Fiber attenuation dB loss finding

Determine if the loss is at the Fiber Connector termination point.

At the point of fiber Splicing or Fiber Connector Termination, all fibers usually have attenuation steps of different loss value.

By testing multiple fiber curves with an OTDR in different fiber or loose tubes of the fiber cable, if all curves show the fiber attenuation loss steps at the same location, it may be a fault at the fiber splicing or termination position.

For the attenuation loss not at the fiber splicing or termination position, some fibers were showed attenuation loss while others fibers won’t, so the fault is in the middle of the fiber optic cable line.

Using OTDR for finding

For fiber attenuation loss points close to the testing end, the distance between the fault and the nearest splice point can be measured using OTDR testing directly at the end station.

For fiber attenuation loss points far from the testing end, due to decreased testing accuracy, open the nearest Fiber Optical box, connect the OTDR for testing, and measure the approximate location of the fault point on-site combined with original construction data and direct burial route information.

In the aerial fiber optic cable lines, if the OTDR at the end station can only measure the obstacle point located between which two connectors, the obstacle can be located again from the opposite end station, and the test results in both directions can be analyzed to determine the fault point.

The end station can be understood as the start or termination site of the fiber optic cable link, that is, the site where the test operation is located. In the fiber optic fault test, OTDR will usually be tested at one end of the fiber optic link (end station), this end station can be a center room, base station, Outdoor Fiber Distribution cross-connection Cabinet and other locations with fiber access and test conditions. For example, in the center room of a community, the maintenance team can connect the OTDR from here to test the fiber optic lines in the community and connect to the outside to find the location of the fault point.

Auxiliary location methods:

After determining that the attenuation point is near a fiber splicing point or fiber connector point, open that fiber optic box and bend the fibers inside (e.g., wrap around a pen holder).

Monitor from the end station using OTDR, observe new attenuation points appearing on the backscattering curve to narrow down the search range.

It is also possible to test in the direction of the line obstacle at this fiber optic box, and due to the shorter test distance, the specific location of the obstacle point can be measured more accurately.

Fiber attenuation dB loss handling

Troubleshooting at the fiber optic box:

Open the fiber optic box, re-fusion the fibers, and take the OTDR real-time monitoring, until the splice loss meets requirements.

If the loss still doesn’t meet standards after several times of re-splices, check if the fiber buffer tube is deformed, if the coiling radius is too small or if the fiber is under pressure. If necessary, cut off a section of the fiber optic cable to re-fusion splicing of all fibers.

Mid-line fault handling:

If the fiber optic cable has cable kinking (Cable Twisting, Excessive Bending, Sharp Bends), is damaged by hard objects, or is flattened and deformed, causing pressure on the fibers, you need to cut off the damaged section of the cable and re-fusion splice.

For cable kinking fault points discovered during construction, leave appropriate slack at the fault point for subsequent handling.

If the damage is serious, you can strip off the outer sheath of the fiber cable, the deformation of the bundle tube to deal with, if necessary, the damaged bundle tube of optical fiber for splicing.

For aerial fiber optic cable lines, if there are spare cables nearby, you can use the spare cable for repair, cut off a small section before and after the fault point, with a reserved spare cable instead.

If there is no spare cable nearby or the length of the spare cable is not enough, you can replace the fiber optic cable. Replacement needs to consider the length of the fiber optic cable, attenuation range, line attenuation affluence and other factors.

Preventive methods

Before splicing or connecting, carefully inspect the remaining fiber optic cables in the fiber optic box, and take the practice of cutting off a portion of the suspect end cables to avoid subsequent problems.

During construction, pay attention to the protection of fiber optic cables to avoid excessive bending, pressure and other situations.