Space division multiplexing device crosstalk implementation method based on light intensity image processing

Abstract

A space division multiplexing device crosstalk implementation method based on light intensity image processing comprises the steps that after two-dimensional light intensity data are imported and light spots are retrieved and recognized, the relative position of each core on a light beam analyzer is determined, then the light spot intensity of a target core and the light spot intensity of a non-target core are calculated, and then background noise and final device crosstalk are obtained. According to the invention, the crosstalk of the device can be quickly and accurately calculated, so that the function of the device can be verified as soon as possible, and the method is suitable for basically all space division devices supporting frequency multiplexing and mode multiplexing.

Description

Technical Field

[0001] The present invention relates to a technology in the field of multi-core multi-mode optical communication testing, in particular to a method for realizing crosstalk of a space division multiplexing device based on light intensity image processing. Background Art

[0002] Space division multiplexing technology is an important part of the field of classical optical communications, which can greatly improve the bandwidth of optical communication systems. The realization of space division multiplexing depends on specific space division multiplexing optical devices, including multi-core optical fibers, femtosecond laser direct writing space division multiplexing chips, and two-dimensional multi-core array devices. One of the important indicators for measuring the performance of such devices is the crosstalk between the cores (channels). The current mainstream testing method is to place the device in the system for testing. This process requires the device to be connected to the pigtail, which increases the test time and reduces the iteration speed of the device process. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a method for realizing crosstalk of space-division multiplexing devices based on light intensity image processing, which can quickly and accurately calculate device crosstalk, thereby verifying device functions as soon as possible and is suitable for basically all space-division multiplexing devices that support frequency multiplexing and mode multiplexing.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to a method for realizing crosstalk of a space division multiplexing device based on light intensity image processing, comprising:

[0006] Step 1. Determine the relative position of each core on the beam analyzer, specifically: through a space division multiplexing device whose output end face structure is consistent with the device under test and all channels can output light spots simultaneously, use the light spot edge retrieval and recognition method to calibrate the size and relative position of all cores.

[0007] The light spot edge retrieval and recognition method adopts 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 by the space-division device passes through the coupling lens, use the beam quality analyzer to record the two-dimensional light intensity data at any point on the propagation path, retrieve the position of the highest light intensity, identify the edge of the light spot and determine the center of the light spot.

[0009] The edge of the light spot is also detected by using the canny edge detection algorithm.

[0010] The center of the light spot is obtained in the following manner: based on the position of the highest light intensity as the center within a certain size of the rectangular range, the row where the highest and lowest points of the light spot edge are located in the edge image, and the column where the leftmost and rightmost points are located. The middle value of the two rows is the row where the center of the light spot is located, and the middle value of the two columns is the column where the center of the light spot is located. The maximum value of the row difference and the column difference is taken as the diameter of the light spot.

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

[0012] 3.1. The target core has the strongest light spot, and its position can be determined directly. The channel position of the non-target core is marked by using the relative position relationship between the target core and the other cores. Specifically, after determining the position and radius of the target core's light spot and its coordinates in the overall device, the position of the light spot center of the non-target core is determined in turn according to the structure of the device. With the light spot center of each core as the center of the circle and the determined light spot radius value as the radius, the light intensity value of each pixel point in the circle is summed to obtain the light spot intensity value without deducting noise.

[0013] 3.2. Pixels not included in the light spot range are called noise pixels. The sum of the light intensities of the 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 light spot pixels gives the light spot intensity after noise is filtered out.

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

[0015] 3.3. The strongest spot intensity is the output spot intensity of the core, and the remaining spot intensity is the crosstalk spot intensity. The logarithm of the ratio of the average crosstalk spot intensity to the output spot intensity is multiplied by -10 to get the crosstalk size of the core of the device in decibels.

