Telecom fibers are optical fibers which are used in optical Fiber communications.

Mainly the following types of telecom fibers are used:

• Fused Silica single-mode fibers with very low losses (e.g. 0.2 dB/km) are used for long-haul Data Transmission (tens or hundreds of kilometers) with very high transmission capacity.
• Fused silica Multimode fibers are suitable for shorter distances of e.g. hundreds of meters (e.g. within storage area networks): they are less critical to handle, essentially due to much larger Core areas, but intermode Dispersion limits the transmission distance.
• Plastic optical fibers (also multimode), typically made of PMMA (acrylic), represent the cheapest solution for short-range data transmission e.g. in home networks.

As a standard telecom fiber for the 1.3-μm or 1.5-μm Wavelength region, one typically takes the SMF-28 of Corning, or the enhanced Version SMF-28e. The Mode field diameter is ≈9.2 μm at 1310 NM (effective mode area = 67 μm2), or 10.4 μm at 1550 nm (85 μm2). The single-mode cut-off is at 1260 nm.