The small network cable also has a big question, that can not be ignored. For example, in the integrated cabling specification, it is required that the horizontal cabling cannot exceed 90 meters, and the total link distance cannot exceed 100 meters. In other words, one hundred meters is the limit for wired Ethernet, and this limit is the distance of the link from the network card to the hub device.
Twisted-pair cable has an “insurmountable” transmission distance of “one hundred meters.” It is a Category 3 twisted-pair cable with a transmission rate of ten meters; a Category 5 twisted-pair cable with a transmission rate of one hundred meters; or even a Category 6 twisted-pair cable with a transmission rate of one thousand meters. The longest effective transmission distance is One hundred meters. Twisted-pair physical factors largely determine the merits of the network cable; poor-quality network cable often uses substandard twisted-pair core winding, low-cost metalcore, to achieve the purpose of cutting corners. This irresponsible behavior directly aggravates the interference of network signals in the network cable, thus making the effective transmission distance of the cable far less than 100 meters. At the same time will also affect the stability of network transmission and the service life of the cable.
Various types of network cable transmission distance
Category 5, and Category 6 are 100 meters.
Coaxial cable thin cable is 185 meters.
Coarse cable 500 meters
Fiber optic transmission rate of 1Gb/s, 850nm (fiber diameter)
- ordinary 50μm multimode fiber transmission distance of 550m
- standard 62.5μm multimode fiber transmission distance of 275m
- the new 50μm multimode fiber transmission distance of 1100m
The transmission rate of 10Gb/s, 850nm.
- ordinary 50μm multimode fiber transmission distance of 250m
- standard 62.5μm multimode fiber transmission distance of 100m
- new 50μm multimode fiber transmission distance of 550m.
Transmission rate 2.5Gb/s, 1550nm
- g.652 single-mode fiber transmission distance of 100km
- g.655 single-mode fiber transmission distance of 390km
The transmission rate of 10Gb/s, 1550nm
- g.652 single-mode fiber transmission distance of 60km
- g.655 single-mode fiber transmission distance of 240km
Transmission rate at 40Gb/s, 1550nm
- g.652 single-mode fiber transmission distance of 4km
- g.655 single-mode fiber transmission distance of 16km
The actual construction of the maximum cable distance
As seen above, when using a PoE power supply, why specify the entire distance of the network cable shall not exceed 100 meters. However, to ensure the project’s quality, the actual construction generally takes 80-90 meters.
Please note that the transmission distance here is for the maximum rate, such as 100M. Suppose the speed is reduced to 10M. In that case, the transmission distance can usually be extended to 150-200 meters, so the PoE-powered transmission distance does not depend on PoE technology but depends on the category and quality of the network cable.
Although the actual construction of better quality network cables can break the 100-meter distance limit and the equipment can work properly, this practice is not recommended. There are potential problems that do not present themselves immediately but slowly emerge over time, which can cause subsequent maintenance problems. In the simplest case, such as the upgrade of bandwidth, so that the original can work properly at a distance of more than 100 meters the network speed is significantly increased after the device does not work correctly.
One hundred meters maximum distance is how to get?
What caused the 100-meter transmission distance of the twisted-pair cable ceiling?
It is to look deeper into the profound physical principles of twisted-pair cable. Network transmission is the network signal transmission on the twisted-pair cable. As an electronic signal, transmission in the twisted-pair cable is bound to be affected by resistance and capacitance, leading to network signal attenuation and distortion. The attenuation or distortion of the signal to a certain degree. It will affect the effective and stable transmission of the signal. Therefore, a twisted-pair cable has a transmission distance limit, so how exactly is the upper limit of 100 meters calculated?
Category 5 UTP, Super Category 5 UTP is mainly for computer networks. According to the Fast Ethernet 100Base-TX regulations, the communication rate of 100mbps, and 100mbps Ethernet transmission of 1 bit of data spent time can be calculated as follows.
1 bit time = 1/100mbps = 10ns
Ethernet uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection), a carrier-surveillance multiple access technology with collision detection to share the communication channel. When the switch is introduced, it is still inseparable from this technology. A link connects to devices at both ends; these two devices may send data simultaneously, resulting in a conflict when the conflict domain is 2. Match will lose packets. Ethernet uses conflict detection and back-off retransmission techniques to avoid packet loss due to competition. One end must ensure that the conflict is detected before a packet is transmitted.
The minimum frame length of Ethernet is 64 bytes, i.e., 512 bits, and at a rate of 100mbps, it takes 512 bits * 10ns = 5120ns to transmit 512 bits, and data information is delayed when passing through different parts of the network. The delay of Category 5 UTP is 5.56ns/m. When designing Ethernet, it is required to follow a relay rule, also known as the Golden Rule or 5-4-3-2-1 rule, which applies not only to 10mbps Ethernet but also to Fast Ethernet. This rule requires that the ring conflict delay should not exceed 512-bit hours, 5120 ns for a 100mbps transmission rate. Ring, network components such as cables, relay units, MAUs, and DTEs are added together and multiplied by 2, giving the ring delay and calculating the ring conflict diameter. Based on this theory, the longest distance a signal can transmit after a minimum frame is sent can be calculated—the reason why the linkspan is limited to 100 meters.
When it exceeds 100 m, the packet is lost because the conflict cannot be detected in time. The competition damages the package. The receiver receives it, and the packet is forced to be discarded because it cannot be verified, and the mechanism of backward retransmission is not activated. When the transmission rate is below 100 Mbps, 100 meters can be relaxed in practical applications. It must state that this, although applicable, does not comply with the standard and must be specified during certification testing; otherwise, there will be potential problems such as product warranties.
