OTDR error of the measurement

by:Fiber Hope     2020-07-19

using optical time domain reflectometer ( OTDR) Measuring optical fiber, sometimes meet short fiber link. In the measurement of short fiber optic link often get bigger attenuation values, make the attenuation index cannot obtain a better evaluation and assessment. Why is this? With what method can obtain a better test results?

OTDR test instrument in general will have a measuring blind spot, the length of the blind area, depending on the quality of testing and the choice of pulse width, and the reflection values, amway, 9083909, JDSU commonly, EXFO - 150, - 200 kind of imported machines, under 5 n seconds pulse width is 20 meters. 100 ns pulse width in the 70 meters, 200 ns in the 140 meters, 1 us at about 180 meters. Domestic some machines, can appear even cannot measure the graph, found the problem such as the node and end point.

due to the short fiber link ( Generally less than 1 km) Has certain volatility, OTDR measurement to curve, these small volatility affects the final numerical calculation. In the description of the OTDR technology parameters, the one about the linear degree of index, general OTDR the index is 0. 05 dB/dB, in fact, the range of OTDR curve are described in the index. So for short fiber, OTDR measurement accuracy is challenged. This problem is also a common problem facing the OTDR, so with what method to reduce this effect?

1, add 2 km test false fiber ( Extended OTDR test line) 。

due to join the 2 km test false fiber, optical fiber length is growing, the impact will be reduced. Should be able to obtain a more satisfactory results. But as a result of increased length, it also introduces the test error, this method still has a certain error test method. But as the test data of the validation project quality is considerable reference value.

2, link loss is measured with light source, optical power meter, using OTDR length measurement.

due to the light source, optical power meter is used to measure the link loss close to standard loss measuring method, so the loss measuring precision is improved. Of course for short fiber as adopt resolution precision grade higher optical power meter, in order to reduce error. Length measurement using OTDR. With loss values divided by the length per unit length can be attenuation values.

3, OTDR measurement curve as a reference only, OTDR measurement focuses on link obstacles.

short fiber optic measurement, OTDR measurement curve is best used as a reference only, as the basis of qualitative analysis, and not as the basis of quantitative. OTDR more tasks for processing link the obstacles, such as the connection of the connector quality, melt contact welding quality of exploration such as fiber optic microbend content.


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