When OM5 was introduced in 2016 it generated considerable interest — a new multimode fibre grade promising wideband capability, more data over fewer fibres, and a clear upgrade path beyond OM4. Nearly a decade on, the reality is more straightforward: OM5 never achieved meaningful commercial adoption, the transceivers it was designed around did not become mainstream, and OM4 remains the correct specification for the vast majority of commercial and enterprise multimode fibre installations. Understanding why tells you something useful about how fibre standards evolve — and confirms that OM4 is where to invest for new installations today.

This guide explains what OM4 and OM5 are, where they differ technically, why OM5 has not caught on, and when each is — and is not — the right choice.

What OM4 is and why it became the standard

OM4 is a laser-optimised multimode fibre standardised in 2009, designed for use with VCSEL (Vertical-Cavity Surface-Emitting Laser) light sources operating at 850nm. It uses a 50µm core and has an effective modal bandwidth (EMB) of 4,700 MHz·km at 850nm — more than double the 2,000 MHz·km of its predecessor OM3. That higher bandwidth directly translates into greater reach at any given data rate: OM4 supports 10 Gigabit Ethernet to 400 metres as standardised by IEEE and TIA, with real-world performance on high-quality fibre reaching up to 550 metres, and 40G and 100G Ethernet to 150 metres using parallel optics over MPO connectors, compared to 300m at 10G and 100m at 40G/100G on OM3.

OM4 also has lower attenuation than OM3 — a maximum of 3.0 dB/km at 850nm versus 3.5 dB/km on OM3 — meaning less signal loss per unit length, which provides additional margin in longer or more complex links with multiple connection points.

The combination of extended reach at 40G and 100G speeds and backward compatibility with OM3 infrastructure established OM4 as the standard for new multimode installations in commercial buildings, enterprise data centres, and campus backbone deployments. It is the current mainstream recommendation from Corning, Cisco, Fluke, and independent standards bodies for any multimode installation that needs to support 40G or 100G now or in the future.

What OM5 is and what it promised

OM5 — also known as Wideband Multimode Fibre (WBMMF) — was standardised in 2016. It uses the same 50µm core as OM4 and has identical bandwidth at 850nm: 4,700 MHz·km. The difference is that OM5 is also specified at additional wavelengths beyond 850nm, with a minimum EMB of 2,470 MHz·km at 953nm. This extended wavelength range enables Short Wavelength Division Multiplexing (SWDM) — a technique that transmits multiple independent data streams simultaneously over a single fibre, each on a different wavelength between 850nm and 940nm.

The headline advantage was fibre count reduction. Where OM4 with parallel optics might use eight fibres to carry a 100G link (four transmit, four receive), SWDM over OM5 could carry the same 100G in just two fibres using bidirectional transmission on multiple wavelengths. For installations with limited duct space or large numbers of long high-speed links, this appeared compelling. OM5 is lime green in jacket colour to distinguish it from OM4’s violet, and it is backward compatible with OM4 — the same connectors, the same termination process, the same test equipment.

On paper, the case for OM5 was clear. In practice, it depended entirely on whether SWDM transceivers became mainstream — and that is where the story diverges from the expectation.

Why OM5 did not catch on

The central problem is that OM5’s advantages only materialise with SWDM or BiDi transceivers — proprietary, multi-wavelength devices that operate across the 850–940nm range. Standard industry transceivers — SR4, SR8, SR4.2 — operate at 850nm only, using VCSEL sources. With standard 850nm transceivers, OM5 and OM4 perform identically. There is no distance benefit, no bandwidth benefit, and no operational advantage. As Corning stated directly in its technical documentation, OM5 provides no value compared to OM4 when standard 850nm optics are used — and standard 850nm optics are what the overwhelming majority of installed equipment uses.

SWDM transceivers did come to market, but they remained a niche product. They carry a significant cost premium over standard SR-type transceivers, are offered by fewer manufacturers, and are not supported across the broad range of switching platforms that drive enterprise purchasing decisions. The ecosystem that OM5 needed to justify itself — low-cost, widely available SWDM transceivers across multiple vendors — did not develop at the scale or price point required for mainstream adoption.

At the same time, the distance advantage OM5 offered over OM4 with SWDM transceivers — typically an extra 50 metres at 100G — turned out not to matter for most installations. Industry data consistently shows that 90–95% of multimode links in enterprise networks and data centres are under 100 metres. OM4 covers those distances comfortably at any speed it supports, without SWDM, without a proprietary transceiver, and at standard market pricing. The headroom OM5 offered for the minority of links over 100 metres did not justify a premium cable specification and non-standard transceiver selection across the rest of the installation.

OM5 does have a genuine use case in very high-density hyperscale data centre environments where cable tray space is genuinely constrained, fibre counts are massive, and reducing fibre infrastructure by half has real value. But that context is specific to hyperscale facilities, not to commercial buildings, enterprise data centres, campus backbones, or the installations that the majority of AV and IT installers are specifying for. For those environments, OM4 is the right answer and has been since it was standardised.

