Fused fiber optical couplers enable us to control and direct light signals in fiber optic networks. They allow us to manipulate something as fast and elusive as light to carry our messages across vast distances.

How Optical Fused Coupler Works

Let’s start with a simple comparison. Imagine you’re pouring water from a big jug into smaller glasses. You can pour all the water into one glass, or you can divide it among several glasses. Fused fiber optical couplers do something similar, but with light instead of water. They take light from one fiber and split it into two or more fibers, or they can do the opposite – combine light from multiple fibers into one.

How Light Behaves in an Optical Fused Coupler

When light enters the fused section, something called “evanescent coupling” occurs. It means that some of the light from one fiber leaks into the other fiber. The amount of light that transfers depends on several factors:

  1. The length of the fused section
  2. How much the fibers were stretched
  3. The wavelength of the light

By carefully controlling these factors during manufacturing, engineers can create optical fused couplers that split light in specific ratios. For example, they might make a coupler that sends 50% of the light to each output fiber, or one that sends 90% to one fiber and 10% to another.

The Making of an Optical Fused Coupler

The process of creating a fused fiber optical coupler is quite interesting. It starts with two or more optical fibers. These fibers are very thin – about as thick as a human hair! Here’s what happens:

  1. Stripping: First, a small section of the protective coating is removed from each fiber, exposing the glass core.
  2. Twisting: The exposed sections are then carefully twisted together.
  3. Heating: This twisted section is then heated until the glass becomes soft and pliable.
  4. Stretching: While it’s hot, the fibers are gently pulled or stretched. This causes the fibers to fuse together and become thinner.
  5. Cooling: Finally, the fused section is allowed to cool, creating a permanent bond.

The result is a section where the light can move between the fibers. It’s like the fibers have become one at this point, allowing light to flow freely between them.

Types of Optical Fused Couplers

There are several types of optical fused couplers, each designed for specific uses:

  1. 2×2 Couplers: These have two input fibers and two output fibers. They’re the most common type.
  2. 1xN Couplers: These split light from one input fiber into multiple output fibers. They’re often used in networks where a signal needs to be sent to many places.
  3. NxN Couplers: These have multiple input and output fibers. They’re used in more complex network designs.
  4. WDM Couplers: These special couplers can combine or separate different colors of light. They’re crucial in systems that send multiple signals on different wavelengths through the same fiber.

Why Optical Fused Couplers Are Important

  1. Network Branching: They allow us to send signals to multiple locations without losing much light. This is crucial for building large networks.
  2. Signal Monitoring: By splitting off a small portion of the light, we can monitor the signal without interrupting the main transmission.
  3. Bidirectional Communication: Some couplers allow signals to travel in both directions, enabling two-way communication on a single fiber.
  4. Wavelength Division Multiplexing: Special couplers enable us to send multiple signals on different wavelengths through the same fiber, greatly increasing the amount of data we can transmit.
  5. Fiber Optic Sensors: Couplers are used in various types of sensors that measure things like temperature, pressure, and strain.

Optical fused couplers help keep us connected. Every time you browse the internet, stream a video, or make a phone call, there’s a good chance that your data is passing through multiple optical fused couplers along the way.