Fiber optic cabling uses either single-mode fiber or multimode fiber, each with their own advantages and use cases. Multimode fiber allows light to travel in multiple paths — or modes — through the fiber core. It comes in five standard grades: OM1, OM2, OM3, OM4, and OM5. Each grade differs in core size, supported data rates, maximum reach, light source, and jacket color. This guide breaks down every grade and when to use each one.
Table of Contents
6 sections — jump to any topic1. Multimode vs Single-Mode Fiber
Single-mode fiber has a very small core (typically 9 um) that allows light to travel in only one path. This eliminates modal dispersion, enabling transmission over very long distances — tens of kilometers — and is the standard for telecom, long-haul data center interconnects, and campus backbone links.
Multimode fiber has a larger core (50 um or 62.5 um depending on grade) that allows light to travel in multiple paths simultaneously. This produces modal dispersion that limits reach, but multimode fiber is less expensive than single-mode and pairs with lower-cost VCSEL-based transceivers — making it the cost-effective choice for intra-building and data center links within a few hundred meters.
Single-Mode Fiber
- Core size: 9 um
- Single light path — no modal dispersion
- Long reach: kilometres to tens of kilometres
- Higher fiber and transceiver cost
- Standard for WAN, DCI, and campus backbone
Multimode Fiber (OM1-OM5)
- Core size: 50 um or 62.5 um
- Multiple light paths — modal dispersion limits reach
- Short to medium reach: up to ~550 m depending on grade
- Lower fiber and transceiver cost (VCSEL-based)
- Standard for intra-building and data center links
2. OM1 and OM2
OM1 and OM2 are the two original multimode cable grades, both using an orange jacket in accordance with industry standards. They are both suited to short-distance applications such as short-haul networks, LANs, and private networks, and both use an LED light source.
OM1 has a core size of 62.5 um and is commonly used for 100 Mb/s applications. At 1 Gb/s (1000BASE-SX), OM1 supports distances up to 275 m. OM2 has a smaller core of 50 um, which reduces modal dispersion and improves bandwidth. OM2 is generally used for 1 Gb/s applications and supports distances up to 550 m at 1 Gb/s.
OM1
- Jacket color: Orange
- Core size: 62.5 um
- Light source: LED
- Max reach at 1 Gb/s: 275 m
- Typical use: 100 Mb/s legacy LANs
OM2
- Jacket color: Orange
- Core size: 50 um
- Light source: LED
- Max reach at 1 Gb/s: 550 m
- Typical use: 1 Gb/s short-haul networks and LANs
3. OM3 and OM4
OM3 and OM4 share an aqua jacket color and a 50 um core size. Both support 10 Gb/s at 850 nm. Unlike OM1 and OM2, both OM3 and OM4 are designed to work with laser light sources — specifically VCSELs (Vertical-Cavity Surface-Emitting Lasers) — which enables them to support 10G, 40G, and 100G Ethernet.
OM3 supports distances up to 300 m at 10 Gb/s. Using an MPO connector for parallel optics, OM3 can carry 40G or 100G traffic up to 100 m. OM3 is commonly used in larger private networks and enterprise data centers. OM4 extends the reach: it supports 10 Gb/s up to 550 m, and 100G up to 150 m over an MPO connector. OM4 is the standard choice for high-speed data centers, financial trading networks, and corporate campuses.
OM3
- Jacket color: Aqua
- Core size: 50 um
- Light source: VCSEL laser
- Max reach at 10 Gb/s: 300 m
- 40G/100G via MPO: up to 100 m
- Typical use: enterprise networks, larger private networks
OM4
- Jacket color: Aqua (sometimes violet/erika)
- Core size: 50 um
- Light source: VCSEL laser
- Max reach at 10 Gb/s: 550 m
- 100G via MPO: up to 150 m
- Typical use: data centers, financial networks, campuses
4. OM5
OM5 is the newest multimode fiber grade and the first designed specifically for SWDM (Short Wavelength Division Multiplexing) technology. While OM3 and OM4 operate only at 850 nm, OM5 specifies a range of wavelengths from 850 nm to 953 nm. This wider wavelength range allows OM5 to carry multiple signals on different wavelengths over a single fiber — which is the core advantage of SWDM.
OM5 shares the 50 um core size of OM3 and OM4, but uses a distinctive lime green jacket for easy identification. By multiplexing multiple wavelengths on a single fiber, OM5 can support 200G and 400G Ethernet while using fewer fiber strands — a significant advantage in high-density installations where fiber count is a constraint. OM5 supports distances up to 150 m for 100G SWDM4 applications.
Distinctive color for easy identification in multi-fiber environments
Wider wavelength window enables SWDM — multiple signals on one fiber
Supports 200G and 400G on fewer fibers vs OM3/OM4
5. Full Comparison Table
← swipe to scroll →| Grade | Jacket Color | Core Size | Light Source | Max Reach (10G) | Max Reach (100G MPO) | Typical Use |
|---|---|---|---|---|---|---|
| OM1 | Orange | 62.5 um | LED | Not recommended | Not supported | 100 Mb/s legacy LANs; 1G up to 275 m |
| OM2 | Orange | 50 um | LED | Not recommended | Not supported | 1 Gb/s short-haul; 1G up to 550 m |
| OM3 | Aqua | 50 um | VCSEL laser | 300 m | 100 m | Enterprise networks, larger private networks |
| OM4 | Aqua / violet | 50 um | VCSEL laser | 550 m | 150 m | Data centers, financial networks, campuses |
| OM5 | Lime green | 50 um | VCSEL + SWDM | 550 m | 150 m (SWDM4) | 200G/400G networks, fiber-count-constrained installations |
All distances are per TIA-568 standards. "100G MPO" reach refers to parallel optics using MPO connectors. OM1/OM2 are not recommended for 10G — use OM3 or higher for any 10G or faster deployment.
6. Which Grade Should You Choose?
For any new installation, OM1 and OM2 should be avoided — they do not support 10G at practical distances, and the cost savings over OM3 are minimal on a per-project basis. OM3 is the entry point for any deployment that needs to support 10G today or may need to support 40G or 100G in the future. OM4 is the practical choice for most modern data center and campus deployments requiring 100G over parallel optics up to 150 m. OM5 is the right choice when fiber count is constrained and the network needs to scale to 200G or 400G without rewiring.
