Friends often ask questions about POE power supply technology, such as how far is the maximum transmission distance of POE power supply? In fact, in the question of the maximum transmission distance of PoE, we must first figure out what is the key factor that determines the maximum distance. In fact, using standard Ethernet cable (twisted pair) to transmit DC power can transmit a long distance, which is far greater than the transmission distance of data signals. Therefore, the maximum distance of data transmission is the key. Next, the editor of Feichang Technology will introduce to you what is the maximum transmission distance of the monitoring POE power supply? Let's take a look!
1. The maximum distance
of network cable data transmission Friends who know more about the network know that twisted pair cables have an "insurmountable" transmission distance of "100 meters". Whether it is a Category 3 twisted pair with a transmission rate of 10M, a Category 5 twisted pair with a transmission rate of 100M, or even a Category 6 twisted pair with a transmission rate of 1000M, the maximum effective transmission distance is 100 meters.
In the integrated wiring specification, it is clearly required that the horizontal wiring cannot exceed 90 meters, and the total link length cannot exceed 100 meters. In other words, 100 meters is a limit for wired Ethernet, and this limit is the length of the link from the network card to the hub device.
2. How did the maximum distance
of 100 meters come about? What caused the upper limit of the transmission distance of 100 meters for twisted-pair cables? It is necessary to delve into the deep physical principles of twisted-pair cables. The transmission of the network is actually the transmission of the network signal on the twisted pair. As an electronic signal, when it is transmitted in the twisted pair, it must be affected by resistance and capacitance, which leads to the attenuation and distortion of the network signal. When the signal attenuation or distortion reaches a certain level, it will affect the effective and stable transmission of the signal. Therefore, twisted pair cables have transmission distance limitations.
3. How to calculate the upper limit of 100 meters?
Category 5 UTP and Category 5 UTP are mainly used for computer network services. According to the 100Base-TX regulations of Fast Ethernet, the communication rate is 100mbps and 100mbps Ethernet transmission. The time spent on 1 bit of data (also known as "bit time") can be calculated as follows:
1 bit time=1/100mbps=10ns
Ethernet uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection) that is the carrier sense multiple access technology with collision detection (Carrier Sense Multiple Access / Collision Detection) to share the communication channel. Do not open this technology.
When it exceeds 100 meters, because the conflict cannot be detected in time, the transmission of the information packet damaged by the conflict is completed and received by the receiver. The information packet is forced to be discarded because it cannot pass the verification. At this time, the mechanism of retransmission is not possible. Is activated, so it will cause packet loss. When the transmission rate is lower than 100 mbps, in practical applications, the length limit of 100 meters can be appropriately relaxed. It must be stated that although this is actually effective, it does not meet the standard. In the certification test, it must be explained, otherwise there may be some problems, such as product warranty.
4. The maximum cable distance during actual construction
As can be seen from the above, when using PoE power supply, why does it stipulate that the maximum length of the network cable shall not exceed 100 meters. However, in actual construction, in order to ensure the quality of the project, it is generally 80-90 meters.
Please note that the transmission distance here refers to the maximum rate, such as 100M. If the rate is reduced to 10M, the transmission distance can usually be extended to 150-200 meters (depending on the quality of the network cable). Therefore, the PoE power transmission distance is not determined by PoE technology, but by the type and quality of the network cable.
Although in actual construction, a better quality network cable can break the 100-meter distance limit and the equipment can work normally, this approach is not recommended. Because some potential problems do not appear immediately, but slowly appear over time, which will cause follow-up maintenance problems. The simplest case is, for example, the bandwidth upgrade, so that the equipment that can work normally at a distance of more than 100 meters will not work normally after the network speed is greatly increased.
Well, the above content is about how far is the maximum transmission distance of the monitoring POE power supply switch of Feichang Technology? A detailed introduction to this issue, I hope it can be helpful to everyone! Feichang Technology has been specialized in the R&D, production and sales of industrial communication equipment such as optical transceivers, industrial switches, optical fiber transceivers, and protocol converters for 20 years. Welcome to come to understand and exchange.