Single-mode fiber supports long-distance transmission up to tens of kilometers, while multimode fiber is limited to short distances, typically under 2 km for high-speed applications.

Transmission Distance Overview

Single-mode fiber (SMF) has a small core diameter of about 8–10 µm, allowing only one mode of light to propagate. This design virtually eliminates modal dispersion, enabling long-distance communication over tens of kilometers without significant signal degradation. Typical operating wavelengths are 1310 nm and 1550 nm, with 1550 nm being ideal for distances over 40 km due to minimal attenuation and high signal efficiency . Multimode fiber (MMF) has a larger core, usually 50 µm or 62.5 µm, which allows multiple light modes to travel simultaneously. This causes modal dispersion, limiting the effective transmission distance. Multimode fiber is generally used for short-range applications, such as within data centers or enterprise networks, with maximum distances typically under 2 km at 100 Mbps and even shorter for higher bandwidths . Common wavelengths for multimode fiber are 850 nm and 1300 nm.

Factors Affecting Distance

1. Modal Dispersion: Present in multimode fiber due to multiple light paths, reducing bandwidth and distance. Single-mode fiber avoids this issue entirely .
2. Attenuation: Light loss occurs in both fiber types, but single-mode fiber experiences lower attenuation at 1550 nm, supporting longer distances .
3. Bandwidth: Multimode fiber's effective modal bandwidth (EMB) decreases with distance, limiting high-speed transmission. Single-mode fiber supports much higher bandwidth over long distances .
4. Cost Considerations: Multimode fiber and transceivers are cheaper for short distances, while single-mode fiber is more cost-effective for long-haul networks despite higher initial transceiver costs .

Typical Applications

• Single-mode fiber: Long-haul telecom, CATV, metropolitan area networks, and backbone links where distances exceed several kilometers .
• Multimode fiber: Local area networks (LANs), data centers, and short-reach high-speed connections where distances are typically less than 300 meters to 2 km .

Summary

In essence, single-mode fiber is optimized for long-distance, high-bandwidth applications, while multimode fiber is suitable for short-range, cost-sensitive deployments. Choosing the right fiber depends on the required transmission distance, bandwidth needs, and budget constraints .