What are the fundamental transmission mechanisms and classification characteristics of optical fiber cables in modern data networks?

Optical fiber cables transmit data via lightwave propagation and are categorized by core design. Here’s the numerical breakdown:   Transmission Mechanisms   1.1 Total Internal Reflection: Light signals propagate by reflecting off the fiber cladding (lower refractive index material), maintaining signal integrity through continuous internal reflection within the core (higher refractive index).   1.2 Signal Conversion Process: Transponders convert electrical data into modulated light pulses (using lasers or LEDs) at the transmitter, then reconvert light back to electrical signals via photodetectors at the receiver.   Classification Characteristics   2.1 Single-Mode Fiber (SMF)   2.1.1 Core Diameter: 8–10 μm (standard: 9 μm), enabling a single light propagation path.   2.1.2 Key Features: Low modal dispersion (minimal pulse spreading), supports distances >100 km (up to 1000 km with optical amplifiers), and uses laser light sources (1310 nm/1550 nm wavelengths).   2.1.3 Applications: Long-haul telecommunications (undersea cables, intercity networks), high-speed backbone infrastructure.   2.2 Multi-Mode Fiber (MMF)   2.2.1 Core Diameter: 50 μm (OM3/OM4) or 62.5 μm (OM1/OM2), allowing multiple light reflection paths.   2.2.2 Key Features: Higher modal dispersion limits range to ~2 km (500 m at 10 Gbps), uses LED/VCSEL light sources (850 nm/1300 nm wavelengths), and offers lower cost than SMF.   2.2.3 Applications: Data centers (rack-to-rack connections), campus local area networks (LANs), short-reach high-bandwidth links.   Specialized Applications   3.1 Power Over Fiber (PoF): Integrates photovoltaic conversion to transmit low power (<100 mW) alongside data, used in EMI-sensitive environments (e.g., MRI facilities, industrial sensors) where copper cables cause interference.