Selecting Fiber Type and Count

Two main types of fiber glass exist: single mode (OS1, OS2) and multimode (OM1, OM2, OM3, OM4).

Single mode fiber has a small light-carrying core of 8 to 10 microns in diameter. It is normally used for long distance transmissions with laser diode-based fiber optic transmission equipment. Single mode fiber, due to its advanced design, has (theoretically) infinite bandwith.

Typical Single Mode Fiber Signal Range1

Type Application Distance Wavelength
Gigabit 1000BASE-LX/LH 10km 1310nm
1000BASE-ZX 70km 1550nm
10 Gigabit 10GBASE-LX4 10km 1300nm CDWM
10GBASE-ER 40km 1550nm
40 Gigabit 40GBASE-LR4 10km (4) 10G 1310nm waves
40GBASE-FR 10km (1) 40G 1550nm wave
100 Gigabit 100GBASE-LR4 10km (4) 25G 1310nm waves, 800GHz spacing
100GBASE-ER4 40km (4) 25G ~1310nm waves, 800GHz spacing

Multimode fiber, on the other hand, has a relatively large light-carrying core, usually about 50 microns or larger in diameter. Multimode is usually used for short distance transmissions with LED or laser-based fiber optic equipment. With the larger core, multiple frequencies of light have room to travel down the cable’s length, bouncing off the cladding around the core. Ultimately, modal dispersion creates distance limitations when working with multimode fiber: at a certain point, the spread of the light waves becomes so great that it becomes difficult to determine the waveform’s leading and trailing edges, making the signal nonfunctional.

Cable Type Bandwith*Length Product
(MHZ*km or GHz*m)
10GBASE-SR
Distance (Meters/Feet)
40GBASE-SR4
and 100GBASE-SR10
Distance (meters)
OM1 Fiber 160-200 33m / 100ft N/A
OM2 Fiber 400-500 82m / 260ft N/A
OM3 Fiber 2000 300m / 1000ft 100
OM4 Fiber 4700 400m / 1300ft 150

Even though multimode has more limited signal distance, it is still the fiber type we would recommend for most inner-premise cabling installations today. (Obviously, the type of fiber you choose is dependent the requirements of the job and equipment you are installing!)

There are several reasons for this. First of all, multimode fiber has a larger core that allows a great of margin of error when terminating the fiber. This means that multimode hardware components are generally lower cost, even though multimode fiber is more expensive to produce. Along similar lines, at the moment many manufacturers are developing proprietary links and using chip sets and light engines that use more frequencies within the fiber than are available with single mode fiber.

However, single mode fiber is often the best options for applications ranging over greater distances.

There are four different types of multimode fiber. Today’s laser-optimized OM2, OM3, and OM4 are the preferred fibers when using multimode.

OM1 is traditionally an older technology that is rarely supported in today’s applications. Some older OM2 was even designed for LED-based transmission. We should note, however, that OM2 patch cable can be used at the end of a long run of OM4 without any signal issues. The basic specifications for different grades of multimode fiber are as follows:

  • OM1: fiber with 200/500 MHz*km overfilled launch (OFL) bandwidth at 850/1300nm (typically 62.5/125um fiber).
  • OM2: laser-optimized with 400/500 MHz*km OFL bandwidth at 850/1300nm (typically 50/125um fiber).
  • OM3: laser-optimized 50um fiber having 2000 MHz*km EMB bandwidth designed for 10 Gb/s, 40 Gb/s, and 100 Gb/s transmission.
  • OM4: laser-optimized 50um fiber having 4700 MHz*km EMB bandwidth designed for 10 Gb/s, 40 Gb/s, and 100 Gb/s transmission.

Choosing the type of fiber glass is the first step when selecting fiber. Next is determining the number of strands needed.

Many fiber optic products are media converters: they essentially change electric 1’s and 0’s to light 1’s and 0’s and back again. Additional fiber strands provide electronics more “lanes” for traffic.

As an example, HDMI is (basically) comprised of four signals or lanes: TMDS 0, TMDS 1, TMDS 2, and TMDS Clock. With HDMI 2.0a (18Gbps) this bandwidth is split into the four signals. TMDS 0-2 are each around 6Gbps, and TMDS clock is a low bandwidth signal (we also combine this with IR, RS232, and a few other signals).

For a 4-fiber optic solution, each of these lanes can be put on a separate fiber optic strand with no bandwith issues and no need to multiplex.

When you reduce the cabling to two fiber optic strands, you need to multiplex two lanes together for each strand. The multiplexer has to send the two lanes as separate beams of light modulating at different frequencies on the same cable. A filter network at the receiver pulls each signal back out.

When you reduce the cabling to one fiber optic strand, you need to multiplex four lanes together, then filter back out on the receiver end.

The number of fiber strands is ultimately determined by installation requirements, including length of cables installed, etc., which ultimately can determine cable type required. We’ve included some recommendations below based on common installations. Please note that it is always best to confirm based on the equipment to be installed:

  1. Equipment to Displays / Projectors
    • Minimum: 2 Strands Multimode 50/125
    • Preferred: 4 Strands Multimode 50/125
  2. Network Switches to Network Switches
    • Minimum: 2 Strands Multimode 50/125 or Single Mode 9/125
    • Preferred: 6-12 Strands Multimode 50/125 or Single Mode 9/125
  3. Network Switches to Access Points
    • Minimum: 1 Strand Multimode 50/125 or Single Mode 9/125
    • Preferred: 2 Strands Multimode 50/125 or Single Mode 9/125
  4. AV Racks to AV Racks
    • Minimum: 2 Strands Multimode 50/125
    • Preferred: 6-12 Strands Multimode 50/125
  5. DVR/NVR to Security Cameras
    • Minimum: 1 Strand Multimode 50/125 or Single Mode 9/125
    • Preferred: 2-4 Strands Multimode 50/125 or Single Mode 9/125

  6. Satellite Dish LNB to Multi-switch
    • Minimum: 2 Strands Single Mode 9/125
    • Preferred: 2 Strands Single Mode 9/125 + Empty Conduit
  7. Service Demarc to Main Structured Cable Distribution
    • Minimum: 2 Strands Single Mode 9/125 + Empty Conduit

1“Ethernet Media Standards and Distances,” University of Wisconsin Knowledge Base