Single mode vs. multimode fiber optic cables: What are the differences?

Fiber optic cables are often regarded as the gold standard in network cabling infrastructure. Compared with copper cables, fiber optics deliver superior performance, enabling data transmission over much longer distances while significantly minimizing signal attenuation and quality degradation.

Fiber optic cables are available in a wide range of types, structures, and designs, and they can be terminated with different kinds of connectors at each end. Depending on the required transmission distance and the expected network performance, selecting the appropriate type of fiber optic cable is essential. Today, there are two main types of fiber optic cables commonly used to interconnect network devices: single mode fiber and multimode fiber.

Learn about the structural characteristics and benefits of using fiber optic cables

1.2 Structure of single mode fiber optic cables

Single mode fiber optic cable consists of the following main components:

• Core: The core is located at the center of the optical fiber and is responsible for guiding light signals. For single-mode fiber, the core diameter typically ranges from 8.3 µm to 10 µm.
• Cladding: The cladding surrounds the core. Both the core and the cladding are made of fused silica glass. The refractive index of the cladding is always lower than that of the core. This difference in refractive indices keeps the light confined within the core and prevents signal leakage. The cladding diameter of single-mode fiber is approximately 125 µm.
• Buffer / Coating: The buffer layer, also known as the coating, is made from specially engineered materials to protect the optical fiber and cladding from mechanical stress and damage. In addition, it helps minimize micro-bending, which is a common cause of signal loss due to light scattering.
• Outer jacket: The outer jacket is the final protective layer of the fiber optic cable. It shields the internal components from external environmental factors such as moisture, temperature variations, and physical impact. In addition, the jacket typically provides identification information about the cable type.

1.3 Types of single mode fiber optic cables

Single mode cables are classified into OS1 and OS2.

2.2 Structure of multimode fiber optic cables

Multimode fiber optic cables have a structure similar to that of single mode fiber, consisting of key components such as the core, cladding, buffer, coating, and jacket.

However, the main structural difference between single mode and multimode fiber lies in the core diameter. Multimode fiber features a larger core, typically ranging from 50 µm to 62.5 µm, depending on the specific multimode fiber type.

2.3 Types of multimode fiber optic cables

Multimode fiber optic cables are primarily used for short-distance transmission, typically under 500 meters. Based on technical standards and bandwidth performance, multimode fiber is commonly classified into OM1, OM2, OM3, and OM4.

• OM1 is the lowest-performance but most cost-effective multimode fiber type, supporting a maximum bandwidth of 10 Gbps over a distance of approximately 30 meters.
• OM2 provides improved link quality and can maintain the same 10 Gbps performance over distances of up to around 80 meters.
• OM3 further enhances transmission capability, allowing 10 Gbps data rates over distances of up to 300 meters.
• OM4 offers the highest performance among these types, supporting 10 Gbps transmission over distances of up to 1,400 meters. In addition, OM4 can support higher data rates such as 40 Gbps and 100 Gbps over distances of up to 150 meters.

3.2 Core diameter of single mode and multimode fiber optic cables

The most obvious difference between single mode and multimode fiber optic cables lies in the core diameter. Single-mode fiber features a much smaller core compared to multimode fiber.

Specifically, the core diameter of single-mode fiber is typically around 9 µm, while multimode fiber has a core diameter of 50 µm or 62.5 µm.

This smaller core diameter significantly reduces signal attenuation, enabling single-mode fiber to transmit data over much longer distances than multimode fiber.

3.4 Bandwidth differences

The difference in bandwidth performance between single mode fiber and multimode fiber mainly stems from the fiber core structure and the light propagation mechanism within the fiber.

• Step-index multimode fiber: This type of fiber offers low bandwidth, typically below 100 MHz/km. It is only suitable for very short-distance links (under 500 m) and does not perform well in high-speed data transmission applications.
• Graded-index multimode fiber: With an improved refractive index profile, this fiber achieves higher bandwidth, usually below 1 GHz/km. Reduced pulse spreading allows it to operate efficiently over medium distances, generally above 500 m.
• Single mode fiber: Single mode fiber delivers superior bandwidth performance, with bandwidths reaching below 10 GHz/km. Because it supports only one light propagation mode, there is no modal dispersion, allowing signals to maintain high quality over very long distances.

3.5 Transmission distance

In multimode fiber, each light ray travels along a different path and reaches the end of the fiber at different times, causing modal dispersion. This phenomenon limits both the available bandwidth and the transmission distance. As a result, the maximum transmission distance of multimode fiber is typically around 300 - 500 meters.

For single mode fiber, the very small core significantly minimizes dispersion and allows high-bandwidth transmission over much longer distances. Thanks to this characteristic, single-mode fiber can be used for transoceanic data transmission, forming the backbone of the global Internet infrastructure. In practical deployments, single mode fiber can support 1Gb Ethernet transmission over distances of up to 5000 meters.

3.6 Cost comparison between single mode and multimode fiber optic cables

When designing a fiber optic cabling system, it is essential to consider both the transmission distance and the cost of optical transceivers and fiber cables. In general, single mode fiber optic cables themselves are often less expensive than multimode fiber cables; however, other system components in single-mode solutions can be more costly compared to multimode-based systems.

To fully leverage the advantages of single mode fiber, it is typically deployed in long-distance transmission applications. As a result, the system requires laser-based optical transceivers, which increases the initial investment cost. In most cases, single-mode transceivers are more expensive than those used for multimode fiber.

In many large-scale data centers, multimode fiber solutions are often preferred due to lower transceiver costs and reduced power consumption. In contrast, for submarine communication systems, single mode fiber is the standard choice thanks to its long transmission reach and high reliability.

HELUKABEL offers a comprehensive portfolio of singlemode and multimode fiber optic cables, fully addressing data transmission requirements across industrial environments, data centers, telecommunications systems, and modern network infrastructure.

HELUKABEL fiber optic cables are designed in compliance with international standards such as ISO/IEC, ITU-T, and TIA/EIA, ensuring low attenuation, high mechanical durability, and stable transmission performance across a wide range of installation conditions, ranging from indoor to outdoor environments, and from static installations to harsh industrial applications.

4.1 Overview of our fiber optic cable portfolio

For most applications, HELUKABEL fiber optic products are available in both singlemode and multimode variants. These fiber optic cables are engineered to serve a broad spectrum of use cases, including:

4.2 Common single mode fiber optic cables

HELUKABEL offers a wide range of single mode fiber optic cables to meet needs ranging from internal networks to telecommunication infrastructure and long-distance transmission systems. All HELUKABEL single mode fiber optic cables are manufactured in accordance with the international ITU-T G.652 (9/125 µm) standard.

In addition, HELUKABEL also offers single mode fiber optic cables in various fiber counts, including 1 fiber, 2 fibers, 10 fibers, 48 fibers, 60 fibers, 96 fibers, 144 fibers…

4.3 Common multimode fiber optic cables