Optical fiber communication technology is a new technology that has developed rapidly in the past 20 years. Because optical fiber communication transmits a large amount of information, a fast rate, and the digitization of information, the transmission of digital signals makes it possible to transmit information such as broadband image signals and computer networking. So, what are the process steps for fiber optic splicing? What are the precautions for fiber optic splicing?
Fiber splicing
What are the process steps for fiber optic splicing?
1. Optical fiber connection
(1) Optical fiber connection. The principle that should be followed for optical fiber splicing is: when the number of cores is equal, it should be connected with the corresponding color optical fiber in the bundle tube.
(2) There are three methods of optical fiber splicing: fusion splicing, active connection, and mechanical connection. Welding is used in most of the work. The joint loss by this welding method is small, the reflection loss is large, and the reliability is high.
(3) The process and steps of optical fiber connection:
① Strip the optical cable and fix the optical cable into 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, and put the optical cable into the splice box. When fixing the steel wire, it must be pressed tightly without loosening. Otherwise, it may cause the fiber optic cable to roll and break the fiber core.
②Split the fiber through the heat shrinkable tube. Separate the fibers of different bundles and colors and pass them through the heat-shrinkable tube. The stripped fiber is very fragile, use heat shrink tubing to protect the fiber splice.
③Turn on the power of the fusion splicer, use the preset program to splicing, and remove the dust in the fusion splicer in time during and after use, especially the fixture, dust and fiber fragments in each mirror surface and v-groove.
The fibers used by catv include conventional single-mode fiber and dispersion-shifted single-mode fiber, and the operating wavelengths are also 1310nm and 1550nm. Therefore, before splicing, an appropriate splicing procedure should be selected according to the optical fiber and working wavelength used by the system. Unless there are 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 quality of the connection, so it is necessary to make a qualified end face before fusion splicing. Use a special wire stripper to peel off the coating layer, then wipe the bare fiber with alcohol-dipped cleaning cotton several times with moderate force, and then use a precision fiber cutter to cut the fiber. For 0.25mm (outer coating) fiber, The cutting length is 8mm-16mm. For 0.9mm (outer coating) fiber, the cutting length can only be 16mm.
⑤Place the optical fiber. Put the optical fiber in the v-shaped groove of the fusion splicer, carefully press the optical fiber pressure plate and the optical fiber clamp, set the position of the optical fiber in the pressure plate according to the fiber cutting length, and close the windshield, the fusion can be automatically completed.
⑥ Remove the optical fiber and heat the heat shrinkable tube with a heating furnace. Open the draft shield, take the fiber out of the fusion splicer, place the heat shrink tube in the center of the bare fiber, and place it in a heating furnace for heating. The heater can use 20mm micro heat shrink tube and 40mm and 60mm general heat shrink tube, 20mm heat shrink tube takes 40 seconds, 60mm heat shrink tube takes 85 seconds.
⑦Fix the disc. Coil the spliced optical fiber onto the optical fiber receiving tray. When coiling the fiber, the larger the radius of the coil and the larger the radian, the smaller the loss of the entire line. Therefore, a certain radius must be maintained to avoid unnecessary losses when the laser is transmitted in the core.
⑧ Seal and hang. The field connection box must be sealed to prevent water from entering. After the fusion splicing box enters the water, due to the long-term immersion of the optical fiber and the optical fiber splicing point in the water, the attenuation of some optical fibers may increase first. Put on stainless steel hooks and hang on the hanging wire. At this point, the optical fiber fusion is completed.
2. Optical fiber test
The measurement of optical fiber loss is very important, it is directly related to the quality of optical fiber communication, and can detect possible fault points in time.
The optical fiber is erected, and the test work is done after the fusion is completed. The instrument used is mainly the otdr tester, which can test the position of the fiber breakpoint; the whole loss of the fiber link; understand the loss distribution along the length of the fiber; the splice loss of the fiber splicing point .
In order to test accurately, the pulse size and width of the otdr tester should be appropriately selected and set according to the index of the refractive index n value 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 put it in the advanced otdr.
Select a smaller pulse size and width, but it should correspond to the length of the optical cable. The blind area is reduced until it coincides with the coordinate line. The smaller the pulse width, the more accurate it is. Then there is the addition of the fiber detection disk, the purpose is to prevent the blind spot in the vicinity from being easily found.
When judging the breakpoint, if the breakpoint is not at the junction box, open the nearest junction box, connect the otdr tester, test the exact distance between the fault point and the test point, and use the meter mark on the optical cable to easily find the fault point. .
When using the meter scale to find faults, there is also a twist rate problem for the twisted optical cable, that is, the length of the optical cable is not equal to the length of the optical fiber, and the length of the optical fiber is about 1.005 times the length of the optical fiber. The above method can be successfully eliminated. Multiple breakpoints and high loss points.
What are the precautions for fiber optic splicing?
1. Pay attention to the depth of feed when stripping the optical cable
The key to stripping the outer sheath of the optical cable is to master the depth of the sheath cutting knife, otherwise fiber breakage will easily occur. In actual operation, the sheath cutting knife should be rotated while observing the incision. If a white polyester tape can be seen, the knife should be stopped and the cutting knife should be removed. This step is a skilled process, and it takes many practice to master the depth of feed.
