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Co-Packaged Optics · LPO → NPO → CPO

LPO vs. NPO vs. CPO: The Road to Co-Packaged Optics

Three ways to bring the optics closer to the switch chip, what each one saves, and where each fits in an AI network.

Join the talk · Oct 12
Home› CPO› LPO vs. NPO vs. CPO
Same switch chip, three places for the optics. Each step shortens the electrical path between the chip and the light.

Every switch in an AI data center has to turn electrical signals into light. The question the industry has been working on is where that happens. The closer the optics sit to the switch chip, the less power it takes to get the signal there.

Linear pluggable optics (LPO), near-packaged optics (NPO) and co-packaged optics (CPO) are three steps along that path. This guide walks through each one, how they compare, and why CPO is the end point.

The one idea behind all three

In a traditional switch, the electrical signal leaves the switch chip (ASIC), travels across centimeters of circuit board to a transceiver in the front panel, and gets cleaned up by a digital signal processor (DSP) before it becomes light. That trip, and the DSP at the end of it, cost a lot of power at 51.2 Tb/s.

LPO, NPO and CPO each attack that cost, in different ways and to different degrees.

What is LPO?

DefinitionLinear pluggable optics (LPO) are front-panel transceivers with the DSP removed. The switch chip drives the optics directly over a linear electrical link.

LPO keeps the form factor data centers already know. Modules still plug into the front panel and can be swapped by hand. Dropping the DSP saves power and latency in each module.

  • What it keeps: the board trace between the chip and the front panel. The chip's SerDes has to be strong enough to drive that distance without help.
  • Where it fits: shorter-reach links where operators want lower power without changing how they buy and service optics.

What is NPO?

DefinitionNear-packaged optics (NPO) move the optical engines off the front panel and onto the board, right next to the switch chip package.

NPO shortens the electrical path from centimeters of board trace to a short hop beside the package. That cuts more power than LPO, and it frees the front panel for fiber connections. The optics are no longer hand-swappable modules, so servicing moves toward the system level.

What is CPO?

DefinitionCo-packaged optics (CPO) put the optical engines inside the same package as the switch chip, on a shared substrate. The signal never crosses the circuit board.
Diagram of a co-packaged optics package: the optical engine sits on the same ASIC substrate as the ASIC die, beneath a shared heat sink.
Inside a CPO package: the optical engine shares the ASIC substrate with the switch die. Source: Micas Networks.

This is the shortest possible path. No board trace, no DSPs, and no transceivers to buy for each port. Fiber connects at the front panel and runs almost directly to the chip package. For the full explainer, see What Is a CPO Switch?

LPO vs. NPO vs. CPO at a glance

LPONPOCPO
Where optics liveFront-panel pluggable modulesOn the board, next to the chip packageInside the chip package
Electrical pathCentimeters of board traceA short hop beside the packageMillimeters, on the substrate
DSPsRemovedNot neededNot needed
Servicing opticsSwap a module by handSystem levelSystem level
Power savingGoodBetterBest (over 50% in Micas testing)

Why CPO is the end point

Each step removes more of the distance between the chip and the light, and CPO removes all of it. In Micas testing at 40 °C ambient with full line-rate bidirectional traffic, a Tomahawk 5 switch with 400G DR4 pluggables drew 3,267 W. The Tomahawk 5 CPO switch drew 1,626 W.

50.23%
Lower switch power vs. pluggable optics
1,626 W
TH5 CPO switch, full line rate
128 × 400G
Ports on the 51.2T CPO switch, air-cooled 4RU
Power comparison: TH5 M2-W6940-128QC with 400G DR4 pluggables at 3,267 W versus TH5 CPO M2-W6940-128X1-FR4 at 1,626 W, a 50.23% reduction.
Pluggable vs. CPO, same Tomahawk 5 switch chip: 3,267 W vs. 1,626 W. Source: Micas Networks.

LPO and NPO are useful steps, and many networks will run a mix for years. But at 51.2T and beyond, the operators who need the most bandwidth per watt are moving to CPO.

Hear it live at OPC 2026

We're walking through the full LPO → NPO → CPO path in a 20-minute talk, with time to see where each one fits in real AI clusters.

Oct
12
Monday
Executive Speaking Session
From LPO to NPO to CPO
Time 12:00 – 12:20 PM Where SJCC · Lower Level · LL21BC

Frequently asked questions

Is LPO the same as CPO?
No. LPO is still a pluggable module on the front panel, just without a DSP. CPO moves the optics inside the switch chip package.
Do I have to go through NPO to get to CPO?
No. NPO is a midpoint, not a requirement. Micas ships a 51.2T CPO switch today, so you can go straight to co-packaged optics.
Does CPO need liquid cooling?
Not the Micas 51.2T CPO switch. It ships as an air-cooled 4RU system that fits existing data center racks.
What happens if an optical engine fails in CPO?
Optics are serviced at the system level rather than by swapping a module. Talk to our team about how Micas handles serviceability and support.

Ready to skip ahead to CPO?

See the Micas 51.2T CPO switch in person, or talk to our team about where co-packaged optics fits in your network.

Talk to our team →
CPO power figures: Micas Networks testing, Tomahawk 5 M2-W6940-128QC with 400G DR4 pluggables vs. Tomahawk 5 CPO M2-W6940-128X1-FR4, 40 °C ambient, full line-rate bidirectional traffic. LPO and NPO descriptions are general industry definitions.