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How to reduce the loss of optical fiber in applications

Subordinate Classification:News CenterRelease Time:2017-08-30
Fiber transmission loss characteristics are one of the most important factors in determining the optical network transmission distance, transmission stability and reliability. There are many reasons for the loss of fiber transmission. Among the construction and maintenance of optical fiber communication networks, the most noteworthy is the causes of transmission loss caused by fiber use and how to reduce these losses. The transmission losses caused by the use of optical fiber are mainly connected loss (loss of fiber, loss of welding loss and movable joint loss) and loss of non-connection loss (bending loss and other construction factors and application environment).
1, continuous loss and its solution
1.1 Continued loss
The splice loss of the optical fiber mainly includes three kinds of welding loss and movable joint loss caused by the intrinsic loss caused by the intrinsic factor of the optical fiber and the non-intrinsic factor.
(1) The inherent loss of the fiber is mainly due to the inconsistency of the fiber field field; the core diameter mismatch; the core section is not round; the core and the cladding concentricity are four points; the most influential is the mode field diameter is inconsistent.
(2) welding loss non-intrinsic factors of the welding loss mainly by the axial dislocation; axis (angle) tilt; end separation (gap); fiber end is not complete; refractive index difference; fiber end face is not clean and the level of personnel operation, Operating procedures, welding machine electrode cleaning degree, welding parameters set, the working environment cleanliness and other factors.
(3) active joint loss of non-intrinsic factors of the activities of the joint loss of the main components by the poor quality of the connector, poor contact, not clean and welding losses with the same number of factors (such as axial dislocation, end gap, angle, refractive index difference ) Caused.
1.2 to solve the loss of the program
(1) engineering design, construction and maintenance work should be used in the same characteristics of high-quality fiber on a line as much as possible with the same batch of high-quality brand-name bare fiber, in order to match the characteristics of optical fiber, mold field diameter on the impact of fiber splice loss To a minimum.
(2) cable construction should be strictly in accordance with procedures and requirements
With the disk as much as possible to do the whole disk configuration (single disk ≥ 500 meters), in order to minimize the number of joints. Laying in strict accordance with the cable number and the end of the order of cloth, so that the loss value to a minimum.
(3) the selection of experienced and well-trained staff to continue and test
The level of the connection personnel directly affects the size of the connection loss. The connection personnel should follow the process of the fiber splicing process strictly and strictly control the loss of the joint. During the welding process, the light field reflectometer (OTDR) is used to monitor the connection loss (≤0.08dB / ), Do not meet the requirements should be re-fused. When using an optical time domain reflectometer (OTDR), the loss of the joint should be measured in both directions and the average of the two results should be obtained to eliminate the human factor error of the one-way OTDR measurement.
(4) to ensure that the environment to meet the requirements
It is strictly forbidden to open operation in dusty and humid environment. The parts and tools and materials of the cable should be kept clean. Do not let the fiber connector be damp. The fiber to be cut must be clean and free from dirt. After cutting the fiber must not be exposed in the air for too long, especially in dusty and humid environments. When the ambient temperature is too low, take the necessary temperature measures.
(5) to prepare a perfect fiber end face
The preparation of fiber end face is the most critical process of fiber connection. The improvement of fiber end face is one of the important reasons to determine the loss of optical fiber connection. High-quality end face should be flat, no burr, no defect, and perpendicular to the axis, the fiber end of the axis of inclination should be less than 0.3 degrees, showing a smooth and smooth mirror, and keep clean, to avoid dust pollution. Should use high-quality cutting knife, and the correct use of cutting knife cutting fiber. Bare fiber cleaning, cutting and welding should be tightly connected, not too long interval. Move the fiber to gently, to prevent wiping with other objects and damage the end of the fiber.
(6) the correct use of welding machine
Proper use of welding machine is to reduce fiber loss is an important guarantee and key links.
① should be in strict accordance with the welding machine operating instructions and operating procedures, the correct operation of welding machine.
② reasonable placement of fiber, the fiber placed in the V-groove welding machine, the action should be light. This is because the core diameter of 10 nm single-mode fiber, if the welding loss is less than 0.1dB, the fiber axis of the radial offset is less than 0.8nm.
③ According to the type of fiber correctly and properly set the welding parameters (pre-discharge current, time and the main discharge current, the main discharge time, etc.).
