How much is the span of the optical fiber cable

The span of an optical fiber cable typically ranges from a few hundred meters for multimode fiber to over 100 kilometers for single-mode fiber without amplification.Definition of Fiber SpanA fiber span is the physical distance between two active network devices, such as a transmitter and a receiver, or between repeaters/amplifiers in long-haul systems. It represents the maximum distance a light signal can travel before its power or shape degrades beyond usable limits due to attenuation and dispersion .Factors Affecting Span LengthFiber Type:Multimode fiber (MMF) has a larger core (50–62.5 µm), allowing multiple light paths. This causes modal dispersion, limiting spans to 300–550 meters in typical enterprise or data center applications .Single-mode fiber (SMF) has a smaller core (8–10 µm), supporting a single light path, which minimizes dispersion and allows spans of 10–80 km or more without amplification .Attenuation: Signal loss occurs as light is absorbed or scattered in the fiber. Modern low-loss single-mode fibers can have attenuation as low as 0.16–0.2 dB/km, enabling long-distance transmission .Dispersion: Pulse spreading due to different light components traveling at slightly different speeds. Chromatic and modal dispersion limit the maximum unamplified distance .Network Equipment: The type of transceivers, wavelength, and use of amplifiers or repeaters can extend the effective span. Long-haul systems often use Erbium-doped fiber amplifiers (EDFAs) to push spans beyond 200 km, and submarine cables can have repeaters every 50–100 km, enabling intercontinental links .Practical Span RangesMultimode fiber: 300–550 meters for 1–10 Gbps links in buildings or campuses .Single-mode fiber: 10–80 km for metro networks; 100–200 km for long-haul terrestrial links without inline amplification .Ultra-long-haul and submarine systems: spans of 50–100 km between repeaters, with total distances reaching thousands of kilometers using amplification .SummaryThe fiber span depends on fiber type, signal wavelength, attenuation, dispersion, and network design. Multimode fibers are suited for short-range applications, while single-mode fibers enable long-distance communication, with spans extending from tens to hundreds of kilometers without amplification, and even longer with advanced amplification technologies .