Multimode logging fiber optic cable size specifications

Multimode fiber optic cables typically have a core diameter of 50 µm or 62. 5 µm, a cladding diameter of 125 µm, and buffer and jacket layers ranging from 250 µm to 3 mm depending on the application.

Core and Cladding

The core of a multimode fiber is the central region that carries light. Standard multimode fibers come in two main core sizes: 50 µm (used in OM2, OM3, OM4, OM5 fibers) and 62. 5 µm (OM1 fiber).

The cladding, which surrounds the core and keeps light confined via total internal reflection, is standardized at 125 µm for all multimode fibers. These dimensions are expressed as 50/125 µm or 62. 5/125 µm, where the first number is the core diameter and the second is the cladding diameter.

Coating and Buffer

Directly applied to the cladding is a protective coating, typically 250 µm in diameter, which shields the fiber from mechanical damage and environmental exposure. For tight-buffered fibers, the coating may be 900 µm, providing additional durability and easier handling, especially in indoor or controlled environments. The buffer layer further enhances durability and facilitates installation, with sizes ranging from 900 µm (tight-buffered) to 2–3 mm (loose-tube fibers for outdoor or rugged environments).

Outer Jacket

The outer jacket provides the final layer of protection against environmental and mechanical stress. Its diameter typically ranges from 1. 6 mm to 3 mm, depending on the cable type and installation requirements.

The jacket material and thickness are chosen based on whether the fiber is intended for indoor, outdoor, or industrial applications.

Summary

Core diameter: 50 µm (OM2/OM3/OM4/OM5) or 62. 5 µm (OM1)Cladding diameter: 125 µmCoating diameter: 250 µm (standard) or 900 µm (tight-buffered)Buffer diameter: 900 µm to 2–3 mmOuter jacket diameter: 1. 6 mm to 3 mm These dimensions ensure compatibility with connectors, splicing equipment, and network performance standards, while also providing mechanical protection and ease of installation.