Fiber Optic Cable Project Acceptance Test Methods

Today, fiber-optic cable in data centers and information centers can be found everywhere, almost the backbone of the network are dominated by fiber. When we are happy for the network speed increase, we have to face the accompanying fiber optic failure of all kinds. This experience is not only in the new network, but also in the process of network renovation and upgrading. The main purpose of fiber optic testing is to ensure the quality of the system connection, to reduce the failure factors and to find out the failure point of the fiber when the failure occurs. Usually we use in the specific construction and testing of fiber optic cable testing methods: connectivity testing, optical power loss testing, transceiver power testing and reflective loss testing.

1.Connectivity test

Optical connectivity of fiber optic system indicates the ability of fiber optic system to transmit optical power. Optical connectivity of a fiber optic system is a basic requirement for a fiber optic system, so testing the optical connectivity of a fiber optic system is one of the basic tests. By connecting a light source at one end of the fiber optic system and an optical power meter at the other end, the optical connectivity of the fiber optic system can be determined by the detected output optical power. When the ratio of the measured optical power at the output end to the actual input optical power at the input end is less than a certain value, the link is considered to be optically disconnected. Optical connectivity test, usually choose a red laser or other visible light as the test light source, the end of the fiber to monitor the light output. If there is a break or other discontinuity in the fiber, the optical power at the output of the fiber will decrease or there will be no light output at all.

2.Optical power loss test

Optical power loss, a term commonly used in the fiber optic field, represents the attenuation of a fiber optic link. Attenuation is an important transmission parameter of fiber optic links and is measured in decibels (dB). When an optical signal propagates in an optical fiber, it plays a decisive role in evaluating the quality of the fiber and determining the relay distance of the fiber optic system. When the optical signal propagates in the optical fiber, the average optical power decreases exponentially over the length of the fiber. In a fiber-optic network cable, the greater the attenuation that exists from the sending end to the receiving end, the shorter the maximum distance that can be transmitted between the two. Attenuation negatively affects all types of cable systems in terms of transmission speed and distance, but fiber optic transmission is particularly sensitive to attenuation because there are no crosstalk, EMI, RFI, etc. problems in fiber optic transmission.

The method is to use a fiber optic power tester and a light source, the first light source and optical power tester directly connected to measure the signal gain value, and then use the light source and optical power tester to test the actual fiber at both ends, test out the end-to-end reference power value, the difference between the two is the actual end-to-end loss value.

3.Transceiver power test

Transceiver power test is more suitable for the already built and put into use, the transmission distance is relatively long. The equipment needed is mainly fiber optic power tester and a section of jumper cable. First of all, the fiber to be tested at the sending end will be removed, replaced by jumper cables, jumper cables at one end of the original transmitter, the other end of the fiber optic power tester, at this time can be measured at the sending end of the value of the optical power; at the receiving end, the jumper cables to replace the original jumper cables, connecting the optical power tester, can be measured at the receiving end of the value of the optical power; the difference between the two that is the fiber optic line generated by the loss.

4.Reflection loss test

Launch loss test is a very effective means of fiber optic line maintenance, the method is also the current acceptance of fiber optic cable engineering, testing and fault location using the most common, the most authoritative method. This method uses optical time domain reflectometer (OTDR, OpticalTime Domain Reflectometer) to complete the test work. OpticalTime Domain Reflectometer (OTDR) performance as a function of fiber loss and distance, according to the principle of backward scattering of light production, the use of light propagation in the optical fiber generated by backward scattering of light to obtain the attenuation of the information can be used to measure the fiber attenuation, connector loss, fiber optic fault location and understanding of the fiber along the length of the distribution of the loss and so on. OTDR only through the end of the optical fiber can be measured by the optical fiber loss. The OTDR trace line gives the location and magnitude of the system attenuation value, such as the location of any connector, splice point, fiber deformity, or fiber break and the magnitude of the loss. With OTDR, technicians can see the entire system profile, identify and measure fiber spans, splices and connectors.

Optical Power Meter   Return loss tester   Optical Multi Meter   OTDR

The above introduces several common methods of testing fiber optic cables, but in practice the situation will be different, we also need to be flexible according to the actual situation on the spot to use a variety of methods to achieve a combination of theory and practice.

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