How does single-mode fiber continue?

2017-09-24
A single-mode fiber is a fiber that transmits only a single base die at a given operating wavelength. He does not exist mode dispersion, so single-mode fiber has a very wide transmission band, used in long-distance, high-capacity transmission. Single-mode fiber core is very fine, core diameter of only 8-10μм, cladding diameter of 125μм, can be made very long, but in order to manufacture, transport, construction convenience, usually the cable length of the factory 1 - The Single-mode fiber transmission loss is now low as low as 0.2dB / (1.55μм), cable connection length is not easy to less than 2.
How does single-mode fiber continue?
Fiber connection method is very much, at this stage to arc welding the most superior, the most widely used. Arc welding method is the use of high-temperature fiber when the melting performance and high-voltage discharge of the high-temperature arc principle, so that the fiber welded together. At present, the production of welding machines are used image processing technology, so that automatically set the fiber end position. Single-mode fiber automatically on the heart and automatic welding, by switching the picture tube screen, you can observe the vertical and horizontal aspects of the fiber on the heart and welding situation. But also according to the deviation of the mandrel and the degree of tilt to estimate the continued loss and display.

In the optical fiber connection, generally according to the following procedures:

⑴ in the fiber on the pre-set on the fiber optic cable connection parts with reinforced wire with heat shrink tubing;

⑵ remove the coating, with the clamp clamp vertical clamp the fiber quickly stripping 20mm - 30mm long primary coating and secondary coating, soaked with alcohol cotton balls or lens paper wipe the fiber, wipe the core Clean, and pay attention to the surface of the fiber should not have cracks, scratches.

⑶ cutting fiber, making the end, in the fiber connection, the fiber end of the production is the most critical process. The improvement of the end of the fiber is one of the important reasons for determining the loss of fiber. It requires a flat finish after the preparation, no burrs, no defects, and perpendicular to the axis, showing a smooth mirror area, and keep clean, to avoid dust pollution. There are three ways to prepare the end face, one is the engraving method, the use of mechanical cutting knife, with a diamond knife on the surface perpendicular to the direction of the fiber scribing marks, from the coating 10 ?, gently bombs, fiber at this mark Position on the natural fracture, the second is the cutting clamp method, it is the use of a homemade hand-held simple clamp for cutting operations. Third, ultrasonic electric cutting method. These three methods as long as the equipment is excellent, proper operation, the preparation of the effect of the face are very good.
In the case of
⑷ will want to take the two fibers into the welding machine for welding, which by the welding machine automatically.

⑸ OTDR instrument with the performance of several tests to meet the successor indicators, and then continue to strengthen the protection of parts, that is, hot melt with a wire heat shrink tube.

⑹ Finally, after the completion of all the core, the income of the tray, with the OTDR instrument for re-measurement, non-grid to be re-installed or re-continue until qualified.

Single-mode fiber connection loss index is now generally set at 0.08dB, in the construction, according to the actual situation of indicators, but generally not more than 0.08dB.

The loss of fiber connection is due to the failure of the connection point is not perfect, affecting the connection point is not perfect many factors, summed up there are two categories, that is, external and internal factors. The internal factors refer to the imperfection of the fiber itself and can not reduce the loss by improving the splicing process. It includes core misalignment, refractive index distribution mismatch, poor fiber concentricity, mode field mismatch, so in the connection test, The value will appear big positive negative phenomenon. Through multiple connections can only make one-way value smaller, the average tends to zero, but positive and negative phenomenon can not be avoided, positive and negative phenomena on the optical fiber transmission loss have a certain impact. In the project, the cable with the disk should try to use the same batch of factory fiber optic cable, A, B side as far as possible one by one correspondence, artificial improvement process to reduce the continued loss.

External factors refer to the non-fiber itself is not perfect, but the continuous process caused by poor, including the core position transverse, vertical, optical fiber axial angle deviation, fiber end contamination, which is due to the process of joining the welding machine is not timely maintenance , Improper operation and other human factors caused by the connection loss is too large.

Here we mainly talk about the common problems in the connection and preventive measures to Japan Fujikura automatic welding machine, for example, the core position of the lateral deviation, longitudinal deviation, axial deviation, because the electrode position is not appropriate, welding machine focus is not good And other circumstances caused by the beginning of the connection before the first field experiment can be selected to follow the fiber is connected to the mode and a variety of parameters. And then the maintenance of the welding machine maintenance of the menu, such as maintenance recovery procedures to adjust the welding machine to focus on the state; dust inspection and maintenance, so that welding machine lens, electrode and other dust pollution to clean; electrode position discharge test Adjust the appropriate electrode position.

In the process of fiber splicing, the discharge time, discharge intensity and propulsion quantity are important factors which can not be neglected, which directly affect the mechanical strength and loss of the fiber joint. The length of the discharge time is proportional to the strength of the fiber connector. Over time will make the fiber due to high temperature aging, so take into account both, usually the discharge time control in the 2 - 5S. Discharge intensity should also choose the appropriate, too strong will make the fiber aging, too weak to complete the fiber is not good, affecting the loss of success, usually according to the actual situation to determine its value, generally between 45 - 65. Propulsion is the fiber is placed in the welding machine welding, must be with the fiber welding, the fiber will be advanced, push a large amount of fiber connector will be thicker, small joints are fine. General push the amount of control 15 - 20μm range. By selecting these values ​​appropriately, the purpose of reducing the loss of the connection is achieved.

Second, the continuation of the staff to strict requirements, in strict accordance with the operating norms and operating procedures to continue. If you put the fiber, the location should be placed properly, the fiber from the electrode position is too large or too small can not be connected; a fiber connection is completed, you must wait for the screen to show recovery standby after opening the cover to remove the fiber; After the tube, you must wait for it to cool after removal and so on.
 
Finally, it is worth noting that the heat shrink tube should also pay attention to clean, clean, clean, or hot melt, the dust on the connection point damage, causing increased wear and tear. To accommodate the storage tray, as far as possible harvest large circle, to avoid the small circle caused by increased wear and tear. Fiber in the tray to use tape to make it fixed, can not appear on the bomb trend, to avoid future damage.

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