In the fast-paced world of data centers, choosing the right fiber is crucial. It impacts speed. It affects reach. It determines your future upgrade path. You’ve likely heard terms like OM3, OM4, and even the newer OM5. But what do these labels really mean for your network?
Many IT professionals feel confused by these multimode fiber types. They all look similar. They all use light. Yet, their performance varies significantly. Making the wrong choice can lead to costly re-cabling or performance bottlenecks down the line.
This comprehensive guide is designed to bring clarity. We will break down the technical differences between OM3, OM4, and OM5. We will compare their capabilities for 10 Gigabit, 40 Gigabit, and 100 Gigabit Ethernet. More importantly, we’ll help you decide which multimode fiber type is the smartest investment for your specific data center needs, showcasing how PHILISUN MPO Cables integrate seamlessly with each.
Understanding Multimode Grading: The Modal Bandwidth
All multimode fiber uses light to send data. But how well it guides that light makes a big difference. This is where “Modal Bandwidth” comes in.
What is Modal Bandwidth?
- Imagine light pulses traveling down a fiber. In multimode fiber, light takes many paths. Some paths are shorter. Some are longer.
- This causes light pulses to spread out. They become “smeared” over distance.
- Modal bandwidth measures how well a fiber maintains the shape of these light pulses. A higher modal bandwidth means less spreading. It means the fiber can carry more data over longer distances.
Effective Modal Bandwidth (EMB)
- Modern OM3, OM4, and OM5 fibers are “laser-optimized.” They are designed for use with VCSEL (Vertical Cavity Surface Emitting Laser) transceivers.
- EMB specifically measures how these fibers perform with VCSELs. This is the key metric for modern data center fiber.
Legacy Fibers: OM1 and OM2
- OM1 (Orange jacket): Designed for older LED light sources. Very low bandwidth. Rarely used in new data centers.
- OM2 (Orange jacket): Also for LEDs, slightly better than OM1. Still not suitable for modern high speeds (10G+).
- Our Focus: We will concentrate on OM3, OM4, and OM5. These are the “laser-optimized” fibers. They are the standard for today’s high-speed networks.
Deep Dive: OM3 (The 10G Standard)
OM3 fiber was the first laser-optimized multimode fiber. It paved the way for faster Ethernet.
- Specs:
- Jacket Color: Aqua (or often light blue). This is a common color in many data centers.
- Light Source: Designed for 850nm VCSEL lasers.
- Modal Bandwidth: According to TIA/EIA standards, OM3 fiber offers an EMB of 2000 MHz·km at 850nm. This is a good leap from older fibers.
- Key Performance:
- 10 Gigabit Ethernet (10GBASE-SR): OM3 can reliably carry 10GbE up to 300 meters. This aligns with IEEE 802.3ae specifications. This made it very popular for connecting switches and servers within a building.
- 40 Gigabit Ethernet (40GBASE-SR4): It can support 40GbE up to 100 meters. This is using PHILISUN QSFP+ SR4 transceivers, a common configuration.
- 100 Gigabit Ethernet (100GBASE-SR4): Its reach for 100GbE is quite short, only 70 meters. This limits its use for 100G backbones in larger data centers.
- Limitations: While good for 10G, its 100G reach is often too short for modern data center links. Most 100G links in data centers need to be at least 100 meters.
Deep Dive: OM4 (The Data Center Workhorse)
OM4 fiber is built upon OM3. It offers significantly improved performance. It is currently the most widely deployed multimode fiber for high-speed data centers.
- Specs:
- Jacket Color: Aqua or Violet (Erika Violet). Many vendors use violet to distinguish it from OM3.
- Light Source: Also designed for 850nm VCSEL lasers.
- Modal Bandwidth: Industry standards (e.g., TIA-492AAAD) define OM4 with an EMB of 4700 MHz·km at 850nm. This is more than double that of OM3.
- Why it Dominates:
- Perfect for 100GBASE-SR4: OM4 fiber can support 100 Gigabit Ethernet (100GbE) up to 100 meters. This is a key requirement for many modern data center spine-leaf architectures. This uses PHILISUN QSFP28 SR4 transceivers with MPO cabling. IEEE 802.3bm specifies this capability.
- Extended 10G/40G: It extends 10GbE to 400 meters. It extends 40GbE to 150 meters.
- Cost-Effectiveness: OM4 offers a great balance of performance and cost. It is much cheaper than single-mode fiber for these distances.
- Applications: Ideal for inter-rack connections, connecting Top-of-Rack (ToR) switches to aggregation (Spine) switches. It is the go-to choice for new multimode deployments.
Deep Dive: OM5 (The Wideband Future)
OM5 fiber is the newest multimode fiber standard. It has a distinct color. It offers a new capability.
- Specs:
- Jacket Color: Lime Green. This color makes it easy to identify.
- Light Source: Designed for 850nm VCSELs, but also for a broader range of wavelengths (850nm to 953nm).
