Ethernet Cables
Introduction
Ethernet cables have been evolving since the beginning of the Ethernet standard in 1985. Many different categories of Ethernet cable have been developed, and each category has different specifications as far as shielding from electromagnetic interference, data transmission speed, and the possible bandwidth frequency range required to achieve that speed. The standard gauge sizes (AWG) are also different in the different categories of cable, and this can have end results for both quality and speed.
Category 3 Ethernet cable, also known as Cat3 or station wire, is one of the oldest forms of Ethernet cable still in use today. It is an unshielded twisted pair (UTP) cable that is capable of carrying 10 Mbps of data or voice transmissions. Its maximum possible bandwidth is 16 MHz. Cat3 cable reached the peak of its popularity in the early 1990s, as it was then the industry standard for computer networks. It still can be seen in use in two-line telephone systems and older 10BASE-T Ethernet installations.
Category 5 (Cat5) Ethernet cable is the successor to the earlier Category 3. Like Cat3, Cat5 is a UTP cable, but it is able to carry data at a higher transfer rate. Cat5 cables introduced the 10/100 Mbps speed to the Ethernet, which means that the cables can support either 10 Mbps or 100 Mbps speeds. A 100 Mbps speed is also known as Fast Ethernet, and Cat5 cables were the first Fast Ethernet-capable cables to be introduced. They also can be used for telephone signals and video, in addition to Ethernet data. This category has been superseded by the newer Category 5e cables.
The Category 5e (Cat5e) standard is an enhanced version of Cat5 cable, which is optimized to reduce crosstalk, or the unwanted transmission of signals between data channels. This category works for 10/100 Mbps and 1,000 Mbps (Gigabit) Ethernet, and it has become the most widely used category of Ethernet cable available on the market. While both Cat5 and Cat5e cables contain four twisted pairs of wires, Cat5 only utilizes two of these pairs for Fast Ethernet, while Cat5e uses all four, enabling Gigabit Ethernet speeds. Bandwidth is also increased with Cat5e cables, which can support a maximum bandwidth of 100 MHz. Cat5e cables are backward-compatible with Cat5 cables.
One of the major differences between Category 5e and the newer Category 6 (Cat6) is in transmission performance. While Cat5e cables can handle Gigabit Ethernet speeds, Cat6 cables are certified to handle Gigabit Ethernet with a bandwidth of up to 250 MHz. Cat6 cables have several improvements, including better insulation and thinner wires. These improvements provide a higher signal-to-noise ratio, and are better suited for environments in which there may be higher electromagnetic interference. Cat6 cables are available in shielded twisted pair (STP) forms or UTP forms. Cat6 cable is also backward-compatible with Cat5 and 5e cables.
Category 6a cable, or augmented Category 6 cable, improves upon the basic Cat6 cable by allowing 10,000 Mbps data transmission rates and effectively doubling the maximum bandwidth to 500 MHz. Category 6A performs at improved specifications, in particular in the area of alien crosstalk as compared to Cat 6 UTP (unshielded twisted pair), which exhibited high alien noise in high frequencies.
Category 7 cable (Cat7), also known as Class F, is a fully shielded cable that supports speeds of up to 10 Gbps (10,000 Mbps) and bandwidths of up to 600 MHz. Cat7 cables consist of a screened, shielded twisted pair (SSTP) of wires, and the layers of insulation and shielding contained within them are even more extensive than that of Cat6 cables. Because of this shielding, they are thicker, bulkier, and are more difficult to bend. Additionally, each of the shielding layers must be grounded, or else performance may be reduced to the point that there is no improvement over Cat6. In fact, performance may be even worse than Cat5. For this reason, it is very important to understand the type of connectors at the ends of a Cat7 cable.