The impact of cable category and quality on transmission distance
We talk about Category 3 cable, Category 5 cable, Category 7 cable. The difference between them is that the copper wire diameter is getting thicker and thicker, the torque is getting smaller and smaller, and the two cables are twisted tighter and tighter. The spacers between the pairs are getting more and more (cross skeleton, aluminum foil, mylar, drain wire, copper wire braid network), and the frequency is from 16MHz to 100MHz, 250MHz, 500MHz, 600MHz, and so on.
As the frequency increases, crosstalk becomes more and more serious. It is necessary to increase the diameter of the copper wire, increase the torque of the cable, increase the cross-frame to separate the cable, increase the thickness of the sheath, or increase the shielding layer to solve the crosstalk problem. Crosstalk makes the cable structure more and more complex. Category 5 wire is now the most common standard network cable on the market, but the quality of different manufacturers varies greatly, especially in this price-oriented environment in China. Many manufacturers reduce costs, the copper wire with copper-clad iron, and copper-clad steel instead, resulting in a decline in the transmission distance of the cable, and even network instability, packet loss, and other phenomena. So if you want to make PoE play the best effect, you must use a suitable quality network cable. You can not lose because of the small, affecting the overall quality of the project.
Super Cat5 cable.
Compared with Category 5 twisted-pair cable, Super Category 5 twisted-pair cable has less attenuation and crosstalk, providing a more solid network foundation. Meet the needs of most applications (primarily to support Gigabit Ethernet 1000Base-T cabling). The network installation and testing have brought convenience, becoming a better solution for current network applications. The transmission characteristics of Super Category 5 cables are the same as those of ordinary Category 5 cables. Still, the Super Category 5 cabling standard stipulates that all four Super Category 5 cables can achieve full-duplex communication.
Cat6 cable.
The transmission frequency of this cable type is 1MHz to 250MHz, and the integrated attenuation crosstalk ratio (PS-ACR) of the Category 6 cabling system should have a more significant margin at 200MHz, which provides two times the bandwidth of Super Cat 5. The transmission performance of Cat 6 cabling is much higher than the Super Category 5 standard and is most suitable for applications with transmission rates higher than 1Gbps.
A difference between Cat6 and Super Cat5
Improved crosstalk and return loss performance, which is critical for next-generation full-duplex high-speed network applications. The essential link model has been eliminated from the Category 6 standard, and the cabling standard uses a star topology.
The required wiring distances are
The distance of the permanent link cannot exceed 90 meters, and the channel length cannot exceed 100 meters. There is no strict difference in transmission distance between Category 6 and Super Category 5 cables, i.e., the maximum transmission distance of a single segment is 100 meters. Still, of course, Cat6 cables can be increased appropriately in transmission distance. The so-called 100 meters refers to more than the 1000M bandwidth and other related technical indicators, bringing speed degradation and other problems.
The higher the network cable’s transmission rate, the greater the frequency, while causing more interference and the need for higher shielding means. In the low-end twisted pair products, the winding distance is a significant reference for the merits. But in the higher end of the twisted pair products, it is the core distance to consider and depends on what the crosstalk shielding means. When it comes to signal crosstalk shielding, we can also divide the cable into shielded twisted pair and unshielded twisted pair from this perspective. Unshielded twisted-pair cables consist of eight different colored wires stranded in four pairs, twisted in pairs to minimize the impact of electromagnetic radiation and external electromagnetic interference.
The shielding method shielded twisted pair, is divided into STP (Shielded Twisted-Pair) and FTP (Foil Twisted-Pair.) STP is a shielded twisted pair where each wire has its shielding layer, while FTP is a shielded twisted pair with overall shielding. Shielded twisted-pair cables have a higher transmission rate of 155Mbps over 100 meters than the corresponding unshielded twisted-pair cables. At present, most of the common types of network cables we have to belong to the unshielded twisted pair type—the wiring transmission medium used by most LANs nowadays. Use Shielded Twisted Pair networking, and the network cable consists of a certain distance long twisted pair cable with RJ45 headers.
Since shielded twisted-pair cable is more resistant to interference and faster transmission than unshielded twisted-pair cable, some people may ask why don’t people use shielded Category 5 twisted-pair cable.
Because the shielded twisted pair requires the entire system to be shielded devices, including cables, sockets, crystal heads, patch panels, etc. At the same time, the building needs to have a good ground system, shielded twisted pair of harsh environmental conditions, and the technology is destined to be “fragile.” Generally speaking, in the actual construction, it is difficult to all be ideally grounded. The shield itself becomes the largest source of interference, resulting in performance inferior to the unshielded twisted pair. Therefore, only unshielded twisted-pair cables are usually used in integrated cabling systems unless there is a particular need.
Unshielded twisted-pair cables use the physical principle to reduce signal crosstalk, bringing about cost reduction and robustness of network cabling. Although a shielded twisted pair is superior to an unshielded twisted pair in direction, its technical vulnerability and high capital investment have become weaknesses. Caution is needed when choosing directly between the two. Suppose you need higher network quality and longer transmission distance. In that case, users can install repeaters between two sections of twisted-pair cable to obtain better wiring cost performance. (A maximum of 4 repeaters is recommended, more will also affect the network transmission)
