Outdoor fiber cable is mainly used for interconnection between buildings and remote networks. Due to the installation environment, it has stronger pressure resistance, corrosion resistance, greater tensile strength and a heavier protective layer than indoor fiber cable. The protective layer is mostly armored. Outdoor optical cables are divided into single-mode and multi-mode in transmission.
The core of a single mode outdoor optical cable is about 10μm, the propagation path is single, there is no dispersion, the light source is mostly laser or laser diode, and the attenuation of the optical signal is much smaller than that of multi-mode outdoor optical cable. For example, in a distance of 1000 meters, the optical signal attenuation of a multi-mode outdoor optical cable may reach 50%, while the optical signal attenuation of a single-mode outdoor optical cable at the same distance is only 6.25%.
The multi-mode outdoor optical cable is named because it divides the propagation mode into multiple modes according to the working wavelength. Its core diameter is 50μm, and the light source is mostly LED or VCSEL (Vertical Cavity Surface Emitting Laser). Due to the diversity of its transmission paths, compared with single-mode outdoor optical cables, its transmission bandwidth is dominated by mode dispersion.
Since the core diameter of the multi-mode outdoor optical cable is larger than that of the single-mode outdoor optical cable, and it is easier to combine with light sources such as LEDs, it has more advantages in many LANs. Therefore, multi-mode outdoor optical cable is mostly used in short-distance outdoor network connections.
In the choice of single-mode outdoor optical cable and multi-mode outdoor optical cable, the transmission distance is often the decisive factor. When the transmission distance is short, a multi-mode outdoor optical cable should be the first choice, because the cost of LED transmitting and receiving device used is much cheaper than the laser required for single-mode. The effective distance of the multi-mode outdoor optical cable from the transmitting end to the receiving end is about 8km, so when the transmission distance is greater than 8km, a single-mode outdoor optical cable should be selected.