A bend-insensitive multimode optical fiber attenuation test device and test method

Abstract

A bend-insensitive multimode optical fiber attenuation test device and method includes a light source, a single-mode or few-mode injection pigtail, a coupling injection device, an optical power detector, and a beam quality analyzer. The light source is connected to the coupling injection device via the single-mode or few-mode injection pigtail, and the coupling injection device and the optical power detector are connected to the multimode optical fiber under test. The beam quality analyzer is connected to the multimode optical fiber under test via a bare fiber adapter. The test device provided by the present invention uses a high-precision five-dimensional adjustment frame to adjust the injection light angle and thus the injection light mode, achieving high flexibility in controlling the target mode during attenuation testing.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber and cable testing, and in particular relates to a bending-insensitive multimode optical fiber attenuation testing device and a testing method. Background Art

[0002] Regarding the attenuation test method for multimode optical fibers, the standard stipulates that the truncation method is the benchmark test method for measuring optical fiber attenuation characteristics. When using the truncation method to test multimode optical fiber attenuation, the light injection system is required to avoid injecting high-order transient modes, so that the power distribution along the optical fiber remains essentially unchanged, thereby making the optical fiber attenuation approximately linear with the optical fiber length. A common method is to use looping to allow unstable high-order modes to leak out of the cladding. However, this method has the following two problems: First, bend-insensitive multimode optical fibers have better bend resistance, which makes the looping filter method less effective and requires a high level of looping technique. Otherwise, the optical fiber will generate axial stress, affecting the attenuation test results. Second, the loop diameter and number of loops may vary for different batches and models of multimode optical fibers, making the test method less universal and compatible. Therefore, how to inject stable low-order modes is a problem that needs to be solved in the attenuation test of bend-insensitive multimode optical fibers. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a bend-insensitive multimode optical fiber attenuation test device and test method, which solves the problem that the loop filtering effect of high-order modes in the prior art is poor.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A bending-insensitive multimode optical fiber attenuation test device includes a light source, a single-mode or few-mode injection pigtail, a coupling injection device, an optical power detector and a beam quality analyzer;

[0006] The light source is connected to the coupling injection device through a single-mode or few-mode injection pigtail. The coupling injection device and the optical power detector are used to connect the multimode optical fiber under test. The beam quality analyzer is used to connect the multimode optical fiber under test through a bare fiber adapter.

[0007] Preferably, the light source is a single wavelength or multi-wavelength narrow linewidth point light source, which is used to test the attenuation of the required wavelength.

[0008] Preferably, the single-mode or few-mode injection pigtail is a single-mode optical fiber or a few-mode optical fiber, one end of the single-mode optical fiber or the few-mode optical fiber is an FC / UPC type connector for connecting to a light source, and the other end is a bare optical fiber.

[0009] Preferably, the core diameter of the single-mode optical fiber is 8.9 μm to 9.2 μm, the cladding diameter is 125 μm, and the coating diameter is 250 μm; the core diameter of the few-mode optical fiber is 19 μm to 21 μm, the cladding diameter is 125 μm, and the coating diameter is 250 μm.

[0010] Preferably, the coupling injection device includes a first high-precision five-dimensional adjustment frame, a second high-precision five-dimensional adjustment frame, a first optical fiber clamp, a second optical fiber clamp, a top zoom lens, and a side zoom lens;

[0011] A first optical fiber clamp is installed on the first high-precision five-dimensional adjustment frame, a second optical fiber clamp is installed on the second high-precision five-dimensional adjustment frame, and a top zoom lens and a side zoom lens are provided between the first high-precision five-dimensional adjustment frame and the second high-precision five-dimensional adjustment frame.

[0012] Preferably, the first high-precision five-dimensional adjustment frame or the second high-precision five-dimensional adjustment frame has an X-axis and Y-axis travel accuracy of 10 mm, a step accuracy of 1 μm, and a Z-axis and Y-axis travel accuracy of 20 mm.

[0013] Preferably, the optical power detector is a single-wavelength or multi-wavelength high-frequency optical power meter, which is connected to the multimode optical fiber to be tested and is used to record the optical power of the light source after passing through the test optical fiber.

[0014] Preferably, the beam quality analyzer is used to detect whether the injected light mode is a stable low-order mode.

