Wiring technology: how to connect copper wires and optical fiber cables to transmit data

1. photoelectric signal conversion method

For a long time, people have been using copper wires to transmit sound and information. However, more and more fiber cables have been used recently. Due to cost problems, we cannot replace all copper wires with optical fiber cables at once. However, to convert some cables into optical signals, the most important thing is to convert the electrical signals into optical signals, and then convert the optical signals into electrical signals.

Using two diodes to convert electrical signals and optical signals requires the use of diode semiconductor components. However, diodes that convert electrical signals into optical signals and diodes that convert optical signals into electrical signals must be of different types. That is to say, two types of diodes are required to connect copper wires and optical fibers.

A laser diode is used to convert electrical signals transmitted from copper wires into optical signals ". The laser diode is made of semiconductors named "GaAs ()". After pressurization, light of a specific wavelength is produced.

When "1" and "0" digital signals are transmitted using copper wires, the high voltage and low voltage statuses usually correspond to "1" and "0" respectively ". When the transmitted signal voltage is applied to the laser diode to convert it into a light signal, the light will generate or disappear. If the light-emitting and disappearing statuses are set to "1" and "0" respectively, digital data can be transmitted through optical fiber.

If the optical signal transmitted from the optical fiber is restored to an electrical signal, the "photosensitive diode" must be used ". This diode has the property of generating a current proportional to the light intensity after being illuminated. When optical signals transmitted by optical fibers pass through a photosensitive diode, they can be directly converted into electrical signals.

2. Combine the optical fiber and the same axis

With the technology of converting electrical signals and optical signals, a high-speed network can be established at a low cost by effectively using optical fiber and copper wires.
CATV is the representative. To send TV programs, thousands of households are connected to catv TV stations on the same axis of copper wires. Recently, Internet connections have been started and used in local telephones. The higher the speed, the more channels, and two-way communication has been started.

It is difficult to transmit high-frequency electrical signals from the same axis over a long distance. Therefore, to increase the communication distance, a large number of amplifiers must be used, and the cost will also increase.

If fiber cables are used to replace the same axis, the communication speed of the CATV network can be improved without using the amplifier too much. However, if you want to introduce optical fiber into every user's home, the cost will increase.

Therefore, a relay device is set up between the catv TV station and the user's home to change the cable between the catv TV station and the relay equipment into optical fiber cables. Diode-based optical-to-electrical converter (O/E) and electro-optical converter (E/O) are used in relay devices ). The original coaxial cable is still used in the shorter area from the relay device to the user's home.

In this way, the main line can support broadband transmission and multi-channel transmission, while the part between the relay device and the user's home will not increase the cost because no change is required.(