Fluke: LAN and WAN Optical Cable

The application of optical fiber cables in telecommunications and long-distance communication networks has become very popular and mature. In recent years, with the application of Gigabit Ethernet and the gradual arrival of 10-Gigabit Ethernet, more and more applications of optical cables in LAN have been made. In recent years, local area networks, man networks, campus networks, and campus networks have almost all been laid with optical cables, and the proportion of optical fiber cables is growing. However, the application of optical cables in the LAN is different from that in the WAN. Many users do not have a deep understanding of the optical cables in the LAN, and the experience of Wan Optical Cables cannot be directly used in the LAN. Below is a brief description of the main differences between the optical cable and the WAN.
Distance
First, the obvious difference is the distance. The distance between the WAN optical cable and the LAN optical cable is short. The key or main consideration of the problem is that there are multiple transfer points in the LAN optical cable with a short distance, including at least two transfer points and two to three jumpers. Due to the short distance of the optical cable, the loss caused by the adapter is the main cause. The main loss of long-distance optical fiber cables is the optical fiber cables themselves.

Optical Cable type and Connection Device
Long-distance optical fiber networks use single-mode optical fiber cables, while local area networks currently use multi-mode optical fiber cables. According to statistics, the current multi-mode optical fiber cables occupy more than 90% of the total. This is mainly because of the price of network devices. Early multi-mode optical fiber cables are cheaper than single-mode optical fiber cables. With the development of optical fiber manufacturing technology and technology, the price of multi-mode and single-mode optical fiber cables is no longer the same, but the key is network equipment. The prices of different types of Optical Cable interfaces between vrouters and vswitches in the local area network vary greatly. This is why multi-mode optical fiber cables and LED or VCSEL light sources are mainly used in local area networks. The output power of the network device light source is directly related to the device price. Therefore, the light source of lan network equipment is much less powerful than that of WAN network connection equipment.

Test threshold

Because the output power of the devices at both ends of the long-distance telecommunication optical cable is very high, the loss or Attenuation Caused by the optical cable can generally meet the requirements as long as it complies with the standard. The optical power of lan network equipment is relatively small (price and distance factors), so the attenuation of a optical cable link is relatively strict, usually only a few decibels (dB ). Therefore, the Optical Cable End Interface is not clean, and the optical cable bending or poor connection at the optical cable connection easily causes the attenuation to exceed the standard.

Test methods and methods

Currently, OTDR and attenuation tester are the main devices used to test optical cables. Long-distance optical cables are mainly used to test distance and optical power. Due to the long distance from the optical cable, the test instrument must have a large dynamic range, which is also the test distance supported by the tester. This is also very important for optical cable fault diagnosis. The attenuation test of long-distance optical fiber cables is a single-end test. Attenuation is calculated by reflection. By testing the optical power at the output end of the optical fiber, you can determine whether the output power meets the requirements.

However, the distance between LAN optical cables is short, but there are many connectors. The standard does not specify the number of connectors used, but only specifies the loss of the entire optical cable link. As mentioned above, the local area network cable link attenuation rules are very strict and the margin is very small, so the attenuation of the local area network cable link must be accurately measured. In addition, when the LAN optical cable is laid, it does not know the future wavelength and the transmission direction. Therefore, the LAN optical cable test requires two-way connection. Dual Wavelength measurement. Due to short LAN distance, the relative distance between optical fiber connectors is very short, and some Jumpers are only 1 meter, the fault diagnosis of LAN Optical Fiber Links requires a higher resolution.

Due to the complexity of the LAN optical cable connection, many users need to know the actual connection of a optical cable link, that is, the optical cable link connection diagram, including jumpers and connectors. This facilitates fault diagnosis. In addition, due to the many connectors of the optical cable, the connector is not clean, which has a great impact. A contaminated connection header may have a loss of 0.3 to DB. However, the overall attenuation of Some Optical Fiber Links is only several dB. Therefore, users also need to know the cleanliness of the optical cable connector to ensure that it is well installed.
Fluke network company's latest OptiFiber Optical Fiber certified OTDR) analyzer is designed for LAN/man Optical Cable Testing. It is the first OTDR certification in the world. It not only has the functions of traditional ODTR, but more importantly, it can accurately measure the attenuation of the optical fiber, the optical fiber connection diagram and the cleanliness of the optical fiber connector. The test report includes all the above content.

The test report includes the optical fiber attenuation test results (bidirectional, dual-wavelength), The OTDR test curve of the optical fiber cable, and the optical fiber connection diagram (Channel DIAGRAM-Channel Map ), the cleanliness of the optical cable connector. Such a complete test report ensures reliable use of optical cables in practical applications. In the draft of the TIA Committee optical fiber testing, new requirements for optical fiber testing have been put forward, including the above content.
The application of long-distance optical fiber cables has become very popular. With the extensive application of optical cables in local area networks and man networks, more and more challenges and problems are posed. Most LAN users are not very familiar with optical cables. Therefore, it is very important to master the characteristics and precautions of LAN optical cable applications, including installation and testing.

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