How to quickly detect the quality of optical fiber

How to quickly detect the quality of optical fiber,In the construction of integrated wiring projects, the construction quality of optical fibers is very important. How to quickly detect the quality of optical fibers? Comprehensive testing of attenuation of optical fibers and connectors; reflection measurement that can generate schematic diagrams of optical fiber connection line loss curves. This measurement also informs people about the length of the connection line and where it goes wrong.

Attenuation measurement

Attenuation measurements, also called first-order measurements, are performed with a high-power calibrated generator that transmits the signal and a fiber optic radiometer that measures reception. It is possible to measure the attenuation on the line and know whether the line or a section of line is within the specified tolerance. This is the first level measurement. All connectors should be cleaned before each measurement. In order to avoid measurement errors, both instruments (generator and receiver) should use the same measurement cable (eg 3 m long). These cables should have the same characteristics as the fiber core being tested.

The test can be carried out in the following two ways: one tester conducts the test, and the two instruments are placed in the same place, but can form a loop with the other; two testers, one tester is placed in each of the two places. All testing procedures begin with calibrating the receiver. To this end, the generator and the receiver must be directly connected together with a 3-meter-long cable, and then transmit high power to the receiver, and then calibrate the receiver until 0dB appears on the liquid crystal display; test with a wavelength of 850nm, test The maximum value of the attenuation obtained in is equal to the attenuation of the fiber, that is, 3.5dB/Km of this wavelength, and the attenuation (connectors and connectors) produced by various connections is added above this. We believe that 90% of connected devices have an attenuation of 0.3dB up to 850nm.

This article specifically introduces the method of testing by a tester. A tester's test requires different optical cables in the final distribution frame to pass through some optical fiber jumpers with a length of 10 meters to form a loop, and then detect the optical core of each pair of optical fibers one by one. The transmitter and receiver are placed at the same location; use a 3-meter fiber optic cable to connect the transmitter to the first fiber on the cable head or fiber drawer; use a second 3-meter fiber-optic cable to connect the receiver Connect to the second fiber.

First measure the loopback situation, and then the tester connects the receiver to the third fiber for the same test, and tests the fourth, fifth and sixth fibers in the same way.

The test procedure is: calibrate the receiver, install the jumper cable, measure the line and store the test results in the computer. When calibrating, use a 3-meter long cable to form a loop between the transmitter and receiver. High power should be transmitted to the receiver and the receiver should be calibrated to 0dB on the LCD. If the tested value exceeds the maximum expected value, the location of the fault should be determined by means of a fiber optic reflectometer.

Measuring with a reflectometer

Measuring with a reflectometer, also known as the second-level measurement, aims to measure the physical state of the fiber core. The distribution of losses can be shown on the display.

The measurement principle is: the reflection measuring instrument emits a high-power calibration beam, and then observes whether there is a visually visible reflection power signal on the display screen. This reflection is due to imperfections in the silicon that makes up the fiber and is consistent with a linear attenuation. The remaining part of the reflected signal is equal to the reflection of the possible faulty part of the plug part. At the same time, these losses can be located and the exact length of the cable detected.

These tests can detect whether the fiber is in an abnormal condition (bend radius, excessive pulling or crushing), and can also detect whether there is a broken line, whether the broken line is due to improper handling. At the same time, it can also know whether the ST connector is connected correctly.