会社のニュース How Does Fiber Optic Work

At its core, fiber optics is a beautiful and powerful technology that uses light to transmit information. Imagine a long, dark, and perfectly straight hallway lined with mirrors. If you shine a flashlight at one end, the light will bounce from mirror to mirror all the way to the other end. Now, imagine you could flick that flashlight on and off very quickly to send a secret code (Morse code).

Fiber optic cable is that hallway, but it's incredibly more efficient. The "flashlight" is a laser or LED, the "mirrors" are the inner walls of the glass fiber, and the "Morse code" is the digital data that makes up your internet, phone calls, and TV signals.

To understand it fully, let's look at the key parts and the physics behind them.

A fiber optic cable has three main parts:

• Core: The central, ultra-thin glass strand where the light travels.

• Cladding: A layer of glass that surrounds the core. It has a different optical density (or refractive index) than the core.

• Buffer Coating: A protective plastic layer that shields the core and cladding from moisture and damage.

This is the magic that keeps the light trapped inside the core. Here's how it works:

• Light travels at different speeds in different materials. When light hits the boundary between two materials at a shallow angle, it bends (this is called refraction).

• The core and cladding are designed so that the core is "denser" optically. This means that when a beam of light inside the core hits the cladding at a very shallow angle, it doesn't escape and bend away. Instead, it completely reflects back into the core.

• This process, called Total Internal Reflection, happens thousands of times per meter, guiding the light pulse down the entire length of the fiber, even around gentle curves, with minimal loss of strength.

A working fiber optic system requires more than just the cable.

• Transmitter: On one end, an electronic device converts your digital data (the 1s and 0s) into light pulses.

  • 1 = Pulse of light "ON"

  • 0 = No pulse of light "OFF"
    A Laser or LED creates these precise, high-speed light pulses.

• Optical Fiber: The cable carries these light pulses over long distances.

• Repeater/Optical Amplifier: For very long distances (like under oceans), the light signal can get weak. Repeaters or amplifiers are used to boost the signal without converting it back to electricity.

• Receiver: At the other end, a photodetector (a light sensor) detects the incoming light pulses and converts them back into electrical signals, which are then decoded back into your original data (email, video, etc.).