④ in use and after use should be promptly removed in the welding machine in the dust (especially the fixture, the mirror and v-groove within the dust and fiber crushing).
⑤ welding machine electrode life is generally about 2000 times, the use of a long time after the electrode will be oxidized, resulting in large discharge current leaving the welding loss value increases. At this point you can remove the electrode, with alcohol dipped in medical cotton cotton gently wipe and then installed on the welding machine, and discharge cleaning time. If the discharge current is still large after several cleaning, the electrode must be replaced again.
(7) try to use high-quality qualified activities of the connector to ensure that the connector performance in line with the relevant provisions of the activities of the connector insertion loss should be controlled at 0.3 dB / below (or even lower), additional loss of not more than 0.2 dB /
(8) the activities of the connector should be plugged well, close tight, to prevent leakage phenomenon
(9) to ensure that the active connector is clean
Construction and maintenance should pay attention to cleaning the plug and adapter (flange) and to ensure clean room and equipment environment, to prevent plugs and adapters (flanges) have dirt and dust, to minimize the scattering loss.
2, non-connected loss and its solution
2.1 Non-connected loss
The use of fiber in the non-loss caused by the main loss of wear and other construction factors and application of the environment caused by the loss.
(1) Radiation loss caused by bending When the fiber is greatly bent, the bending radius is comparable to its core diameter, its transmission characteristics will change. A large number of conduction modes are converted into radiation patterns, no longer continue to transmit, but into the cladding layer or cladding absorption, resulting in additional loss of fiber. The bending loss of the fiber has two types: macro bending loss and micro bending loss.
(1) The additional losses caused by the bending (radius) of the fiber with a radius of curvature greater than that of the fiber are mainly due to the bending of the routing and laying; the bending of the fiber optic cable Circle, a variety of take the bend, natural bending); joint box in the fiber of the disk, the engine room and equipment, such as the coiled fiber.
② Micro-bend loss Fiber-optic axis to produce μm-level bending (micro-bend) caused by additional losses, the main reasons are: fiber into a cable, the surface of the small irregular surface caused by uneven stress and the formation of random microbend; Core and cladding interface is not smooth formation of the micro-bend; cable laying, uneven tension throughout the formation of the micro-bend; fiber by the side of the uneven pressure and the formation of micro-bend; fiber encountered temperature changes, due to heat Expansion and contraction formed by the micro-bend.
(2) other construction factors and application environment caused by the loss
① non-standard cable caused by the loss of the shelves. Layer-type loose-type structure of the cable is easy to produce such losses, because one is the cable on the shelves of multiple loose tube twist each other; the second is the use of cable ties loose tube to the joint box of the fiber tray Mouth, so that the loose tube appears sharp bend; the third is the cable when the metal reinforcement components and fiber loose tube appear dislocation. These factors can cause increased wear and tear.
② heat loss caused by heat shrinkage. The main reason is that one is the quality of the hot melt protection tube itself, after the hot melt distorted, resulting in bubbles; the other is the welding machine heater heating, heating parameters set improperly, resulting in hot melt protection tube deformation or bubble ; The third is the heat shrink tube is not clean, there are dust or gravel, hot melt when the point of damage, causing increased wear and tear.
③ direct buried cable is not standardized construction caused by the loss. The reason is that one is the depth of the cable is not enough, by the load after rolling damage; the other is the cable routing improper choice, due to environmental and terrain changes to the cable beyond its allowable load range of external forces; the third is the cable trench Uneven, the cable appears arched, hang the phenomenon, after the backfill residual stress; the other four other causes of damage to the outer sheath of the cable and water, resulting in hydrogen damage.
④ overhead cable is not standardized construction caused by the loss. The main reason is that one is in the cable laying construction, the cable to play a small circle, bending, twisting and playing back, pulling when pulling, there is a surge, the moment the maximum traction is too large; the second is the cable hook used improperly, The cable is not consistent with the direction of the snake bend, the interval is too sparse, the cable is too large due to the vertical force; the third is to stay in the rod on the cable is not fixed firmly, the cable by long-term external force and short-term impact and damage; Fourth, the cable is too tightly armed, did not consider the natural elongation of the cable; the other five causes the outer sheath of the cable damage and water, resulting in hydrogen damage.
