Fiber optic connector loss can affect testing

Fiber optic connector loss is measured using an optical loss test set or a light source and power meter, and should be compared against calculated loss budgets to ensure acceptable performance.

Methods for Testing Connector Loss

1. Optical Loss Test Set (OLTS) or Light Source and Power Meter (LSPM) This is the most accurate method for measuring connector loss. The test involves connecting a calibrated light source to one end of the fiber and a power meter to the other, then measuring the signal attenuation across the connector. Testing should be performed at the wavelength the network will operate, such as 850 nm for multimode or 1310/1550 nm for singlemode fibers, and can be done unidirectionally or bidirectionally for more precise results .
2. Visual Fault Locator (VFL) A VFL uses visible light to detect breaks, bends, or misaligned connectors. While it does not quantify loss, it helps identify physical issues that could contribute to high connector loss .
3. Fiber Inspection Probes Inspecting the connector end face for dirt, debris, or damage is essential, as contamination can significantly increase loss. Clean connectors before testing to ensure accurate measurements .

Step-by-Step Connector Loss Testing

1. Turn on the test equipment and allow it to warm up.
2. Clean all connectors and mating adapters thoroughly.
3. Set a 0 dB reference using a launch cable of the same fiber type.
4. Connect the launch cable to the source and the receive cable to the power meter.
5. Measure the loss across the connector. For patch cords, the measured loss may represent the connector itself if fiber loss is negligible. Reverse the test to measure the connector on the other end .

Acceptable Loss Limits

Connector loss is typically low, but acceptable values depend on fiber type and standards:

• Multimode fiber: Less than 3.0 dB/km at 850 nm is considered good .
• Singlemode fiber: Less than 0.5 dB/km at 1310 nm or 1550 nm is ideal . The loss budget is calculated by summing expected losses from fiber, connectors, splices, and any passive components. Measured loss should not exceed this budget significantly; otherwise, segment-by-segment testing is recommended to locate high-loss components .

Best Practices

• Always clean and inspect connectors before testing.
• Use launch and receive reference cables compatible with the fiber type.
• Perform bidirectional testing when possible to account for connector variability.
• Compare measured loss to the calculated loss budget to determine if the connector meets performance requirements . By following these procedures, technicians can accurately assess connector loss, ensure network reliability, and maintain compliance with industry standards.