Method for realizing crosstalk of space division multiplexing device based on light intensity image processing

Abstract

The application discloses a method for realizing crosstalk of a space division multiplexing device based on light intensity image processing. After two-dimensional light intensity data is imported and light spots are searched and recognized, the relative positions of cores on a light beam analyzer are determined, the light spot intensity of target cores and non-target cores is calculated, and finally, the background noise and the device crosstalk are obtained. The application can quickly and accurately calculate the device crosstalk, so that the device function can be verified as soon as possible, and is suitable for basically all space division devices supporting frequency multiplexing and mode multiplexing.

Description

Technical Field

[0001] This invention relates to a technology in the field of multi-core, multi-mode optical communication testing, specifically a method for implementing crosstalk in spatial multiplexing devices based on optical intensity image processing. Background Technology

[0002] Space division multiplexing (SDM) technology is a crucial component of classical optical communication, significantly increasing the bandwidth of optical communication systems. The implementation of SDM relies on specific SDM optical devices, including multi-core optical fibers, femtosecond laser-written SDM chips, and two-dimensional multi-core array devices. One of the key performance indicators for these devices is crosstalk between the individual cores (channels). Currently, the mainstream testing method involves placing the device within the system for testing. This process requires connecting the device to a fiber optic pigtail, increasing testing time and slowing down the iteration speed of device manufacturing processes. Summary of the Invention

[0003] To address the aforementioned shortcomings of existing technologies, this invention proposes a method for realizing crosstalk in spatial multiplexing devices based on light intensity image processing. This method enables rapid and accurate calculation of device crosstalk, thereby facilitating the quick verification of device functionality. It is applicable to virtually all spatial multiplexing devices that support frequency and mode multiplexing.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to a method for implementing crosstalk in a spatial multiplexing device based on light intensity image processing, comprising:

[0006] Step 1: Determine the relative position of each core on the beam analyzer. Specifically, use a spatial multiplexing device with an output end face structure consistent with the device under test and all channels capable of simultaneously outputting beams to calibrate the size and relative position of all cores using a beam edge retrieval and identification method.

[0007] The method for retrieval and recognition of light spot edges employs, but is not limited to, the Canny edge detection algorithm.

[0008] Step 2: Import two-dimensional light intensity data and retrieve and identify the light spot. Specifically, after the light beam emitted from the space separation device passes through the coupling lens, the two-dimensional light intensity data recorded at any point on the propagation path is obtained using a beam quality analyzer. The position of the highest light intensity is then retrieved, the edge of the light spot is identified, and the center of the light spot is determined.

[0009] The edges of the light spots were also detected using the Canny edge detection algorithm.

[0010] The center of the light spot is obtained as follows: Within a rectangular area of ​​a certain size, using the position of the highest light intensity as the center, the row containing the highest and lowest points of the light spot edge, and the column containing the leftmost and rightmost points, are retrieved from the edge image. The midpoint between the two rows is the row containing the center of the light spot, and the midpoint between the two columns is the column containing the center of the light spot. The maximum value of the row difference and column difference is taken as the diameter of the light spot.

[0011] Step 3: Calculate the spot intensity of the target core and non-target cores to obtain the background noise and final device crosstalk, specifically including:

[0012] 3.1 The target core emits the strongest light spot, and its position can be directly determined. The channel positions of non-target cores are marked by using the relative positional relationship between the target core and the other cores. Specifically, after determining the position and radius of the target core's emitted light spot and its coordinates in the overall device, the positions of the light spot centers of non-target cores are determined sequentially according to the device structure. Taking the center of each core's light spot as the center, and using the determined light spot radius as the radius, the light intensity value of each pixel within the circle is summed to obtain the light spot intensity value before noise subtraction.

[0013] 3.2 Pixels not included in the light spot area are called noise pixels. The sum of the light intensities of noise pixels divided by the number of noise pixels gives the noise of each pixel. The light intensity of a single light spot minus the product of the pixel noise and the number of pixels in the light spot gives the intensity of the light spot after filtering out noise.

[0014] If the value obtained after filtering out noise is negative, the light intensity of the light spot is recorded as zero.

[0015] 3.3 The strongest light spot intensity is the output light spot intensity of the core, and the intensity of the remaining light spots is the intensity of the crosstalk light spots. The crosstalk magnitude of the core device is obtained by taking the logarithm of the ratio of the average crosstalk light spot intensity to the output light spot intensity and then multiplying it by -10, in decibels.

