3` is used to store the values ​​that meet the condition. The obtained All in the combination A list of components; Step 4.9: If the judgment condition in Step 4.7 is not met, determine whether the value in the lst_WGD2 list corresponding to the left pointer left_index is consistent with the value in the lst_WGD2 list corresponding to the right pointer right_index, and whether the difference between the value in the lst_WGD3 list corresponding to the left pointer left_index and the value in the lst_WGD3 list corresponding to the right pointer right_index is less than the threshold. Step 4.10: If the conditions in step 4.9 are met, add the corresponding value of the right pointer right_index in lst_WGD3 to the temporary list lst, and set the left pointer left_index to the index value currently pointed to by the right pointer right_index; Step 4.11: Further determine whether the current right pointer right_index is equal to the length of the lst_WGD2 list minus 1. If it is, store the string formed by concatenating the number of elements in the list lst with the minimum and maximum values ​​in the list lst as the key in dict1, interrupt the for loop, and enter the next while loop. Step 4.12: If the condition in step 4.9 is not met, store the string formed by concatenating the number of elements in list lst as the value and the minimum and maximum values ​​in list lst as the key in dict1, interrupt the for loop, and enter the next while loop.

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