[0015] A method for testing a bend-insensitive multimode optical fiber attenuation test device comprises the following steps:

[0016] S1. Use a bare fiber adapter to connect one end of the multimode fiber to be tested (length L1) to a light source, and the other end to a beam quality analyzer. Record the light spot after passing through the multimode fiber to be tested and analyze its transmission mode.

[0017] S2. Select a single-mode or few-mode injection pigtail with a length of 1 to 2 meters, with an FC / APC connector at one end to connect to the light source, and a bare fiber end at the other end. Cut the end face and fix it to the first high-precision five-dimensional adjustment frame using a fiber clamp.

[0018] S3. Cut a length of L2 of multimode fiber sample to be tested, cut one end, fix it to the second high-precision five-dimensional adjustment frame using a fiber clamp, and connect the other end to the beam quality analyzer using a bare fiber adapter;

[0019] S4. By adjusting the relative position of the single-mode or few-mode injection pigtail and the multimode fiber sample with a length of L2, the injection light angle is changed to selectively excite the fundamental mode and some higher-order modes. The specific operation is as follows:

[0020] First, under the top zoom lens and the side zoom lens, coarsely adjust the first high-precision five-dimensional adjustment frame and the second high-precision, and at the same time observe the output spot pattern and intensity of the multimode optical fiber sample of length L2 in the beam quality analyzer. After the corresponding coupled output light can be received, the coarse adjustment is completed, and then fine-tune the second high-precision five-dimensional adjustment frame. The spot pattern is the same as the spot pattern in step S1, and the adjustment is stopped; keep the first high-precision five-dimensional adjustment frame and the single-mode or few-mode injection pigtail coupling end unchanged, connect the output end to the optical power meter, and record the power value P1;

[0021] S5. Keeping the first high-precision five-dimensional adjustment frame, the second high-precision five-dimensional adjustment frame, and the single-mode or few-mode injection pigtail unchanged, replace the multimode fiber sample of length L2 with the multimode fiber to be tested of length L1-L2. Connect the other end to the optical power meter and record the power value P2.

[0022] S6. Calculate the attenuation coefficient of multimode optical fiber: α = (P1-P2) / (L1-2L2).

[0023] The present invention can achieve the following beneficial effects:

[0024] (1) The test device provided by the present invention uses a high-precision five-dimensional adjustment frame to adjust the angle of the injected light and thus adjust the injected light mode, thereby achieving control of the target mode during the attenuation test and having high flexibility.

[0025] (2) The test device provided by the present invention uses a high-precision adjustment frame instead of manual circling operation, which does not require high operator proficiency and is easy to use.

[0026] (3) The test method provided by the present invention has high universality and compatibility, and the same test steps can be applied to bend-insensitive multimode optical fibers of different batches and models. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below with reference to the accompanying drawings and examples:

[0028] Figure 1 This is a system connection diagram of a bend-insensitive multimode optical fiber attenuation test device according to the present invention;

[0029] Figure 2 This is a schematic structural diagram of the coupling injection device of the present invention;

[0030] Figure 3 Schematic diagram of the refractive index cross section of the bend-insensitive multimode optical fiber of the present invention.

[0031] In the figure: light source 1, single-mode or few-mode injection pigtail 2, coupling injection device 3, multimode optical fiber to be tested 4, optical power detector 5, beam quality analyzer 6, first high-precision five-dimensional adjustment frame 7, second high-precision five-dimensional adjustment frame 8, first optical fiber clamp 9, second optical fiber clamp 10, top zoom lens 11, side zoom lens 12. DETAILED DESCRIPTION

[0032] The preferred solution is Figures 1 to 3 As shown, a bending-insensitive multimode optical fiber attenuation test device includes a light source, a single-mode or few-mode injection pigtail, a coupling injection device, a multimode optical fiber to be tested, an optical power detector and a beam quality analyzer.

[0033] The light source can be a single wavelength or multiple wavelength narrow linewidth light source, which is injected into the multimode optical fiber to be tested after passing through a single-mode or few-mode injection pigtail and a coupling injection device.

[0034] The single-mode or few-mode injection pigtail can be a single-mode fiber or few-mode fiber, with an FC / UPC connector at one end for connection to a light source and a bare fiber at the other end. A coupling injection device is used for coupling injection with the multimode fiber under test. The single-mode fiber has a core diameter of 8.9μm to 9.2μm, a cladding diameter of 125μm, and a coating diameter of 250μm. The few-mode fiber has a core diameter of 19μm to 21μm, a cladding diameter of 125μm, and a coating diameter of 250μm. It can be a quad-mode fiber, a hexa-mode fiber, a deca-mode fiber, or other higher-order few-mode fibers.