OM4 vs OM5 at a glance

View our full fibre range: DTECH fibre optic systems

DTECH OM4 products

DTECH’s OM4 range covers the full installed fibre system — bulk cable, patch leads, pigtails, and adaptors — all in the violet jacket that identifies OM4 throughout the installation.

The OM4 tight-buffered 8-fibre LSZH bulk cable is the backbone of any OM4 installation — tight-buffered construction for intra-building and campus runs, LSZH jacket for fire safety in occupied buildings, and 8-fibre count as the most practical configuration for commercial structured cabling backbone deployments. Tight-buffered construction provides mechanical protection to individual fibres without the gel-filled loose-tube construction of outdoor cable, making it suitable for direct termination without a breakout or fanout kit.

For patch leads, DTECH’s OM4 LC UPC to LC UPC duplex patch lead in violet LSZH is the standard connection for OM4 links — LC is the dominant connector type for OM4 in commercial and data centre environments due to its small form factor and high port density. The duplex configuration provides the transmit and receive path in a single lead.

Where field termination of bulk cable is required, DTECH’s OM4 LC UPC pigtails — supplied in packs of 12 — are factory-terminated on one end and fusion-spliced to the installed bulk cable on the other, providing a clean, low-loss connection at the patch panel or enclosure. Factory-terminated pigtails consistently deliver lower insertion loss than field-polished connectors, making them the preferred termination method for OM4 installations.

The OM4 LC UPC flangeless duplex adaptor in violet completes the system at the panel face — the fibre adaptor that accepts patch leads at the front of the patch panel or enclosure. The flangeless design fits flush-mount panel apertures without the retention flange required by flanged variants, making it suitable for high-density panel configurations where every millimetre of panel space matters.

Frequently asked questions

Can I use OM4 patch leads with OM5 cable?

Yes — OM4 and OM5 share the same 50µm core diameter and connector types, making them physically compatible. The overall link will perform at OM4 specification when OM4 components are mixed with OM5, since performance defaults to the lower-rated component. In practice, mixing OM4 and OM5 in the same link is not recommended for documented, certified installations — consistent specification throughout the channel is preferable for test certification and documentation purposes.

Is OM5 future-proof in a way OM4 is not?

The argument made for OM5 at its introduction was that SWDM would become mainstream and OM5 would be the required infrastructure for future high-speed links. That has not happened at the scale predicted. Standard 850nm transceiver technology has continued to advance — 400G SR8 and 400G SR4.2 are both supported over OM4 — and there is no current indication that SWDM transceivers will displace standard parallel optics as the dominant transceiver type in commercial installations. OM4 provides a clear upgrade path from 10G through 100G to 400G with standard, widely available transceivers.

What is the difference between tight-buffered and loose-tube OM4 cable?

Tight-buffered cable has each individual fibre directly coated in a protective buffer layer, giving each fibre mechanical protection and making the cable suitable for direct termination without breakout hardware. It is the correct construction for intra-building runs, riser applications, and installations where the cable terminates at multiple points. Loose-tube cable encases fibres in a gel-filled tube that protects against moisture, making it suited to outdoor and direct burial applications. DTECH’s OM4 bulk cable uses tight-buffered construction for internal and campus installations.

Why are pigtails preferred over field-polished connectors for OM4?

Field polishing connectors on multimode fibre requires careful control of the polishing process to achieve a clean, low-loss endface. Factory-terminated pigtails are polished under controlled conditions and inspected before leaving the factory, consistently delivering insertion loss below 0.1 dB — significantly lower than typical field-polished results. For OM4 installations where the loss budget is tighter due to longer runs or more connection points, the lower and more consistent insertion loss of pigtails is a practical advantage.

Should I specify OM4 or OS2 for a new backbone installation?

It depends on distance and application. OM4 multimode is the correct and cost-effective specification for intra-building backbone runs within its supported distances — up to 550m at 10G and 150m at 40G/100G — because multimode transceivers and components are significantly less expensive than single-mode equivalents at these distances. OS2 single-mode is the correct specification for longer inter-building and campus links where OM4’s distances are exceeded, or for installations that need to support very high-speed links at distances multimode cannot cover. For a typical multi-floor commercial building with telecommunications rooms on each floor and an equipment room in the basement or plant room, OM4 backbone is the standard specification.

Summary

OM4 is the current mainstream standard for multimode fibre installations — laser-optimised, VCSEL-compatible, and capable of supporting 10G, 40G, and 100G Ethernet with standard, widely available transceivers over the distances that commercial and enterprise installations require. OM5 was designed for wideband SWDM operation, but the transceivers it depended on never achieved mainstream adoption, and with standard 850nm optics OM5 offers no performance advantage over OM4. For new commercial building, campus, and enterprise data centre installations, OM4 is the correct specification. OM5 remains a niche product for specific hyperscale scenarios where SWDM transceiver economics and fibre count reduction justify the premium — a description that applies to very few installations outside the hyperscale data centre market.

If you need help specifying OM4 fibre for a commercial or data centre installation, get in touch with the DTECH team — we supply OM4 bulk cable, patch leads, pigtails, and adaptors to installers and IT teams across the UK, Europe, and the Middle East.