Wavelengths used in previous fiber optic communication

Early fiber optic communication primarily used 850 nm, 1300 nm, and 1550 nm wavelengths, with multimode fibers operating at 850 and 1300 nm and single-mode fibers at 1310 and 1550 nm.

Historical Wavelengths

• 850 nm: This was the first widely used wavelength for short-distance, low-cost multimode fiber links. It was compatible with LEDs and later VCSELs, making it ideal for high-bandwidth networks up to approximately 500 meters, such as in data centers and corporate campuses .
• 1300 nm / 1310 nm: Multimode fibers often used 1300 nm LEDs, while single-mode fibers used 1310 nm lasers. This wavelength offered lower chromatic dispersion than 850 nm, allowing longer transmission distances without significant signal distortion .
• 1550 nm: Single-mode fibers increasingly used 1550 nm lasers due to the lowest attenuation in silica fibers and compatibility with Erbium-Doped Fiber Amplifiers (EDFAs), which enabled long-haul and high-capacity communication .

Wavelength Bands

• O-band (1260–1360 nm): Early single-mode systems used this band for minimal distortion over long distances, despite slightly higher attenuation compared to longer wavelengths .
• C-band (1530–1565 nm) and L-band (1565–1625 nm): These bands became important with the advent of WDM systems, allowing multiple channels to be transmitted simultaneously over a single fiber, significantly increasing network capacity .

Evolution to WDM

As fiber optic technology advanced, Wavelength Division Multiplexing (WDM) allowed multiple wavelengths to coexist on a single fiber. Early systems still relied on the 850, 1310, and 1550 nm windows, but WDM expanded the usable spectrum from 1260 nm to 1670 nm, enabling dense and coarse multiplexing for long-haul and metropolitan networks .

Summary

In summary, previous fiber optic communication systems relied on 850 nm for short-range multimode links, 1300/1310 nm for longer multimode and single-mode links, and 1550 nm for long-haul single-mode transmission. These wavelengths were chosen based on fiber attenuation, chromatic dispersion, and the availability of compatible optical sources and detectors, forming the foundation for modern high-capacity optical networks .