⑤ pipe cable is not standardized construction caused by the loss. The reason is that one is the cable with net sets of law when the deployment, the traction speed control is not good, the cable appears playing back button, surge; the second is put on the cable, no deployment of plastic pipe, cable was scratched; Is caused by other causes of damage to the outer sheath of the cable and water, resulting in hydrogen damage.
⑥ room, equipment, pigtail fiber and fiber jumper banding, coiling is not standardized, there are cross-winding phenomenon caused by loss.
⑦ fiber connector box quality is poor, the connector box package, the installation is not standardized, due to external effects caused by damage to the joint box, resulting in water and hydrogen loss.
⑧ cable in the erection process of the tensile deformation, then the box clamping the cable pressure is too large, the capacity of the disk in the hot melt pipe pressure too tight, the fiber tray in the fiber coil is not standardized and other losses caused.
2.2 to solve the problem of non-connected loss
(1) engineering survey design, construction, should choose the best route and line laying.
(2) formation, choose a high-quality construction team to ensure the quality of construction, which is essential, any construction of the negligence are likely to cause fiber loss increases.
(3) design, construction, maintenance, and actively take effective cable line "four anti" measures (lightning, anti-power, anti-corrosion, anti-mechanical damage), strengthen the protection work.
(4) use the bracket to hold the cable laying cable, do not put the cable down after the use of a similar way from the spool on the layout of the cable, do not let the cable by the torque. When laying the cable, should be unified command, strengthen contact, to adopt a scientific and reasonable traction method. Arming speed should not be too fast; continuous arming length should not be too long, if necessary, should be used down "8" word, from the middle to the two cloth. In the corner, etc. may damage the cable where the place must be careful and take the necessary means of protection. Encountered in the downtown area, such as cable laying cable, such as the need for temporary placement of the cable, the use of 8-shaped disk to stay, do not let the cable by the torque.
(5) When laying the cable, it is necessary to pay attention to the limit of the rated tension and bending radius. In the cable laying construction, it is strictly forbidden to make small circle and bend, twist and prevent the buckle and surge phenomenon. Traction does not exceed 80% of the allowable cable, instantaneous maximum traction does not exceed 100%, traction should be added to the reinforcement of the cable, with particular attention can not pull and kink phenomenon. When the cable bending corner radius should not be less than 15 to 20 times the outer diameter of the cable.
(6) Do not use poor, especially heat-shrink tubing that has been bent, so that the casing will generate stress internally during heat shrinkage and exert an increase in wear on the fiber. Carry, storage casing, pay attention to clean, do not let foreign body into the casing.
(7) in the follow-up operation, according to the size of the tray to determine the length of stripping, as far as possible to peel some of the longer fiber so that coiled in the closing (disk length of 60 ~ 100cm). Should pay attention to the fiber after the welding (fiber optic disc and fixed), disk, the larger the radius of the circle, the greater the curvature of the whole line, the smaller the loss, so be sure to maintain a certain radius (R ≥ 40mm) , To avoid unnecessary losses, the number of large number of fiber optic cable connection in the shelter. Continued operation, the cable cutter into the depth of the cable to grasp, do not crush the loose tube to make the fiber force. The use of qualified joint materials and in accordance with the norms and operational requirements, the correct package, install the connector box.
(8) the machine room as clean as possible, the pigtail should be surrounded by band protection, or alone to the pigtail using a line, not between the pigtail or between the other lines of cross-winding, but also try not to pigtail (even Temporary use) placed on the foot where you can step on. Fiber optic cable terminal to avoid jumper in the alignment of the right angle, in particular, should not use the plastic belt jumper into a right angle, or fiber due to long-term stress caused by increased wear and tear. Jumper in the corner should take the curve, bending radius should not be less than 40mm. Laying to ensure that the jumper is not force, not pressure, in order to avoid long-term stress fatigue jumper. When the fiber is operated (ODF), do not tighten the tail fiber.
(9) to strengthen the daily maintenance of fiber optic cable lines and technical maintenance work.
Fiber Optic Home (FTTH) is the inevitable development of the information age, optical network interconnection is the digital earth tomorrow. With the large number of various types of optical fiber communication network construction and operation, face and solve the use of optical fiber caused by the transmission loss problem in the optical fiber communication engineering design, construction, maintenance greatly improve and optimize the optical fiber communication network transmission performance.