Which of the following ethernet standards support a maximum cable length of longer than 100 meters

The Category 6a, or Cat6a, cable is the latest iteration of Gigabit Ethernet cabling. The a stands for "augmented" and is a nod to Cat6a's improved specifications compared with its predecessor, the Category 6, or Cat6 cable.

The Cat6a doubles data transmission bandwidth, from 250 to 500 MHz; decreases the chance of crosstalk interference; and provides superior reliability and transmission speeds through greater lengths of cable. Unlike most Cat6 cables, Cat6a cables are also often shielded, making them ideal for industrial use where additional interference may be a concern.

Cat6 and Cat6a cables have their identifiers printed on the cable jacket itself — Category 6 or Category 6a, respectively. Another quick way to tell the two cables apart is to note that Cat6a cables are much thicker and bulkier than Cat6 cables. Note that both types of cables use the same connector — RJ45 — so that is not a way to differentiate between them.

Wiring

The latest network cables are made of tightly twisted pairs of copper wires — from 4-10 pairs in each cable. Through these wires, data is transmitted, but cable length and interference can get in the way of data transmission. More tightly woven wire pairs can solve both problems, or at least improve reliability, so one of the biggest differences between older and newer Ethernet cable versions usually comes down to wiring.

Cat6 cables were created under a more exacting standard than previous versions of Ethernet cables to facilitate data transmission speeds of up to 10 gigabits per second (10 Gbps). This higher standard, known as the 10GBASE-T standard, was also implemented to improve the signal-to-noise ratio (interference caused within the cable itself and the peripherals it is connected to) and crosstalk (interference caused by the presence of other nearby cables).

Performance Improvements

While Cat6a does not increase the amount of speed or data transmitted — it still transmits up to 10 Gbps — it does double the bandwidth frequency at which data is transmitted, from 250 MHz (Cat6) to 500 MHz. This allows for more reliable data transmission, even across greater distances. One of the ways the Cat6a accomplishes these feats is by further twisting the twisted wire pairs around an equally twisted and flexible plastic support.

Shielded vs. Unshielded Ethernet Cables

Another similar, though relatively minor, difference between Cat6 and Cat6a comes down to insulation. Some cables have additional insulation in the form of one or more thin jackets to surround their inner twisted wire pairs. When an additional jacket is present, the cable is known as a shielded twisted pair (STP) cable; when it is absent, the cable is known as an unshielded twisted pair (UTP) cable.

While it is possible to purchase shielded Cat6 cables, unshielded versions are much more common. In contrast, nearly all Cat6a cables are shielded.

Extra shielding helps boost reliability and block out interference in areas that may suffer from heavy electromagnetic interference (EMI). The average home office or small business user will rarely need a shielded Ethernet cable. Shielding benefits industrial environments the most.

Maximum Lengths

For Cat6 cables, maximum lengths depend heavily on network speeds and crosstalk conditions. For example, in lower speed networks such as 10, 100, or 1,000 megabit systems (the 10/100/1000BASE-T standards), the maximum cable length is 100 meters (330 feet), with about 90% of that length used to transmit data between systems and the remaining 10% for the connection itself. When crosstalk conditions are ideal in higher speed 10 gigabit (10GBASE-T) networks, the maximum Cat6 cable length is 55 meters (165 feet), but it is only 33 meters (110 feet) when the potential for crosstalk is high, as when several cables are bundled tightly in one area.

Cat6a cables make use of their higher standards by allowing full 10GBASE-T transmission speeds of up to 10 Gbps, at 500MHz of signal bandwidth, over 100 meters (330 feet).

To determine the level of crosstalk in either Ethernet cable, data transmission speeds need to be electrically tested after installation.

Durability

Due to its new central column support and ubiquitous shielding, the Cat6a is much heavier and bulkier than the Cat6. Cable trays will not hold nearly as many Cat6a cables as they can Cat6 cables.

Though Ethernet cables can seem sturdy on the outside, their inner workings are fragile. In other words, it is important not to bend cables too much, as this can damage wiring and decrease performance quality. The minimum radius a cable can be bent without damaging it is called the bend radius. The lower the bend radius, the more you can bend the cable i.e., the more flexible it is. The bend radius is roughly four times the cable diameter. Because of their bulkiness, Cat6a cables take up more room and have a larger bend radius than Cat6 cables.

Is It Worth Upgrading?

It is possible to run a busy home or small office network with Cat5e cables. However, greater bandwidth provides more potential resources for processing needs. Cat6 and Cat6a cables might provide bandwidth beyond that currently needed by residential and small business customers, but the trend in technology is towards greater use of bandwidth, so the investment in higher-grade cables is not a bad idea.

In small home or business offices where many cables might be in close proximity to one another, the Cat6a is likely to outperform the Cat6 when it comes to alien crosstalk — specifically, interference from nearby cables. Cat6 cables, particularly unshielded varieties, are much more prone to alien crosstalk than Cat6a, which uses superior insulation to protect its wiring.

It is also important to upgrade network equipment like routers and cable modems to be compatible with Cat6 or Cat6a cables; you may not be able to take full advantage of the higher bandwidth afforded by the cables if the bottleneck in the network is a slow modem or router.

Cat6 vs. Cat6a Cost

Cat6 and Cat6a cables are more expensive than Cat5e cables, with the cost depending primarily on length. The cost differences between Cat6 and Cat6a cables are relatively small, around 20-35%. For example, a 25 ft unshielded Cat6 cable goes for $8 on Amazon, while a 25 ft shielded Cat6a goes for $11.

