Single-mode duplex fiber optic cables feature a 9-micron core, support long-distance high-speed transmission, and consist of two fibers for simultaneous bi-directional communication.

Core and Light Propagation

Single-mode fiber has a small core diameter of approximately 9 microns, allowing only a single light mode to propagate. This minimizes modal dispersion, enabling long-distance transmission with low signal loss and high bandwidth efficiency ( ). The cladding surrounding the core is typically 125 microns in diameter and reflects light back into the core to maintain signal integrity ( ).

Duplex Configuration

A duplex cable contains two fibers, usually arranged side-by-side in a zipcord style. One fiber is used for transmitting data, and the other for receiving, enabling full-duplex communication. This configuration is essential for network devices such as switches, servers, and fiber modems that require simultaneous bi-directional data transfer ( ). In contrast, simplex cables contain a single fiber for one-way transmission.

Optical Performance

Single-mode duplex fibers are optimized for long-haul and high-speed networks, including telecommunications, data centers, and internet backbones. Typical specifications include:

• Attenuation: OS1 cables have 0.4 dB/km at 1310 nm and 0.3 dB/km at 1550 nm; OS2 cables have 0.3 dB/km at 1310–1550 nm ( ).
• Bandwidth: OS1 supports 200 MHz·km at 1310 nm, while OS2 supports 500 MHz·km at 1310 nm ( ).
• Wavelength compatibility: Designed for 1310 nm and 1550 nm regions, suitable for both analog and digital transmission ( ).

Mechanical and Environmental Attributes

Single-mode duplex cables are available with various jackets for indoor and outdoor use:

• PVC: Standard indoor applications.
• LSZH (Low Smoke Zero Halogen): Fire-safe indoor environments.
• Plenum-rated: Air-handling spaces with strict fire codes.
• Outdoor jackets: UV-resistant and water-blocking for external installations ( ).

Applications

Single-mode duplex fiber is ideal for:

• Long-distance telecommunications and metro networks.
• High-speed data center interconnects.
• Full-duplex point-to-point links requiring minimal signal degradation over tens of kilometers ( ). In summary, single-mode duplex fiber optic cables combine a small core for single-mode light propagation with two fibers for bi-directional communication, offering low attenuation, high bandwidth, and suitability for long-distance, high-speed network applications.