An undersea optical cable bending stiffness test device and test method

Abstract

The present invention discloses an undersea optical cable bending stiffness test device and a test method. The device includes: a test platform, a steel wire rope, a scale ruler, a controller, and a force sensor. The controller includes a housing and a first rotating shaft disposed in the housing. The housing is arranged on the test platform. A through hole corresponding to the steel wire rope is axially provided in the first rotating shaft. The steel wire rope passes through the through hole and both ends extend to both sides of the housing. The force sensor is connected in series on the steel wire rope. The scale ruler is arranged at intervals on the test platform and is located behind the housing. By the above method, the undersea optical cable bending stiffness test device and the test method of the present invention are easy to operate, can achieve step-by-step loading and unloading, are used to study the variation relationship between the bending stiffness of the undersea optical cable and the curvature, are convenient for accurately evaluating the bending stiffness of the undersea optical cable, and obtain the corresponding relationship between the curvature and the bending moment of the undersea optical cable.

Description

Technical Field

[0001] The present invention relates to the technical field of submarine optical cable testing, and in particular to a submarine optical cable bending stiffness testing device and a testing method. Background Art

[0002] Submarine optical cables carry more than 95% of international communications and are the key carriers of global network communications. They are of great significance, and in-depth research on submarine optical cable related theories, processes and experiments is necessary. Submarine optical cables are mainly composite components formed by some or all of the components such as optical fibers, fiber jelly, stainless steel tubes, inner armored steel wires, water-blocking glue, copper tubes, HDPE insulation, HDPE sheaths, outer armored steel wires, and PP ropes. Due to the complexity of their structures and the diversity of their components, the bending stiffness of submarine optical cables is generally difficult to accurately evaluate through theoretical calculations. The bending stiffness of submarine optical cables is crucial to the manufacture, storage, transportation, construction, operation, and maintenance of submarine cables. It is the theoretical source of their minimum bending radius, and it is necessary to design an accurate submarine optical cable bending stiffness test model and evaluation method.

[0003] At present, a typical method for testing the bending stiffness of submarine cables is as follows: Figure 1 As shown, it consists of a clamping device 5, a submarine cable sample 4, and a weight 1. During the test, one end of the submarine cable sample 4 is fixed to the clamping device 1, and the other end is hung with the weight 1. The horizontal distance L ( Figure 1 The mark 3 in the figure) and the vertical distance y from the end of the submarine cable ( Figure 1 2) Evaluate the bending stiffness EI of the submarine cable. The bending stiffness EI of the submarine cable is calculated by the following formula: EI = W*L 3 / 3y.

[0004] The above test methods generally have the following defects:

[0005] 1. The test environment for the bending stiffness of submarine optical cables is in a vertical state, but the influence of the submarine optical cable's own weight is not considered when calculating the bending stiffness of submarine optical cables;

[0006] 2. The bending stiffness of submarine optical cables is not calculated based on a relatively accurate deflection curve equation, but some approximate assumptions are introduced, such as ignoring the influence of shear force and considering the deflection curve to be a circular arc.

[0007] 3. Only the bending stiffness of the submarine optical cable under a specific load is obtained, and the corresponding relationship between the curvature and the bending moment of the submarine optical cable is not obtained. In fact, the bending stiffness of the submarine optical cable changes with the curvature, which needs to be improved. Summary of the invention

[0008] The main technical problem to be solved by the present invention is to provide a submarine optical cable bending stiffness test device and a test method, which can accurately evaluate the bending stiffness of the submarine optical cable and obtain the corresponding relationship between the curvature and bending moment of the submarine optical cable.

[0009] To solve the above technical problem, a technical solution adopted by the present invention is: to provide a submarine optical cable bending stiffness test device, including: a test platform 6, a steel wire rope 8, a scale ruler 9, a controller 10, a force sensor 11. The controller 10 includes a housing 27 and a first rotating shaft 15 disposed in the housing 27. The housing 27 is arranged on the test platform 6. A through hole 151 corresponding to the steel wire rope 8 is axially provided in the first rotating shaft 15. The steel wire rope 8 passes through the through hole 151 and both ends extend to both sides of the housing 27. The force sensor 11 is connected in series on the steel wire rope 8. The scale ruler 9 is arranged at intervals on the test platform 6 and is located behind the housing 27.

