What is the difference between multimode and single mode fiber optic cable?

Many businesses struggle with the question of what the best fiber options are for their company. Before we get into what is best, let’s try to answer the question what is the difference between single-mode and multi-mode cable? To begin, we’ll give a breakdown of each cable type.

Multi-mode cable

Multi-mode cable is comprised of glass fibers, with diameters in the 50-to-100-micron range. It provides high bandwidth at high speeds over medium distances, as light waves at 850 or 1300nm are dispersed into numerous paths traveling through the cable’s core. In long cable runs (over 3,000 feet), multiple paths of light can cause distortion in signal on the receiving end, which results in an incomplete data transmission; this is where single-mode fiber becomes relevant.

Single-mode cable

Single-mode cable, also called uni-mode or single-mode fiber, is a single strand of glass fiber with a narrow diameter of between 8 and 10.5 microns, transmitting at wavelengths of 1310 nm or 1550 nm. Single-mode fiber typically carries higher bandwidth than multi-mode fiber, but requires a light source with a narrow spectral width.

Single-mode fiber provides a higher transmission rate and up to 50x more distance than multi-mode, but the drawback is it typically costs more. Single-mode fiber has a much smaller core than multi-mode which nearly eliminates any distortion from overlapping light pulses, providing the least signal attenuation and the highest transmission speeds of any fiber optic cable type.


What is the difference between multi-mode and single mode fiber?

Multi-mode fiber has a relatively large light carrying core, and is commonly used for short distance transmissions with LED based fiber optic equipment. On the other hand, single-mode fiber has a smaller light carrying core and is routinely used for long distance transmissions with laser diode-based fiber optic transmission equipment.

What type of fiber I need for my business?

Determining what type of fiber, you need depends on your business needs. Ultimately this boils down to two criteria:

  • Transmission distance to be covered

  • Budget constraints

If the distance is less than a couple miles, multi-mode cable will be sufficient, and transmission system costs (both transmitter and receiver) will be in the $500 to $800 range.

If the distance needed is 3 miles or more, single mode fiber is the optimal decision. Transmission systems with this fiber can cost more than $1,000.

Should I install single-mode or multi-mode fiber?

Again, this depends on the business and the application. Multi-mode fiber will allow transmission distances of up to 10 miles and will utilize relatively inexpensive fiber optic transmitters and receivers. This may come with bandwidth limitations of a few hundred MHz per Km of length.

Single-mode fiber is better served for distances in excess of 10 miles but will require the use of single-mode transmitters which normally use solid-state laser diodes. The higher cost of these optical emitters mean that single-mode equipment can be anywhere from 2 to 4 times as expensive as multi-mode equipment.

To answer all your cabling questions for your business needs, reach out for a free assessment from professionals at Millennium Communications.