Copper vs. fiber considerations for industrial networks

Oct. 1, 2016
An industrial environment's harsh conditions will require certain physical characteristics, regardless of which media type you choose.

By Brian Shuman, Belden Inc.

Engineers strive for maximum productivity with minimal downtime, but this goal is only attainable with the right network infrastructure. No matter the industry, if a team doesn’t have the right cabling system in place, network reliability and performance can be compromised, leading to very costly production downtime.

This is why investing in high-quality, rugged cabling is crucial; it can reduce both the direct and indirect costs of network failure and give you peace of mind that the system is working properly. There are a variety of cabling options out there, so how do teams know they have the right one to support their specific infrastructure and network requirements? Deciphering whether you need fiber or copper cabling is a great place to start.

Copper: The classic cabling mix

Copper cabling is the traditional option in industrial installations and is best suited for the majority of industrial data transmission needs. Copper cables come in a variety of forms, including Category 5e, Category 6 and Category 6A twisted-pair cables using any number of conductor types, insulations, shielding and jackets. Armoring is also available for extremely harsh environments.

Category 5e cables are the most widely used copper cables today, but new installations favor the use of Category 6 cables to meet required Gigabit speeds and increased headroom. Category 6A cables are also an option for extreme futureproofing, minimizing the lack of bandwidth and headroom.

Teams must be careful when using copper cabling as it can stimulate potential failure points due to ingress from electrical noise, also known as electromagnetic interference (EMI) or radio-frequency interference (RFI). In light of this risk, these cables can also limit bandwidth capacity and signal transmission at extended distances.

Whether twisted-pair copper or optical-fiber cable is the choice for industrial-network cabling, the medium’s physical characteristics have to stand up to the network’s environmental conditions.

Fiber: The ultimate for futureproofing

Fiber-optic cabling is ideal for industrial environments in which high-speed, high-bandwidth data solutions are needed. Because fiber-optic cables are typically superior in bandwidth, low attenuation and complete electrical noise immunity, more information can be carried across the network without interruption. They are also smaller and lighter than copper cables, extremely durable and intrinsically safe, with no risk of spark hazards.

Fiber-optic Ethernet cables are available for both indoor and outdoor use, including situations where cables need to be buried underground. For example, fiber-optic cabling is great for campus and in-building data backbones because they can anchor to an operator’s Ethernet, and also for point-to-point digital signal transmission.

Other important considerations for fiber-optic cables include the following.

  • Typical designs for fiber-optic cables consist of multimode fibers in a loose-tube configuration, commonly available in 2 to 72 fiber constructions.
  • To handle Gigabit Ethernet light sources and any expanded bandwidth requirements, some cables use a laser-optimized fiber.
  • A basic commercial off-the-shelf (COTS) fiber-optic cable will likely not withstand industrial conditions given it is intended for enterprise applications. A fiber-optic cable that is designed with ruggedized features to operate in industrial settings is needed.
  • In particularly harsh environments, a chlorinated polyethylene (CPE) outer jacket will provide additional protection against chemicals or abrasion. An armor tape or aluminum/steel interlocked armoring may also be appropriate for extreme environments.
  • For moisture protection, a water-blocking agent should be included in the cable construction.
  • Look for fiber-optic cabling with key industry ratings, including IEEE 1202-2006 for flame test and Underwriters Laboratories (UL) ratings for optical fiber, non-conductive riser (OFNR).

Four questions for copper cables

Once teams understand whether they need copper or fiber cabling, it’s important to consider several physical components and surroundings of the cabling system. Here are four questions engineers need to ask when faced with a purchasing decision.

  1. Should my cable be shielded or unshielded? Unshielded products can be used in most environments, while shielded products are recommended for environments with high noise. A foil is typically used to protect the integrity of the signal and screen out any undesirable interference or noise. To provide extra durability and protection against noise, a foil/braid combination should be used.
  2. Should my conductors be solid or stranded? Solid conductors are appropriate for most installations, while stranded conductors provide extra flexibility for handling smaller spaces, such as robotic or continuous flex operations.
  3. Should I go with bonded or non-bonded cables? Bonded-pair cables provide resistance to the rigors of installation by using a manufacturing technique that affixes the insulation of the cable pairs along their longitudinal axes so that no gaps can develop between the conductor pairs. A non-bonded-pair cable construction can be susceptible to pair-gapping during installation, which results in impedance mismatches.
  4. What insulation material should my cable employ? It depends on the application scenario. Most industrial-grade Ethernet cables use a polyolefin insulation. For extreme temperatures, a fluorinated ethylene propylene (FEP) insulation and jacket are recommended for extended operating temperatures of -70 to +150 degrees Celsius.
    • For oil- and sunlight-resistant cables, polyvinyl chloride (PVC) jackets are typically used. If the cables are exposed to moisture, a water-blocking agent should be part of the cable’s construction, as well as inner and outer polyethylene (PE) jackets if the cable is buried.
    • Gas resistance cables call for FEP jackets, while low-smoke zero-halogen (LSZH) jackets are available for environments in which acidic smoke and flames are a key risk. This helps avoid smoke toxicity.
    • For continuous flexing or robotic applications, cables with thermoplastic elastomer (TPE) inner and outer jackets are recommended due to the risks and complications involved with caterpillar track (c-track) installation.

Knowing whether you need copper or fiber-optic cables and understanding the physical cabling components critical to the success of your application are the first steps in ensuring optimal performance in the face of demanding environments.

During the product selection process, it is very important to take the time to evaluate the marketplace and select top-quality, end-to-end cabling that can withstand tough environmental conditions and also fit with your specific application needs.

Taking this kind of total system approach will result in a more-integrated system with all products seamlessly matched to deliver tremendous interoperability and consistently reliable performance every day.

Brian Shuman is a senior product development engineering project manager at the Belden Engineer Center in Richmond, IN (www.belden.com).

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