Specifications for ordinary optical cables

Ordinary optical cables are characterized by their core and cladding dimensions, attenuation, bandwidth, dispersion, and mechanical construction, following standards like ITU-T G.652.

Core and Cladding

The core of an optical fiber is the central glass region that guides light, while the cladding surrounds the core with a lower refractive index to enable total internal reflection. In single-mode fibers, the core diameter is typically around 8–10 µm, and the cladding diameter is standardized at 125 µm. Multi-mode fibers have larger cores, usually 50 µm or 62.5 µm, with the same cladding diameter. The mode field diameter in single-mode fibers measures the transverse extent of the light field and affects coupling efficiency and bending sensitivity .

Attenuation and Bandwidth

Attenuation represents the signal loss per kilometer and is wavelength-dependent. For single-mode fibers, typical attenuation values are around 0.35 dB/km at 1310 nm and 0.22 dB/km at 1550 nm. Multi-mode fibers have higher attenuation due to modal dispersion. Bandwidth is determined by the fiber type and core size, with single-mode fibers supporting very high bandwidth over long distances, while multi-mode fibers are suitable for shorter links .

Dispersion

Chromatic dispersion affects pulse broadening and limits transmission distance. Single-mode fibers like ITU-T G.652 are optimized for zero-dispersion near 1310 nm but can also operate at 1550 nm. Polarization mode dispersion (PMD) is another factor in high-speed systems, typically specified in ps/√km .

Cable Construction

Optical cables are built to protect fibers mechanically and environmentally. Common constructions include:

• Loose Buffer Construction: Fibers are housed in a buffer tube with a small gap, providing protection against external forces and moisture. Suitable for outdoor and long-distance applications .
• Tight Buffer Construction: Fibers are coated directly with a protective layer, making the cable more compact and easier to handle, ideal for indoor installations . Cables also include strength members (e.g., aramid yarn) and an outer jacket for mechanical protection.

Mechanical and Environmental Parameters

Ordinary optical cables are designed to withstand tensile stress, bending, and temperature variations. Typical specifications include minimum bend radius, maximum tensile load, and operating temperature range. These parameters ensure reliable performance during installation and operation .

Standards

Most ordinary optical cables follow ITU-T G.652 for single-mode fibers, which defines geometrical, optical, and mechanical parameters, including core/cladding concentricity, macrobending loss, and attenuation limits. Compliance with these standards ensures interoperability and predictable performance across networks . In summary, ordinary optical cables are defined by core/cladding dimensions, attenuation, dispersion, bandwidth, and mechanical construction, with variations depending on single-mode or multi-mode design and intended application. Proper selection requires considering both optical performance and environmental resilience.