A method for identifying an optical fiber based on a root raised cosine filter

Abstract

The application discloses a kind of root raised cosine filter-based optical fiber identification method, first utilize optical fiber imaging system to obtain optical fiber image, then adjust to certain width with fiber core width, utilize root raised cosine filter to the optical fiber brightness curve filtering, calculate the height difference, height ratio or width ratio of peak and valley in the filtered optical fiber brightness curve and other characteristic parameters to distinguish four common optical fibers.The application first applies root raised cosine filter in signal processing to optical fiber identification, realizes the wave formation shaping process of optical fiber brightness curve by filter, makes optical fiber brightness curve more standard, more easily extracts the characteristics of optical fiber brightness curve, so as to realize the rapid identification of optical fiber type, and improve the accuracy of optical fiber identification.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic image processing and analysis, and specifically relates to a fiber optic identification method based on a root-raised cosine filter. Background Technology

[0002] Currently, fiber optic identification primarily relies on acquiring the brightness curve from fiber images and extracting characteristic parameters from this curve to identify the fiber type. One method for acquiring fiber images utilizes the thermal radiation emitted from the fiber core and cladding during fiber splicing, creating a thermal image observable by an optical imaging system. Another method involves side-view imaging of the fiber. Common thermal imaging and fiber end-face imaging identification methods typically perform blurring, smoothing, and enhancement operations on the acquired fiber image before using extracted characteristic parameters for identification. In thermal imaging, the light intensity distribution varies, and a peak structure appears in the fiber core. The width of the peak is highly correlated with the fiber's mode field diameter. This correlation is used to measure the fiber's mode field diameter. End-face imaging involves processing the parameter data of the brightness distribution waveform captured from the fiber end face using an image processing unit. A fuzzing operation is then used to determine the degree of classification of the measured parameter data, and the fiber type is identified through fuzzing.

[0003] The two methods described above have the following problems and shortcomings. Thermal imaging requires precise control of the arc intensity during splicing; if the arc intensity is too strong, it can easily cause image brightness saturation, making it impossible to identify the fiber. Because the fiber itself exhibits very little difference in side imaging and is highly susceptible to the brightness of the illumination in the fiber optic imaging system, this method places high demands on image quality.

[0004] This invention is the first to apply the root-raised cosine filter from signal processing to fiber optic identification. By using the filter, the waveform of the fiber optic brightness curve is shaped. This process makes the fiber optic brightness curve more standardized, reduces the dependence on the lighting in the fiber optic imaging system, and makes it easier to extract the features of the fiber optic brightness curve, thereby improving the accuracy of fiber optic identification. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an optical fiber identification method based on a root-raised cosine filter. This method is rationally designed, overcomes the deficiencies of existing technologies, and has excellent performance.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A fiber identification method based on a root-raised cosine filter is used to identify four types of optical fibers: multimode fiber (MMF), standard single-mode fiber (SMF), dispersion-shifted single-mode fiber (DSF), and non-zero dispersion-shifted single-mode fiber (NZDSF). The method includes the following steps:

[0008] S1. Use a fiber optic imaging system to acquire the image of the fiber to be identified, drive the focusing motor in the fiber optic imaging system to make the fiber core imaging width W1, obtain the brightness data of the cladding part in the fiber image, construct a brightness curve from the brightness data, and smooth the brightness curve.

[0009] S2. Set the root-raised cosine filter roll-off factor to 0.5, the truncation sign range to 20, and use a sampling rate of 6 times. Use this root-raised cosine filter to filter the brightness curve and obtain the filtered brightness curve.

[0010] S3. Perform a convolution operation on the brightness curve in S1 and the filtered brightness curve in S2 to obtain the convolutioned brightness curve.

[0011] S4. Calculate the height difference between the peaks and troughs in the brightness curve after convolution. If the height difference is greater than 10, the fiber to be identified is a single-mode fiber; otherwise, it is a multimode fiber.

[0012] S5. Drive the focusing motor to make the fiber core imaging width W2, obtain the brightness data of the cladding part in the fiber image, construct a brightness curve from the brightness data, and smooth the brightness curve.

[0013] S6. Set the root-raised cosine filter roll-off factor to 0.9, the truncation sign range to 30, and use a sampling rate of 9 times. Use this root-raised cosine filter to filter the brightness curve in S5 and obtain the filtered brightness curve.

[0014] S7. Perform a convolution operation on the brightness curve in S5 and the filtered brightness curve in S6 to obtain the convolved brightness curve.

[0015] S8. Calculate the width ratio of the peaks and valleys in the brightness curve after convolution in S7. If the width ratio is greater than 2, the fiber to be identified is a standard single-mode fiber; otherwise, it is a dispersion-shifted single-mode fiber or a non-zero dispersion-shifted single-mode fiber. Then calculate the height ratio of the peaks and valleys. If the height ratio is greater than 5, the fiber to be identified is a dispersion-shifted single-mode fiber; otherwise, it is a non-zero dispersion-shifted single-mode fiber.

