Optical Fiber and Twisted Pair Cable Technologies

Multimode Fiber

A multimode fiber is one in which light beams can circulate in more than one mode or path. This allows for multiple light paths within the fiber. A multimode fiber can support more than a thousand ways of spreading light.

Multimode fibers are commonly used in short-distance applications (less than 1 km) due to their simple and economical design. Its maximum transmission distance is typically 2 km, and they use low-intensity laser diodes.

The core of a multimode fiber has a higher refractive index, but of the same order of magnitude as the cladding. Due to the large core, multimode fibers are easier to connect and have a higher tolerance for lower-precision components.

Singlemode Fiber

A single-mode fiber is an optical fiber in which only one mode of light propagates. This is achieved by reducing the diameter of the fiber core to a size (typically 8.3 to 10 microns) that allows only a single mode of propagation. Its transmission is parallel to the fiber axis.

Unlike multimode fiber, single-mode fiber can reach great distances (up to 300 km maximum, using a high-intensity laser) and transmit high data rates (tens of Gb/s).

Twisted Pair Cables

UTP Cable

UTP stands for Unshielded Twisted Pair. It is a twisted pair cable without a metallic shield or outer coating, making it susceptible to interference. However, the twisting compensates for electromagnetic induction produced by adjacent cable lines.

It is important to maintain the correct numbering of the pairs, as otherwise the twisting effect will not be effective, significantly reducing or even preventing transmission capacity. UTP cable is cheap, flexible, and easy to install. The impedance of a UTP cable is 100 ohms. A typical UTP cable consists of several twisted pairs, as often illustrated in diagrams.

STP Cable

STP stands for Shielded Twisted Pair. This cable is similar to UTP but includes a metallic shield to prevent external interference. Therefore, it is a more secure cable, but less flexible than UTP. The twisting system is identical to that of UTP cable. The impedance of an STP cable is typically 150 ohms.

Fiber Optic Connectors

The FC Connector

The FC connector is a fiber optic connector with a threaded body, designed for use in high-vibration environments. The FC connector has been standardized as FOCIS 4 (Fiber Optic Connector Intermateability Standard) in EIA/TIA-604-04.

The SC Connector

The SC connector is a fiber optic connector with a push-pull latching mechanism, providing quick insertion and removal while ensuring a positive connection. The SC connector has been standardized as FOCIS 3 (Fiber Optic Connector Intermateability Standard) in EIA/TIA-604-03.