[0016] This invention relates to a system for implementing the above method, comprising: a spatial division multiplexing device, a spot edge recognition unit, and a light intensity calculation and processing unit, wherein: the spatial division multiplexing device calibrates the spatial position and corresponding spot size of all outgoing channels; the spot edge recognition unit obtains the edge information of each spot of the device under test through the Canny edge detection algorithm; and the light intensity calculation and processing unit calculates the light intensity of each channel and the corresponding crosstalk magnitude based on the edge information, channel spatial position, and spot size.

[0017] Technical effect

[0018] This invention targets integrated space-division multiplexing (SDM) chips. Through performance testing and the SDM chip, the position and radius of the output light spot of each channel are determined. The positions of the output light spot and the crosstalk light spot are determined by the Canny edge detection algorithm. Then, the intensity of each light spot and the corresponding device crosstalk value are calculated using an integral method. Compared with the prior art, this invention does not require a complex on-chip information acquisition system. It only needs to collect the two-dimensional light intensity information output after the light passes through the integrated SDM device to quickly locate the position of the output light spot and the crosstalk light spot and calculate the light intensity of each light spot and the corresponding device crosstalk value. This is beneficial for the optimization and iteration of integrated SDM devices. Attached Figure Description

[0019] Figure 1 a is a schematic diagram of a 37-core femtosecond laser direct-write space-division multiplexing chip; Figure 1 b is a microscopic image of end face A. Figure 1 c is a microscopic image of the B-end face;

[0020] In the diagram: End face A is interconnected with a 37-core multimode fiber. After spatial separation is achieved through devices, crosstalk between cores is tested at end face B.

[0021] Figure 2 This is a schematic diagram of the overall optical path design;

[0022] In the diagram: the beam analyzer is positioned appropriately behind the coupling lens, so that the beam spot is focused and imaged on the plane of the beam analyzer;

[0023] Figure 3 Edge image obtained by the Canny edge algorithm

[0024] In the image: the white area represents the edge of the light spot detected by the algorithm.

[0025] Figure 4 ; This is the output two-dimensional light intensity map;

[0026] In the diagram: the red circles represent the positions of the light spots as determined by the algorithm. Detailed Implementation

[0027] This embodiment relates to a method for, for example Figure 1 The method for implementing crosstalk in a 37-core space-division multiplexing chip based on light intensity image processing, as shown in the example, involves setting a very small port spacing on the A-side of the multiplexing chip to ensure that the crosstalk is large enough so that when one channel is input, other channels also have strong light output.

[0028] In such Figure 2In the measurement optical path shown, a CCD camera records the two-dimensional light intensity data of the marker device. Each port of the thirty-seven channels in this data has an output light spot, and the center position and radius of each light spot can be determined using the previously described Canny edge detection algorithm. The average light spot radius is 26 pixels wide, which is set as the fixed light spot radius for subsequent measurements. The average center-to-center distance of the light spots is 108.766 pixels wide, which is set as the fixed light spot distance for subsequent measurements.

[0029] This embodiment specifically includes the following steps:

[0030] Step 1) In such Figure 2 In the measurement optical path shown, a CCD camera is used to record the two-dimensional light intensity data of the marker device;

[0031] Step 2) Determine the position of each light spot, specifically including:

[0032] 2.1) The location of the maximum light intensity is obtained, and a square area with a side length of 75 pixels and centered at this location is set as the search area;

[0033] 2.2) The two-dimensional light intensity data is converted into a grayscale image format. Next, a Gaussian filter is applied with a standard deviation of 1. Then, the Canny edge detection algorithm is used to obtain the edge image. The two thresholds in the Canny algorithm are set to 0.01 and 0.05 respectively. The detection results are as follows: Figure 3 As shown. Within the square search area, the search retrieves the rows containing the highest and lowest points of the spot edge in the edge image, and the columns containing the leftmost and rightmost points. The midpoint between the two rows is the row containing the center of the output spot, and the midpoint between the two columns is the column containing the center of the output spot. The maximum of the row difference and column difference is used as the diameter of the spot.

[0034] Step 3) Based on the device characteristics, the center position of the crosstalk spot is obtained sequentially. The spot radius is set to 39 pixels, such as... Figure 4 As shown

[0035] Step 4) Calculate the background noise level and the intensity of the light spot after filtering out the noise.

[0036] Step 5) Calculate the crosstalk magnitude of the device when it is input to the chip.