[0035] The coupling injection device includes a first high-precision five-dimensional adjustment frame, a second high-precision five-dimensional adjustment frame, a first fiber clamp, a second fiber clamp, a top zoom lens, and a side zoom lens. The five-dimensional adjustment frame can perform precise adjustments on the X-axis, Y-axis, Z-axis, θX-axis, and θY-axis. The fiber clamp can be fixed on the high-precision adjustment frame. The bare fiber end of the single-mode or few-mode injection pigtail and the multimode optical fiber to be tested are clamped using the fiber clamp. Preferably, the five-dimensional adjustment frame has an X-axis and Y-axis travel of 10 mm, with a step of 1 μm, a Z-axis and Y-axis travel of 20 mm, with a step of 1 μm, and an angle of 8° between the θX-axis and the θY-axis, with a step of 0.5°. The top zoom lens and the side zoom lens are used for visual adjustment during the coupling process to facilitate the coupling of the single-mode or few-mode injection pigtail and the multimode optical fiber to be tested.

[0036] The multimode optical fiber under test is a bend-insensitive multimode optical fiber with a core diameter of 47.5-52.5 μm, a cladding diameter of 125 μm, and a coating diameter of 250 μm, or a core diameter of 60-62.5 μm, a cladding diameter of 125 μm, and a coating diameter of 250 μm.

[0037] The optical power detector may be a single wavelength or multi-wavelength high frequency optical power meter, which is connected to the multimode optical fiber to be tested and records the optical power of the light source after passing through the test optical fiber.

[0038] The beam quality analyzer is used to detect whether the injected light mode is a stable low-order mode, and is connected to the multimode optical fiber to be tested.

[0039] The method of using this device is:

[0040] S1. Use a bare fiber adapter to connect one end of the multimode fiber to be tested (length L1) to a light source, and the other end to a beam quality analyzer. Record the light spot after passing through the multimode fiber to be tested and analyze its transmission mode.

[0041] S2. Select a single-mode or few-mode injection pigtail with a length of 1 to 2 meters, with an FC / APC connector at one end to connect to the light source, and a bare fiber end at the other end. Cut the end face and fix it to the first high-precision five-dimensional adjustment frame using a fiber clamp.

[0042] S3. Cut a length of L2 of multimode fiber sample to be tested, cut one end, fix it to the second high-precision five-dimensional adjustment frame using a fiber clamp, and connect the other end to the beam quality analyzer using a bare fiber adapter;

[0043] S4. By adjusting the relative position of the single-mode or few-mode injection pigtail and the multimode fiber sample with a length of L2, the injection light angle is changed to selectively excite the fundamental mode and some higher-order modes. The specific operation is as follows:

[0044] First, under the top zoom lens and the side zoom lens, coarsely adjust the first high-precision five-dimensional adjustment frame and the second high-precision, and at the same time observe the output spot pattern and intensity of the multimode optical fiber sample of length L2 in the beam quality analyzer. After the corresponding coupled output light can be received, the coarse adjustment is completed, and then fine-tune the second high-precision five-dimensional adjustment frame. The spot pattern is the same as the spot pattern in step S1, and the adjustment is stopped; keep the first high-precision five-dimensional adjustment frame and the single-mode or few-mode injection pigtail coupling end unchanged, connect the output end to the optical power meter, and record the power value P1;

[0045] S5. Keeping the first high-precision five-dimensional adjustment frame, the second high-precision five-dimensional adjustment frame, and the single-mode or few-mode injection pigtail unchanged, replace the multimode fiber sample of length L2 with the multimode fiber to be tested of length L1-L2. Connect the other end to the optical power meter and record the power value P2.

[0046] S6. Calculate the attenuation coefficient of multimode optical fiber: α = (P1-P2) / (L1-2L2).

