Professional Knowledge

How to perform fiber splicing and testing?

1. Optical fiber connection
(1) Optical fiber connection. The principle that the fiber connection should follow is: when the number of cores is equal, the corresponding color fiber in the bundle tube should be connected. When the number of cores is different, connect the larger number of cores first, and then the smaller number of cores in order. 
(2) There are three methods of fiber connection: fusion splicing, movable connection, and mechanical connection. Welding methods are mostly used in engineering. The contact loss using this welding method is small, the reflection loss is large, and the reliability is high. To
(3) Process and steps of fiber connection:
① Strip the fiber optic cable and fix the fiber optic cable in the splice box. Be careful not to injure the bundle tube. Take about 1m for the stripping length. Wipe the ointment clean with toilet paper. Pass the optical cable into the splice box. When fixing the steel wire, it must be pressed tightly without looseness. Otherwise, it may cause the optical cable to roll and break the core. 
② Split the fiber through the heat shrinkable tube. Separate different bundle tubes and optical fibers of different colors and pass them through the heat shrinkable tube. The optical fiber with the coating layer stripped is very fragile, and the use of heat shrinkable tube can protect the optical fiber fusion splice. 
③Turn on the power of the Furukawa S176 fusion splicer, use the preset 42 programs to perform the fusion, and remove the dust in the fusion splicer in time and after use, especially the fixtures, the dust in the mirrors and the V-groove, and the broken fiber. . CATV uses conventional single-mode fiber and dispersion-shifted single-mode fiber. The working wavelength is also 1310nm and 1550nm. Therefore, the appropriate fusion splicing procedure should be selected according to the optical fiber and working wavelength used by the system before fusion splicing. If there are no special circumstances, the automatic welding procedure is generally used. 
④ Make the fiber end face. The quality of the fiber end face will directly affect the splicing quality, so a qualified end face must be made before fusion splicing. Use a special wire stripper to peel off the coating, then wipe the bare fiber with a clean cotton moistened with alcohol several times with moderate force, and then cut the fiber with a precision fiber cleaver. For the 0.25mm (outer coating) fiber, The cutting length is 8mm-16mm. For 0.9mm (outer coating) optical fiber, the cutting length can only be 16mm. After cutting, carefully put the optical fiber into the V-shaped groove of the fusion splicer, close the windshield, and press the discharge button of the fusion splicer. The splicing can be automatically completed, which only takes 11 seconds. 
⑥ Remove the optical fiber and heat the heat shrinkable tube with a heating furnace. Open the windshield, take the optical fiber out of the fusion splicer, and place the heat shrinkable tube in the center of the bare fiber and heat it in the heating furnace. The heater can use 20mm miniature heat shrinkable tubing and 40mm and 60mm general heat shrinkable tubing. It takes 40 seconds for 20mm heat shrinkable tubing and 85 seconds for 60mm heat shrinkable tubing. To
⑦Fixed fiber. Reel the spliced optical fiber onto the fiber receiving tray. When reeling the fiber, the larger the radius of the coil, the greater the arc, and the smaller the loss of the entire line. Therefore, a certain radius must be maintained to avoid unnecessary loss when the laser is transmitted in the fiber core. To
⑧ Seal and hang. The external refill box must be sealed well to prevent water ingress. After the fusion splice box enters water, the optical fiber and the optical fiber fusion splice point may be soaked in water for a long time.
2, optical fiber test
The optical fiber is set up and the test is completed after the fusion splicing. The instrument used is mainly an OTDR tester or a light source optical power meter, using the FTB-100B portable Chinese color touch screen OTDR tester from Canada EXFO Company (the dynamic range is 32/31, 37.5/ 35, 40/38, 45/43db), you can test the position of the fiber breakpoint; the overall loss of the fiber link; understand the loss distribution along the length of the fiber; the joint loss of the fiber connection point. 
In order to test accurately, the pulse size and width of the OTDR tester should be selected appropriately, and set according to the index of refractive index n given by the manufacturer. When judging the fault point, if the length of the optical cable is not known in advance, it can be placed in the automatic OTDR first to find out the general location of the fault point, and then placed in the advanced OTDR. Select a smaller pulse size and width, but should correspond to the length of the optical cable. The blind area should be reduced until it coincides with the coordinate line. The smaller the pulse width, the more accurate it is. Of course, when the pulse is too small, the curve shows noise, which should be just right. Then there is the addition of a fiber probe, the purpose is to prevent blind spots in the vicinity that are not easy to detect. When judging the breakpoint, if the breakpoint is not at the junction box, open the nearby junction box, connect the OTDR tester, and test the exact distance between the fault point and the test point. It is easy to find the fault point by using the meter mark on the optical cable . When using the meter mark to find the fault, there is also a twisting rate problem in the twisted optical cable, that is, the length of the optical cable and the length of the optical fiber are not equal, the length of the optical fiber is about 1.005 times the length of the optical cable, and the above method can be successfully eliminated. Multiple breakpoints and high loss points.