[0016] Furthermore, the range of W1 is 50 to 55 pixels, and the range of W2 is 80 to 84 pixels.

[0017] Furthermore, the fiber optic imaging system includes a light source, a reflector, an optical fiber, and a camera assembly. The camera assembly is fixed on the driving assembly and includes a high-power microscope and a CMOS image sensor. The driving assembly includes a linear guide rail and a focusing motor. The focusing motor is used to drive the high-power microscope and the CMOS image sensor to move linearly along a direction perpendicular to the target surface of the image sensor.

[0018] The beneficial effect of this invention is that, compared with the prior art, this invention is the first to apply the root-raised cosine filter in signal processing to optical fiber identification. The filter realizes the waveform shaping process of the optical fiber brightness curve, making the optical fiber brightness curve more standard and easier to extract the features of the optical fiber brightness curve, thereby improving the accuracy of optical fiber identification. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the fiber optic imaging system in this invention;

[0020] Figure 2 This is a schematic diagram of the fiber optic microscopy imaging principle in this invention;

[0021] Figure 3 This is a graph showing the fiber optic brightness curve after filtering by the root-raised cosine filter in this invention.

[0022] Among them, 1-reflector; 2-optical fiber; 3-light source; 4-high-power microscope; 5-focusing motor; 6-linear guide rail; 7-microscope adjustment area; 8-imaging target surface; 9-optical fiber image; Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] A fiber identification method based on root-raised cosine filter is used to identify four types of optical fibers: multimode fiber (MMF), standard single-mode fiber (SMF), dispersion-shifted single-mode fiber (DSF), and non-zero dispersion-shifted single-mode fiber (NZDSF).

[0025] This method employs a fiber optic imaging system, such as... Figure 1 As shown, the fiber optic imaging system includes a light source 3, a reflector 1, an optical fiber 2, and a camera assembly. The camera assembly is fixed on the drive assembly. The camera assembly includes a high-power microscope 4 and a CMOS image sensor. The drive assembly includes a linear guide rail 6 and a focusing motor 5. The focusing motor 5 is used to drive the high-power microscope 4 and the CMOS image sensor to move linearly along a direction perpendicular to the target surface of the image sensor.

[0026] After being reflected by mirror 1, light source 3 horizontally illuminates optical fiber 2. Due to the different refractive indices of air, fiber cladding, and fiber core, and the different object distances between the edges of the fiber core and the fiber relative to the high-power microscope 4, a bright and dark image will be produced on the focal plane. The corresponding images of the fiber core and cladding can be seen on the LCD screen, which are displayed as two thin black stripes with low gray values. The part sandwiched between the two thin black lines is the fiber core.

[0027] The camera assembly is mounted on the linear guide rail 6. This design allows the microscope's position to be adjusted arbitrarily within a certain range, i.e., the image distance is fixed while the object distance is adjustable. Two focusing motors 5 control the movement of the camera assembly on the precision miniature linear guide rail 6, causing the high-magnification microscope 4 and the CMOS image sensor to move together in a linear motion perpendicular to the image sensor target surface 8. Figure 2 As shown, the object distance is adjusted to achieve optimal width and clarity for the fiber core in the fiber image. A schematic diagram of fiber optic microscopy is shown below. Figure 2 As shown, it includes a parallel light source 3, an optical fiber 2, an imaging target surface 8, an optical fiber image 9, and a microscope adjustment area 7.

[0028] The fiber core width is adjusted to W1 pixels using a focusing motor, and the fiber image data of the cladding region is acquired at this point. The root-raised cosine filter parameters are set to a roll-off factor of 0.5, a truncation sign range of 20, and a sampling rate of 6. This filter is then used to filter the fiber brightness curve, and the result is as follows. Figure 3 As shown. According to Figure 3 The characteristic parameters of the two types of optical fibers can be extracted, and then single-mode and multimode optical fibers can be identified based on these parameters. For different types of single-mode optical fibers, the fiber core width needs to be adjusted to W2 pixels, and then the root cosine filter parameters are set to a roll-off factor of 0.9, a truncation sign range of 30, and a sampling rate of 9x. Finally, the filtered fiber brightness curve is obtained, and the characteristic parameters of the three types of optical fibers are analyzed. In this invention, the peak-to-trough height ratio and width ratio in the fiber brightness curve are used to distinguish them.

