Analysis of common problems during fiber testing

Optical fiber is an important transmission medium for a comprehensive wiring project. Its performance is particularly important, especially for optical fiber cables laid in overhead or underground pipelines. Therefore, before laying the optical fiber, we must test the optical fiber and the optical fiber equipment. What problems will we encounter during the test? 1. Why should I use a special reference jumper to set the reference value when testing the fiber? The accuracy of the test results is closely related to the setting of the reference value. If the reference value is not set properly, the test results will be inaccurate or negative. The recommended method is to use a reference optical jumper and adapter when setting the reference value. In the TIA / EIA 568-B.3 and ISO 11801 standards, the loss requirement for a fiber coupling is less than 0.75dB. The performance of fiber optic jumpers and adapters produced by most manufacturers can meet or exceed this requirement. However, many people don't know that the standard has special requirements for reference jumpers and adapters. In the IEC 14763-3 standard, it is stipulated that when using reference patch cords and adapters, the coupling loss of multimode fiber is less than 0.1dB, and the loss of singlemode fiber is less than 0.2dB. Conventional fiber optic jumpers simply cannot meet this requirement. Therefore, it is recommended to purchase special reference jumpers from manufacturers and test instrument manufacturers for testing. When setting the reference value, an optical fiber adapter using zirconia ceramic sleeve material is required to obtain the best coupling effect. The conventional method is to set the reference value with a single-mode fiber adapter to test the multi-mode or single-mode fiber link to obtain the best coupling effect. 2. What is the importance of the tester's warm-up during the optical fiber link loss test? Generally, the higher the temperature of the light source module, the greater the light source power value it emits. During the test, the light source module needs a period of warm-up time to stabilize the transmitted light source power value. If the reference value is set before the light source module warms up, as the temperature of the light source module rises, the test result will have a gain, which will affect the accuracy of the test result. For example, when the reference value is initially set, the power value accepted and stored by the optical power meter is -6.00dB. At this time, when the reference value setting model is maintained, and the test is performed directly without adding the measured link, a test result of 0.00dB should be obtained. However, after the optical power module is warmed up, the power it emits will increase, and the power value received by the power meter may rise to -6.20dB. Test again at this time and you will get a gain of -0.2dB. The warm-up time of the light source module is related to the temperature of the test environment. The method of checking whether the light source module is stable is simple. As long as the reference value is set, the reference value model is tested, and the test value obtained is -0.04dB ～ 0.04dB. Value, you need to wait for a while and reset the reference value. 3. Why do negative values ??occur when testing for loss? Does the link under test not only have no loss but also gain? When testing a single-mode fiber link, if the length of the link under test is less than 100m, and the entire link is connected by pigtail fusion, the loss of the entire link may only be 0.15dB. In this case, the preheating time of the light source module is insufficient, the test environment temperature changes greatly, the coupling effect of the reference jumper and the test instrument, and the reference value is not set accurately enough. -0.03dB. At this time, it is necessary to fully warm up the machine and reset the reference value.