Types of Fiber Optic Glass
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 (μm) 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 | 5 km | 1310 nm |
| 10 Gigabit | 10GBASE-LX4 | 10 km | 1310 nm |
| 10GBASE-E | 40 km | 1550 nm | |
| 40 Gigabit | 40GBASE-LR4 | 10 km | 1310 nm |
| 40GBASE-FR | 2 km | 1310 nm | |
| 100 Gigabit | 100GBASE-LR4 | 10 km | 1310 nm |
Multimode Distance Limitations
Multimode fiber, on the other hand, has a relatively large light-carrying core, usually about 50 μm 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) |
10 Gb Ethernet Distance 10GBASE-SR |
40 Gb/100 Gb Ethernet Distance 40GBASE-SR4 and 100GBASE-SR10 |
|---|---|---|---|
| OM1 Fiber | 160-200 | 33 m / 100 ft | N/A |
| OM2 Fiber | 400-500 | 82 m / 260 ft | N/A |
| OM3 Fiber | 2000 | 300 m / 1000 ft | 100 m / 330 ft |
| OM4 Fiber | 4700 | 400 m / 1300 ft | 150 m /500 ft |
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 greater 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.
Types of Multimode Fiber
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 850/1300 nm (typically 62.5/125 μm fiber).
- OM2: laser-optimized with 400/500 MHz*km OFL bandwidth at 850/1300 nm (typically 50/125 μm fiber).
- OM3: laser-optimized 50 μm fiber having 2000 MHz*km EMB bandwidth designed for 10 Gb/s, 40 Gb/s, and 100 Gb/s transmission.
- OM4: laser-optimized 50 μm fiber having 4700 MHz*km EMB bandwidth designed for 10 Gb/s, 40 Gb/s, and 100 Gb/s transmission.
Choosing Strand Count
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 bandwidth 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.
General Residential Strand Count Recommendations
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. You can also view this information or download this chart . Please note that it is always best to confirm based on the equipment to be installed.
1 ANSI/TIA-568.0-D-1