There is a bright spot in the middle of the optical cable splice

A bright spot in the middle of a fiber splice usually indicates light leakage due to misalignment, poor fusion, or contamination at the splice point.Possible CausesMisalignment or Poor Fusion: If the fiber cores are not perfectly aligned during fusion splicing, light can escape at the splice, creating a visible bright spot. This can result from improper cleaving, incorrect arc calibration, or mechanical stress during splicing .Contamination: Dust, oil, or fingerprints on the fiber ends can prevent proper fusion and allow light to leak through the splice . Even a small particle can cause significant signal loss and a visible bright spot.Microbends or Macrobends: Excessive bending near the splice can cause light to escape through the fiber jacket, making the splice appear brighter when using a visual fault locator (VFL), .Splice Defects: Cracks, bubbles, or gaps in the splice can also produce a bright spot. These defects are often visible under a microscope or video inspection probe .Troubleshooting StepsVisual Inspection: Use a microscope or video inspection probe to examine the splice for contamination, misalignment, or defects .Test with a VFL: A visual fault locator can help identify the exact location of light leakage and confirm whether the splice is the source of the problem .Measure Splice Loss: Use a power meter or optical loss test set (OLTS) to quantify the loss at the splice. A good splice typically has less than 0.1 dB loss .Corrective Actions: Depending on the findings, you may need to clean the fiber ends, re-cleave, or re-fuse the splice. For persistent issues, replacing the splice with a new fusion or mechanical splice may be necessary .Prevention TipsEnsure proper cleaving and alignment before splicing.Perform arc calibration on the fusion splicer for current environmental conditions.Keep fiber ends clean and free of dust or oil.Avoid excessive bending or strain on the fiber near the splice .By following these steps, you can identify the cause of the bright spot and restore optimal signal transmission through the fiber splice.