Which of the following options correctly lists a commonly used single-mode wavelength pair?

Which of the following options correctly lists a commonly used single-mode wavelength pair?

• A. 1310 and 1550
• B. 850 and 1300
• C. 1550 and 1625
• D. 1310 and 1000

Answer: (A)

1310 and 1550 nanometers are the two main low‑loss windows in standard single‑mode fiber, making them the most practical pair for telecom systems. The 1310 nm region sits near a dispersion minimum, so signals experience low dispersion and can travel with relatively clean timing over shorter links. The 1550 nm region has the lowest fiber attenuation, which means signals can travel much farther before needing amplification, and it aligns with efficient erbium-doped fiber amplifiers. Using these two wavelengths together lets designers leverage mature, widely available components—lasers, detectors, fibers, and amplifiers—and optimize performance across local and long‑haul links. Other options place wavelengths outside these standard windows or in regions less favorable for single‑mode fiber. For example, 850 nm is typical of multimode, short‑reach systems; 1625 nm lies in the L band and is used in some specialized setups but isn’t the standard paired window with 1310 nm for common single‑mode networks; 1000 nm isn’t a common telecom window due to higher loss and less established device performance.

1310 and 1550 nanometers are the two main low‑loss windows in standard single‑mode fiber, making them the most practical pair for telecom systems. The 1310 nm region sits near a dispersion minimum, so signals experience low dispersion and can travel with relatively clean timing over shorter links. The 1550 nm region has the lowest fiber attenuation, which means signals can travel much farther before needing amplification, and it aligns with efficient erbium-doped fiber amplifiers. Using these two wavelengths together lets designers leverage mature, widely available components—lasers, detectors, fibers, and amplifiers—and optimize performance across local and long‑haul links.

Other options place wavelengths outside these standard windows or in regions less favorable for single‑mode fiber. For example, 850 nm is typical of multimode, short‑reach systems; 1625 nm lies in the L band and is used in some specialized setups but isn’t the standard paired window with 1310 nm for common single‑mode networks; 1000 nm isn’t a common telecom window due to higher loss and less established device performance.