1. Introduction
In this tutorial, we’ll systematically compare optical fiber and twisted pair (copper) cables. In particular, we’ll discuss the main aspects one should consider when choosing between fiber and twisted pair cables for a network.
First, we’ll briefly describe both types of cables. Next, we’ll compare optical fiber and twisted pair cables, considering various factors. Finally, we’ll cover some common usage scenarios for both cables.
2. What Are Optical Fiber and Twisted Pair Cables?
Optical fiber cables are made of thin strands of glass or plastic called optical fibers. In such cables, data is transmitted using light signals. The core of the fiber reflects light internally, allowing data to be propagated over long distances with minimal signal loss.
Moreover, optical fiber cables can transmit data via single or multiple propagation paths (also called transverse modes). Thus, we call Single-Mode Fibers (SMF) those that support only a single transverse mode. Naturally, the term Multi-Mode Fibers (MMF) refers to those that propagate signals via many modes.
Twisted pair cables consist of pairs of insulated copper wires twisted together. Networks using this type of cable transmit data through electrical signals. Indeed, this is the reason for the twisting, as it reduces electromagnetic interference and crosstalk between adjacent pairs.
There are several categories of twisted pair cables, with CAT5e, CAT6, CAT6A, CAT7, CAT7A, CAT8.1, and CAT8.2 being the ones used in computer networks nowadays. In addition, while CAT5e and CAT6 cables are Unshielded twisted pair (UTP), all the latest categories are based on a Shielded twisted pair (STP) design.
3. Comparison
Now, let’s systematically compare both types of network cables.
3.1. Electromagnetic Interference
Electromagnetic interference (EMI) is a disturbance caused by an outside source that affects an electrical path or circuit by electromagnetic induction, electrostatic coupling, or conduction. In computer networks, this can lead to an increase in the error rate or even a total loss of data.
Since twisted pair cables are made of copper and transmit data using electrical signals, they’re susceptible to electromagnetic interference. However, the level of vulnerability to interference can vary according to the category of cable. For example, a Cat5e twisted pair cable is much more susceptible to electromagnetic interference than a Cat6A cable.
On the other hand, optical fiber cables are completely immune to electromagnetic interference. Indeed, the reason is that data is transmitted via light pulses in these cables, not electrical signals. Therefore, in environments with high levels of electromagnetic interference, optical fiber cables may be a better option than twisted pair cables.
3.2. Maximum Cable Length and Transmission Speed
The maximum length of a communication cable can vary drastically depending on the material it’s composed of and the way it’s constructed. This is because the level of degradation of the transmitted signal can differ according to the characteristics of the cable material and the way it was designed.
Also, the maximum data transmission speed in a network can be affected by various factors, including the limitations of the underlying physical medium. Thus, in wired networks, these limitations are related to both the composition material and the length of the cable.
Therefore, this implies that the maximum length of a cable can also vary according to the desired data transfer speed. Typically, the shorter the cable length, the higher the speed achieved. Now, let’s examine the maximum length and corresponding speed achieved by both optical fiber and twisted pair cables.