Although for a small network this could mean a difference of less than $100 in cable costs, one needs to consider that connection components and patch cables are more expensive for Cat6 cabling than for Cat5e or earlier versions. This is due to the higher requirements needed to ensure transmission speeds and sustained performance. The bottom line is that the initial investment is probably higher, but the network's capacity and performance will most likely be much better and more reliable.

References

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Every type of cable has a maximum distance. These distance limits can vary greatly from one type of cable to the next. Along with determining whether a cable will work, distance limits will also determine how well a cable works. Knowing the fundamentals behind cable distance limits is the first step in selecting the best cable for your needs.

Cables will always have some sort of “maximum signal” rating, depending on the type of the cable. For ethernet cables, it will be the maximum upload/download speed. For HDMI, it will be the maximum resolution of the video. And so on and so forth for other cables. Any type of “maximum” rating should be taken with a grain of salt.

Those ratings are the best possible rating the cable is capable of under theoretical, perfect conditions. For example, modern HDMI cables are all rated for 4k. But if the HDMI cable is running through a coupler, users will almost certainly not get 4k. Each time a signal passes through a connection, even just connecting a cable to something like a TV or computer, the signal quality degrades a little. Using devices like extenders and couplers will make the signal weaker; for example, coupling a 10’ cable to a 5’ cable will result in a weaker signal than just using a single 15’ cable.

Another key factor for signal quality is the distance of the cable. The further a signal has to travel, the more it will degrade by the time it gets from Point A to Point B. Going back to our HDMI example, a 15’ cord will give a clearer image than a 50’ cable. It is possible to get around this issue using an extender/booster. Some cables are also more subject to this issue than others, so doing a little research before running a particularly long cable never hurts.

When using cables with two different ends, the distance limit will be subject to whichever type of connector has the shorter maximum distance. For example, a standalone HDMI cable can go up to 65’ while a standard DisplayPort cable can go up to 15’. Therefore, an HDMI to DisplayPort cable will be stuck at 15’ for its maximum length.

Other factors such as electromagnetic interference or radio wave interference can also come into play. If the cable will be run near electrical cords or in an area near something like a radio tower, these issues can be mitigated by using shielded cables.

With this information in mind, remember that the rest of this article highlights the maximum distance a cable can run and still work. Some of these numbers are not officially acknowledged as industry standards, but real-world experience has taught us what to look for.

For information on audio/video cable distance limits, click here.

Data Cables

Ethernet - 100 meters (328 feet)

There are a few different versions of ethernet cable, but they all have a maximum distance of 100 meters (328 feet). It should be noted that Cat7 cable has harsher distance limits than Cat5e, Cat6, and Cat6a. Cat7 gets advertised for its 100 Gbps speed, but that will only work for distances up to 15 meters (slightly over 49 feet). Beyond that, it drops to the same 10 Gbps speed of Cat6 and Cat6a (although it still retains its superior 850 Mhz bandwidth).

USB - 15 feet (passive); 95 feet (passive + active extension); 200 feet (ethernet extension)

Passive (standard) USB cables have a maximum length of 15’. This limit can be overcome by using active USB extension cables. The active cables contain a microchip repeater that bypasses the normal 15’ limit of passive cables.

When daisy-chaining USB cables, there can be no more than 15’ of passive cable total. If you have a 10’ passive USB cable and try to attach a passive 10’ extension cord to it, the cable will not work. However, using a 5’ passive extension would work because the total amount of passive cable would only be 15’. These passive/active rules hold true for all the different types of USB cables.

An extender balun allows users to use an ethernet cable as an extension for USB. Different extenders have different maximum distance ratings but generally range somewhere from 150’ to 200’.

FireWire - 72 meters (236 feet)

FireWire has a maximum length of 72 meters (236 feet). Individual cables are only manufactured up to 4.5 meters (14.8 feet) long; going further than that means the cables must be daisy-chained together. A maximum of 16 cables can be used in a single chain.

Serial Cables - 15 meters (49 feet, standard); 60 meters (197 feet, with signal degradation)

Serial cables primarily consist of DB9, DB15, DB25, and DB37. They are also called RS-232, although that term usually refers to DB9 specifically. All of these have a maximum individual length of 15 meters (slightly over 49 feet). Extension cords can be used but past the 15-meter length, the signal will start to degrade. At 30 meters, the signal will have half the normal strength. At 60 meters, ¼ the normal strength. Going beyond 60 meters is not recommended.

Single-Mode Fiber Optic - No Practical Limit

Single-mode fiber can run for many kilometers before it stops working. Unless the cable is being lain long-distance for a telecom company, distance limits should never be an issue for single-mode fiber.

OM1 Multimode Fiber Optic - 300 meters

OM1 is the basic version of multi-mode cable, being able to maintain 1GB data speeds for up to 300 meters.

OM2 Multimode Fiber Optic - 600 meters

OM2 has the same data transmission speed as OM1 but doubles its maximum length for 600 meters total.

OM3 Multimode Fiber Optic - 300 meters

OM3 has the same 300-meter distance limit as OM1 but is also capable of transmitting data ten times faster at 10GB.

OM4 Multimode Fiber Optic - 550 meters

OM4 carries a 10GB up to 550 meters, providing a distance upgrade to OM3 (similar to how OM2 has the same speed but a greater maximum length than OM1).