Single-mode optical fiber core diameter is normally which microns?

Single-mode optical fiber core diameter is normally which microns?

• A. 9 microns
• B. 50 microns
• C. 125 microns
• D. 100 microns

Answer: (A)

The core diameter for single-mode fiber is kept very small so that only one light path (mode) can propagate, which minimizes modal dispersion over long distances. That usually means a core about 9 microns in diameter, with a surrounding cladding of about 125 microns. The other numbers here aren’t the core size: 50 microns is a typical core size for multimode fiber (which supports many modes), 125 microns describes the cladding diameter rather than the core, and 100 microns isn’t a standard core dimension for single-mode fiber. So, the normal core diameter for single-mode fiber is about 9 microns.

The core diameter for single-mode fiber is kept very small so that only one light path (mode) can propagate, which minimizes modal dispersion over long distances. That usually means a core about 9 microns in diameter, with a surrounding cladding of about 125 microns. The other numbers here aren’t the core size: 50 microns is a typical core size for multimode fiber (which supports many modes), 125 microns describes the cladding diameter rather than the core, and 100 microns isn’t a standard core dimension for single-mode fiber. So, the normal core diameter for single-mode fiber is about 9 microns.