Single Mode vs. Multi Mode Fiber: Key Differences Explained

This section delves into the distinctions between single mode and multi mode fiber optic systems. We’ll explore these differences by comparing various factors like data rate, distance, attenuation, and signal travel time. We will also cover single mode and multimode fiber definitions, dimensions, types, applications, merits, and demerits.

Definitions

• Single Mode Fiber: Due to its small core diameter (8-10 microns), single mode fiber allows only one mode of light to propagate.

• Multi Mode Fiber: With a larger core diameter (approximately 62.5 microns), multi mode fiber enables multiple simultaneous modes of light to propagate.

Dimensions

• Single Mode Fiber: Core-to-cladding diameter is approximately 9 microns by 125 microns.
• Multi Mode Fiber: Core-to-cladding diameter is approximately 50 (or 62.5) microns by 125 microns.

The image above illustrates the core and cladding components of a fiber optic cable.

Transmission Distance and Rate

• Multi Mode Fiber: Suitable for signal transmission up to about 10 miles. It utilizes more affordable optical transmitters and receivers.
• Single Mode Fiber: Capable of covering distances greater than 10 miles. It requires more expensive laser diodes as optical transmitters.

The transmission rate of single mode fiber is generally higher than that of multi mode fiber. It’s also about 2 to 4 times more expensive than multi mode fiber.

Attenuation and Signal Travel Time

• Single Mode Fiber: Due to its single core, light reflections are minimized, leading to lower attenuation and faster signal propagation.
• Multi Mode Fiber: Multiple cores result in more light reflections, leading to higher attenuation and slower signal propagation. However, it can carry more data due to simultaneous transmissions.

Merits and Demerits

Each type of fiber possesses its own advantages and disadvantages, depending on the specific application. A key limitation of multi mode fiber is its inability to propagate broadband RF signals effectively.

Applications

• Single Mode Fiber: Employed for long-distance communication and high-bandwidth signal transmission. Common applications include CATV, telecommunications, universities, and colleges. Laser diodes are used as the optical transmission system equipment.

• Multi Mode Fiber: Utilized for short-distance communication, particularly for video, audio, and data-based Wireless LAN applications. LED-based fiber optic equipment is typically used.

Types

There are two primary types of multi mode fiber: Step-Index and Graded-Index Multi mode Fiber. For more details, refer to Single Mode Step Index vs Multi mode Graded Index Fiber.

Comparison Table: Single Mode vs. Multi Mode Fiber