1. 双绞线：
电线成对绞在一起。每对由用于正数据信号的导线和用于负数据信号的导线组成。出现在该对正/负线上的任何噪声都会出现在另一条线上。由于导线极性相反，因此它们的相位相差 180 度(180 度或相反极性的定义)。当噪声出现在两条线上时，它会在所使用的接收端抵消或消除自身。
双绞线电缆有两种类型——
- 屏蔽双绞线电缆 –
双绞线电缆最有效地用于使用平衡线路传输方法的系统。带屏蔽的电缆称为屏蔽双绞线电缆，通常缩写为 STP。 - 非屏蔽双绞线电缆 –
没有屏蔽的电缆称为非屏蔽双绞线电缆或 UTP。将电线绞在一起会导致电缆的特性阻抗。 UTP 电缆用于以太网。
2.同轴电缆：
同轴电缆由两根导体组成。内导体包含在绝缘体内部，其他导体围绕其编织提供屏蔽。称为护套的绝缘保护涂层覆盖外导体。外屏蔽保护内导体免受外部电信号的影响。外导体和内导体之间的距离加上用于绝缘内导体的材料类型决定了电缆的特性。
3. 光纤电缆：
光纤由细玻璃纤维组成，可以在可见光谱的频率上传输信息。典型的光纤由非常窄的玻璃线组成，称为包层。典型的纤芯直径为 62.5 微米。
通常包层的直径为 125 个小直径。涂层包层是一种由塑料组成的保护涂层，称为护套。生成消息的设备将其置于电磁(电信号)中。这必须转换成光以通过光纤电缆发送。
双绞线、同轴电缆和光纤电缆的区别
| Characteristics | Twisted pair cable | Co-axial cable | Optical fiber cable |
|---|---|---|---|
| Signal transmission | Takes place in the electrical form over the metallic conducting wires. | Takes place in the electrical form over the inner conductor of cable. | Takes place in an optical form over a glass fiber. |
| External magnetic field | Affected due to external magnetic field. | External magnetic field is less affected . | External magnetic field is not affected. |
| Cause of power | Power loss due to conduction and radiation. | Power loss due to conduction. | power loss due to absorption, scattering and bending. |
| Bandwidth | Twisted pair cable has low bandwidth. | Co-axial cable has moderately high bandwidth. | Optical fiber cable has very high bandwidth. |
| Electromagnetic interference(EMI) | EMI can take place. | EMI is reduced to shielding. | EMI is not present. |
| Installation | Easy installation. | Fairy easy installation. | Difficult to install. |
| Attenuation | In twisted pair cable has very high attenuation. | In co-axial cable has low attenuation. | In optical fiber cable has very low attenuation. |
| Data rate | Twisted pair cable supports low data rate. | Moderately high data rate. | Very high data rate. |
| Noise immunity | Twisted pair cable has low noise immunity. | Co-axial cable has higher noise immunity. | Optical fiber cable has highest noise immunity. |