MMF stands for “Multi-mode Fiber.” It is another primary type of optical fiber used in fiber-optic communications, distinct from Single-mode Fiber (SMF). Here’s an overview of Multi-mode Fiber:

1. Basic Characteristics:

  • Core Diameter: Larger than that of single-mode fiber, typically ranging from 50 to 62.5 micrometers (μm). This larger core allows the fiber to carry multiple modes or rays of light.
  • Wavelength: Commonly operated at 850 nm and 1300 nm wavelengths.

2. Transmission:

  • Transmits multiple rays or modes of light simultaneously, each reflecting at a slightly different angle within the fiber core.
  • Suited for short-distance transmissions, typically up to 2 km, but advancements have extended its reach under specific conditions.

3. Light Source: Typically uses LED (light-emitting diodes) or VCSELs (vertical-cavity surface-emitting lasers) as the light source because of the fiber’s large core size.

4. Applications:

  • Local Area Networks (LANs): Especially within buildings or campuses.
  • Data Centers: Where the distances between connections are relatively short.
  • Backbone Applications: Within certain ranges in large corporate settings.

5. Advantages:

  • Cost: Generally less expensive than single-mode fiber, both in terms of the fiber itself and the required light sources.
  • Ease of Use: The larger core size makes connections slightly easier, as it’s less sensitive to light being perfectly aligned.

6. Disadvantages:

  • Distance Limitations: Due to modal dispersion (where different light rays travel at different speeds), MMF has a more limited transmission distance compared to SMF.
  • Bandwidth Limitations: Lower bandwidth compared to single-mode fibers, especially over long distances.

7. Types of MMF:

  • OM1, OM2, OM3, OM4, OM5: These are standards that categorize different types of MMFs based on their bandwidth and distance capabilities, with OM1 being the oldest and OM5 being the most recent and capable of supporting multiple wavelengths.

8. Connectors: Multi-mode connectors and equipment typically have a beige (OM1 & OM2) or aqua (OM3 & OM4) color code for easy identification.

In summary, MMF is well-suited for short-distance applications where high bandwidth and low latency are needed, such as in data centers and LANs.