[0029] The specific implementation method includes the following steps:

[0030] S1. Use a fiber optic imaging system to acquire the image of the fiber to be identified, drive the focusing motor in the fiber optic imaging system to make the fiber core imaging width W1, where W1 ranges from 50 to 55 pixels, acquire the brightness data of the cladding part in the fiber image, construct a brightness curve from the brightness data, and smooth the brightness curve.

[0031] S2. Set the root-raised cosine filter roll-off factor to 0.5, the truncation sign range to 20, and use a sampling rate of 6 times. Use this root-raised cosine filter to filter the brightness curve and obtain the filtered brightness curve.

[0032] S3. Perform a convolution operation on the brightness curve in S1 and the filtered brightness curve in S2 to obtain the convolutioned brightness curve.

[0033] S4. Calculate the height difference between the peaks and troughs in the brightness curve after convolution. If the height difference is greater than 10, the fiber to be identified is a single-mode fiber; otherwise, it is a multimode fiber.

[0034] S5. Drive the focusing motor to make the fiber core imaging width W2, where W2 ranges from 80 to 84 pixels, acquire the brightness data of the cladding portion in the fiber image, construct a brightness curve from the brightness data, and smooth the brightness curve.

[0035] S6. Set the root-raised cosine filter roll-off factor to 0.9, the truncation sign range to 30, and use a sampling rate of 9 times. Use this root-raised cosine filter to filter the brightness curve in S5 and obtain the filtered brightness curve.

[0036] S7. Perform a convolution operation on the brightness curve in S5 and the filtered brightness curve in S6 to obtain the convolved brightness curve.

[0037] S8. Calculate the width ratio of the peaks and valleys in the brightness curve after convolution in S7. If the width ratio is greater than 2, the fiber to be identified is a standard single-mode fiber; otherwise, it is a dispersion-shifted single-mode fiber or a non-zero dispersion-shifted single-mode fiber. Then calculate the height ratio of the peaks and valleys. If the height ratio is greater than 5, the fiber to be identified is a dispersion-shifted single-mode fiber; otherwise, it is a non-zero dispersion-shifted single-mode fiber.

[0038] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A fiber optic identification method based on a root-raised cosine filter, characterized in that, The identification of four types of optical fibers—Multimode Fiber (MMF), Standard Single-Mode Fiber (SMF), Dispersion-Shifted Single-Mode Fiber (DSF), and Non-Zero Dispersion-Shifted Single-Mode Fiber (NZDSF)—includes the following steps: S1. Use a fiber optic imaging system to acquire the image of the fiber to be identified, drive the focusing motor in the fiber optic imaging system to make the fiber core imaging width W1, obtain the brightness data of the cladding part in the fiber image, construct a brightness curve from the brightness data, and smooth the brightness curve. S2. Set the root-raised cosine filter roll-off factor to 0.5, the truncation sign range to 20, and use a sampling rate of 6 times. Use this root-raised cosine filter to filter the brightness curve and obtain the filtered brightness curve. S3. Perform a convolution operation on the brightness curve in S1 and the filtered brightness curve in S2 to obtain the convolutioned brightness curve. S4. Calculate the height difference between the peaks and troughs in the brightness curve after convolution. If the height difference is greater than 10, the fiber to be identified is a single-mode fiber; otherwise, it is a multimode fiber. S5. Drive the focusing motor to make the fiber core imaging width W2, obtain the brightness data of the cladding part in the fiber image, construct a brightness curve from the brightness data, and smooth the brightness curve. S6. Set the root-raised cosine filter roll-off factor to 0.9, the truncation sign range to 30, and use a sampling rate of 9 times. Use this root-raised cosine filter to filter the brightness curve in S5 and obtain the filtered brightness curve. S7. Perform a convolution operation on the brightness curve in S5 and the filtered brightness curve in S6 to obtain the convolved brightness curve. S8. Calculate the width ratio of the peaks and valleys in the brightness curve after convolution in S7. If the width ratio is greater than 2, the fiber to be identified is a standard single-mode fiber; otherwise, it is a dispersion-shifted single-mode fiber or a non-zero dispersion-shifted single-mode fiber. Then calculate the height ratio of the peaks and valleys. If the height ratio is greater than 5, the fiber to be identified is a dispersion-shifted single-mode fiber; otherwise, it is a non-zero dispersion-shifted single-mode fiber. The range of W1 is 50-55 pixels, and the range of W2 is 80-84 pixels.

2. The fiber optic identification method based on a root-raised cosine filter according to claim 1, characterized in that, The fiber optic imaging system includes a light source, a reflector, an optical fiber, and a camera assembly. The camera assembly is fixed on a drive assembly and includes a high-power microscope and a CMOS image sensor. The drive assembly includes a linear guide rail and a focusing motor. The focusing motor is used to drive the high-power microscope and the CMOS image sensor to move linearly along a direction perpendicular to the target surface of the image sensor.

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