Fiber Optic Cable Fusion Splicing, The Ultimate Guide

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From the perspective of the main factors affecting fiber optic cable fusion splicing loss, the problems to be noted in fiber optic cable fusion splicing and the method of testing splicing are introduced to provide a reference for future fiber optic splicing.

The factors affecting optical cable splicing loss can be divided into intrinsic and non-intrinsic factors.

The intrinsic factors are some factors of the fiber itself, such as varying mode field diameter of the two threads, fiber core diameter mismatch, the core cross-section is not round, core and cladding concentricity, etc., where the varying mode field diameter has a more significant impact on fiber optic cable fusion splicing loss, the International Consultative Committee on Telegraphy and Telephone (CCITT) G652 The standard stipulates that the direct nominal value of the mode field of the 1310nm window is within 9~10pm, and the deviation shall not exceed 10% of the little weight.

In this tolerance range, a fiber with a mode field diameter of 11 pm and another fiber with a mode field diameter of 9 pm are fused under perfect splicing conditions, and the theoretically calculated value of splice loss at the splice can reach 0.17 dB, which is higher in the actual splice.

Non-intrinsic factors refer to the impact of various human factors and equipment on the fusion loss, such as the fusion of the fiber is not aligned so that the two fiber core axis radial shift of 2 Pm fusion loss of theoretical value can reach 0.74dB.

The theoretical value of two fiber axial tilt in the tilt angle of 1-degree fiber cable splicer loss can reach 0.46dB.

The theoretical value of optical cable splicing can reach 0.21dB when the sum of fiber end cutting tilt angle comes to 1 degree.

Splicer operation level also affects the fusion loss. There is information about the exact equipment operated by different people, ten fusion points of the total loss difference of up to 0.32dB.

In addition, the coiling of the fiber in the wiring kit, the coiling of the reserved fiber optic cable, the fusion splicing parameters of the fusion splicing machine settings, and the cleanliness of the discharge electrode, as well as the splicing work environment are clean, etc. on optical cable splicing loss have different degrees of impact.

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Many factors affect fiber optic cable fusion splicing loss, only to eliminate the impact of various undesirable factors to fundamentally reduce the fusion loss of fiber optic splices, thereby reducing fiber optic line transmission loss.

According to practice and relevant information, it is recommended that the following measures can be taken to reduce the fusion splicing loss of optical fiber connectors.

(1) to strictly splicing process while fusing fiber optic cable fusion splicing loss, fusion loss does not meet the requirements of the joint must be re-fiber cable splicer, the number of repeated fusion splicing to 3 to 4 times is appropriate after three consecutive fusion splicing is still not much improvement, in the exclusion of fusion machine generally causes as long as it reaches three times Fusing in the most coin value can be, do not repeatedly fuse to avoid excessive consumption of optical fiber weld tray to bring adverse effects.

Coiled in the wiring package on the fiber storage disk, fiber residual length should be not less than 60cm, spiral circle radius to be as large as possible, splicing if the same fiber on the previous joint fusion loss is harmful, then the immediately following a joint fusion loss value can be larger, if the fusion loss value of the front joint is more significant. Immediately following a joint fusion, the loss value shall be more negligible or negative to avoid the end of the fiber optic cable Fiber damage to the end of the fusion loss in the fusion of optical cable preparation work can cut off some of the cable head.

(2) Splicing fiber must be in a clean environment, such as in a construction vehicle or small tent, in a dusty and humid climate unsuitable for fusion splicing.

Fiber optic splicing parts and splicing tools must be kept clean and dry, the preparation of the fiber optic cross-section must be wiped first after cutting, and the practice of the fiber cross-section must be pure without dirt. It should not be exposed to air for long and not let it get wet.

The fiber section should be cut neatly, and the inclination angle between the two teams should be less than 0.3 degrees.

The fiber is placed into the V-slot of the fusion splicer when the action should be light; this is because the core diameter of 10 Pm single-mode fiber if the fusion loss is less than 0.1dB, the radial offset of the fiber axis to be less than 0.8Pm.

(3) the ends of the cable into the junction box must be fixed securely so as not to hang the junction box due to the twisting of the fiber optic connector position misalignment, resulting in the loss of the standard measurement value is enormous.

In the fusion construction often found fusion, the fusion loss value measured under the 1550nm window meets the requirements. Still, after sealing the junction box to retest, the value of the loss of the joint is significant, which is usually caused by the fiber joint position misalignment; this can be changed in the 1310nm window retest if the measured value is small is the fiber joint position misalignment, to recoil the remaining length of the fiber, if the large is the fusion problem, to re To avoid this phenomenon, the fiber optic splice and fiber residual length must be firmly fixed in the fiber storage plate with self-adhesive tape.