[0037] Through specific experiments, a Gaussian beam in the 1550 nm band was output using an infrared fiber laser at room temperature of 21°C. The Gaussian beam was modulated into a vortex beam of the target order by a spatial light modulator and then injected into a spatial division multiplexing chip. The output beam spot was captured using a 1550 nm band CCD camera. The light intensity information was imported into a computer and the aforementioned algorithm was executed. The crosstalk values ​​for different orders of vortex beams incident on various channels were obtained, as shown in Table 1. It can be observed that the overall crosstalk remains below one-thousandth.

[0038] Table 1 shows the crosstalk values ​​between each core of the 37-core, 3-mode space division multiplexing device processed by femtosecond laser, calculated using an image recognition algorithm.

[0039] Table 1

[0040]

[0041] Compared to existing technologies, this method eliminates the need for additional complex devices such as v-grooves and power meters to collect the output power of each channel of the integrated spatial division multiplexing (SDM) device. Instead, it uses a specially designed SDM device to confirm the spatial distribution of the output light spot. Then, using only the two-dimensional light intensity information recorded by a CCD, the corresponding crosstalk value can be quickly analyzed and obtained. Therefore, this method significantly reduces the complexity of the measurement device and improves the measurement efficiency of crosstalk, a crucial parameter, playing an important role in the development and performance evaluation of integrated SDM devices.

[0042] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A method for implementing crosstalk in a spatial multiplexing device based on light intensity image processing, characterized in that, include: Step 1: Determine the relative position of each core on the beam analyzer. Specifically, use a space-division multiplexing device with an output end face structure consistent with the device under test and all channels capable of simultaneously outputting beam spots to calibrate the size and relative position of all cores using a beam spot edge retrieval and identification method. Step 2: Import two-dimensional light intensity data and retrieve and identify the light spot. Specifically, after the light beam emitted from the space separation device passes through the coupling lens, the two-dimensional light intensity data recorded at any point on the propagation path is obtained using a beam quality analyzer. The position of the highest light intensity is then retrieved, the edge of the light spot is identified, and the center of the light spot is determined. Step 3: Calculate the spot intensity of the target core and non-target cores to obtain the background noise and final device crosstalk, specifically including: 3.1 The target core emits the strongest light spot, and its position can be directly determined. The channel positions of non-target cores are marked using the relative positional relationship between the target core and the other cores. Specifically, after determining the position and radius of the target core's emitted light spot and its coordinates in the overall device, the positions of the light spot centers of the non-target cores are determined sequentially according to the device structure. Taking the center of each core's light spot as the center of a circle, and using the determined light spot radius as the radius, the light intensity value of each pixel within the circle is summed to obtain the light spot intensity value before noise subtraction. 3.2 Pixels not included in the light spot area are called noise pixels. The sum of the light intensities of noise pixels divided by the number of noise pixels is the noise of each pixel. The light intensity of a single light spot minus the product of the pixel noise and the number of pixels in the light spot is the light spot intensity after filtering out noise. If the value obtained after filtering out noise is negative, the light intensity of the light spot is recorded as zero. 3.3 The strongest light spot intensity value is the output light spot intensity of the core, and the intensity of the remaining light spots is the intensity of the crosstalk light spots; the crosstalk magnitude of the core of the device can be obtained by taking the logarithm of the ratio of the average crosstalk light spot intensity to the output light spot intensity and multiplying it by -10, in decibels.

2. The method for implementing crosstalk in a spatial multiplexing device based on light intensity image processing according to claim 1, characterized in that, The center of the light spot is obtained as follows: based on the position of the highest light intensity as the center, within a rectangular range of a certain size, the row containing the highest and lowest points of the light spot edge, and the column containing the leftmost and rightmost points of the edge image are retrieved; the midpoint of the two rows is the row containing the center of the light spot, and the midpoint of the two columns is the column containing the center of the light spot; the maximum value of the row difference and column difference is taken as the diameter of the light spot.

3. A system for implementing crosstalk in a spatial multiplexing device based on light intensity image processing, comprising: The system comprises a spatial division multiplexing device, a spot edge recognition unit, and a light intensity calculation and processing unit. Specifically: the spatial division multiplexing device calibrates the spatial location and corresponding spot size of all outgoing channels; the spot edge recognition unit obtains the edge information of each spot on the device under test using the Canny edge detection algorithm; and the light intensity calculation and processing unit calculates the light intensity of each channel and the corresponding crosstalk magnitude based on the edge information, channel spatial location, and spot size.

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