What are the two general types of fiber optic cable found in current networking environments?

  • Red and Green
  • Singlemode and Multimode (Correct)
  • High-frequency and Low-frequency
  • Narrowband and Wideband

There are two general types of fiber optic cable found in LAN and WAN networking equipment—singlemode and multimode. The fiber core used in singlemode cable is significantly smaller (typically between 8 and 10 microns) than the core used is multimode cable (usually 50 or 62.5 microns but sometimes larger). The smaller core size allows only a single ray of light (or mode) to travel through the cable.

Multimode cable can use either an LED or laser light source and operate at wavelengths of 850 nm and 1,300 nm.

Singlemode cable uses laser sources exclusively and operates at wavelengths of 1310 nm or 1550 nm. Singlemode cabling is less susceptible to attenuation than multimode cable, and is used to transmit data at extremely high bandwidth or over great distances. Most campus and single-building fiber networks use multimode cable.

Note: While the cores of singlemode and multimode cables have traditionally been made from glass and in some cases quartz, multimode cables can also have a plastic core—usually made from acrylic or a perfluorinated polymer. Plastic optical fiber (POF) has a much larger core (100, 200, or often 980 microns) than traditional glass optical fiber (GOF). POF is more susceptible to attenuation than glass fiber and is often used for short runs, less than 50 meters. POF is designed to work with light sources operating at wavelengths visible to the human eye, typically 650nm. The tools and equipment need to install and use POF is typically much cheaper than GOF. The installation process is also much easier.