2. The fixing of the optical cable and the stripping of the fiber core bundle
After the optical cable is stripped, fix the optical cable in the optical cable splice box, open and strip the fiber core bundle, and do all the preparations before the optical fiber splicing.
At this point it should be noted:
a) The core bundle tube cannot be twisted. Before fixing the optical cable, you must pay attention to the position of the core bundle tube. When the reinforcing member passes through the fixing screw, the underside of the reinforcing member must be a filling bundle tube, not a fiber core bundle tube. The core bundle tube must be in the position where the reinforcing member enters the optical fiber. The same side of the receiving tray cannot be twisted on the reinforcement.
If the reinforcement is pressed on the core bundle tube, the core bundle tube will be deformed by force, which will cause excessive loss, and the optical fiber in the core bundle tube will also break due to long-term stress, leaving hidden dangers to the project.
b) The length of the reinforcement should be appropriate. After the position of the core bundle tube is determined, the optical cable can be fixed. The fixation of the optical cable must ensure that the position of the optical fiber in the splice box will not be loosened, so as to avoid the problem of increased optical fiber loss or fiber breakage due to the movement of the optical cable position.
The fixing of the optical cable is divided into the fixing of the reinforcement and the fixing of the rest of the optical cable. The fixing of the reinforcement should pay attention to its length. If it is too long, it will not fit in the splice box; if it is too short, it will not be able to fix the optical cable.
Generally, when cutting the strength member, the distance between the splint for fixing the optical cable and the screw for fixing the strength member should be equal to the length left. The fixing of the rest of the optical cable is to tighten the splint with screws after the reinforcement is fixed, and fix it tightly at the optical cable entrance of the splice box.
c) The stripping length of the core bundle tube should be appropriate. After the optical cable is fixed, the fiber core bundle can be opened and stripped. If the stripping length is too long, it will reach the groove of the fiber heat shrinkable tube, and the remaining fiber will be damaged when the fiber is coiled. .
Therefore, it is generally advisable to open and strip it past the two fixing bayonets. At this length, the fiber core bundle will not cause any mechanical damage to the fiber, and it can also be well fixed. However, the clips should not be too tight when fixing, otherwise the optical fibers in the core bundle tube will increase the loss due to the force, and the optical fibers will break after a long time, leaving hidden dangers to the project.
3. Fusion of optical fibers
The splicing of the optical fiber is directly related to the quality and life of the project, and the key lies in the preparation of the optical fiber end face. The fiber end face is smooth, without burrs or defects, the fusion splicer can accept the confirmation well, and can make the joints that meet the engineering requirements. Meet engineering requirements. In the process of making the fiber end face, when stripping the fiber coating layer, the stripper should be perpendicular to the axis of the fiber to ensure that the stripper does not scratch the fiber;
When cutting the optical fiber, it is necessary to strictly follow the procedures. When using the end face cutter, the cutting length should be accurate, the action should be fast, and the force should be skillful, so as to ensure that the optical fiber is broken, not crushed; when taking the optical fiber, it is necessary to Make sure that the optical fiber does not touch any objects and avoid bumping the end face. The end face obtained by doing this is smooth and qualified. The fusion splicer is the key equipment for optical fiber fusion, and it is also a high-precision and expensive equipment.
In the process of use, it must be operated in strict accordance with the regulations, otherwise it may cause heavy losses. Special attention should be paid to the operation procedure of the fusion splicer, and the length setting of the heat shrinkable tube should be consistent with the requirements.
4. Protection of residual fiber
After the optical fiber is spliced, it is necessary to protect the optical fiber with a heat-shrinkable tube and to reserve the remaining fiber.
Attention should be paid to:
a) During the fiber coiling process, the bending radius of the coiled fiber should not be too small, generally not less than 4mm. If the bending radius is too small, it is easy to cause excessive refraction loss and increased dispersion. Over time, fiber breakage may also occur.
b) When coiling the fiber, pay attention to the twisting direction of the fiber, which is generally an inverted "8" shape. Be careful not to twist the fiber. After the coil is completed, put all the fiber under the baffle of the receiving tray to avoid damage to the fiber during packaging.
5. Sealing of the joint box
In practical engineering, the sealing of optical cable splice box is very important. Because the surface of the optical fiber is prone to micro-cracks after the splice box enters the water, the optical fiber will break after a long time, and most of the splice boxes are buried underground, so the sealing of the splice boxes must be done well.
The sealing of the splice box is mainly the sealing of the two parts between the optical cable and the splice box and the upper and lower covers of the splice box. When sealing the optical cable and the splice box, first grind the optical cable sheath at the sealing place, and use gauze to grind the outer sheath perpendicular to the axial direction of the optical cable, so that the optical cable and the sealing tape can be combined more tightly and sealed better. . The sealing between the upper and lower cover plates of the joint box is mainly to pay attention to that the sealing tape should be evenly prevented from being in the sealing groove of the joint box, and the screws should be tightened without leaving a gap.
The above are the key points of the relevant knowledge about optical fiber splicing that we have brought to you, and I hope to give your friends help. In fact, the growing maturity of optical fiber transmission technology and the need for multi-functional development of cable television in the future make more and more cable television stations use optical fiber to transmit cable television signals. Optical fiber splicing is an important process with a large amount of engineering and the most complex technical requirements in the optical fiber transmission system, and its quality directly affects the transmission quality and reliability of the optical fiber line.