[0010] In a preferred embodiment of the present invention, threading holes 271 corresponding to the steel wire rope 8 are provided on both sides of the housing 27. A node 13 is provided on the steel wire rope 8. The diameter of the node 13 is larger than the diameter of the threading hole 271 and is restricted from moving outwards.

[0011] In a preferred embodiment of the present invention, the controller 10 further includes a second rotating shaft 18, a first gear 26, a second gear 17, a loading knob 22, an unloading knob 21 and a ratchet mechanism 19. The second rotating shaft 18 is arranged in the housing 27 and is parallel to the first rotating shaft 15. The first gear 26 is arranged on the first rotating shaft 15. The second gear 17 is arranged on the second rotating shaft 18 and meshes with the first gear 26. The front end of the second rotating shaft 18 extends to the outside of the housing 27. The loading knob 22 is arranged at the front end of the second rotating shaft 18. The ratchet mechanism 19 includes a first pawl 28, a first baffle 29, a retaining ring 20, a second pawl 30, a second baffle 31, a ratchet 32, a third baffle 33 and a fourth baffle 34. The ratchet 32 is concentrically arranged on the second rotating shaft 18. The first pawl 28 and the second pawl 30 are arranged at intervals along the circumferential direction of the ratchet 32 in the housing 27 and respectively point to the ratchet 32. The retaining ring 20 is arranged on one side of the ratchet 32. The first baffle 29, the second baffle 31, the third baffle 33 and the fourth baffle 34 are annularly arrayed on the retaining ring 20 and extend to the circumferential edge of the ratchet 32. The retaining ring 20 extends to the outside of the housing 27 and is connected to the unloading knob 21.

[0012] In a preferred embodiment of the present invention, a first bearing 14 and a second bearing 25 corresponding to the first rotating shaft 15 are arranged at intervals in the housing 27. A third bearing 16 and a fourth bearing 23 corresponding to the second rotating shaft 18 are arranged at intervals in the housing 27. A fifth bearing 24 corresponding to the retaining ring 20 is arranged in the housing 27.

[0013] In a preferred embodiment of the present invention, the loading knob 22 is concentrically arranged inside the unloading knob 21, and the fourth bearing 23 is concentrically arranged inside the fifth bearing 24.

[0014] In a preferred embodiment of the present invention, the submarine cable sample 35 is placed on the upper surface of the test platform 6 and behind the housing 27. Ring grooves 351 are provided on both sides of the outer circumference of the submarine cable sample 35, and lassos 81 corresponding to the ring grooves 351 are provided at both ends of the steel wire rope 8.

[0015] In a preferred embodiment of the present invention, a workbench 12 is provided at the bottom of the test platform 6. A stepped hole 7 is concavely provided in the test platform 6, and a screw 71 connected to the workbench 12 is provided in the stepped hole 7.

[0016] To solve the above technical problems, a technical solution adopted by the present invention is: to provide a test method for the bending stiffness of a submarine optical cable, including the following steps:

[0017] Step 1: Fabricate the submarine cable sample 35. Take a section of submarine optical cable, straighten it, cut off part of the material from the outer circumference at both ends to form the ring grooves 351, and make the submarine cable sample 35. The part between the ring grooves 351 at both ends of the submarine cable sample 35 is the effective test length, and this length should be equivalent to the length of the steel wire rope 8 in the initial state.

[0018] Step 2: Initialize the test device. Pull the steel wire rope 8 from both sides, rotate the unloading knob 21, observe the loading knob 22 until the loading knob 22 stops rotating, and finally pull the steel wire rope 8 left and right to adjust the position of the steel wire rope 8 so that the lengths of the steel wire rope 8 on both sides of the first rotating shaft 15 are equivalent.

[0019] Step 3: Bending stiffness test. Place the submarine cable sample 35 on the scale 9 on the test platform 6 and behind the housing 27. Put the lassos 81 at both ends of the steel wire rope 8 on the ring grooves 351 at both ends of the submarine cable sample 35. Rotate the loading knob 22 to simultaneously tighten both ends of the steel wire rope 8 and drive the submarine cable sample 35 to bend to any position. For a specific position, record the lateral load F applied to the submarine cable sample 35 through the force sensor 11, and record the coordinate information of the key positions of the submarine cable sample 35 through the scale 9. The coordinate information corresponding to the specific position includes the first coordinate, the second coordinate, the third coordinate, the fourth coordinate, and the fifth coordinate. The first coordinate and the fifth coordinate correspond to the two positions where the lassos 81 at both ends of the steel wire rope 8 contact the ring grooves 351 at both ends of the submarine cable sample 35. The third coordinate is the position where the bending deflection of the submarine cable sample 35, that is, the maximum value of the ordinate. The second coordinate is located between the first coordinate and the third coordinate, and the fourth coordinate is located between the third coordinate and the fifth coordinate.

