What was the transmission before optical fiber?

　　Before fiber optics, the main tranSMission medium was metal cables, especially copper cables. These cables were widely used in telephone communications, telegraphy, fax, and early computer networks. However, with the continuous development of communication technology and the increasing demand for data transmission, metal cables gradually exposed some limitations, such as limited transmission capacity, signal attenuation and interference.

　　Specifically, when metal cables transmit high-frequency signals, they can cause signal attenuation and distortion due to factors such as skin effect and resistance. In addition, metal cables are also susceptible to electromagnetic interference, such as lightning, electromagnetic pulses, etc., which affect the transmission quality. These problems limit the application of metal cables in high-speed, high-capacity communications.

　　In contrast, optical fiber, as a new type of transmission medium, has many advantages. Optical fiber uses light waves as a carrier and optical fiber as a channel for information transmission. Since the frequency of light is much higher than radio waves and microwaves, the transmission capacity of optical fiber is very large, which can meet the growing demand for data transmission. At the same time, the transmission loss of optical fiber is very low, and the signal can maintain high strength and quality over long distances. In addition, optical fiber also has good anti-electromagnetic interference performance, which can ensure the security and stability of information transmission.

　　Therefore, with the continuous development and maturity of optical fiber technology, it has gradually replaced metal cables and become the main transmission medium in modern communication networks. Today, optical fiber communication technology has been widely used in various fields, such as telecommunications, Internet, radio and television, medical care, etc., bringing great convenience and benefits to people's daily lives and work.