OM3 and OM4 should be compared together with the intended optical interface and complete channel requirements. The source products on this site both use 50/125 μm geometry and list effective modal bandwidth at 850 nm, with a higher reference value for OM4. That difference does not independently guarantee a particular Ethernet distance. Record the transceiver interface, total channel length, connector and splice losses, and acceptance criteria before choosing. Also separate coated-fiber procurement from the performance of a finished cable assembly: connectors, manufacturing and installation introduce requirements beyond the bare-fiber table. Use the comparison below to review the source values, then confirm the offered grade and the design requirements with the relevant supplier or engineering team.
Reference specification comparison
Values below are the same supplier reference data shown on the product pages. Different test conditions occupy separate rows; “Not listed” means the cited product table does not provide that entry.
| Parameter / condition | OM3 | OM4 |
|---|---|---|
| Core diameter | 50.0 ± 2.5 μm | 50.0 ± 2.5 μm |
| Cladding diameter | 125 ± 1.0 μm | 125 ± 1.0 μm |
| Attenuation at 850 nm | ≤ 2.4 dB/km | ≤ 2.4 dB/km |
| Attenuation at 1300 nm | ≤ 0.6 dB/km | ≤ 0.6 dB/km |
| Effective modal bandwidth at 850 nm | ≥ 2000 MHz·km | ≥ 4700 MHz·km |
| Coating diameter | 245 ± 7 μm | 245 ± 7 μm |
Bandwidth is one part of the design
The supplied reference literature lists effective modal bandwidth at 850 nm of at least 2,000 MHz·km for OM3-300 and 4,700 MHz·km for the OM4 product. These are reference limits for the source grades, not measured results for a new batch. Retain the wavelength and bandwidth type when copying the values into a comparison.
Do not substitute an overfilled bandwidth value for effective modal bandwidth. If an offered datasheet uses different terminology, ask the supplier to identify the test basis before comparing the numbers.
Evaluate the whole channel
Identify the intended optical module and the requirements of its channel. Include total length, connections and splices in the review. The channel loss budget and supported interface requirements remain relevant even when the fiber has a higher bandwidth specification.
Avoid a universal reach table unless it is tied to a specific interface and verified source. This guide intentionally does not derive Ethernet reach from the bandwidth-length product alone.
Specify the material and verify the offered batch
For coated fiber on reels, specify the grade, geometry, attenuation, coating and required quantity. If purchasing finished assemblies elsewhere, include their connector and completed-assembly requirements as a separate scope. Bare-fiber data cannot confirm the performance of an untested assembly.
Request the supplier product sheet, reel identifiers and applicable quality records. Explain whether the fiber is intended for a new design or an extension of existing infrastructure, and make any qualification requirement explicit before placing the order.
What to confirm
- Required optical interface and channel length
- Effective modal bandwidth at the stated wavelength
- Connector and splice allowances
- Coating, geometry and total fiber quantity
- Applicable supplier and batch documents
Frequently asked questions
Does OM4 always give a longer link than OM3?
The actual supported channel depends on the optical interface and complete channel requirements. A bandwidth value alone is not a distance guarantee.
Are OM3 and OM4 the same core size in these references?
Both listed products use 50/125 μm geometry. Review the complete tolerances and offered specifications, not just the nominal dimensions.
Does this comparison cover OM1?
OM1 has a separate reference geometry and bandwidth specification. Review the installed network and the OM1 product table before considering an extension or substitution.
Sources & reference context
This guide is published by OpticFiberHub and summarizes the supplier literature identified below with editorial purchasing guidance. Product values describe the source grade, not a measured result or a conformity guarantee for a new order.
- OM3 reference specifications — Jiangsu Nanfang Optical Fiber Product Manual, pages 13–14.
- OM4 reference specifications — Jiangsu Nanfang Optical Fiber Product Manual, pages 15–16.
Quality & technical resources explains source selection, translated documents and the limits of historical batch records. Request the current specification and applicable records for the actual offered material.
Further terminology reference: The Fiber Optic Association: optical fiber fundamentals.