[0020] Step 4: Data processing. According to the coordinate information, fit the curve of the submarine optical cable bending. Use the Spline function in Matlab for fitting. Calculate the bending curvature of the submarine optical cable at the third coordinate according to the fitted curve. Suppose the calculated curvature is κ. Calculate the bending moment M acting on the submarine optical cable at the third coordinate position according to the tension F on the wire rope measured by the force sensor. M = F * y3, where y3 is the ordinate of the third coordinate. Calculate the bending stiffness EI of the submarine optical cable according to κ and M. The calculation formula is as follows:

[0021] EI = M / κ;

[0022] Step 5: Repeat Step 3 and Step 4 to obtain the corresponding relationship between the bending moment and curvature of the submarine optical cable under the loading state, and thus obtain the variation of the bending stiffness of the submarine optical cable with the curvature accordingly.

[0023] In a preferred embodiment of the present invention, it further includes Step 6. Rotate the unloading knob 21, repeat Step 3 and Step 4 to obtain the corresponding relationship between the bending moment and curvature of the submarine optical cable under the unloading state, and thus obtain the variation of the bending stiffness of the submarine optical cable with the curvature accordingly.

[0024] The beneficial effects of the present invention are as follows: A submarine optical cable bending stiffness test device and test method provided by the present invention are easy to operate, can achieve step-by-step loading and unloading, are used to study the variation relationship between the bending stiffness of the submarine optical cable and the curvature, give the test steps and test data processing methods for the bending stiffness of the submarine optical cable, can conduct the bending stiffness test of the submarine optical cable in a horizontal state, avoid the influence of the self-weight of the submarine optical cable, construct a pure bending working condition of the submarine optical cable, facilitate a more accurate evaluation of the bending stiffness of the submarine optical cable, obtain the corresponding relationship between the curvature and bending moment of the submarine optical cable, and are used to study the hysteresis phenomenon of the bending stiffness of the submarine optical cable. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings, where:

[0026] Figure 1 is the structural diagram of a device of a relatively typical current submarine cable bending stiffness test method in the background art;

[0027] Figure 2 is the structural schematic diagram of a preferred embodiment of a submarine optical cable bending stiffness test device of the present invention;

[0028] Figure 3 is Figure 2 the top view;

[0029] Figure 4 is Figure 3 a schematic diagram of the internal structure of the controller in

[0030] Figure 5 is Figure 4 the front view of the controller in

[0031] Figure 6 is Figure 4 a cross-sectional view of the first rotating shaft 15 in

[0032] Figure 7 is Figure 4 a schematic diagram of the structure of the ratchet mechanism 19 before unloading in

[0033] Figure 8 is Figure 7 a schematic diagram of the structure of the ratchet mechanism 19 shown during stepwise unloading

[0034] Figure 9 is Figure 8 a schematic diagram of the structure of the ratchet mechanism 19 shown after unloading

[0035] Figure 10 is a schematic diagram of the structure of a preferred embodiment of a test method for the bending stiffness of a submarine optical cable according to the present invention;

[0036] Figure 11 is Figure 10 a schematic diagram of the straightened structure of the submarine cable sample 35 in

[0037] Figure 12 is a corresponding relationship diagram of the bending moment and curvature of a typical submarine optical cable;

[0038] Figure 13 is a schematic diagram of the pure bending condition of the submarine cable sample 35 in a test method for the bending stiffness of a submarine optical cable according to the present invention. Detailed implementation manners

[0039] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0040] Please refer to Figures 2 to 13 , the embodiments of the present invention include:

[0041] As shown in Figures 2 to 9The submarine optical cable bending stiffness test device shown includes a test platform 6, a wire rope 8, a scale ruler 9, a controller 10, and a force sensor 11. In this embodiment, a workbench 12 is provided at the bottom of the test platform 6 to support the test platform 6. A stepped hole 7 is concavely provided on the test platform 6, and a screw 71 connected to the workbench 12 is provided in the stepped hole 7, with a stable structure to avoid the shaking of the test platform 6 during operation.

