Indoor Single-Mode and Multi-Mode Optical Cable Specifications

Indoor single-mode fiber has a 9µm core for long-distance, high-speed transmission, while multimode fiber has a 50–62.5µm core optimized for short-distance, high-bandwidth applications.

Core and Light Propagation

Single-mode fiber (SMF) features a narrow core of approximately 8–10 µm, allowing only one mode of light to propagate. This minimizes modal dispersion, enabling long-distance transmission up to 100 km with high signal integrity, making it ideal for carrier-grade networks and campus backbones . SMF typically uses lasers as the light source and operates at wavelengths of 1310 nm or 1550 nm . Multimode fiber (MMF) has a larger core, typically 50 µm or 62.5 µm, which supports multiple light modes simultaneously. This allows for easier coupling with LEDs or VCSELs but introduces modal dispersion, limiting effective distance to 400 meters for high-speed applications . MMF is commonly used in indoor environments like data centers and office networks.

OM Classifications and Performance

Multimode fibers are categorized by OM (Optical Multimode) standards:

• OM1: 62.5 µm core, suitable for legacy 1 Gbps networks, short distances.
• OM2: 50 µm core, supports 1–10 Gbps over moderate distances.
• OM3: 50 µm core, optimized for 10G Ethernet up to 300 m.
• OM4: 50 µm core, supports 10G up to 400 m and 100G-SR4 up to 100 m, with bandwidth of 4700 MHz·km at 850 nm .
• OM5: 50 µm core, wideband multimode fiber for SWDM, capable of carrying four wavelengths on a single fiber, supporting 40 Gbps up to 1000 m and 100 Gbps up to 150 m .

Indoor Cable Construction

Indoor fiber optic cables are designed for controlled environments and include:

• Core fibers: Glass or plastic strands for data transmission.
• Buffer coating: Protects fibers from bending and stretching.
• Strength members: Aramid or fiberglass for structural support.
• Outer jacket: Protects against abrasion, moisture, and environmental factors . Connector types commonly used for indoor applications include ST, SC, and LC, with LC being popular for high-density racks in data centers.

Applications

• Single-mode indoor fiber: Long-distance links within buildings, inter-building backbones, and future-proofing for high-speed upgrades.
• Multimode indoor fiber: Short-reach connections in data centers, server rooms, and office LANs, balancing cost and performance .

Summary

Choosing between single-mode and multimode indoor fiber depends on distance, bandwidth requirements, budget, and future scalability. Single-mode is preferred for long-distance, high-speed applications, while multimode is cost-effective for short-reach, high-density environments .