What Are the Common Causes of High Attrition?
When you turn on Wi-Fi at home and pull out your mobile phone to surf the Internet, you must have experienced this: The closer you are to the wireless router, the faster the Internet speed; the farther you are, the slower the Internet speed. Why is this? It turns out that this is because the wireless signal is lost when it travels through the air. The longer the propagation distance, the greater the loss.
- Chinese name
- loss
- influences
- Loss may cause optical signals during transmission
- Classification
- Inherent loss
- Meaning
- When wireless signals travel through the air
- Inherent loss
- Additional loss
- When you turn on Wi-Fi at home and pull out your mobile phone to surf the Internet, you must have experienced this: The closer you are to the wireless router, the faster the Internet speed; the farther you are, the slower the Internet speed. Why is this? It turns out that this is because the wireless signal is lost when it travels through the air. The longer the propagation distance, the greater the loss.
- If you turn on a flashlight and illuminate it in the distance, you will find that the light is not far away, and the closer the place is, the brighter it is, and the farther away it is, the darker it is. This is also because light is lost as it travels through the air. Similarly, when an optical signal propagates through an optical fiber, there is a loss phenomenon.
- Attrition (sn hào) generally refers to loss, loss or expense. In the signal profession, a reduction in signal level or intensity, usually expressed in decibels. Also refers to power dissipation without practical use.
Loss primer
- When you turn on Wi-Fi at home and pull out your mobile phone to surf the Internet, you must have experienced this: The closer you are to the wireless router, the faster the Internet speed; the farther you are, the slower the Internet speed. Why is this? It turns out that this is because the wireless signal is lost when it travels through the air. The longer the propagation distance, the greater the loss.
- If you turn on a flashlight and illuminate it in the distance, you will find that the light is not far away, and the closer the place is, the brighter it is, and the farther away it is, the darker it is. This is also because light is lost as it travels through the air.
Similarly, when an optical signal propagates through an optical fiber, there is a loss phenomenon.
Loss effect
- Why should we care about losses in fiber optic communications? What are the effects of loss?
- Loss may cause errors in the optical signal during transmission, affecting transmission quality. At the same time, the loss will affect the distance that the optical signal can travel.
Cause of loss
- First, let's go back to a day in history, when people were still tirelessly advancing on the road of exploring fiber optic communication ...
- From 1961 to 1970, people mainly researched using the atmosphere to transmit optical signals. Practice has proved that due to the severe impact of the climatic environment, normal communication cannot be achieved. Among other transmission media considered by people, the use of optical fibers, namely optical fibers, made of quartz glass materials to transmit optical signals has become the focus of research. However, the loss of ordinary quartz glass materials was very high (1000 dB / km), and the transmission distance was very limited. In July 1966, Dr. KCKao and Dr. GAHocKham of the British Standard Chinese Telecommunications Research Institute pointed out that the high loss of optical fiber is not inherent in itself, but by materials Caused by impurities. And predict that if the content of impurities in the material is reduced, the loss of the optical fiber can be reduced to 20 dB / km, or even smaller. In 1970, Corning Glass Co., Ltd. successfully developed a low-loss quartz fiber with a loss of 20 dB / km, which made the fiber fully capable of being used as a transmission medium for transmitting light waves, and also opened up a new era of optical fiber communication.
Loss of fiber loss mainly includes two aspects
- The transmission loss of an optical fiber can be roughly divided into the inherent loss of the optical fiber and the additional loss caused by the use conditions after the optical fiber is made.
- The inherent loss is caused by the characteristics of the optical fiber itself, and can be improved through the continuous improvement of the optical fiber manufacturing process. The inherent loss mainly includes absorption loss and scattering loss.
- Absorption loss is caused by the absorption of optical energy by optical fiber materials and impurities. They consume optical energy in the form of thermal energy in the optical fiber, which is an important loss in optical fiber loss.
- The most important of the scattering is Rayleigh scattering, which is caused by changes in density and composition inside the fiber material. Scattering inside the fiber will reduce the transmitted power and cause losses. During the heating process of the optical fiber material, due to thermal turbulence, the compressibility of the atoms is not uniform, the density of the substance is uneven, and the refractive index is uneven. This unevenness is fixed during the cooling process and its size is smaller than the wavelength of the light wave. When light encounters these non-uniform substances with a smaller wavelength than the light wave and random fluctuations, it changes the transmission direction, generates scattering, and causes loss. In addition, uneven oxide concentration and uneven doping contained in the optical fiber also cause scattering and loss.
- The additional loss is further divided into microbend loss, connection loss in bending loss optical fiber lines, and coupling loss between optical devices.
- The additional loss is caused artificially during the laying of the optical fiber. In practical applications, it is inevitable to connect the optical fibers one by one, and the optical fiber link will cause loss. Optical fiber bending, squeezing, and tensile stress can also cause losses, which are all losses caused by the conditions under which the fiber is used. The main reason is that under these conditions, the transmission mode in the fiber core has changed. Additional losses can be minimized or even avoided.
- The optical fiber is flexible and can be bent, but after being bent to a certain degree, although the optical fiber can guide light, it will change the transmission path of light. The transmission mode is converted into a radiation mode, so that a part of the light energy penetrates into the cladding layer or passes through the cladding layer and becomes a radiation mode to be leaked and lost, thereby generating losses. When the bending radius is larger than 5 cm ~ 10 cm, the loss caused by bending can be ignored.
Low-loss window for lossy fiber
- The attenuation spectrum of the fiber is shown in Figure 1 below. The average loss value of window I is 2dB / km, the average loss value of window II is 0.3dB / km ~ 0.4dB / km, the average loss value of window III is 0.19dB / km ~ 0.25dB / km, and the window V is at 1380nm There is an OH absorption peak.
- Figure one
- The marking, wavelength range, fiber type and application of the optical signal in the five windows are shown in the following table:
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- Line loss of common fiber
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