扩展线缆覆盖范围的4项考虑因素

Generally, cable performance is tested against industry cabling standards, such as ANSI/TIA-568, and not the requirements of applications standards, such as those from IEEE 802.3.

Although following industry cabling standards ensures that the applications of today and tomorrow will run effectively, there are applications that may call for cable distances that go beyond the 100 m limitation set forth by TIA.

In these situations, the standards can create frustration: such as when a surveillance camera needs to be moved a bit closer to a parking lot or when wireless access points need to be placed in various locations all across a corporate campus to ensure that wireless access is available everywhere.

A good example of a real-world situation we recently encountered was the need to connect a roof-mounted fan to the network. Embedded with a sensor, the fan needed to be able to transmit data about on/off status. The fan’s location on the roof was just far enough away that a telecommunications closet was going to be needed to support it.

The thought of making this infrastructure investment – not to mention the additional square footage it would require – just didn’t make financial sense. This was a low-speed, low-bandwidth application: Couldn’t we go just a little beyond the 100 m standard set forth by TIA?

The short answer: Yes, we can – as long as some guidelines are followed.

1. Use a Well-Constructed Cable with Low Insertion Loss

How far can the signal travel down the cable before it loses so much strength that the active equipment can no longer recognize or interpret it? The answer depends on the cable construction. If you’re going to push the distance limit of your cabling, then you need to use the best possible components to do so. Only a well-designed cable with plenty of headroom will allow you to reach cable distances beyond 100 m while maintaining performance.

In simple terms, to measure cable performance, we analyze the ratio of signal power to noise power to generate a signal-to-noise ratio; the ratio between the desired information (the signal) and the undesired information (background noise). Once more noise than signal is present, signal loss occurs. This signal loss is experienced in the application as a packet loss or possibly a dropped channel.

2. Make Sure Your Application Operates at Low Speeds

Consider what you’re trying to accomplish. Lower-speed applications that require minimal bandwidth can run over extended cable distances. Examples include surveillance cameras, access control systems, PoE LED lighting and building management systems and sensors. Higher-speed applications won’t be able to do so (streaming uncompressed video, for example).

3. Watch Your Cable Temperatures

Many factors cause cable temperatures to rise, including power transmission through bundles (via Power over Ethernet technology, for example).

Cables are rated to transmit data over a certain distance up to a certain temperature. High cable temperatures can cause cable performance to degrade before reaching a cable distance of 100 m, resulting in derating. As temperatures rise, so does cable insertion loss.

A cable can fulfill its full 100 m reach (and possibly go beyond) under higher temperatures only if it’s designed to do so.

4. Use a Category 6A Cable

Category 6A cabling offers significantly more room to operate, with greater bandwidth and higher data transfer rates. It provides performance of up to 500 MHz (in comparison, Category 5e cable only supports up to 100 MHz). It’s also designed to withstand higher temperatures.

A Category 6A solution, Belden’s REVConnect 10GXS System supports high-density, high-bandwidth applications and can exceed 100 m channel requirements in certain applications with a maximum channel length of up to 185 m. It features insertion loss performance with 8% headroom, offering industry-leading Category 6A system guaranteed performance parameters: insertion loss, NEXT, ACRF and PSAACRF.

The REVConnect 10GXW System – another Category 6A solution – offers best-in-class noise immunity with 4 dB of PSANEXT and 10 dB of PSAACRF headroom. The system supports high-density, high-bandwidth applications and can exceed 100 m channel requirements in certain applications with a maximum channel length of up to 140 m.

Both cables are constructed to reach longer cable distances in specific situations – without any performance degradation.