Modern data networks rely on high-performance cabling to transmit ever-growing volumes of information efficiently. Among the most essential components are multimode fiber (MMF) cables, which enable high-speed data transfer over short to medium distances.
The most common multimode classifications—OM1, OM2, OM3, and OM4—each serve different performance and distance requirements. Understanding these differences helps network engineers and IT planners make informed decisions about cost, performance, and scalability.
What Is Multimode Fiber?
Multimode fiber (MMF) is an optical cable that carries multiple light rays, or “modes,” simultaneously through a larger-diameter glass core—typically 50 µm or 62.5 µm. This enables high data throughput but limits transmission distance due to modal dispersion (different light paths arriving at slightly different times).
Each multimode fiber cable is built from key structural layers:
- Core: The central path for light transmission.
- Cladding: Reflects light back into the core using total internal reflection.
- Coating and Jacket: Protective layers that shield the fiber from moisture, heat, and physical damage.
How the OM Series Evolved
The OM (Optical Multimode) classification, defined by ISO/IEC 11801 and TIA/EIA-568 standards, represents successive generations of fiber with improved bandwidth and distance performance.
- OM1 (62.5 µm): The original standard, designed for LED light sources.
- OM2 (50 µm): Improved bandwidth, still LED-based.
- OM3 (50 µm): Laser-optimized for VCSEL sources.
- OM4 (50 µm): Enhanced version of OM3 with greater reach and higher bandwidth.
The evolution from LED to VCSEL laser technology dramatically improved transmission efficiency, making OM3 and OM4 fibers the current standards for high-speed applications like 10G, 40G, and 100G Ethernet.
Detailed Sections for Each OM Type
OM1 Fiber
OM1 is the earliest type of multimode fiber, with a 62.5 µm core designed for LED light sources. It is suitable for short-distance LANs and older enterprise networks that primarily operate at 1G Ethernet speeds. Although its bandwidth is limited, OM1 remains in use in legacy systems where full-speed, high-bandwidth connections are not required. For small-scale or legacy applications, OM1 provides a cost-effective solution. Some high-quality multimode fiber providers, such as PHILISUN, still offer tested OM1 solutions for maintaining the reliability of existing networks.
OM2 Fiber
OM2 fiber introduced a smaller 50 µm core and improved bandwidth, while still supporting LED-based light sources. This type is commonly used in medium-speed enterprise networks and campus environments. OM2 can support 10G Ethernet over short distances, making it suitable for gradual network upgrades from older OM1 systems. Its balance of performance and affordability makes it a practical choice for organizations looking to enhance network capabilities without a full-scale overhaul.
OM3 Fiber
OM3 fiber marked a shift to laser-optimized designs, supporting VCSEL light sources that significantly increase bandwidth and transmission distance. With OM3, 10G, 40G, and even 100G Ethernet applications are feasible, making it a standard in modern data centers and high-density enterprise networks. The laser-optimized core allows for lower signal loss and consistent performance across large-scale deployments. OM3 fiber is ideal for organizations seeking reliable high-speed connections while maintaining cost efficiency.
OM4 Fiber
OM4 is an enhanced version of OM3, designed to offer higher bandwidth and longer reach. It is fully compatible with OM3 but provides extended distance for 40G and 100G Ethernet connections, making it suitable for next-generation data centers and high-performance computing environments. OM4 allows organizations to future-proof their infrastructure while maintaining backward compatibility with existing multimode systems. High-quality manufacturers, including PHILISUN, provide OM4 fibers that undergo stringent quality control to ensure stability and low insertion loss in demanding applications.
OM1 vs OM2 vs OM3 vs OM4 vs OM5: What’s the Difference?
Physical Difference
Physical difference mainly lies in core size, bandwidth, max distance, jacket color, and light source bandwidth, which is described in the following table.
| Parameter | OM1 | OM2 | OM3 | OM4 |
| Core Size (µm) | 62.5 | 50 | 50 | 50 |
| Bandwidth (MHz·km @850 nm) | 200 | 500 | 2000 | 4700 |
| Max Distance (10GBASE-SR) | 33 m | 82 m | 300 m | 550 m |
| Max Distance (40G/100G) | — | — | 100 m | 150 m |
| Jacket Color | Orange | Orange | Aqua | Aqua / Violet |
| Light Source | LED | LED | VCSEL | VCSEL |
Practical Difference
| Ethernet Speed | OM1 | OM2 | OM3 | OM4 |
| 1GBASE-SX | 300 m | 550 m | 550 m | 550 m |
| 10GBASE-SR | 33 m | 82 m | 300 m | 550 m |
| 40GBASE-SR4 | — | — | 100 m | 150 m |
| 100GBASE-SR10 | — | — | 100 m | 150 m |
What’s the Difference Between Single Mode and Multimode Fiber?
