The Difference Between Single Mode and Multimode Fiber Cabling

As industrial networks continue to improve, cabling remains a constant and important factor. For many companies, designing and installing an entirely new network may be financially counterproductive. Devices such as serial to fiber converters allow companies to benefit from the initial investments on a network and allow newer technologies to be added later. Perhaps the most important aspect of industrial networking is the cable type used to connect devices. Most legacy devices use copper cabling, but as industry standards have sifted to fiber optic cabling, many networks need to understand the role fiber plays in network design.

When you deploy cabling, it helps to understand that not all fiber optic cable is the same and the difference between single mode and multimode fiber cabling can affect your network’s performance. Fiber optic cables come in two types, both with their own benefits and detriments depending on the type of deployment.

Single Mode Fiber Optic Cable

Single mode fiber optic cable refers to the diametrical core of the cable that allows a single signal of light to pass through it. As light is allowed to pass through, the diameter of core decreases. In turn, as the core decreases in diameter, the light attenuation increases and allows the signal to travel greater distances. Single mode fiber cable has a core to cladding ratio of about 9 microns to 125 microns. A single mode design allows all aspects of the signal to travel at the same speed and arrive to the next device at approximately the same time. Single mode cablings lose virtually no signal over long distances from device to device.

Multimode Fiber Optic Cabling

Multimode fiber optic cables derive their name from the wider core and ability to allow multiple modes of lights to pass through. The larger core drastically increases the number of light reflections that can be created as the light passes the core. All those increases ultimately mean the cable can allow more data to transverse the length of the fiber cabling. Multimode cabling can handle more data, but the decrease in cladding material also decreases the attenuation, which results in a much higher dispersion rate as the signal travels. Conventional thought follows that multipurpose cabling is best suited for shorter distances.

Best Use Cases for Single Mode and Multimode Fiber Optic Cabling

With the ability to maintain signal integrity over long distances, single mode cabling is ideal for several use cases. Telecommunication networks commonly utilize single mode cabling as its infrastructure backbone. College campuses, universities, and cable networks can benefit from running single core cabling. Any instance of an industrial network in which a large amount of bandwidth is needed over long distances is a great use case for single mode fiber optic cabling.

Multimode cabling is excellent for handling the bandwidth requirements of audio and video transmissions, so multimode is the ideal cabling for enterprise use. With digital conferencing in the enterprise world, these networks can greatly benefit from the proper cabling. Using multimode fiber within a building allows a space to benefit from the extreme speeds without a concern for running cable over long distances.

Types of Single Mode and Multimode Fiber Optic Cabling

Single Mode Cabling Types

Within the destinations of single mode cabling, each type of cabling has a subsection.

• 652 (Standard single mode fiber) - The zero-dispersion wavelength is the wavelength where the group delay dispersion is zero.
• 653 (Dispersion shifted fiber) - Has a smaller core than the most commonly used fiber cabling G.652. DSF also has a higher operation range.
• 654 (Cutoff shifted fiber) - Ultra low loss optical fiber that is most commonly used for transoceanic cabling.
• 655 (Non-zero dispersion shifted fiber) - Has a dispersion rate that is close to zero, but does not hit zero.
• 657 (Bend-insensitive fiber) - Is single mode cabling that is designed to maintain performance while allowing fibers to bend.

Multimode Cabling Type

Multimode cabling can be broken down into two subsections, Step Index and Graded Index. Step Index is a now an antiquated technology rarely used in any networks today. Graded Index fiber is now the most common fiber optic cabling type. Graded Index fiber produce smoother waveforms than the zig-zag transmissions of Step Index. Graded Index multimode cabling are more efficient than ragged waveforms, and it decreases signal degradations.

Multimode cabling further breaks down into another subsection based on the different generations of multimode fibers.

• OM1 is the first generation and has a 62.5µm core diameter.
• OM2, OM3 and OM4 share a 50µm core diameter, but OM2 is most commonly used.
• OM3 and OM4 fibers differ from other generation in that both types are laser-optimized multimode fibers.

Cost Benefits Analysis

Multimode is usually found to be more cost effect. With the high bandwidth over shorter distances, multimode cabling is usually more than sufficient for most enterprise uses. For companies with a larger budget, or a profitable deal on cabling, single mode can be excellent source for Local Access Network (LANs). Any case where two devices need to be connected, but the devices are more than a mile apart, means single mode cable is the ideal option.  Many network designers believe that if single mode fiber optic cabling can be deployed it should be. The front-end investment is really an investment in the future. Single mode cabling quickly became the standard cabling across industries because of this.

The Future

As more cities invest in becoming smart cities, the need for fiber optic cabling for major industrial scenarios will greatly increase. Local and federal governments have seen the benefits industrial networking provides in tollway monitoring systems and transit monitoring systems. Interconnectedness is exploding in the private sector; networks have become the backbone of manufacturing lines and other industrial production. Cabling that allows network devices to communicate efficiently and effectively drive all these systems. Those designing the system have the tremendous responsibility to not only meet the current networking needs, but to also lay the foundation for these systems to move into the future.