Bending insensitive multimode optical fiber attenuation testing device and testing method

Abstract

The invention discloses a bending insensitive multimode optical fiber attenuation testing device and a testing method. The bending insensitive multimode optical fiber attenuation testing device comprises a light source, a single-mode or few-mode injection tail fiber, a coupling injection device, an optical power detector and a light beam quality analyzer, the light source is connected with the coupling injection device through a single-mode or few-mode injection tail fiber, and a detected multimode optical fiber is connected between the coupling injection device and the optical power detector; the light beam quality analyzer is used for being connected with the tested multimode optical fiber through the bare fiber adapter. According to the testing device, the high-precision five-dimensional adjusting frame is used for adjusting the injection light angle so as to adjust the injection light mode, control over the target mode in the attenuation testing process is achieved, and flexibility is high.

Description

Technical Field

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

[0002] Regarding the attenuation test method of multimode optical fiber, the standard stipulates that the truncation method is the benchmark test method for measuring the attenuation characteristics of optical fiber. When using the truncation method to test the attenuation of multimode optical fiber, the light injection system is required to avoid injecting high-order transient modes, so that the power distribution along the optical fiber remains basically unchanged, so that the optical fiber attenuation is approximately linear with the optical fiber length. The common method is to use looping to make the unstable high-order mode leak out of the cladding, but this method has the following two problems: First, the bending resistance of bend-insensitive multimode optical fiber is better, and the effect of the looping filter mode becomes worse, and the looping technique is required to be high, otherwise the optical fiber will produce axial stress, affecting the attenuation test results; second, the looping diameter and number of loops for multimode optical fibers of different batches and models may be different, and the universality and compatibility of the test method are poor. 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 fiber. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a bending-insensitive multimode optical fiber attenuation test device and test method, so as to solve the problem that the prior art has poor effect in filtering out high-order modes by looping.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: A bending-insensitive multimode optical fiber attenuation test device comprises 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 through a single-mode or few-mode injection pigtail, and the coupling injection device and the optical power detector are used to connect the multimode optical fiber to be tested; the beam quality analyzer is used to connect the multimode optical fiber to be tested through a bare fiber adapter. Preferably, the light source is a single wavelength or multi-wavelength narrow line width point light source, which is used to test the attenuation of the required wavelength.

[0005] 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.

[0006] 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.

[0007] Preferably, the coupling injection device comprises 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; 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 arranged between the first high-precision five-dimensional adjustment frame and the second high-precision five-dimensional adjustment frame.

[0008] 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 stepping accuracy of 1 μm, and a Z-axis and Y-axis travel accuracy of 20 mm.

[0009] 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.

[0010] Preferably, a beam quality analyzer is used to detect whether the injected light mode is a stable low-order mode.

[0011] A testing method for a bending-insensitive multimode optical fiber attenuation testing device comprises the following steps: S1. Use a bare fiber adapter to connect one end of the multimode optical fiber to be tested with a length of L1 to a light source, and the other end to a beam quality analyzer, record the light spot after passing through the multimode optical 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, one end of which is an FC / APC connector, connected to the light source, and the other end is a bare fiber end, the end face is cut, and the fiber clamp is used to fix it to the first high-precision five-dimensional adjustment frame; S3. Cut a section of L2 multimode fiber sample from the multimode fiber to be tested, cut one end, fix it on 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 optical fiber sample with a length of L2, the injection light angle is changed, thereby selectively exciting the fundamental mode and some high-order modes; the specific operation is: 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 observe the output spot pattern and intensity of the multimode optical fiber sample of length L2 in the beam quality analyzer at the same time. After receiving the corresponding coupled output light, 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, keep 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 multi-mode optical fiber sample with a length of L2 with the multi-mode optical fiber to be tested with a length of 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).

[0012] The present invention can achieve the following beneficial effects: (1) The test device provided by the present invention uses a high-precision five-dimensional adjustment frame to adjust the injection light angle and thus adjust the injection light mode, thereby achieving control of the target mode during the attenuation test and having high flexibility.

[0013] (2) The testing device provided by the present invention uses a high-precision adjustment frame to replace the manual circle operation, which does not require high proficiency of the operator and is easy to use.

[0014] (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

[0015] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 A system connection diagram of a bending-insensitive multimode optical fiber attenuation test device according to the present invention; Figure 2 It is a schematic diagram of the structure of the coupling injection device of the present invention; Figure 3 It is a schematic diagram of the refractive index profile of the bend-insensitive multimode optical fiber of the present invention.

[0016] 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

[0017] 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.

[0018] The light source may be a single wavelength or multiple wavelength narrow line width 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.

