Hybrid Cable

What Is a Hybrid Cable?

A hybrid cable combines optical fibers and copper wires in a single jacket, serving as a medium for both power supply and data transmission. This feature makes hybrid cables ideal for connecting switches and APs, or for linking switches and remote units in campus networks. As advanced WLAN technologies like Wi-Fi 6 and Wi-Fi 7 become more prevalent, traditional twisted pairs struggle to meet the bandwidth requirements. Additionally, optical fibers cannot be used for PoE power supply, highlighting the importance of hybrid cables in such scenarios.

Why Are Hybrid Cables Necessary?

To ensure the normal operation of network services, cables connecting devices must fulfill two roles: providing power to devices and transmitting data between them. However, certain network devices are often installed in complex environments where suitable power outlets are scarce. To address this issue, a cable that can simultaneously supply power and transmit data has become essential.

Typically, communication cables are classified into optical cables and copper cables based on their transmission media. Optical fibers are predominantly used for transmitting light through total internal reflection, offering advantages such as high bandwidth, low loss, and long transmission distances. However, being made of glass fibers, they cannot conduct electricity and thus cannot be used for Power over Ethernet (PoE) supply. On the other hand, copper cables consist of copper wires that transmit data through electromagnetic waves. While copper is an excellent conductor of electricity and heat, copper cables can heat up rapidly during transmission, leading to significant transmission losses. To mitigate this, regulations on network integrated cabling stipulate that the total length of twisted pairs should not exceed 100 meters.

To address these challenges and design a cable suitable for PoE power supply without hindering long-term bandwidth evolution, the concept of a hybrid cable emerges. This type of cable integrates optical fibers and copper wires within the same jacket. It utilizes optical fibers for data signal transmission and copper wires for electrical signal transmission, enabling long-distance power supply while ensuring high-speed data transmission. In essence, hybrid cable optimizes the advantages of both optical fibers and copper cables while minimizing their respective disadvantages.

How Do Hybrid Cables Work?

A hybrid cable contains both optical fibers and copper wires within a single jacket. It uses optical fibers for transmitting data signals and copper wires for transmitting electrical signals, enabling long-distance power supply while maintaining high-speed data transmission. You might wonder why hybrid cables can support long-term bandwidth evolution and long-distance PoE power supply while twisted pairs and optical fibers cannot.

Firstly, hybrid cables maximize the advantages of optical fibers. They use optical fibers to transmit data signals, which are ideal for long-distance and high-bandwidth data transmission. In contrast, twisted pairs transmit data signals through copper wires, where transmission quality can be affected by wire resistance and capacitance, leading to signal attenuation and distortion. Additionally, the attenuation of data signals is influenced by the cable length, with longer cables experiencing higher attenuation. To address this, regulations on integrated network cabling specify that the distance for twisted pairs should not exceed 90 meters, with a total link length not exceeding 100 meters. However, data transmission through optical fibers is not impacted by resistance or capacitance, as they rely on total internal reflection. This results in longer transmission distances and higher bandwidth capabilities.

Secondly, hybrid cables minimize the drawbacks of copper wires. Copper wires in hybrid cables only transmit DC electrical signals. Tests have shown that hybrid cables can support 60W PoE power supply even at distances of 300 meters, indicating a significant power supply range. Nonetheless, copper wires still exhibit resistance, and thermal effects occur during transmission, leading to some energy attenuation. Consequently, the transmission distance of copper wires for DC electrical signals is limited. The transmission distance of a hybrid cable ultimately depends on the transmission distance of DC electrical signals over copper wires. However, as technologies advance, we anticipate transmission distances reaching 1000 meters or more, meeting the requirements for long-distance PoE power supply in most scenarios.

Applications of Hybrid Cables

In campus networks, hybrid cables are commonly employed to connect Access Points (APs) or remote units to switches. Traditionally, switches and APs are linked using twisted pairs, serving as a medium for both PoE power supply to APs and data transmission between switches and APs. However, with the continuous evolution of Wi-Fi technologies, there is an increasing demand for higher cable performance. Looking ahead, the future-oriented Wi-Fi 7 standards will demand even higher performance, requiring cables to deliver a maximum bandwidth of 40 Gbit/s while supporting long-distance PoE power supply to APs.In many instances, APs are installed in challenging environments, requiring PoE power supply over distances exceeding 100 meters, and sometimes much longer.

When using twisted pairs to connect switches and remote units, the data transmission distance must be within 100 meters. This distance is insufficient for certain environments such as hotels, hospitals, and educational institutions. Alternatively, if optical fibers are used for this connection, supplying power to remote units becomes a concern, leading to additional power deployment and management costs. In contrast, using hybrid cables allows for long-distance PoE power supply and high-speed data transmission, enabling remote units to be installed on user desktops rather than being limited to weak-current rooms. This significantly reduces cabling and management expenses.