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Intro
Multimode fiber (MMF) continues to play a critical role in today's high-bandwidth, short-range optical networks. While single-mode fiber (SMF) dominates long-distance and carrier-grade infrastructure, multimode fiber remains the most cost-efficient and practical choice for enterprise buildings, campus networks, and modern data centers.
This guide explains the five generations of multimode fiber - OM1, OM2, OM3, OM4, and OM5 - covering their physical characteristics, color coding, bandwidth, maximum distances at different data rates, optical sources (LED, VCSEL, SWDM), and real-world applications in enterprise networks and data centers.
It also compares multimode fiber with single-mode fiber, describes the connector types commonly used with multimode cabling, highlights advantages of multimode fiber, and provides a clear selection guide for choosing the right OM standard.
Practical engineering insights from Network-Switch.com, supported by CCIE/HCIE/RCNP-certified experts, complete the article with recommendations for building reliable short-range 10G/25G/40G
Multimode Fiber Overview
What is Multimode Fiber?
Multimode fiber (MMF) uses a larger glass core—50 µm or 62.5 µm—allowing multiple light modes to propagate simultaneously. This makes multimode fiber ideal for:
- High-speed short-range links
- Enterprise and campus deployments
- Data center rack-to-rack and row-to-row connections
- Environments where cost, density, and ease of installation matter
Typical distance capabilities include:
- 10 Gigabit Ethernet up to ~300–550 m (depending on OM rating)
- 1 Gigabit Ethernet up to ~550 m or more
- Lower data rates (100 Mb/s) up to ~2 km
Multimode fiber pairs naturally with VCSEL-based transceivers, which are cheaper, consume less power, and support high-speed applications at lower cost than single-mode laser modules.
Understanding the OM Standard
Multimode fiber types are defined by ISO/IEC 11801 and classified into five generations:
- OM1 — legacy LED-optimized fiber
- OM2 — early 50 µm LED fiber
- OM3 — laser-optimized multimode
- OM4 — enhanced OM3 with higher performance
- OM5 — wideband multimode fiber (WBMMF)
Each generation improves bandwidth, supported speeds, and maximum distances.
OM1 to OM5 Explained
Below is a detailed explanation of each multimode fiber type, including characteristics, performance, and ideal use cases.
1. OM1 - Legacy Multimode Fiber (62.5 µm)
- Core diameter: 62.5 µm
- Jacket color: Orange
- Optical source: LED
- Bandwidth: 200 MHz·km
- 10G distance: 33 m
OM1 is commonly found in older buildings, campuses, and legacy network environments. It was widely used before VCSEL lasers became mainstream. OM1 does not support high-bandwidth modern applications and is considered obsolete for 10G+ networking.
2. OM2 - Early 50 µm Fiber
- Core diameter: 50 µm
- Jacket color: Orange
- Optical source: LED
- Bandwidth: 500 MHz·km
- 10G distance: 82 m
OM2 is suitable for 1G Ethernet and limited 10G applications. It offers compatibility with modern 50 µm systems but is not ideal for high-density or high-speed networks.
3. OM3 - Laser-Optimized 50 µm Fiber
- Jacket color: Aqua
- Optical source: VCSEL
- Bandwidth: 2,000 MHz·km
- 10G distance: 300 m
- 40G/100G distance: 100 m
OM3 introduced VCSEL optimization, enabling scalable high-speed applications in enterprise networks and data centers. It remains a cost-effective option for 10G/25G and moderate-distance 40G/100G links.
4. OM4 - Enhanced Laser-Optimized Multimode
- Jacket color: Aqua
- Bandwidth: 4,700 MHz·km
- 10G distance: 550 m
- 40G/100G distance: 150 m
OM4 improves on OM3 with significantly higher bandwidth. It supports longer distances at high speeds, making it the mainstream standard for new data center and enterprise deployments.
5. OM5 - Wideband Multimode Fiber (WBMMF)
- Jacket color: Lime green
- Core: 50 µm
- Optical source: VCSEL/SWDM
- Bandwidth: 28,000 MHz·km
- Supports: 4+ wavelengths from 850–953 nm
OM5 enables short-wave division multiplexing (SWDM), allowing multiple wavelengths to travel simultaneously through a single fiber strand. This enhances scalability for 100G/200G/400G short-range data center applications.
While OM5 offers advanced capabilities, adoption is still growing due to higher cost and limited SWDM module availability.
OM1 vs OM2 vs OM3 vs OM4 vs OM5: Full Comparison
1. Physical Characteristics
| Type | Core Size | Jacket Color | Light Source | Bandwidth |
| OM1 | 62.5 µm | Orange | LED | 200 MHz·km |
| OM2 | 50 µm | Orange | LED | 500 MHz·km |
| OM3 | 50 µm | Aqua | VCSEL | 2000 MHz·km |
| OM4 | 50 µm | Aqua | VCSEL | 4700 MHz·km |
| OM5 | 50 µm | Lime Green | VCSEL/SWDM | 28000 MHz·km |
OM1 stands alone with a 62.5 µm core, while all modern fibers (OM2–OM5) use 50 µm.