[0047] In data center applications, multimode optical fiber is often used for short-distance connections within cabinets or between racks. The application scenarios are relatively complex, so high bending resistance is required. During the manufacturing process of bend-insensitive multimode optical fiber, compared with conventional multimode optical fiber, fluorine is added to the interface between the core layer and the cladding to reduce the refractive index at the interface, forming a "depression layer" to improve the macrobending performance of the optical fiber. For a schematic diagram of the refractive index profile of bend-insensitive multimode optical fiber, see Figure 2 . The improvement of macrobending performance has caused the unstable high-order modes excited by the conventional light source injection method to be filtered out by looping during the attenuation test to be less effective. Therefore, the present invention provides a test device that changes the light source injection method and adjusts the incident light angle to control the incident light mode. The single-mode or few-mode injection pigtail 2 can stably transmit the fundamental mode or part of the high-order mode. As an injection fiber, it can avoid introducing unstable high-order modes. When coupled with a multi-mode fiber, it can selectively excite some modes by adjusting the incident angle. The core diameter of the single-mode optical fiber is 8.9μm~9.2μm, the cladding diameter is 125μm, and the coating diameter is 250μm. The core diameter of the few-mode optical fiber is 19μm~21μm, the cladding diameter is 125μm, and the coating diameter is 250μm. The few-mode optical fiber can be a four-mode optical fiber, a six-mode optical fiber, a ten-mode optical fiber or other higher-order few-mode optical fibers, and can be selected according to actual needs. The coupling injection device 3 includes a first high-precision five-dimensional adjustment frame 7, a second high-precision five-dimensional adjustment frame 8, a first fiber clamp 9, a second fiber clamp 10, a top zoom lens 11, and a side zoom lens 12. The first and second high-precision five-dimensional adjustment frames 7 and 8 can be precisely adjusted along the X, Y, Z, θX, and θY axes. The first and second fiber clamps 9 and 10 can be fixed to the first and second high-precision five-dimensional adjustment frames 7 and 8, respectively. The first and second high-precision five-dimensional adjustment frames 7 and 8 are manually adjustable devices. The X and Y axes are used to adjust the alignment of the single-mode or few-mode injection pigtail 2 and the multimode fiber 4 under test. The Z axis is used to adjust the spacing between the two fibers. The θX and θY axes are used to adjust the incident angle of the injected light to excite different high-order modes. The optical power detector 5 is a high-precision optical power meter that records the power after the system passes through different lengths of multimode fiber and calculates the optical power difference to obtain the multimode fiber attenuation. The beam quality analyzer 6 is used to observe the light spot, analyze the output light mode and the light intensity after coupling, and adjust the first high-precision five-dimensional adjustment frame 7 and the second high-precision five-dimensional adjustment frame 8 in real time according to the optical signal obtained by the beam quality analyzer to obtain the optimal coupling position of the single-mode or few-mode injection pigtail 2 and the multimode optical fiber 4 to be tested.

[0048] The above embodiments are merely preferred technical solutions of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention shall be the technical solutions set forth in the claims, including equivalent alternatives to the technical features of the technical solutions set forth in the claims. In other words, equivalent alternatives and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A bend-insensitive multimode optical fiber attenuation test device, characterized by: It includes a light source (1), a single-mode or few-mode injection pigtail (2), a coupling injection device (3), an optical power detector (5) and a beam quality analyzer (6); The light source (1) is connected to the coupling injection device (3) through a single-mode or few-mode injection pigtail (2); the coupling injection device (3) and the optical power detector (5) are used to connect to the multimode optical fiber (4) under test; the beam quality analyzer (6) is used to connect to the multimode optical fiber (4) under test through a bare fiber adapter; The coupling injection device (3) comprises a first high-precision five-dimensional adjustment frame (7), a second high-precision five-dimensional adjustment frame (8), a first optical fiber clamp (9), a second optical fiber clamp (10), a top zoom lens (11), and a side zoom lens (12); A first optical fiber clamp (9) is mounted on the first high-precision five-dimensional adjustment frame (7), a second optical fiber clamp (10) is mounted on the second high-precision five-dimensional adjustment frame (8), and a top zoom lens (11) and a side zoom lens (12) are provided between the first high-precision five-dimensional adjustment frame (7) and the second high-precision five-dimensional adjustment frame (8); The top zoom lens and the side zoom lens are used for visual adjustment during the coupling process, which facilitates the coupling of the single-mode or few-mode injection pigtail and the multimode fiber under test; The first high-precision five-dimensional adjustment frame 7 and the second high-precision five-dimensional adjustment frame 8 are used for precise adjustment of the X-axis, Y-axis, Z-axis, θX-axis and θY-axis; the X-axis and Y-axis are used to adjust the alignment of the single-mode or few-mode injection pigtail 2 and the multi-mode optical fiber 4 to be tested, the Z-axis is used to adjust the spacing between the two optical fibers, and the θX-axis and θY-axis are used to adjust the incident angle of the injected light to excite different high-order modes.