[0042] As Figure 4 shown, the controller 10 includes a housing 27, a first rotating shaft 15, a second rotating shaft 18, a first gear 26, a second gear 17, a loading knob 22, an unloading knob 21, and a ratchet mechanism 19 disposed in the housing 27. The housing 27 is arranged on the test platform 6 and can be fixed by bolts, with a firm structure.

[0043] As Figure 6 shown, a through hole 151 corresponding to the wire rope 8 is axially provided in the first rotating shaft 15. The wire rope 8 passes through the through hole 151 and both ends extend to both sides of the housing 27. Threading holes 271 corresponding to the wire rope 8 are provided on both sides of the housing 27, facilitating assembly. A node 13 is provided on the wire rope 8. The diameter of the node 13 is larger than that of the threading hole 271, so it is restricted from moving outward, which is beneficial to the reset of the wire rope 8. In addition, the node 13 can be a perforated steel ball or a steel ring. The node 13 can be sleeved on the wire rope 8 and then fixed by bolts or welding.

[0044] As Figure 3 shown, the force sensor 11 is connected in series on the wire rope 8 to detect the tensile force. The scale ruler 9 is arranged on the test platform 6 at intervals and is located behind the housing 27. In this embodiment, the scale ruler 9 includes an abscissa and a plurality of ordinates arranged at intervals on the abscissa.

[0045] The second rotating shaft 18 is arranged in the housing 27 and is parallel to the first rotating shaft 15. In this embodiment, a first bearing 14 and a second bearing 25 corresponding to the first rotating shaft 15 are arranged at intervals in the housing 27, and a third bearing 16 and a fourth bearing 23 corresponding to the second rotating shaft 18 are arranged at intervals in the housing 27, which is beneficial to the rotation of the first rotating shaft 15 and the second rotating shaft 18 and reduces the frictional resistance.

[0046] The first gear 26 is arranged on the first rotating shaft 15, and the second gear 17 is arranged on the second rotating shaft 18 and meshes with the first gear 26 to transmit the first rotating shaft 15 and the second rotating shaft 18. Moreover, the transmission ratio of the first gear 26 to the second gear 17 is greater than 6:1, making the operation easier. The front end of the second rotating shaft 18 extends to the outside of the housing 27, and the loading knob 22 is arranged at the front end of the second rotating shaft 18, facilitating rotation for loading the driving force.

[0047] In order to achieve the step-by-step loading of the driving force, a ratchet mechanism 19 is specifically designed. As Figures 7 to 9 shown, the ratchet mechanism 19 includes a first pawl 28, a first baffle 29, a retaining ring 20, a second pawl 30, a second baffle 31, a ratchet 32, a third baffle 33, and a fourth baffle 34. The ratchet 32 is concentrically arranged on the second rotating shaft 18 and rotates with the second rotating shaft 18.

[0048] The first pawl 28 and the second pawl 30 are circumferentially spaced along the ratchet 32 in the housing 27 and respectively point to the ratchet 32. At least one of the first pawl 28 and the second pawl 30 extends into the tooth groove of the ratchet 32 for unloading and locking. The retaining ring 20 is concentrically arranged on one side of the ratchet 32. The first baffle 29, the second baffle 31, the third baffle 33, and the fourth baffle 34 are annularly arrayed on the retaining ring 20 and extend to the circumferential edge of the ratchet 32, with a stable structure. Moreover, the first baffle 29, the second baffle 31, the third baffle 33, and the fourth baffle 34 rotate synchronously with the retaining ring 20. The retaining ring 20 extends to the outside of the housing 27 and is connected to the unloading knob 21, and is manually driven through the unloading knob 21, with simple operation.

[0049] In this embodiment, the first pawl 28 and the second pawl 30 alternately perform step-by-step unloading and limiting of the ratchet 32. As Figure 7 shown, the second pawl 30 extends into the tooth groove of the ratchet 32 for unloading and locking. At this time, the second baffle 31 is located behind the second pawl 30, and the first pawl 28 is located on the fourth baffle 34. At this time, the unloading knob 21 is rotated, so that the first baffle 29, the second baffle 31, the third baffle 33, and the fourth baffle 34 rotate counterclockwise. As Figure 8 shown, the second baffle 31 pushes the second pawl 30 out of the tooth groove, and the first pawl 28 separates from the fourth baffle 34 and contacts the ratchet 32. Finally, as Figure 9 shown, the first pawl 28 extends into the tooth groove of the ratchet 32 for unloading and locking, realizing step-by-step unloading.