The maximum acceptable length limit for twisted pair cables can range from 37m to 100m. In addition, such cables can achieve a maximum data transmission rate of 10 Gbps. To summarize, the table below shows the general specifications of twisted pair cables concerning the length and data rate transmission limits:
| Cable Category | Maximum Data Rate | Maximum Distance Supported |
|---|---|---|
| CAT5e | 1 Gbps | 100m |
| CAT6 | 1 Gbps | 100m |
| 10 Gbps | 37m | |
| CAT6A | 10 Gbps | 100m |
| CAT7 | 10 Gbps | 100m |
| CAT7A | 10 Gbps | 100m |
| 40 Gbps | 50m | |
| CAT8.1 | 25 Gbps | 30m |
| CAT8.2 | 40 Gbps | 30m |
In the case of optical fiber cables, the length and speed limits can also differ depending on the transceivers used at the ends of the cable. The table below illustrates some common combinations:
| Types of Optical Fiber | Supported Speed | Supported Distance | Compatible Transceivers/Modules | |
|---|---|---|---|---|
| Single Mode Fiber (SMF) | Gigabit (1G) | 5 km | 1000Base-LX | |
| 10 Gigabit (10G) | 40 km | 10GBASE-E | ||
| 40 Gigabit (40G) | 10 km | 40GBASE-LR4 | ||
| 100 Gigabit (100G) | 10 km | 100GBASE-LR4 | ||
| Multi-Mode Fiber Cables (MMF) | OM1 and OM2 | Gigabit (1G) | 550m | 1000Base-LX |
| 10 Gigabit (10G) | 300m | 10GBASE-LX4 | ||
| OM3 | Gigabit (1G) | 550m | 1000Base-LX | |
| 10 Gigabit (10G) | 300m | 10GBASE-LX4 | ||
| 40 Gigabit (40G) | 100m | 40GBASE-SR4 | ||
| 100 Gigabit (100G) | 100m | 100GBASE-SR10 | ||
| OM4 | Gigabit (1G) | 550m | 1000Base-LX | |
| 10 Gigabit (10G) | 300m | 10GBASE-LX4 | ||
| 40 Gigabit (40G) | 125m | 40GBASE-SR4 | ||
| 100 Gigabit (100G) | 125m | 100GBASE-SR10 | ||
For other possible combinations, please refer to the FOA (The Fiber Optic Association) Reference Guide.
In general, we can conclude that optical fiber cables can reach much higher speeds and distances than twisted-pair cables.
3.3. Types of Connectors and Devices
Network cables need connectors to be plugged into network devices. In addition, cables made of different materials require completely different connectors.
In the case of twisted pair cables, the most commonly used and widely known connector is the RJ45. However, high-performance connectors such as GG45 and TERA are more recommended for the most recent categories of twisted pair cables. Both offer backward compatibility with RJ45 connectors.
The following table provides a list of the categories and their respective connectors:
| Cable Category | Connector |
|---|---|
| CAT5e | RJ45 |
| CAT6 | RJ45 |
| CAT6A | Shielded RJ45 |
| CAT7 | GG45 or TERA |
| CAT7A | GG45 or TERA |
| CAT8.1 | GG45 or TERA |
| CAT8.2 | GG45 or TERA |
Naturally, optical fiber cables also require specific connectors. These include connectors such as LC (Lucent Connector), SC (Standard Connector), MPO (Multiple-fiber Push-On/Pull-off), and others. Moreover, a more comprehensive list of the main optical fiber connectors can be found here.
However, optical fiber cables still require the use of special devices called transceivers (also known as optical modules). An optical module has two interfaces: one electrical and one optical. In brief, the electrical interface connects to the inside of a system (e.g., a switch), and the optical interface connects to the optical fiber cable.
Therefore, we should make sure that the devices we plan to use support the type of cable we choose. For example, we’d be underusing a CAT6a twisted pair cable to interconnect devices with 10/100/1000BASE-T network interfaces. This is because we’d never use the maximum potential of 10Gbps supported by the CAT6A cable.
In this sense, we also need to pay attention to incompatibility issues. For example, if we choose to use optical fiber cables, we must ensure that the devices we wish to interconnect support the type of transceiver that we plan to use in the cable.
4. Common Usage Scenarios
Both types of cable are widely used in computer networks. However, we typically use twisted pair and optical fiber cables in different contexts and scenarios.
In this sense, optical fiber cables are more present in long-distance and high-speed data networks. Therefore, we commonly employ optical fiber cables in backbone infrastructures, data centers, and at the core of the organization’s networks.
On the other hand, twisted pair cables are typically used in short-distance communication networks. This makes them very popular in LANs, which interconnect networks with lower speed requirements, like home and office networks.
5. Conclusion
In summary, optical fiber cables are outstanding for high-speed, long-distance communication with immunity to interference. In contrast, twisted pair cables are cost-effective and commonly used for shorter-distance networking applications.
The choice between them depends on factors such as the required data transmission rate, distance, environmental conditions, and types of available or desired devices.