To amplify a fiber optic signal for longer reach, at which wavelength should the laser emit?

To amplify a fiber optic signal for longer reach, at which wavelength should the laser emit?

• A. 1310 nm
• B. 1550 nm
• C. 850 nm
• D. 1060 nm

Answer: (B)

The main idea is choosing the wavelength that minimizes fiber loss and matches available amplification technology for long distances. The 1550 nm region is the sweet spot for long-haul fiber because standard silica fiber has its lowest attenuation there (about 0.2 dB per kilometer). That means less signal power is lost as it travels. In addition, erbium-doped fiber amplifiers are optimized for this band, providing efficient, low-noise amplification that makes it practical to boost signals many kilometers down the line. The other wavelengths don’t offer the same combination. 850 nm sits in the near-visible range and suffers higher loss in standard silica fiber, making it unsuitable for long reach. 1060 nm isn’t the low-loss telecom window and lacks the widely available, optimized amplification options used for long-distance links. 1310 nm has its own advantages (like lower dispersion in some systems), but for maximum reach with proven amplification, 1550 nm is the best choice.

The main idea is choosing the wavelength that minimizes fiber loss and matches available amplification technology for long distances. The 1550 nm region is the sweet spot for long-haul fiber because standard silica fiber has its lowest attenuation there (about 0.2 dB per kilometer). That means less signal power is lost as it travels. In addition, erbium-doped fiber amplifiers are optimized for this band, providing efficient, low-noise amplification that makes it practical to boost signals many kilometers down the line.

The other wavelengths don’t offer the same combination. 850 nm sits in the near-visible range and suffers higher loss in standard silica fiber, making it unsuitable for long reach. 1060 nm isn’t the low-loss telecom window and lacks the widely available, optimized amplification options used for long-distance links. 1310 nm has its own advantages (like lower dispersion in some systems), but for maximum reach with proven amplification, 1550 nm is the best choice.