[0050] In order to improve the rotational stability of the retaining ring 20, a fifth bearing 24 corresponding to the retaining ring 20 is arranged in the housing 27. As Figure 4 shown, the loading knob 22 is concentrically arranged inside the unloading knob 21, with a compact structure, and the rotation directions are respectively marked. In this embodiment, the fourth bearing 23 is concentrically arranged inside the fifth bearing 24. The tail of the retaining ring 20 is reduced in diameter and adopts a cylindrical structure. The cylindrical structure is located in the annular gap between the fifth bearing 24 and the fourth bearing 23, and can be rotationally supported by the outer ring of the fourth bearing 23 and the inner ring of the fifth bearing 24, and is convenient for connection with the unloading knob 21.

[0051] Place the submarine cable sample 35 on the upper surface of the test platform 6 and behind the housing 27. Ring grooves 351 are provided on both sides of the outer circumference of the submarine cable sample 35. Lassoes 81 corresponding to the ring grooves 351 are provided at both ends of the steel wire rope 8. Through the cooperation of the lassoes 81 and the ring grooves 351, the two ends of the steel wire rope 8 are connected and fixed to the two ends of the submarine cable sample 35. In order to reduce the influence of friction on the submarine cable sample 35, it is necessary to limit the surface roughness of the upper surface of the test platform 6. The recommended surface roughness of the top surface of the test platform 6 is Ra3.2.

[0052] As Figures 10 to 13 shown, a test method for the bending stiffness of an undersea optical cable includes the following steps:

[0053] Step 1: Fabricate the submarine cable sample 35. Take a section of undersea optical cable, straighten it, cut off part of the material from the outer circumference at both ends to form the ring grooves 351, and make the submarine cable sample 35. The part between the ring grooves 351 at both ends of the submarine cable sample 35 is the effective test length, and this length should be equivalent to the length of the steel wire rope 8 in the initial state;

[0054] Step 2: Initialize the test device. Pull the steel wire rope 8 from both sides, rotate the unloading knob 21, observe the loading knob 22 until the loading knob 22 stops rotating, and finally pull the steel wire rope 8 left and right to adjust the position of the steel wire rope 8 so that the lengths of the steel wire rope 8 on both sides of the first rotating shaft 15 are equivalent;

[0055] Step 3: Bending stiffness test. Place the submarine cable sample 35 on the test platform 6 and on the scale 9 behind the housing 27. Put the lassoes 81 at both ends of the steel wire rope 8 on the ring grooves 351 at both ends of the submarine cable sample 35. Rotate the loading knob 22 to simultaneously tighten both ends of the steel wire rope 8 and drive the submarine cable sample 35 to bend to any position. For a specific position, record the lateral load F applied to the submarine cable sample 35 through the force sensor 11, and record the coordinate information of the key positions of the submarine cable sample 35 through the scale 9. In this embodiment, the coordinate information corresponding to the specific position includes the first coordinate, the second coordinate, the third coordinate, the fourth coordinate, and the fifth coordinate. The first coordinate and the fifth coordinate correspond to the two positions where the lassoes 81 at both ends of the steel wire rope 8 contact the ring grooves 351 at both ends of the submarine cable sample 35. The third coordinate is the position where the bending deflection of the submarine cable sample 35, that is, the maximum value of the ordinate. The second coordinate is located between the first coordinate and the third coordinate, and the fourth coordinate is located between the third coordinate and the fifth coordinate;

[0056] Step 4: Data processing. According to the coordinate information, fit the curve of the submarine optical cable bend. Use the Spline function in Matlab for fitting. Calculate the bending curvature of the submarine optical cable at the third coordinate according to the fitted curve. Assume the calculated curvature is κ. Calculate the bending moment M acting on the submarine optical cable at the third coordinate position according to the tension F on the wire rope measured by the force sensor. M = F * y3, where y3 is the ordinate of the third coordinate. Calculate the bending stiffness EI of the submarine optical cable according to κ and M. The calculation formula is as follows:

[0057] EI = M / κ;

[0058] Step 5: Repeat Step 3 and Step 4 to obtain the corresponding relationship between the bending moment and curvature of the submarine optical cable under the loading state, and thus obtain the change of the bending stiffness of the submarine optical cable with the curvature accordingly;

[0059] Step 6: Rotate the unloading knob 21, and repeat Step 3 and Step 4 to obtain the corresponding relationship between the bending moment and curvature of the submarine optical cable under the unloading state, and thus obtain the change of the bending stiffness of the submarine optical cable with the curvature accordingly.

