What is the identifier for a four-core single-mode fiber optic cable

A four-core single-mode fiber optic cable is typically identified as a 4-core OS2 (or OS1) fiber, compliant with ITU G.652 standards, with individual fibers color-coded according to TIA-598-C.

Core Identification and Standards

A four-core single-mode fiber optic cable contains four individual optical fibers within a single protective jacket, each capable of independent data transmission . The single-mode designation indicates a 9 µm core diameter with 125 µm cladding, optimized for long-distance, low-loss transmission . These fibers are usually classified under OS1 or OS2 standards for indoor/outdoor applications, with OS2 being optimized for outdoor or long-haul use . ITU G.652 is the most common standard for single-mode fibers, specifying geometrical and transmission properties suitable for FTTH, GPON, and other telecom networks .

Color Coding and Fiber Arrangement

Per the TIA-598-C standard, the first four fibers in a multi-fiber cable follow a consistent color sequence: Blue, Orange, Green, Brown . This color coding allows technicians to quickly identify individual fibers for splicing, termination, or testing. In a loose-tube construction, the tube holding the fibers is often Blue or White, while the fibers inside follow the standard sequence .

Typical Applications

Four-core single-mode cables are commonly used to support:

• Two duplex links (one transmit and one receive per link)
• One duplex link with two backup fibers for redundancy
• FTTH (Fiber to the Home) or GPON networks, connecting end users to the optical distribution network

Summary

To identify a four-core single-mode fiber optic cable:

• Core count: 4 fibers
• Fiber type: Single-mode (9/125 µm)
• Standard: OS2 (ITU G.652)
• Color sequence: Blue, Orange, Green, Brown (TIA-598-C)
• Applications: Duplex links, FTTH, GPON, or redundant connections .

This identifier ensures proper selection, installation, and maintenance in both indoor and outdoor optical networks.