How to Choose the Right Fiber Optic Cable for Your Business

Written by Don Schultz, Senior Technical Marketing Specialist, Fluke Networks Certified Copper/Fiber CCTT, BICSI TECH, INSTC, INSTF Certified

Are you purchasing fiber optical cable for your business but have limited background in selecting the correct type and associated accessories? Perhaps you received a specification from IT but not all of your questions have been adequately addressed. Either way, someone (likely you) has to figure out what to actually order. Fiber cable is really a specification with five or six independent variables, each determined by a different aspect of your project. Get one wrong and you've ordered cable that won't work in your environment or won't support your speed requirements. This guide walks through each decision in order so you can specify with confidence!

Start with Performance — Distance and Speed Determine Your Fiber Type

The first and most fundamental question is what do you need the fiber to do? Certain types of fiber can go much longer distances and at higher speeds than others.

Singlemode vs. Multimode — The Distance Decision

Essentially, the decision on speed and distance will determine whether you need multimode (MM) or singlemode (SM) fiber optical cable.

• Multimode fiber (OM3, OM4, OM5): uses a larger core (50 micron) that allows multiple light modes to travel simultaneously.
  • Multimode fiber is best for shorter runs — up to approximately 550m for OM4/OM5 at 10G, up to 300m for OM3.
  • Multimode fiber makes use of low cost transceivers, which is the device that translates electrical data to optical data. These transceivers are the size of a pack of gum and slide into ports on the network switches. Multimode transceivers are typically operating at 850nm wavelength and usually in a package called a SFP (1G) or SFP+ (10G) module. SFP means “Small Form-factor Pluggable”.
  • OM4 MMF and OM5 MMF are the modern choices for new multimode fiber installations. Only pick OM3 if you are retrofitting or expanding an existing system that makes use of OM3 fiber optical cable.

Multimode technology (OM1 through OM5) has been improving over the years, but has resulted in some confusion around OM grade and what should be used. This chart demonstrates the performance capability of each OM grade. Technically, each new OM grade obsoletes the previous grades for new installs!

Multimode fiber is best for in-building LAN, data centers, small sized campus, and short backbone runs up to 1,800 feet. Most business LAN and campus installations fall in this category.

If the differences between the various multimode fiber optic cable OM types still confuses you, please see A Guide to Multimode Fiber Types (OM1-OM5) for a great explainer!

• Singlemode fiber (OS1, OS2): uses a smaller core (9 micron) and a single light path. The tolerances are far tighter than multimode optical fiber.
  • Singlemode fiber cable (seen abbreviated as SM or SMF) supports much longer distances — kilometers rather than hundreds of meters.
  • For shorter distances, singlemode fiber also may scale to extremely high speeds.
  • The SFP+ transceiver cost is higher for singlemode fiber optics due to the need for more precise lasers.
  • OS2 SMF is the modern and up to date choice for singlemode fiber.

Singlemode fiber is best for inter-building runs, campus backbone over long distances, WAN connections, or any run exceeding the multimode distance limit. Singlemode is also best suited for extremely high speed runs, even at short distances that could have been addressed with multimode fiber (albeit at slower speeds). OS2 is the modern pick.

Decision shortcut: If your runs are within a single building or between buildings less than ~500m apart, multimode is almost always the right choice. If you're connecting buildings across a campus or between sites, then singlemode.

If there are lingering questions in your mind about singlemode fiber, a great resource is this easy to read blog aimed at beginners: Singlemode vs Multimode Fiber Optic Cable.

Strand Count — How Much Capacity Do You Need?

Strand count refers to how many actual individual fibers are found inside of a cable, under the cable jacket itself. Therefore, a single 12-strand fiber cable will look remarkably similar to traditional Cat6 copper twisted pair “Ethernet” cable until you strip it back!