[0060] The relationship between the bending moment and curvature of a typical submarine optical cable is as Figure 12 shown. It can be seen from Figure 12 that the bending stiffness of the submarine optical cable is not fixed. During loading, when the curvature of the submarine optical cable is small, the bending stiffness shows a relatively large value. As the curvature increases, the bending stiffness of the submarine optical cable decreases. At the beginning of unloading, the bending stiffness of the submarine cable shows a relatively large value. As the degree of unloading increases, the bending stiffness of the submarine optical cable decreases.

[0061] As Figure 13 shown, it is a schematic diagram of the submarine optical cable in the bent state. Take the cable cross-section A - A at the third coordinate for force analysis. There is no shear force on the cross-section A - A, and there is a force F' that balances with F and a bending moment M that balances with the couple F - F'. Since the introduction of shear force is avoided, a pure bending state is constructed.

[0062] In summary, a test device and test method for the bending stiffness of a submarine optical cable pointed out by the present invention can conduct a test on the bending stiffness of a submarine optical cable in a horizontal state, avoid the influence of the self-weight of the submarine optical cable, is beneficial to improving the accuracy of the test, is easy to operate, can realize two-way step-by-step operation of loading and unloading, and is beneficial to data recording.

[0063] The above are only embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A bending stiffness test device for submarine optical cables, which is used for the bending stiffness test of a submarine cable sample (35), and is characterized in that, Comprising: A test platform (6), a wire rope (8), a scale ruler (9), a controller (10), a force sensor (11), wherein the controller (10) includes a housing (27) and a first rotating shaft (15) disposed in the housing (27), the housing (27) is arranged on the test platform (6), a through hole (151) corresponding to the wire rope (8) is axially arranged in the first rotating shaft (15), the wire rope (8) penetrates through the through hole (151) and both ends extend to both sides of the housing (27), the force sensor (11) is connected in series on the wire rope (8), the scale ruler (9) is arranged on the test platform (6) at intervals and is located behind the housing (27), the controller (10) further includes a second rotating shaft (18), a first gear (26), a second gear (17), a loading knob (22), an unloading knob (21) and a ratchet mechanism (19), the second rotating shaft (18) is arranged in the housing (27) and is parallel to the first rotating shaft (15), the first gear (26) is arranged on the first rotating shaft (15), the second gear (17) is arranged on the second rotating shaft (18) and meshes with the first gear (26), the front end of the second rotating shaft (18) extends to the outside of the housing (27), the loading knob (22) is arranged at the front end of the second rotating shaft (18), the ratchet mechanism (19) includes a first pawl (28), a first baffle (29), a retaining ring (20), a second pawl (30), a second baffle (31), a ratchet (32), a third baffle (33) and a fourth baffle (34), the ratchet (32) is concentrically arranged on the second rotating shaft (18), the first pawl (28) and the second pawl (30) are arranged in the housing (27) at intervals along the circumferential direction of the ratchet (32) and respectively point to the ratchet (32), the retaining ring (20) is arranged on one side of the ratchet (32), the first baffle (29), the second baffle (31), the third baffle (33) and the fourth baffle (34) are annularly arrayed on the retaining ring (20) and extend to the circumferential edge of the ratchet (32), and the retaining ring (20) extends to the outside of the housing (27) and is connected to the unloading knob (21).

2. The submarine optical cable bending stiffness test device according to claim 1, wherein, Threading holes (271) corresponding to the wire rope (8) are arranged on both sides of the housing (27), a node (13) is arranged on the wire rope (8), and the diameter of the node (13) is larger than the diameter of the threading hole (271), so that the node is restricted from moving outwards.