[0016] The present invention relates to a system for implementing the above method, comprising: a space division multiplexing device, a light spot edge recognition unit and a light intensity calculation and processing unit, wherein: the space division multiplexing device calibrates the spatial positions and corresponding light spot sizes of all outgoing channels; the light spot edge recognition unit obtains edge information of each light spot of the device to be tested through a canny edge detection algorithm; and the light intensity calculation and processing unit calculates the light spot intensity of each channel and the corresponding crosstalk size according to the edge information, the channel spatial position and the light spot size. Technical Effects

[0017] The present invention is aimed at an integrated space division multiplexing chip. Through performance testing and the space division multiplexing chip, the position and radius of the output light spot of each channel are determined, and the position of the output light spot and the crosstalk light spot is determined by a canny edge detection algorithm, and then the intensity of each light spot and the corresponding device crosstalk value are calculated using an integral method. Compared with the prior art, the present invention does not require the aid of a complex on-chip information acquisition system, and only needs to collect the two-dimensional light intensity information output after the light passes through the integrated space division multiplexing device, so as to quickly lock 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 size, which is beneficial to the optimization and iteration of the integrated space division multiplexing device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 a is a schematic diagram of a femtosecond laser direct writing 37-core space division multiplexing chip; Figure 1 b is the microscopic image of the end face of A. Figure 1 c is the microscopic image of the end surface of B;

[0019] In the figure: the A end face is interconnected with a 37-core multimode optical fiber, and the core-to-core crosstalk test is performed on the B end face after spatial separation is completed by the device;

[0020] Figure 2 This is a schematic diagram of the overall optical path design;

[0021] In the figure: the beam profiler is located at a suitable position after the coupling lens, so that the light spot is focused and imaged on the beam profiler plane;

[0022] Figure 3 The edge image obtained by the canny edge algorithm

[0023] In the figure: the white part is the edge of the light spot detected by the algorithm.

[0024] Figure 4 ; is the output two-dimensional light intensity map;

[0025] In the figure: the red circles represent the spot positions calibrated by the algorithm. DETAILED DESCRIPTION

[0001] This embodiment relates to a method for Figure 1 The method for realizing crosstalk of space-division multiplexing device based on light intensity image processing of femtosecond laser direct writing thirty-seven-core space-division multiplexing chip shown in the figure has a port spacing of the end face A of the multiplexing chip set very small to ensure that the crosstalk is large enough so that when a certain channel is input, other channels also have strong light output.

[0002] In such Figure 2In the measurement optical path shown, a CCD camera is used to record the two-dimensional light intensity data of the marking device. In the data, each port of the thirty-seven channels has an output light spot, and the center position and radius of each light spot can be determined using the canny edge detection algorithm described above. The average value of the light spot radius is 26 pixels wide, which is set as the fixed light spot radius for subsequent measurements, and the average value of the light spot center spacing is 108.766 pixels wide, which is set as the fixed light spot spacing for subsequent measurements.

[0003] This embodiment specifically includes the following steps:

[0004] Step 1) In Figure 2 In the measurement optical path shown, a CCD camera is used to record the two-dimensional light intensity data of the marking device;

[0005] Step 2) determining the position of each light spot, specifically including:

[0006] 2.1) The location of the maximum light intensity is retrieved, and a square area with a side length of 75 pixels and a width of the location as the center is set as the search area;

[0007] 2.2) Convert the two-dimensional light intensity data into grayscale data format. Next, perform Gaussian filtering on it and set the standard deviation to 1. Then use the Canny edge detection algorithm 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. In the square search area, search for the row where the highest and lowest points of the edge of the spot are located, and the column where the leftmost and rightmost points are located. The middle value of the two rows is the row where the center of the output spot is located, and the middle value of the two columns is the column where the center of the spot is located. The maximum value of the row difference and column difference is taken as the diameter of the spot.

[0008] Step 3) Combined with the device characteristics, the center position of the crosstalk spot is retrieved in sequence. The spot radius is set to 39 pixels, such as Figure 4 Shown

[0009] Step 4) Calculate the background noise and the intensity of the light spot after filtering out the noise.

[0010] Step 5) Calculate the crosstalk size corresponding to the device when it is input to the core.

