Difference Between Single-Fiber and Dual-Fiber

The biggest difference between single-fiber and dual-fiber optical terminals lies in the optical modules on their mainboards; everything else is basically the same.

Single-fiber optical terminal: transmit and receive data over one fiber;

Dual-fiber optical terminal: transmit and receive data over two separate fibers respectively.

As the name implies, a single-fiber optical terminal can save half of the cable resources, i.e., data transmission and reception are achieved over a single fiber, which is highly suitable for applications where fiber resources are scarce. A dual-fiber optical terminal, on the other hand, requires two fibers: one for transmission (Tx) and one for reception (Rx). Single-fiber optical terminals commonly use paired wavelengths of 1310nm and 1550nm, i.e., one end operates at 1310nm and the other at 1550nm, allowing both transmission and reception. Dual-fiber optical terminals, however, use a uniform wavelength, meaning both ends of the equipment operate at the same wavelength.

However, since there is no unified international standard for optical terminal products, incompatibility issues may arise during interconnection between products from different manufacturers. In addition, due to the use of wavelength-division multiplexing, single-fiber optical terminal products suffer from signal attenuation issues, making their stability slightly inferior to that of dual-fiber products. That is, single-fiber optical terminals have higher requirements for optical modules, which is why single-fiber optical terminals are generally more expensive than dual-fiber ones on the market. Currently, most optical terminals on the market are dual-fiber products, which are more mature and stable but require more fiber resources.

The transmission distance of an optical terminal mainly depends on its optical module. The most common transmission distances on the domestic market are: 10km/20km/40km/60km/80km/100km/120km. Generally, single-fiber equipment uses SC connectors for optical interfaces, while dual-fiber equipment uses FC connectors. If one end has an FC connector and the other end has an SC connector, we can use a hybrid pigtail, i.e., an FC-SC patch cord, to connect them. If both ends have FC connectors, we can use a dual-fiber FC pigtail.