• A standard link requires two strands (one transmit, one receive). This is known as duplex communication where each fiber is carrying data in a different direction. The exception is singlemode fiber with BiDi (Bi-Directional) transceivers, which transmit and receive over a single fiber by using a different wavelength for each direction. The fiber itself is simplex (one strand), but the communication is still full duplex.
• BiDi transceivers, combined with OS2 singlemode fiber, can greatly increase the density of an installation.
• Higher strand count \= more capacity for parallel links, future expansion, and the ability to combine multiple fibers into a single link to dramatically increase speeds.
• Common strand counts (keep in mind if using duplex transceivers you get exactly ½ of the stated strand count for actual communications channels, but you will achieve the stated strand count for communications channels with BiDi data transmission):
  • 2-strand (typical point to point links and patch cords -- ideal for residential installations)
  • 6-strand (typically seen in small business bulk distribution fiber to remote workstations)
  • 12-strand (typical for small business backbone)
  • 24-strand and above (typical for larger installations and data centers)
• Rule of thumb: order more strands than you think you need. Running additional fiber through conduit is essentially free compared to the cost of pulling cable again later. A 12-strand cable costs little more than a 6-strand in most cases.
• Consider MPO/MTP trunk cables for high-density applications, where many fibers are in a single high density connector. This requires the requisite compatible transceivers or fiber splice/break-out trays.

2, 6, and 12 strand bulk distribution fiber cable (in this case OM4 multimode)

Both singlemode and multimode fiber optical systems can be duplex. BiDi simplex data transmission, however, is normally associated with singlemode fiber. Transceiver costs can be high, but you get many more communications channels since BiDi only requires a single fiber to work!

Environment — Construction, Jacket Rating, and Routing Determine What You Can Install

Once you have settled upon whether you require singlemode or multimode fiber and the strand counts, the next decision revolves around physical cable construction (the plastics used, armor, etc.). Your physical environment tells you what cable construction will be required.

Indoor, Outdoor, or Both?

Here are the common cables you will see on the market. Usually each one serves a specific environmental purpose, but there are dual use cables on the market that may serve indoor and outdoor situations.

• Indoor only cable
  • Typically tight buffer construction (increases resilience to fiber optical core/cladding glass damage)
  • Designed for climate-controlled environments
  • Not UV resistant
  • Not moisture rated
  • Don’t install outdoors as cable life will suffer
• Outdoor only cable
  • Usually seen as “loose tube” construction (fibers are permitted to freely move as the cable expands and contracts with unstable temperature environments, reducing damage over time) but can be tight buffered as well
  • Often seen with metallic armor under the cable jacket
  • Gel-filled or dry-type tubes protect the fiber from moisture, UV exposure, and temperature extremes
  • Required for any run exposed to weather or direct burial
  • Never install indoors, as the majority of outdoor-only fiber optical cable will not meet building fire Code requirements!
• Indoor/outdoor rated dual-rated cable
  • Can be transitioned from outside directly inside without a splice or transition point
  • Ideal for runs that enter a building and continue to a termination point inside
  • Normally has all the advantages of outdoor-only cable but meets indoor fire rating requirements too

Wondering what armor is and what it looks like inside of fiber optical cable? You are not alone! Please read Armored vs. Unarmored Fiber Optic Cables: Determining the Best Solution for Your Network Infrastructure.

Jacket Fire Rating — Plenum, Riser, or General Use?

After mode, fiber count, and general cable construction have been decided upon consideration must be given to cable fire rating.

Cable fire rating is often heavily related to the cable construction as the different plastics used in cable construction to address various environments will impact where the cable can be legally installed.

• Plenum (OFNP): required in air-handling spaces — above drop ceilings or under raised floors where HVAC air circulates. Low-smoke, flame-retardant. Required by building code in plenum spaces. Do not substitute riser cable in plenum spaces.
• Riser (OFNR): required in vertical runs between floors — elevator shafts, conduit between floors. Flame-retardant but not plenum-rated. Cannot be used in plenum spaces, but is an excellent all-round indoor cable otherwise.
• General use (OFN): for horizontal runs within a single floor in non-plenum spaces. Most common for in-rack and data center patch applications.
• When in doubt, plenum-rated cable can always be substituted for riser or general use — it's rated higher. Riser can substitute for general use. Never substitute down.