- Modal Bandwidth: As defined by TIA-492AAAE and IEC 60793-2-10, OM5 provides an EMB of 4700 MHz·km at 850nm (same as OM4). But it also specifies 2470 MHz·km at 953nm across multiple wavelengths.
- The “Secret Weapon”: SWDM
- SWDM (Short Wave Division Multiplexing): This is where OM5 shines. SWDM technology sends multiple wavelengths (colors) of light down a single fiber strand.
- How it works: Imagine sending four 25G signals (at different colors) down one fiber. This allows a 100G link to use only two fibers (one transmit, one receive) instead of eight fibers (four transmit, four receive) with traditional SR4.
- Fiber Savings: This means less fiber is needed. It reduces cable bulk.
- Critique: Do You Need It?
- Niche Market (for now): OM5 is specifically designed for SWDM transceivers. These transceivers are still newer. They can be more expensive than standard SR4 transceivers.
- OM4’s Strength: If you are using standard PHILISUN QSFP28 SR4 modules (which send 4 parallel streams at 850nm), OM4 fiber performs just as well as OM5 for 100m.
- Decision Point: Only consider OM5 if you specifically plan to deploy SWDM transceivers. For most data centers using standard 100G-SR4, OM4 is still the most cost-effective and high-performing choice.
Distance & Speed Comparison Table
This table shows the maximum reach for different speeds across OM3, OM4, and OM5 fiber types. These distances are derived from IEEE Ethernet standards and TIA cabling specifications.
| Ethernet Speed | OM3 (Aqua) | OM4 (Aqua/Violet) | OM5 (Lime Green) | Transceiver Type (Example) |
| 10 Gigabit (10GBASE-SR) | 300 meters | 400 meters | 400 meters | PHILISUN SFP-10G-SR |
| 40 Gigabit (40GBASE-SR4) | 100 meters | 150 meters | 150 meters | PHILISUN QSFP-40G-SR4 |
| 100 Gigabit (100GBASE-SR4) | 70 meters | 100 meters | 100 meters | PHILISUN QSFP28-100G-SR4 |
| 100 Gigabit (100G SWDM4) | Not supported | Not supported | 150 meters | (Special SWDM4 Transceiver) |
| 400 Gigabit (400GBASE-SR8) | Not supported | 70 meters | 70 meters | (Special 400G Transceiver) |
Note: 400G distances shown are for parallel optics (SR8), which use multiple fibers.
FAQ: Multimode Fiber Types
Q: Can I mix OM3 and OM4 fiber in the same link?
A: Yes, you can. However, the link’s performance will drop to the level of the lowest-grade fiber in the path. If you connect an OM4 cable to an OM3 cable, your maximum reach will be limited by the OM3’s specifications. This is a crucial point for network performance.
Q: Can I plug an OM4 patch cable into an OM5 patch panel?
A: Yes, you can. All OM3, OM4, and OM5 fibers use the same LC or MPO connectors. They are physically compatible. The issue is performance, as explained above. The link will only perform at the level of the lowest-grade fiber.
Q: Which fiber is best for MPO trunk cables in a new data center?
A: For most new data center deployments requiring 40G or 100G over multimode, OM4 fiber is currently the cost/performance sweet spot. It reliably supports 100G-SR4 links up to 100 meters. This is a common requirement, backed by widespread industry adoption. PHILISUN’s Certified OM4 MPO Trunk Cables are designed for this exact purpose. If you specifically plan to use SWDM technology, then OM5 would be an option.
Q: Do I need OM5 if I am going to 400G?
A: Not necessarily. For 400G, there are several standards. Many 400G multimode solutions (like 400GBASE-SR8) use 8 pairs of fibers (16 total fibers) and run over OM4 fiber for 70-100 meters. OM5 offers advantages for specific SWDM-based 400G solutions, but it’s not universally required. Consulting the specific transceiver’s data sheet is always recommended.
Conclusion: Choose Wisely for Your Network’s Future
Multimode fiber technology continues to evolve. OM3 laid the groundwork for 10G. OM4 became the staple for 100G in data centers. OM5 introduces a new capability with SWDM.
- OM3: Still fine for existing 10G links up to 300m. But it’s fading for new high-speed deployments.
- OM4: The current industry standard. It offers excellent performance for 10G, 40G, and especially 100G-SR4 links over 100 meters. It provides the best value. This is why it is so widely used.
- OM5: A niche solution for now. It is powerful if you specifically plan to use SWDM transceivers. For traditional parallel optics (like SR4), OM4 offers equivalent performance at a lower cost.
When building a high-speed backbone, make an informed choice. Consider your current needs. Think about future upgrades. PHILISUN’s Certified MPO Fiber Optic Cables provide guaranteed 100G performance. They are reliable. They are cost-effective for most data center needs. If you’re exploring the wideband future, we also offer OM5 solutions.
Ready to optimize your data center’s fiber infrastructure? Shop PHILISUN’s Certified MPO Fiber Optic Cables for guaranteed performance and a future-ready network.
