400G & 800G QSFP-DD Transceivers Australia | Buyer’s Guide

Quick answer: 400G and 800G QSFP-DD transceivers are the pluggable optical modules that carry 400 or 800 gigabits per second between switches, routers, servers and sites. They are used in data centres, telecommunications and ISP backbones, enterprise cores and research networks. Choose one in this order: match your switch port (QSFP-DD, QSFP-DD800 or OSFP), then the distance (SR, DR, FR, LR or ZR), the fibre and connector, the breakout plan, the power budget and the vendor coding. In Australia, Cloudtronics supplies and codes 400G and 800G optics with local support from Sydney and Melbourne.

For years, 10G and then 100G did the heavy lifting in most Australian networks. Traffic hasn’t stopped growing, though. Cloud apps, video streaming, 5G, remote work, backups and, more recently, AI workloads all push more data through the same racks and fibre. When 100G ports fill up, you have two choices: add more switches and fibre, or make each port faster. 400G and 800G optics let you do the second.

• More bandwidth per port: one 400G port carries what four 100G ports do, and one 800G port replaces eight.
• Lower cost and power per bit: fewer switches, fewer cables and less power for the same capacity.
• Less space: QSFP-DD keeps the same port density as QSFP28, so a 1RU switch can carry up to 14.4 Tb/s at 400G and roughly double that at 800G.
• Flexible breakout: one fast port can split into several 100G or 400G links, so you can upgrade the core first and the edge later.
• Future-ready: 800G Ethernet is a ratified IEEE standard, and the next step (1.6T) is on the way. Buying into QSFP-DD keeps your upgrade path open.

You don’t need an AI supercomputer to benefit. Any network that’s outgrowing 100G is a candidate. We cover the main use cases further down, from AI and data centres through to telcos, enterprise and research.

QSFP-DD stands for Quad Small Form-factor Pluggable Double Density. It looks almost exactly like the QSFP28 module you’d use for 100G, but it has a second row of electrical contacts. That doubles the lanes from four to eight.

New to transceivers? Start with our guide to types of SFP transceivers, then come back here.

Faster isn’t always better value. Here’s a simple way to decide:

Plenty of Aussie sites run both: 400G for the existing core and 800G for the new AI pod. If you’re still mostly on 100G, see our 100G QSFP28 module guide. Those modules will keep working in your new QSFP-DD ports.

Yes. It’s the first thing to check. At 800G you’ll see two main form factors:

• QSFP-DD800: compact and backward compatible with QSFP28 and 400G QSFP-DD. Popular on Ethernet switches where you want to reuse existing optics.
• OSFP: slightly bigger, with more room for heat and power. Common on GPU-centric platforms and InfiniBand fabrics.

The two are not interchangeable. An OSFP module won’t fit a QSFP-DD cage, and the reverse is also true. Match what’s on the switch or NIC. For a deeper dive into the two packages, read our article on 800G optical modules.

Distance is the biggest factor in picking a module. The good news is that 400G and 800G share the same “reach classes”, so once you know the distance the choice is easy.

400G and 800G optics turn up anywhere a network has outgrown 100G. These are the most common use cases we see.

1. The rise of AI and data centres

AI is the fastest-growing use case right now. GPU clusters move huge amounts of data between servers, and every GPU needs a fast, low-latency path to the others. At that scale 100G becomes the bottleneck, so new AI halls are built on 400G and 800G from day one. The wider data centre boom is adding to the demand.

2. Telcos, ISPs and 5G backhaul

Carriers and regional ISPs use 400G in their core and aggregation layers as mobile and fixed broadband traffic keeps climbing. 400G LR4 covers links up to 10 km, and coherent 400ZR/ZR+ plugs straight into routers for longer runs.

3. Data centre interconnect (DCI)

400ZR and 800ZR coherent modules link sites across a metro area, for example between Sydney’s western suburbs and the CBD, without a separate optical shelf.

4. Enterprise and campus core

Large enterprises, banks, hospitals and councils are moving their core and storage networks to 400G to cope with cloud, backup and video traffic. Breakout lets one 400G port feed four 100G switches.

5. Universities, research and government

HPC clusters, research networks and secure government sites need high-bandwidth links. Some also have supply chain rules. See our article on TAA-compliant transceivers.

6. Broadcast, media and live events

Uncompressed 4K/8K video and remote production move huge streams between studios, stadiums and playout centres. 400G links keep those workflows running smoothly.

Cloudtronics is an Australian network solutions company headquartered in Brookvale, NSW, with an office in Cranbourne West, VIC. We help data centres, carriers, ISPs, MSPs, enterprises and research teams get high-speed optics that just work.

• 400G and 800G supply: QSFP-DD and QSFP-DD800 modules across SR8, DR4/DR8, FR4/2×FR4, LR4 and ZR, plus OSFP when your platform needs it.
• Coded for your switch: compatible coding for the major switch and router brands, backed by our programmable transceivers range and coding lab.
• Local help: a team in Sydney and Melbourne on Australian time, with no overseas ticket queues.
• Bulk and project supply: staged deliveries for large data centre, carrier and AI roll-outs. See our bulk supply guide.
• Everything around the optics: passive CWDM/DWDM components, ConsoleMate console servers for out-of-band access, and MAXIMATE remote transceiver support.

Comparing suppliers? Here’s how we stack up as an FS.com alternative in Australia.