Keep in mind the vast majority of outdoor grade fiber optical cable is NOT suitable for indoor installation and would trigger a fire Code violation. Always check the cable specifications!

If picking the correct fire rated cable for your environment is still a lingering question in your mind, please read Fiber Optic Cable: Jacket & Fire Rating.

Connector Type — Match Your Transceivers

At this point, we need to discuss fiber optical transceivers briefly. Once you have selected the fiber optical cable you need, this will directly dictate the transceivers required and thus the connectors for your cable too!

Fiber optical transceivers translate electrical signals into optical signals, and they come in a dizzying variety!

Fiber optic transceivers are what permits your fiber optic cable, that transmits light pulses, to communicate with your network switches which rely upon electrical signals. It is a translation bridge between electrons and photons. Here are some of the considerations around fiber transceiver selection:

• Your fiber optical cable and the connectors you have spliced or terminated to it will dictate what kind of transceivers you will require
• Network speed will also dictate the transceiver you select
• Transceivers are normally seen in SFP form factors (SFP for 1G, SFP+ for 10G, SFP28 for 25G)
• Transceivers will slide into a SFP/SFP+ port on your network switches, usually right next to the traditional copper RJ45 networks ports you are already familiar with
• Transceivers will almost always use LC type (Lucent) connectors
• It is important to ensure compatibility between the transceiver and network switch, usually by brand matching or checking specification sheets

The Most Common Fiber Connector Types

In discussing transceivers, this segues into the various connector types you will encounter. Just like transceivers, there is a dizzying array of connectors out there not only with different physical formats but also with different end face polishes (APC and UPC). Here are the most common ones:

• LC (Lucent Connector)
  • Small form factor, most widely used in modern SFP+ and SFP28 transceivers
  • Standard for 10G, 25G, and higher speed applications
  • Default for new installations.
• SC (Subscriber Connector)
  • Larger push-pull connector
  • Still common in older equipment, some legacy data center environments, and some passive WDM components
  • Less common in new deployments
• ST (Straight Tip)
  • Bayonet-style connector
  • Largely legacy — found in older LAN installations, some campus networks, and security camera systems
  • Rarely specified for new installations
• MPO/MTP
  • Multi-fiber push-on connector that terminates 8, 12, or 24 fibers simultaneously
  • Used in high-density data center pre-terminated trunk cable systems and 40G/100G parallel optic applications
  • Extremely common in high density installations

LC, ST, and MPO/MTP connectors may also have UPC (Ultra Physical Contact) or APC (Angled Physical Contact) end face polishes. Less likely, you may encounter PC (Physical Contact) connectors, but those have been obsolete for some time.

Essentially, APC connectors are polished on an angle to reduce reflections at connection points to increase performance where UPC connectors are not. Associated with singlemode fiber, APC end face polish may be required to achieve your fiber optical splice budget. If end face polish has you puzzled, please see PC vs UPC vs APC Fiber Connectors – What is the Difference?

Normally, these connectors will be spliced (fusion or mechanical) onto your bulk unterminated fiber optical cable. Fiber optical pigtails come ready to splice onto your bulk cable. In other situations, you will pick a fiber optical patch cord that is ready to go with connectors already installed. In edge case situations, the fiber connector may also be field terminated by crimping them on.

The transceiver your equipment accepts determines your connector type — LC is the default for any modern equipment.

The big take-away here is that your fiber optical installation will end up as a system and each component of that system will heavily influence what components go with what. From the cable itself to the connector type and finally the transceivers, it’s all interdependent.

