Structure, Types, and Installation Guidelines of Communication Optical Fibers

Communication optical fibers consist of a glass core that transmits light by total internal reflection, surrounded by a cladding with a lower refractive index, and protected by one or more coating layers; the standard glass fiber diameter is 125 µm with coating layers of 250 µm or 900 µm.

There are three typical coating structures: primary coating fibers (0.25 mm UV‑cured acrylic resin for high density), secondary coating fibers (0.9 mm thermoplastic resin for greater robustness), and ribbon fibers that bundle 4, 8, or 12 fibers to improve connector assembly efficiency.

Common fiber categories include multi‑mode fibers (MMF) such as OM1 (62.5/125 µm) and OM2/OM3 (50/125 µm), and single‑mode fibers (SMF) defined by ITU‑T standards G.652, G.653, G.654, G.655, G.656, and G.657, each offering specific dispersion and attenuation characteristics for various transmission distances.

Fiber‑to‑fiber connection techniques are divided into fusion splicing, mechanical splicing, and connector mating; fusion splicing further includes core‑alignment (microscope‑assisted) and V‑groove alignment methods, both aiming to minimize insertion loss.

Splicing loss originates mainly from axis offset, angular offset, end‑face gaps, and reflections; each factor can be quantified (e.g., axis offset loss ≈ 0.2 dB · (Δµm)² at 1310 nm) and mitigated through careful preparation.

Fusion splicing procedures involve inserting protective tubing, stripping the coating, cleaning the glass with ethanol, cutting the fiber to the proper length, performing the splice, and reinforcing the splice with a protective tube while avoiding excessive bending or contamination.

Key technical parameters for fibers include core diameter (typically 50 µm for multimode), mode field diameter (MFD) for single‑mode, cladding diameter, cutoff wavelength, shielding level, attenuation (α = -(10/L)·log(P₂/P₁)), bandwidth, zero‑dispersion wavelength, and zero‑dispersion slope.

Cable specifications cover maximum allowable tension, minimum bend radius (≈20× fiber radius during installation, 10× after), operating temperature range (‑20 °C to +60 °C outdoors, ‑10 °C to +40 °C indoors), and waterproof rating (IP54, IP3X, IPX7) to ensure durability.

Common connector types are FC/PC, SC/PC, LC, ST, MT‑RJ, and MU, each with distinct mechanical designs, polishing styles (PC, APC), and typical application scenarios; adapters and couplers (splitters) are used to interface different connector families and to distribute optical signals.

Overall, proper selection of fiber type, adherence to splicing and installation best practices, and compliance with the specified technical parameters are essential for achieving low‑loss, reliable optical communication networks.