Key physical parameters and test methods of cable wiring

After the installation of the cable wiring system, the link transmission characteristics need to be tested, among which the main test items are the attenuation characteristics of the link, the insertion loss of the connector, the return loss and so on. The following is a brief introduction to the measurement of key physical parameters of optical cable wiring and troubleshooting and maintenance in the network.
　　
First, the key physical parameters of the cable link
　　
Attenuation:
　　
1, attenuation is light in the optical fiber transmission process during the reduction of light power.
2. Calculation of the total attenuation of optical fiber networks: Optical fiber loss (LOSS) is the ratio of the output power of the optical fiber to the power at the end of the transmission to the optical fiber.
3, the loss is proportional to the length of the optical fiber, so the total attenuation not only indicates the fiber loss itself, but also reflects the length of the fiber.
4, optical cable loss factor (α): In order to reflect the characteristics of fiber attenuation, we introduce the concept of optical fiber loss factor.
5, the attenuation of the measurement:
　　
Because the optical connection to the light source and the optical power timing will inevitably introduce additional losses. Therefore in the field test must first carry on the test instrument's test reference point's setting (that is, the zero setting). There are several ways to test reference points, mainly based on the methods that are selected for the link object being tested. In the cable wiring system, because the length of the fiber itself is usually not long, so in the test method will pay more attention to connectors and test jumper, the method is more important, on this point see Arnhem Cabling Test Technology article
　　
Echo Loss:
　　
Reflective loss is also known as return loss, it refers to the fiber junction, backward reflected light relative to the ratio of the number of decibels, the greater the return loss of the better, to reduce the impact of reflected light on the light source and system.
　　
To improve the return loss, it is an effective method to improve the echo loss by using the optical fiber end as the spherical or oblique spherical surface. (Computer science)
　　
Insertion loss:
　　
Insertion loss refers to the number of decibels in which the output light power of an optical fiber is relative to the input optical power after the optical signal is passed through the active connector.
　　
The smaller the insertion loss, the better.
　　
The method of measuring insertion loss is the same as that of attenuation.
　　
Second, the optical fiber network testing and measuring equipment
　　
1, optical fiber recognizer.
　　
It is a very sensitive photoelectric detector. When you bend a fiber, some light radiates from the core. The light will be detected by the optical fiber recognizer, which allows technicians to identify a single fiber in a multi-core optical cable or a connector board from another fiber. The optical fiber recognizer can detect the state and direction of light without affecting the transmission. To make this work simpler, the test signal is typically modulated to 270Hz, 1000Hz, or 2000Hz and injected into a specific fiber at the sender end. Most fiber-optic recognizers are used for single mode fiber optic cables with a working wavelength of 1310nm or 1550nm, and the best fiber-optic recognizer is the use of macro-bending technology to identify optical cables and test the transmission direction and power of optical cables online.
　　
2, the fault locator (fault tracker).
　　
The device is based on the laser diode visible light (red light) source, when optical injection of optical fiber, if the fiber fracture, connector failure, bending over, welding quality, such as the failure of the same, through the light emitted into the optical fiber can be a visual positioning of the fault. A visual fault locator is launched as a continuous wave (CW) or pulse mode. The typical frequency is 1Hz or 2Hz, but it can also work in the range of khz. The output power is typically 0dBm (1Mw) or less, operating at a distance of 2 to 5km, and supports all universal connectors.
　　
3, optical loss test equipment (also known as optical multimeter or optical power meter).
　　
In order to measure the loss of a cable link, it is necessary to emit the calibrated stabilized light at one end and read out the output power at the receiving end. These two kinds of equipment constitute the optical loss tester. When a light source and a power meter are synthesized into a set of instruments, it is often called a light loss tester (also known as a light multimeter). When we measure the loss of a link, we need a person to operate the test light at the transmitter and the other person to measure in the receiver using a power meter, which can only produce a loss value in one Direction.
　　
Usually, we need to measure the loss in two directions (because there is a connection loss or is due to the asymmetry of optical cable transmission loss). At this point, the technician must exchange the device and carry out another direction measurement. But what should they do when they are more than 10 floors or tens meters apart? Obviously, if these two people each have a light source and a light power meter, then they can be measured on both sides, now for the certification test of the Advanced optical cable test sleeve machine can achieve two-way dual-wavelength test, such as: Fluke Certifiber and DSP cable Test series of FTA cable test kits.
　　
In short, to complete a measurement of optical loss, a calibrated light source and a standard optical power meter are indispensable. For more detailed technical information, please refer to the Arnhem Company's wiring test equipment classification of related products.