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Fiber Type Reference: OS2, OM3, OM4 and OM5

Choosing between OM3, OM4, OM5 and OS2 comes down to distance, data rate and cost. This table lists the core size, loss, bandwidth, usual jacket color and reach so you can compare fiber types in seconds.

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Fiber typeModeCore / cladding (um)Standard referenceMax attenuation (dB/km)Modal bandwidth (MHz.km)Typical jacket color10G reach40G SR4 reachNotes
OM1
Multimode
62.5/125
ISO/IEC 11801, IEC 60793-2-10 A1b
3.5 at 850 nm, 1.5 at 1300 nm
200 at 850, 500 at 1300
Orange
33 m
Not supported
Legacy LED-based installations. Not recommended for new builds.
OM2
Multimode
50/125
ISO/IEC 11801, IEC 60793-2-10 A1a.1
3.5 at 850 nm, 1.5 at 1300 nm
500 at 850, 500 at 1300
Orange
82 m
Not supported
Common in older building backbones.
OM3
Multimode
50/125
ISO/IEC 11801, IEC 60793-2-10 A1a.2
3.5 at 850 nm (3.0 in TIA), 1.5 at 1300 nm
1500 overfilled, 2000 EMB at 850
Aqua
300 m
100 m
Laser-optimized for VCSEL sources.
OM4
Multimode
50/125
ISO/IEC 11801, IEC 60793-2-10 A1a.3
3.5 at 850 nm (3.0 in TIA), 1.5 at 1300 nm
3500 overfilled, 4700 EMB at 850
Aqua (some vendors use violet)
400 m
150 m
Common for data center backbones and short reach links.
OM5
Multimode
50/125
ISO/IEC 11801, IEC 60793-2-10 A1a.4, TIA-492AAAE
3.0 at 850 nm, 1.5 at 1300 nm
3500 at 850 overfilled, 1850 at 953; EMB 4700 and 2470
Lime green
400 m
150 m
Wideband multimode designed for short wavelength division multiplexing (SWDM). Backward compatible with OM4.
OS1
Single-mode
9/125
ISO/IEC 11801, ITU-T G.652
1.0 at 1310 and 1550 nm
Not applicable
Yellow
10 km (10GBASE-LR)
Not applicable
Tight-buffered indoor cable. Higher attenuation than OS2.
OS2
Single-mode
9/125
ISO/IEC 11801, ITU-T G.652.D
0.4 at 1310 and 1550 nm
Not applicable
Yellow
10 km (10GBASE-LR), 40 km (ER)
Not applicable
Loose-tube indoor/outdoor and campus or metro links. Typical installed loss is lower than the maximum.
G.652.D
Single-mode
9/125
ITU-T G.652
0.4 at 1310 and 1550 nm
Not applicable
Yellow
Depends on transceiver
Not applicable
Standard single-mode fiber with low water peak. Basis of most OS2 cable.
G.657.A1
Single-mode
9/125
ITU-T G.657
Similar to G.652.D
Not applicable
Yellow
Depends on transceiver
Not applicable
Bend-insensitive, compatible with G.652.D. Minimum bend radius 10 mm.
G.657.A2
Single-mode
9/125
ITU-T G.657
Similar to G.652.D
Not applicable
Yellow
Depends on transceiver
Not applicable
Bend-insensitive, compatible with G.652.D. Minimum bend radius 7.5 mm.
G.657.B3
Single-mode
9/125
ITU-T G.657
Similar to G.652.D
Not applicable
Yellow
Depends on transceiver
Not applicable
Strong bend resistance for in-building and drop cables. Minimum bend radius 5 mm.
G.655
Single-mode
About 9/125
ITU-T G.655
About 0.35 at 1550 nm
Not applicable
Yellow
Long-haul DWDM
Not applicable
Non-zero dispersion shifted fiber for DWDM at 1550 nm.
G.654
Single-mode
9/125 class
ITU-T G.654
About 0.17 to 0.20 at 1550 nm
Not applicable
Yellow
Subsea and ultra-long haul
Not applicable
Cut-off shifted fiber with a large effective area and very low loss at 1550 nm.

Values are typical standards-based figures for planning. Always confirm limits against the cable datasheet and the specific standard edition. Reach shown is for the stated Ethernet PHY and depends on the transceiver.

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How to use the table

Search by type, standard or jacket color to filter the rows. Multimode fiber (OM1 to OM5) has a 50 or 62.5 micron core and is used with short wavelength VCSEL transceivers for runs inside buildings and data centers. Single-mode fiber (OS1 and OS2) has a 9 micron core, uses 1310 or 1550 nm lasers, and covers kilometers. Use the reach columns to match a fiber type to an Ethernet PHY, then check cost and transceiver availability before you decide.

  • Under 300 m inside a building: OM3 or OM4 is usually enough
  • 400 m and above or campus links: OS2 single-mode
  • SWDM transceivers: OM5 to get the benefit of wideband multimode
  • New builds: skip OM1 and OM2 unless you must match existing plant

How to read the columns

Attenuation is the maximum loss per kilometer used for acceptance testing, though installed cable is often better. Modal bandwidth in MHz.km limits the distance for multimode at high rates. Overfilled launch values apply to LED sources, while effective modal bandwidth (EMB) applies to laser launch and is what matters for OM3, OM4 and OM5. Jacket colors are conventions from TIA-598 and not a guarantee, so confirm the type from the cable print line or datasheet before you connect anything.

OM4 versus OM5

OM4 and OM5 have the same core and the same performance at 850 nm. OM5 adds specified bandwidth at 953 nm so that SWDM transceivers can run four wavelengths over a single pair of fibers, cutting fiber count for 40G and 100G links. If you use only standard 850 nm optics, OM5 gives no distance advantage over OM4. Many projects still choose OM5 for future flexibility, but OM4 is often cheaper and fully adequate.

Common mistakes

Mixing multimode core sizes is a frequent error: connecting 62.5 micron to 50 micron can add several dB of loss in one direction. Another is assuming all yellow cable is OS2, since some indoor tight-buffered cable is OS1 with higher loss. Also check the reach assumption: the 10G, 40G and 100G distances depend on the transceiver type and connector count, and long links may need a loss budget calculation as well.

Frequently Asked Questions

What is the difference between OS1 and OS2?

Both are 9/125 single-mode fibers. OS1 is usually tight-buffered indoor cable with up to 1.0 dB/km loss, while OS2 is loose-tube cable with up to 0.4 dB/km. OS2 is preferred for new designs and longer runs.

Is OM5 backward compatible with OM4?

Yes. OM5 has the same 50/125 core and works with standard 850 nm transceivers like OM4. Its extra specification at 953 nm only matters when you use SWDM optics that run multiple wavelengths.

What color is each fiber type?

Commonly OM1 and OM2 are orange, OM3 and OM4 are aqua, OM5 is lime green and single-mode is yellow. These are conventions, not guarantees, so verify the type from the cable marking or datasheet.

Can I mix OM3 and OM4 in one link?

You can physically, but the link performance is limited by the weaker fiber, and the reach must be calculated for the lower grade. Keep one fiber grade per channel when possible to avoid surprises.

If you manage fiber and cable inventory as items in an ERP, we can help structure the attributes so types and specs are searchable. Reach out if you want to talk about it.

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