2. The bend-insensitive multimode optical fiber attenuation test device according to claim 1, characterized in that: The light source (1) is a single wavelength or multi-wavelength narrow line width point light source, which is used to test the attenuation of the required wavelength.

3. The bend-insensitive multimode optical fiber attenuation test device according to claim 1, characterized in that: The single-mode or few-mode injection pigtail is a single-mode optical fiber or a few-mode optical fiber. One end of the single-mode optical fiber or the few-mode optical fiber is an FC / UPC type connector for connecting to a light source, and the other end is a bare optical fiber.

4. The bend-insensitive multimode optical fiber attenuation test device according to claim 3, characterized in that: The core diameter of single-mode optical fiber is 8.9μm~9.2μm, the cladding diameter is 125μm, and the coating diameter is 250μm; the core diameter of few-mode optical fiber is 19μm~21μm, the cladding diameter is 125μm, and the coating diameter is 250μm.

5. The bend-insensitive multimode optical fiber attenuation test device according to claim 1, characterized in that: The first high-precision five-dimensional adjustment frame (7) or the second high-precision five-dimensional adjustment frame (8) has an X-axis and Y-axis travel accuracy of 10 mm, a stepping accuracy of 1 μm, and a Z-axis and Y-axis travel accuracy of 20 mm.

6. The bend-insensitive multimode optical fiber attenuation test device according to claim 1, characterized in that: The optical power detector (5) is a single-wavelength or multi-wavelength high-frequency optical power meter. The optical power detector (5) is connected to the multimode optical fiber to be tested and is used to record the optical power of the light source after passing through the test optical fiber.

7. The bend-insensitive multimode optical fiber attenuation test device according to claim 1, characterized in that: The beam quality analyzer (6) is used to detect whether the injected light mode is a stable low-order mode.

8. A testing method for a bend-insensitive multimode optical fiber attenuation testing device according to any one of claims 1 to 7, characterized in that The following steps are involved: S1. Use a bare fiber adapter to connect one end of the multimode fiber to be tested (length L1) to a light source, and the other end to a beam quality analyzer. Record the light spot after passing through the multimode fiber to be tested and analyze its transmission mode. S2. Select a single-mode or few-mode injection pigtail with a length of 1 to 2 meters, with an FC / APC connector at one end to connect to the light source, and a bare fiber end at the other end. Cut the end face and fix it to the first high-precision five-dimensional adjustment frame using a fiber clamp. S3. Cut a length of L2 of multimode fiber sample to be tested, cut one end, fix it to the second high-precision five-dimensional adjustment frame using a fiber clamp, and connect the other end to the beam quality analyzer using a bare fiber adapter; S4. By adjusting the relative position of the single-mode or few-mode injection pigtail and the multimode fiber sample with a length of L2, the injection light angle is changed to selectively excite the fundamental mode and some higher-order modes. The specific operation is as follows: First, under the top zoom lens and the side zoom lens, coarsely adjust the first high-precision five-dimensional adjustment frame and the second high-precision, and at the same time observe the output spot pattern and intensity of the multimode optical fiber sample of length L2 in the beam quality analyzer. After the corresponding coupled output light can be received, the coarse adjustment is completed, and then fine-tune the second high-precision five-dimensional adjustment frame. The spot pattern is the same as the spot pattern in step S1, and the adjustment is stopped; keep the first high-precision five-dimensional adjustment frame and the single-mode or few-mode injection pigtail coupling end unchanged, connect the output end to the optical power meter, and record the power value P1; S5. Keeping the first high-precision five-dimensional adjustment frame, the second high-precision five-dimensional adjustment frame, and the single-mode or few-mode injection pigtail unchanged, replace the multimode fiber sample of length L2 with the multimode fiber to be tested of length L1-L2. Connect the other end to the optical power meter and record the power value P2. S6. Calculate the attenuation coefficient of multimode optical fiber: α = (P1-P2) / (L1-2L2).

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