3. The submarine optical cable bending stiffness test device according to claim 1, characterized in that, A first bearing (14) and a second bearing (25) corresponding to the first rotating shaft (15) are arranged in the housing (27) at intervals, a third bearing (16) and a fourth bearing (23) corresponding to the second rotating shaft (18) are arranged in the housing (27) at intervals, and a fifth bearing (24) corresponding to the retaining ring (20) is arranged in the housing (27).

4. The submarine optical cable bending stiffness test device according to claim 3, characterized in that, The loading knob (22) is concentrically arranged inside the unloading knob (21), and the fourth bearing (23) is concentrically arranged inside the fifth bearing (24).

5. The submarine optical cable bending stiffness test device according to claim 1, characterized in that The submarine cable sample (35) is placed on the upper surface of the test platform (6) and behind the housing (27). Ring grooves (351) are provided on both sides of the outer circumference of the submarine cable sample (35), and lassoes (81) corresponding to the ring grooves (351) are provided at both ends of the wire rope (8).

6. The submarine optical cable bending stiffness test device according to claim 1, characterized in that, A workbench (12) is provided at the bottom of the test platform (6). A stepped hole (7) is concavely provided on the test platform (6), and a screw (71) connecting to the workbench (12) is provided in the stepped hole (7).

7. A test method for the bending stiffness of a submarine optical cable, based on the submarine optical cable bending stiffness test device according to any one of claims 1 to 6, characterized in that, It includes the following steps: Step 1: Fabricate the submarine cable sample (35). Take a section of submarine optical cable, straighten it, cut off some materials from the outer circumference at both ends to form ring grooves (351), and make the submarine cable sample (35). The part between the ring grooves (351) at both ends of the submarine cable sample (35) is the effective test length, and this length should be equivalent to the length of the wire rope (8) in the initial state; Step 2: Initialize the test device. Pull the wire rope (8) from both sides, rotate the unloading knob (21), observe the loading knob (22) until the loading knob (22) stops rotating, and finally pull the wire rope (8) left and right to adjust the position of the wire rope (8) so that the lengths of the wire rope (8) on both sides of the first rotating shaft (15) are equivalent; Step 3: Bending stiffness test. Place the submarine cable sample (35) on the scale (9) on the test platform (6) and behind the housing (27). Put the lassoes (81) at both ends of the wire rope (8) on the ring grooves (351) at both ends of the submarine cable sample (35). Rotate the loading knob (22) to simultaneously tighten both ends of the wire rope (8) and drive the submarine cable sample (35) to bend to any position. For a specific position, record the lateral load F applied to the submarine cable sample (35) through the force sensor (11), and record the coordinate information of the key positions of the submarine cable sample (35) through the scale (9). The coordinate information corresponding to the specific position includes the first coordinate, the second coordinate, the third coordinate, the fourth coordinate, and the fifth coordinate. The first coordinate and the fifth coordinate correspond to the two positions where the lassoes (81) at both ends of the wire rope (8) contact the ring grooves (351) at both ends of the submarine cable sample (35). The third coordinate is the position where the bending deflection of the submarine cable sample (35), that is, the maximum value of the ordinate. The second coordinate is located between the first coordinate and the third coordinate, and the fourth coordinate is located between the third coordinate and the fifth coordinate; Step 4: Data processing. According to the coordinate information, fit the curve of the bending of the submarine optical cable. Use the Spline function in Matlab for fitting. Calculate the bending curvature of the submarine optical cable at the third coordinate according to the fitted curve. Assume the calculated curvature is κ. Calculate the bending moment M acting on the third coordinate position of the submarine optical cable according to the tension F on the wire rope measured by the force sensor. M = F * y3, where y3 is the ordinate of the third coordinate. Calculate the bending stiffness EI of the submarine optical cable according to κ and M, and its calculation formula is as follows: EI = M / κ; Step 5: Repeat Step 3 and Step 4 to obtain the corresponding relationship between the bending moment and the curvature of the submarine optical cable under the loading state, and thus obtain the change of the bending stiffness of the submarine optical cable with the curvature accordingly.

8. The test method for the bending stiffness of the submarine optical cable according to claim 7, characterized in that, It further includes Step 6 of rotating the unloading knob (21), repeating Step 3 and Step 4 to obtain the corresponding relationship between the seabed optical cable bending moment and curvature in the unloading state, and thereby correspondingly obtaining the variation of the seabed optical cable bending stiffness with curvature.

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