The coiling diameter of the remaining length of the fiber optic cable on both sides of the junction box straight control at about 40cm should not be too small to avoid damage to the fiber in the unified due to excessive distortion.

(4) fusion splicing machine and cutting tools, such as optical cable splicing loss, also have a more significant impact; fusion splicing according to the type of fiber correctly and reasonably sets the fusion parameters, such as pre-melt current, pre-melt time, and the primary fusion current, central fusion time, etc.

The fiber cable splicer should be removed promptly when the fusion splicer V groove and cutting tool in the fiber debris and dust. After using the fusion splicer, remove the dust on the machine shell; if used in a humid environment, you must also do the moisture-proof treatment.

The service life of the fusion splicer electrode is generally about 2000 times, requiring each discharge fusion 20 times after running the cleaning program to clean the electrode, but in the case of clean fiber and good splicing conditions can be fused about 60 times discharge cleaning, poor working conditions can be fused 30 to 40 times after the discharged cleaning, to extend the service life of the electrode and not to increase the fusion loss. The use of a long-time fusion machine electrode above a layer of grayscale will lead to a large discharge current and increase the value of fusion loss, this time you can remove the electrode, gently wipe it with alcohol cotton, and then install it on the fusion machine and discharge cleaning once, if the discharge current is still significant after several cleaning, it is necessary to replace the electrode.

In addition, it is to select a solid dust-proof ability suitable for fusion splicing machine in the wild night operations to fiber optic cable fusion splicing.

In addition, the choice of fiber optic cable, because the fiber is disconnected at a certain point after the disconnection of the mode field diameter is the same, so the fusion splicing at the disconnection of the fiber optic mode field diameter on the fusion loss of the most negligible impact, so the cable manufacturer must be required to use the same production batch of high-quality brand-name bare optical fiber according to the order length of continuous production, according to the specified disk length will be disconnected from the cable winding disk, the winding of the cable disk serial number and clear A, B end (disconnected in the previous tray if the B end in the immediately after a range of tray for the A end), shall not jump number or confusion.

Laying according to the determined route according to the numbering order of the unified disk and the B end of the previous disk cable to be connected to the A end of the next disk, to ensure that the disconnection fiber optic cable fusion splicing, to avoid the inconsistency of the fiber optic mode field diameter and lead to fiber optic cable fusion splicing loss is large The shortcomings of the fiber optic cable fusion splicing.

And in laying the traction speed wood greater than 20m/min step-less speed regulation of the mechanical traction method, traction force shall not exceed 80% of the allowable tension of the cable. The maximum instantaneous traction force does not exceed 100%; the traction force must be applied to the reinforcement in the line after the erection of the cable by the maximum load elongation rate should be less than 0.2% to avoid the traction process of fiber optic stress and distortion, in the necessary to make Fiber optic cable traction end, the construction of the bending radius of the cable should be more significant than 25 times the diameter of the thread (DL/T 788-2001), the cable must be released from the top of the unified plate and maintain a loose arc and no twist, forbidden to play a small circle bending twisting, etc., to minimize the chance of damage to the fiber in the cable, to avoid damage to the thread at the end of the line and increase the splice fusion loss.

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A fusion splicing machine in the fusion of a fiber core after the fusion point is generally given the estimated fade value; the estimate is naturally the local fiber core visual monitoring, that is, by observing the good or lousy fiber butt to estimate the fade value. This is not very accurate.

In particular, the fusion splicer in the Riyubu work, the cleanliness of its working environment can not be effectively guaranteed, coupled with fiber quality, climatic conditions and the fusion splicer’s state and other complex factors, often make the estimated value and the actual value of a significant deviation between. Even if the splicing quality is good, for not very skilled operators, the process of residual disc fiber may also be negligent and cause more significant additional loss or even broken thread.

To ensure the quality of fiber optic cable splicing, to avoid rework, the splicing process should generally be monitored with an optical time domain reflectometer (OTDR); this instrument uses the backward scattering method to measure the fusion loss value at the fiber splice.

Controlled measurement with OTDR, but according to the tester’s location and the test’s exact requirements, can be divided into the following three methods.

OTDR in the fiber optic splicing direction before a splice point for testing, the instrument is always ahead of the transfer. Using this monitoring method, the test and splice points are always only separated by a tray of cable length, testing the splice decay accurately and easy to communicate.

