To know the maximum transmission distance of PoE, we must first figure out what are the key factors that determine the maximum distance. In fact, using standard Ethernet cables (twisted pair) to transmit DC power can be carried over a long distance, which is far greater than the transmission distance of data signals. Therefore, the maximum distance of data transmission is the key.

1. The maximum distance of network cable data transmission

We know more about the network know that twisted pair has an “insurmountable” transmission distance of “100 meters”. Whether it is Category 3 twisted pair with 10M transmission rate, Category 5 twisted pair with 100M transmission rate, or even Category 6 twisted pair with 1000M transmission rate, the longest effective transmission distance is 100 meters.

In the integrated wiring specification, it is also clearly required that the horizontal wiring should not exceed 90 meters, and the total length of the link should not exceed 100 meters. That said, 100 meters is a limit for wired Ethernet, which is the length of the link from the network card to the hub device.

2. How did you get the maximum distance of 100 meters?

What caused the upper limit of the 100-meter transmission distance of the twisted pair? This requires a deep dive into the deep physical principles of the twisted pair. The transmission of the network is actually the transmission of the network signal on the twisted pair line. As an electronic signal, when it is transmitted in the twisted pair line, it must be affected by resistance and capacitance, which leads to the attenuation and distortion of the network signal. When the attenuation or distortion of the signal reaches a certain level, the effective and stable transmission of the signal will be affected. Therefore, the twisted pair has a transmission distance limitation.

3. Maximum cable distance during actual construction

It can be seen from the above why the maximum length of the network cable should not exceed 100 meters when using PoE power supply. However, in the actual construction, in order to ensure the quality of the project, generally take 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 transmission distance of PoE power supply is not determined by PoE technology, but by the type and quality of the network cable.