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POF Measurement: Cutback Method

POF Measurement: Cutback Method

The cutback method is a destructive method of measuring attenuation of long run lengths of optical fiber. It typically takes the following form:

Diagram showing both stages of the cutback test method.
  1. Set up a transmitter and receiver on both ends of the fiber optic cable to be tested, with a known transmitter power, P0.
  2. Measure the power received, P1 (Part 1 in diagram).
  3. Cut the fiber, leaving 1 to 2 meters at the transmitter end, and repeat test, measuring the power received, P2 (Part 2 in diagram).
  4. Use the following equation to calculate attenuation of the cable under test, in dB/km. L1 and L2 are the original and cut lengths of the fiber in meters, respectively.
Equation for calculating a fiber’s attenuation per unit length.

By cutting fiber on the receiver end, variables introduced by variations in signal launch conditions are mitigated. Note that power must be in linear units (watts), instead of dBm for this formula.

Cut Back Method POF Testing (PDF)

References

POF Data Book, Tokyo, Japan: MRC Techno Research Inc, 1993, pp.37