Quantity — How Much Fiber Optic Cable to Order

Nobody wants to underestimate the amount of cable required, but it is also important to not significantly overestimate the amount required as well. Here are some general guidelines for adding up to the right amount of cable:

• Total distance of all runs plus a buffer is the starting point — use the same estimation methodology as structured copper cabling (measure, add vertical drops, add service slack, add a waste buffer of 7–10%)
• Number of runs multiplied by average run length gives your total footage requirement
• Strand count multiplied by number of runs determines the minimum fiber count — always round up to the next standard strand count (2, 4, 6, 12, 24) and err on the higher side
• Lead time note: fiber optic cable lead times can vary significantly by manufacturer and strand count. Higher strand counts and specialty constructions (armored, direct burial) often have longer lead times. If your project has a hard deadline, factor lead time into your supplier decision.

When selecting a cable supplier, don’t select upon price alone! Does your supplier have specification sheets readily available, reachable and responsive customer support, and extensive on-line helpful blogs/videos? Choose your supplier wisely!

Estimating cable length required need not be complex. Please read Cable Waste Math: How to Estimate Your Box Count to help you plan this out.

Accessories — What Else You'll Need

What fun is shopping without the ability to accessorize? Don’t forget these items when placing your order and be sure to throw in a pair of nice shoes for yourself! All kidding aside, there are some extremely specific tools to fiber optical installation.

• Pigtails:
  • Factory-terminated fiber stubs (one end has a connector, the other is bare fiber for fusion or mechanical splicing)
  • Used when terminating bulk unterminated fiber cable to a patch panel or enclosure via fusion splice rather than field termination
  • Pigtails are extremely effective, and when fusion spliced offer a cleaner, low loss alternative to field-terminated connectors for permanent installations

• Kevlar cutters
  • Fiber cables normally include strength members include aramid yarn that cannot be cut with standard scissors or wire cutters, usually referred to by the brand name “Kevlar”
  • Kevlar shears/scissors are required for clean cable cuts
  • Kevlar scissors may also be used to score the outer jacket on a fiber optical cable to expose the interior fibers, but a specialized fiber optical “ringing” tool is preferred for this task
• Cable stripper:
  • A proper fiber stripping tool is absolutely required to remove the buffer coating from individual fiber strands without damaging the glass
  • Standard wire strippers will damage or break the fiber
• Fiber cleaning supplies
  • When stripping, cleaving, splicing, or placing connectors onto fiber optical cable you will require a supply of specialized non-linting wipes and fiber optical cleaning solution
  • NEVER substitute isopropyl alcohol or other non-approved cleaning solution for fiber optical specific cleaning solution as non-approved solutions will often leave a film behind
• End face/bulkhead click cleaners
  • Click cleaners are a pen shaped cleaner that cleans with a push and clicks to advance a thin ribbon
  • Click cleaners are useful for both fiber optical connector end faces and bulkhead couplers
  • Click cleaners are available in multiple types for specific connectors such as LC click cleaners and ST click cleaners and even high density MPO/MTP connector click cleaners
  • Click cleaners are fast and effective for field use
• End face cassette cleaners
  • Cassette cleaners are useful for cleaning end faces only, but a cassette cleaner may be used for ANY end face
  • Cassette cleaners are reel-based cleaning systems for higher-volume connector end face cleaning
  • Cassette style cleaners are common in data center environments

Every connector should be inspected and cleaned (if necessary) before mating. In the past, the mantra was “clean, clean, clean”. That method worked, but could introduce contamination when none was present. Now the mantra is “inspect, inspect, inspect.”

Conclusion

So there you have it! Buying fiber optic cable for a business installation comes down to a sequential decision process: performance first, then environment, then connectors, then quantity, then accessories. Get those five questions answered in order and you have a complete specification ready to order. trueCABLE stocks a full range of singlemode and multimode fiber in every jacket type, with fast turnaround for business projects. Oh, and our customer support is responsive and we offer a massive collection of educational blogs and videos when you wish to self-pace!

HAPPY NETWORKING!!

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