A tray of fiber optic cable is generally only 2 ~ 5km. The general terrain of the intercom can ensure contact. This test method also has disadvantages.

OTDR to each test point to test, back and forth to move the instrument is both laborious and time-consuming and is not conducive to the protection of the device, such as test points without a reliable power supply to bring their own generators, especially lines away from the highway, the terrain is more complex trouble.

OTDR position is still the same as the “forward one-way” monitoring, but at the beginning of the direction of the connection will be two optical fibers short, respectively, to form a circuit.

Since the loopback point is added, the bidirectional value of the splice attenuation can be measured on the OTDR.

The advantage of this method is that the splice can be accurately evaluated.

Due to the test principle and fiber structure, unidirectional monitoring with OTDR can result in dishonest gain and correspondingly false significant attenuation.

For a connector, the mathematical average of the attenuation values in both directions can accurately reflect its actual attenuation value.

For example, if the attenuation of a connector is 0.20dB from A to B, and -0.16dB from B to A, the attenuation of this connector is actually (0.2+(-0.16))/2=0.02dB.

However, if only the one-way value of 0.2dB to judge, it may be wrongly considered as unqualified, pinch off, and reconnecting, which will be time-consuming and laborious.

For the same connector, if you connect again, from B to A measured loss of 0.02dB, from the surface of a good connection generally will be judged as qualified, but if the value of the A to B test is 0.38dB, the actual value of this connector in 0.2dB, large, should be reconnected. So the two-way test avoids the one-way measurement that can not be measured in time to fusion loss and lead to later rework consumption value that exceeds the standard of the joint.

This two-way forward monitoring is pervasive, especially for new operators, new fusion splicing for domain new brand of fiber optic cable; this test method facilitates the operator to choose the best procedure for the fiber spliced so that the fusion splicer work in good condition, and can understand the fiber optic cable fusion splicing fir blanket out of the estimated value, one-way test value and the actual decay value between relationship for one-way monitoring.

Disadvantages of the two-way forward test.

First, the same as the one-way forward test needs to move the test instrument, which is time-consuming and laborious constantly.

Second, the two-way test increases the workload, slowing down the speed.

Third, for the more extended relay section of the line, 40km from the beginning of the connection, such as a tray of cable length of 2km, then 42km from the beginning of the test, the measured forward value is estimated at 2km, measured reverse fading is measured 82km at the fading value. Due to the long distance, the signal is weaker than the reverse value and can not be accurately tested. To continue the two-way monitoring, it is necessary to loop back to the other end so that, eventually there must be a head that can not be monitored in both directions.

In fiber optic cable fusion splicing construction, effective liaison between testers and splicers is one of the necessary conditions to ensure the quality and progress of construction.

In the early days, metal signal lines were inside the fiber optic cable, and the communication problem was well solved. And now, due to the need for lightning protection, fiber optic cables generally do not have metal signal lines inside, especially in power communication systems. More metal-free ADSS fiber optic cable avoids the accumulation of induced lightning currents in the fiber optic cable. This makes it impossible to contact magnetic phones.

Currently, there are two general ways to solve this problem.

(1) Use cell phones to communicate in areas where cell phone signals can be covered, such as within cities and on the outskirts of cities. The cell phone can make the testers and the relay personnel keep in touch with each other at any time, which is easy to organize and coordinate and is conducive to improving efficiency.

(2) Contact by optical telephone—the agreement to use an optical fiber connected to the optical phone as a contact line. Of course, the last fiber for contact in the fusion and coiled fiber can not be monitored because of the inability to contact. Even so, the possibility of problems is significantly reduced (in the case of a 16-core fiber optic cable, the probability of the issues is reduced to less than 1/16 of the original).

The practice has proved that this monitoring to ensure quality and reduce rework is effective. Of course, communication contacts should depend on the specific situation, such as mobile network coverage can not be covered, Unicom network may be protected, staff can carry different networks of cell phones respectively.

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Fiber optic cable fusion splicing and testing can effectively ensure the smooth implementation of fiber optic cable splicing construction. The purpose is to minimize the fusion splicing loss, and reduce the transmission loss of optical cable lines, thereby improving the transmission quality of the optical transmission system.

As long as the fiber optic cable fusion splicing for the text and the appropriate test method can be selected according to local conditions to reduce the fusion splicing loss to a certain extent, the transmission system with high-quality fiber optic cable transmission line for power communications and power automation data transmission to provide a reasonable basis.