[0019] The single-mode or few-mode injection pigtail can be a single-mode optical fiber or a few-mode optical fiber, one end of which is an FC / UPC type connector connected to a light source, and the other end is a bare optical fiber, and a coupling injection device is used to couple and inject with the multimode optical fiber under test. 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. It 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.

[0020] 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 of the X-axis, Y-axis, Z-axis, θX-axis and θY-axis, and 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 a fiber clamp. Preferably, the five-dimensional adjustment frame has an X-axis and Y-axis stroke of 10mm, a step of 1μm, a Z-axis and Y-axis stroke of 20mm, a step of 1μm, 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, which is convenient for coupling the single-mode or few-mode injection pigtail and the multimode optical fiber to be tested.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] The method of using this device is: S1. Use a bare fiber adapter to connect one end of the multimode optical fiber to be tested with a length of L1 to a light source, and the other end to a beam quality analyzer, record the light spot after passing through the multimode optical 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, one end of which is an FC / APC connector, connected to the light source, and the other end is a bare fiber end, the end face is cut, and the fiber clamp is used to fix it to the first high-precision five-dimensional adjustment frame; S3. A multimode optical fiber sample of length L2 is cut from the multimode optical fiber to be tested, one end is cut, and the sample is fixed to the second high-precision five-dimensional adjustment frame using an optical fiber clamp, and the other end is connected 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 optical fiber sample with a length of L2, the injection light angle is changed, thereby selectively exciting the fundamental mode and some high-order modes; the specific operation is: 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 observe the output spot pattern and intensity of the multimode optical fiber sample of length L2 in the beam quality analyzer at the same time. After receiving the corresponding coupled output light, 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, keep 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 multi-mode optical fiber sample with a length of L2 with the multi-mode optical fiber to be tested with a length of 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).

[0025] 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 the bending resistance is required to be high. 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 causes the effect of filtering out unstable high-order modes excited by conventional light source injection methods through circling to deteriorate during attenuation testing. 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 optical fiber, it can avoid introducing unstable high-order modes. When coupled with a multi-mode optical fiber, some modes can be selectively excited 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, which 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 high-precision five-dimensional adjustment frame 7 and the second high-precision five-dimensional adjustment frame 8 can be used for precise adjustment of the X-axis, Y-axis, Z-axis, θX-axis and θY-axis. The first fiber clamp 9 and the second fiber clamp 10 can be fixed on the first high-precision five-dimensional adjustment frame 7 and the second high-precision five-dimensional adjustment frame 8 respectively. The first high-precision five-dimensional adjustment frame 7 and the second high-precision five-dimensional adjustment frame 8 are manual adjustment devices. The X-axis and the Y-axis are used to adjust the alignment of the single-mode or few-mode injection pigtail 2 and the multimode optical fiber 4 to be tested, the Z-axis is used to adjust the interval between the two optical fibers, and the θX-axis and the θY-axis 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, which is used to record the power of the system after passing through multimode optical fibers of different lengths, and calculate the optical power difference to obtain the multimode optical 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 multi-mode optical fiber 4 to be tested.

[0026] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A bending-insensitive multimode optical fiber attenuation test device, characterized in that: It comprises 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 a coupling injection device (3) via a single-mode or few-mode injection pigtail (2); the coupling injection device (3) and an optical power detector (5) are used to connect to a multimode optical fiber (4) to be tested; and the beam quality analyzer (6) is used to connect to the multimode optical fiber (4) to be tested via a bare fiber adapter.

2. A bending-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. A bending-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 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).

6. A bending-insensitive multimode optical fiber attenuation test device according to claim 5, 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.

7. 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.

8. 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.

9. A testing method for a bending-insensitive multimode optical fiber attenuation testing device according to any one of claims 1 to 8, characterized in that The following steps are involved: S1. Use a bare fiber adapter to connect one end of the multimode optical fiber to be tested with a length of L1 to a light source, and the other end to a beam quality analyzer, record the light spot after passing through the multimode optical 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, one end of which is an FC / APC type connector, connected to the light source, and the other end is a bare fiber end, the end face is cut, and it is fixed to the first high-precision five-dimensional adjustment frame using a fiber clamp; S3. A multimode optical fiber sample of length L2 is cut from the multimode optical fiber to be tested, one end is cut, and the sample is fixed to the second high-precision five-dimensional adjustment frame using an optical fiber clamp, and the other end is connected 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 optical fiber sample with a length of L2, the injection light angle is changed, thereby selectively exciting the fundamental mode and some high-order modes; the specific operation is: 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 observe the output spot pattern and intensity of the multimode optical fiber sample of length L2 in the beam quality analyzer at the same time. After receiving the corresponding coupled output light, 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, keep 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 multi-mode optical fiber sample with a length of L2 with the multi-mode optical fiber to be tested with a length of 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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