2. Performance Comparison (Speed × Distance)
| Type | 1GbE | 10GbE | 40GbE | 100GbE |
| OM1 | 275 m | 33 m | — | — |
| OM2 | 550 m | 82 m | — | — |
| OM3 | 550 m | 300 m | 100 m | 70 m |
| OM4 | 550 m | 550 m | 150 m | 150 m |
| OM5 | 550 m | 550 m | 150 m | 150 m (+ SWDM benefits) |
OM3 is sufficient for most 10G deployments. OM4 is the recommended standard for high-speed enterprise and data center links. OM5 enhances capacity for next-generation SWDM technologies.
Multimode vs Single-Mode Fiber
A practical comparison helps clarify when MMF or SMF is appropriate.
1. Technical Differences
| Parameter | Multimode | Single-Mode |
| Core diameter | 50–62.5 µm | 8–10 µm |
| Light source | LED/VCSEL | Laser diode |
| Modal dispersion | High | Very low |
| Bandwidth | Lower | Extremely high |
| Distance | Up to ~550 m | Tens of kilometers |
2. Practical Differences
Distance: SMF supports far longer transmission distances.
Cost: MMF transceivers are significantly cheaper than SMF modules, reducing total project cost.
Installation: MMF tolerates more alignment variance, simplifying installation and lowering maintenance complexity.
Application Fit
- MMF: Data centers, enterprise buildings, short-range links
- SMF: Metro/backbone, telecom, long-haul, large campus
When to Choose Which?
Choose multimode (OM3/OM4/OM5) when:
- Distances are <600 meters
- Budget is a priority
- Deploying high-density 10G/25G/40G/100G
- Using LC/MPO SR or SR4 optics
Choose single-mode (OS2) when:
- Distances exceed 600 meters
- Planning for long-term high-speed scalability
- Connecting buildings, campuses, or metro networks
Multimode Fiber Connector Types
Multimode fiber supports various connector types. The most common include:
LC - The Modern Standard
- Ferrule: 1.25 mm
- High density, low loss
- Default connector on SFP/SFP+/SFP28 modules
SC - Older but Still Found in Legacy Networks
- Square push-pull design
- Common in OM1/OM2 environments
FC - Threaded Precision Connector
Used in laboratory or vibration-sensitive environments.
ST - Traditional Bayonet Connector
Older campus and industrial systems.
MPO/MTP - Parallel Optics for 40G/100G
- 12/24/48 fibers
- Backbone cabling in data centers
- Essential for high-speed MPO-SR4 or breakout deployments
Advantages of Multimode Fiber
Multimode fiber offers several advantages that make it ideal for modern in-building deployments:
1. Cost-Effective Optical Links
VCSEL-based multimode transceivers are far cheaper than single-mode modules.
2. Ideal for Data Centers
OM3/OM4/OM5 support high-density, short-reach connectivity with LC or MPO connectors.
3. High Compatibility with Enterprise Protocols
Supports Ethernet, Fibre Channel, InfiniBand, and more.
4. Lower Power Consumption
VCSEL light sources typically consume less power.
5. Easier Installation and Maintenance
Larger core size → larger alignment tolerance → easier splicing and termination.
Practical Selection Guide (Engineering-Based)
Below is a simple decision guide based on performance, budget, and deployment scenarios.
1. If maintaining legacy networks:
Use OM1 or OM2 (only when required).
2. If deploying 10G cost-effectively:
Use OM3.
3. If deploying 10G/25G/40G/100G in modern environments:
Use OM4 — the mainstream choice for new builds.
4. If preparing for SWDM-based 100G–400G:
Use OM5.
5. If exceeding 600 meters:
Switch to single-mode OS2 fiber.
Deployment Scenarios
Data Centers
- Leaf–spine architecture
- TOR → EOR links
- 25G/40G/100G structured cabling
Recommended: OM4 or OM5
Enterprise Campuses
- Building-to-closet links
- Floor-to-floor fiber trunks
Recommended: OM3 or OM4
Telecom/Edge Locations
- CO racks
- Short-reach interconnects
Recommended: OM4
Industrial Environments
- Automation networks
- Sensor connectivity
Recommended: OM3/OM4 with armored options
Conclusion
Multimode fiber remains the most cost-effective and practical medium for short-range, high-bandwidth applications across enterprise networks and data centers. OM1 and OM2 support legacy systems, OM3 provides affordable 10G performance, OM4 is the mainstream high-speed standard, and OM5 offers advanced wideband capabilities for emerging SWDM deployments.
Choosing the right multimode fiber depends on required bandwidth, transmission distance, existing infrastructure, and long-term upgrade plans. For most modern networks, OM4 delivers the best balance of performance, scalability, and cost.
At Network-Switch.com, our engineering team can help you select the right OM fiber, optical modules, connectors, and cabling solutions for your environment. We supply complete fiber connectivity solutions - including LC/MPO assemblies, OM3/OM4/OM5 patch cables, Cisco/Huawei/Ruijie/NS-compatible transceivers, and pre-terminated fiber systems—with global 5-day delivery, 3-year warranty, and lifetime support.
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