[0026] After specific practical experiments, an infrared fiber laser was used to output a 1550-wavelength Gaussian beam at room temperature of 21°C. The Gaussian beam was modulated into a vortex light of the target order by a spatial light modulator and then injected into the space division multiplexing chip. The output light spot was collected using a 1550-wavelength CCD camera. The light intensity information was imported into the computer and the above algorithm was executed. Finally, the crosstalk values ​​of each channel when vortex light of different orders was incident were obtained as shown in Table 1. It can be found that the overall crosstalk is kept below one thousandth.

[0027] As shown in Table 1, the inter-core crosstalk values ​​of the 37-core 3-mode space division multiplexing device processed by femtosecond laser are calculated according to the image recognition algorithm.

[0028] Table 1

[0029] Compared with the existing technology, this method does not need to rely on additional complex devices such as v-groove and power meter to collect the output power of each channel of the integrated space division multiplexing device, but uses a specially designed space division multiplexing device to confirm the spatial distribution of the output light spot, and then only needs to use the two-dimensional light intensity information recorded by CCD to quickly analyze and obtain the corresponding crosstalk value. Therefore, this method greatly reduces the complexity of the measurement device and improves the measurement efficiency of the important parameter of device crosstalk, which can play an important role in the development and performance evaluation of integrated space division multiplexing devices.

[0030] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A method for realizing crosstalk of space division multiplexing devices based on light intensity image processing, characterized in that: include: Step 1, determine the relative position of each core on the beam analyzer, specifically: through a space division multiplexing device whose output end face structure is consistent with the device under test and all channels can output light spots at the same time, use the light spot edge retrieval and recognition method to calibrate the size and relative position of all cores; Step 2, importing two-dimensional light intensity data and retrieving and identifying the light spot, specifically: after the light beam emitted by the space division device passes through the coupling lens, the two-dimensional light intensity data recorded at any point on the propagation path by the beam quality analyzer is retrieved, the position of the highest light intensity is 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 the non-target core, and then obtain the background noise and the final device crosstalk.

2. The method for realizing crosstalk of space division multiplexing device based on light intensity image processing according to claim 1 is characterized in that: The center of the light spot is obtained in the following manner: based on the position of the highest light intensity as the center within a certain size of the rectangular range, the row where the highest and lowest points of the light spot edge are located in the edge image, and the column where the leftmost and rightmost points are located. The middle value of the two rows is the row where the center of the light spot is located, and the middle value of the two columns is the column where the center of the light spot is located. The maximum value of the row difference and the column difference is taken as the diameter of the light spot.

3. The method for realizing crosstalk of space division multiplexing device based on light intensity image processing according to claim 1, characterized in that said step 3 specifically comprises: 3.

1. The target core has the strongest light spot, and its position can be determined directly. The channel position of the non-target core is marked by using the relative position relationship between the target core and the other cores. Specifically, after determining the position and radius of the target core's light spot and its coordinates in the overall device, the position of the light spot center of the non-target core is determined in turn according to the structure of the device. With the light spot center of each core as the center of the circle and the determined light spot radius value as the radius, the light intensity value of each pixel point in the circle is summed to obtain the light spot intensity value without deducting noise. 3.

2. Pixels not included in the light spot range are called noise pixels. The sum of the light intensities of the 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 light spot pixels gives the light spot intensity after noise is filtered out. When the value obtained after filtering out the noise is a negative number, the light intensity of the light spot is recorded as zero. 3.

3. The strongest spot intensity is the output spot intensity of the core, and the remaining spot intensity is the crosstalk spot intensity. The logarithm of the ratio of the average crosstalk spot intensity to the output spot intensity is multiplied by -10 to get the crosstalk size of the core of the device in decibels.

4. A system for realizing crosstalk of space division multiplexing devices based on light intensity image processing for realizing the method described in any one of claims 1 to 3, comprising: A space division multiplexing device, a light spot edge recognition unit and a light intensity calculation and processing unit, wherein: the space division multiplexing device calibrates the spatial position and corresponding light spot size of all outgoing channels; the light spot edge recognition unit obtains the edge information of each light spot of the device under test through the canny edge detection algorithm; the light intensity calculation and processing unit calculates the light spot intensity of each channel and the corresponding crosstalk size according to the edge information, the channel spatial position and the light spot size.

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