While both types transmit data using light, single-mode and multimode fibers differ significantly in design, distance, and application.
| Parameter | Single Mode Fiber (SMF) | Multimode Fiber (MMF) |
| Core Diameter | ~9 µm | 50 µm or 62.5 µm |
| Light Source | Laser | LED or VCSEL |
| Transmission Distance | Up to 100 km+ | Typically < 2 km |
| Bandwidth | Extremely high | Moderate to high |
| Cost (Transceivers) | Higher | Lower |
| Applications | Long-haul, telecom, MAN | Data centers, LAN, enterprise |
Single-mode fiber transmits one light path, providing minimal signal loss and extremely long reach, making it ideal for telecommunication backbones and metropolitan networks.
Multimode fiber, on the other hand, is optimized for shorter distances and cost efficiency, often used within data centers, campuses, and enterprise LANs where link distances are under 2 km.
PHILISUN manufactures both SMF and MMF cables, but for short-range, high-density networks, multimode fiber remains the preferred choice due to its versatility and affordability.
What Are the Advantages of Multimode Fiber?
Multimode fiber remains a favorite for short-range networking because it offers an excellent balance between speed, cost, and installation simplicity.
Cost-Effective Setup
MMF systems use lower-cost optics and cabling, reducing total infrastructure costs.
Easier Installation
The larger core simplifies alignment and connectorization, reducing technical complexity.
High Bandwidth Over Short Distances
OM3 and OM4 fibers support 10G, 40G, and 100G links efficiently within data centers.
Future Scalability
Modern VCSEL-based designs ensure long-term compatibility with emerging Ethernet standards.
Compatibility with Existing Networks
Newer multimode fibers are backward-compatible with earlier OM generations.
Use Cases & Deployment Scenarios
- OM1: Legacy LANs, 1G Ethernet systems.
- OM2: Small enterprise networks and building backbones.
- OM3: Standard choice for 10G–40G data centers.
- OM4: Future-ready solution for 40G/100G high-performance computing.
PHILISUN’s multimode fiber portfolio supports a wide range of deployment needs—from high-density data centers to long-term enterprise infrastructure—with consistent quality and customizable configurations.
Migration & Future-Proofing
As bandwidth demands rise, upgrading from OM1/OM2 to OM3/OM4 ensures your network can handle higher data rates and longer distances efficiently.
Upgrade Strategy:
- Assess existing optical transceivers and cabling paths.
- Replace older LED-based systems with VCSEL-compatible fiber (OM3/OM4).
- Choose OM4 for optimal 100G scalability and investment protection.
While OM5 wideband fiber introduces advanced SWDM support, OM4 remains the most widely adopted and cost-effective choice today.
Conclusion
Each OM fiber type offers unique advantages based on performance and reach:
- OM1/OM2: For legacy and cost-sensitive applications.
- OM3: For most 10G–40G networks.
- OM4: For 100G and future-ready infrastructures.
PHILISUN provides high-quality multimode fiber solutions with customizable lengths, connector options (MTP/MPO, LC, SC, APC), and low-loss performance for any deployment.
👉 Ready to upgrade your network?
Explore PHILISUN’s Multimode Fiber Series or contact our team for expert consultation on OM fiber selection and integration.
FAQs
Q1. Can I mix OM1 and OM3 cables?
No. Mixing different core sizes (62.5 µm and 50 µm) can cause high signal loss.
Q2. Will OM3 support 100G in the future?
Yes, OM3 supports 100GBASE-SR10 up to 100 meters; OM4 extends this to 150 meters.
Q3. Is OM4 backward compatible?
Yes, OM4 is fully backward compatible with OM3 systems.
Q4. What’s the main advantage of multimode fiber?
Cost-effective short-range performance with simple installation and scalability.
