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Date: 10/27/26

LPO vs DSP-Based 800G Optics: Power, Latency and Signal Integrity

Article Summary

Removing the retiming DSP changes more than power consumption.

Linear Pluggable Optics (LPO) can reduce 800G module power, heat and processing latency, but removing the DSP also shifts more responsibility for signal integrity to the switch ASIC, SerDes, electrical channel, firmware and NIC.

Lower Power Axiom's modeled example compares 18W DSP optics with 9W LPO.
Less Retiming LPO removes the DSP processing stage from the optical module.
More Host Dependence SerDes, equalization and channel quality become more important.
More System Validation The optic, switch, NIC, firmware and link should be qualified together.

For the deeper technology guide, review Linear Pluggable Optics (LPO) for 800G Networks .

1. What Actually Changes?

The DSP Changes Where Signal Conditioning Happens

Traditional retimed optics perform significant digital equalization and signal conditioning inside the transceiver. LPO removes that retiming DSP and relies more heavily on the host system.

DSP-Based Optics vs. Linear Pluggable Optics
The key architectural difference is where signal recovery and equalization responsibility live.
DSP / Retimed
More conditioning inside the module
Switch ASIC
→
SerDes
→
Retiming DSP
→
Optics

The DSP helps compensate for channel loss, reflections, crosstalk, PCB losses and host impairments.

LPO
More responsibility moves to the host
Switch ASIC
→
Advanced SerDes
→
Linear Driver
→
Optics

LPO depends more heavily on switch and NIC SerDes performance, equalization and electrical channel quality.

This is the key engineering distinction. LPO does not simply remove a high-power component. It changes the system boundary.

2. The Obvious Benefit

Lower Optical Module Power

Axiom engineering modeled an 800G DSP optic at 18W and an Axiom 800G LPO at 9W.

That represents a modeled 9W difference per module, or approximately 50 percent lower optical-module power in this specific comparison.

The exact savings vary by implementation, reach, host platform and operating conditions.

Modeled 800G Module Power
Axiom engineering model: 18W DSP vs. 9W LPO.
DSP-Based 800G 18W
Axiom 800G LPO 9W
9W modeled difference per module
576W modeled difference across 64 populated 800G ports
36.9 kW modeled direct difference across 4,096 modules
3. The Tradeoff

LPO Buys Power Efficiency by Making the Host More Important

Neither architecture is automatically better. They optimize different parts of the system.

Linear Pluggable Optics
LPO Advantages
  • Lower optical-module power
  • Lower module heat dissipation
  • No retiming DSP dependency
  • Lower optical processing latency
  • Strong fit for controlled AI and HPC environments
LPO Requires More Attention To
  • Host SerDes capability
  • Electrical channel quality
  • Equalization and lane margin
  • Platform interoperability
  • System-level validation
DSP / Retimed Optics
DSP Advantages
  • Greater tolerance to channel variation
  • Stronger module-level signal conditioning
  • Broader interoperability
  • More mature deployment model
  • Cleaner troubleshooting boundary
DSP Tradeoffs
  • Higher module power
  • Higher faceplate thermal load
  • Additional DSP processing stage
  • Retiming DSP component dependency
  • Higher cooling burden at scale
4. The Less Obvious Change

The LPO Failure Domain Gets Larger

With a retimed optic, the module provides a stronger boundary between the host and optical path.

With LPO, a marginal link may involve the switch ASIC, SerDes, board channel, connector, optic, fiber, firmware, FEC or NIC.

Troubleshooting therefore becomes more system-oriented.

LPO System Boundary
An unstable link can originate well outside the optical module.
Switch ASIC
→
SerDes / EQ
→
PCB / Connector
→
LPO
→
Fiber
→
NIC SerDes
Engineering Variable
LPO
DSP / Retimed
Host SerDes dependence
Higher
Lower
Electrical channel sensitivity
Higher
Lower
Module signal conditioning
Lower
Higher
Module power
Lower
Higher
System-level validation need
Higher
Moderate
5. Choose Based on the Environment

Where LPO and DSP-Based Optics Fit Best

LPO Is Attractive When
You Control the Complete Link
  • The switch platform is tightly controlled.
  • Host SerDes capability is well understood.
  • Power and faceplate thermals are constrained.
  • The network uses dense 800G AI or HPC links.
  • Cabling and firmware can be standardized.
  • You can perform system-level qualification.
DSP Is Often Safer When
The Environment Is More Variable
  • Hosts or switch platforms are heterogeneous.
  • Channel margin is uncertain.
  • Broad third-party interoperability matters.
  • Longer reach requirements are important.
  • Frequent re-cabling or platform changes are expected.
  • Fast component-level fault isolation is a priority.
6. Why the Switch Matters

Axiom Treats LPO as an Integrated System

Axiom pairs its 800G Linear Pluggable Optics with an Axiom Broadcom Tomahawk 6-based network switch.

The Axiom LPO is equalized for the Axiom switch platform so the switch, SerDes and optical module can be engineered together rather than treated as unrelated components.

Explore the Axiom 800G AI Networking Platform →

Integrated 800G Architecture
The switch and LPO are engineered as part of the same high-speed signal path.
Axiom TH6 Switch
102.4 Tbps
→
Advanced
SerDes
→
Axiom
800G LPO
→
Fiber
→
NIC / GPU
Server
102.4 Tbps TH6 switching architecture
64 x 800G OSFP front-panel interfaces
RoCEv2 PFC, ECN and MMU support
7. Link-Up Is Only the Beginning

What Engineers Need to Validate

Because LPO depends more heavily on the complete host-to-optic path, qualification should continue beyond basic interface recognition and link-up.

System-Level LPO Qualification
Validation should move from physical-layer performance through real network and AI workload behavior.
01 Optical TX/RX power
OMA
TDECQ
02 Signal Integrity PAM4
Equalization
Lane margin
03 BER + FEC Pre-FEC
Post-FEC
Error trends
04 Ethernet Throughput
Traffic stability
Latency
05 RoCEv2 PFC
ECN
RDMA
06 AI Workloads All Reduce
All Gather
Stability

Axiom's engineering framework includes extended BER and stability testing through 24-hour, 72-hour, 7-day and 30-day periods.

For the deeper qualification workflow, review the 800G Transceiver Validation Guide .

8. Troubleshooting Changes Too

The Optic Is Not Always the Problem

With LPO, replacing the transceiver may not isolate the root cause.

Engineers may also need to investigate SerDes behavior, equalization, FEC, firmware, board-channel conditions, fiber-path issues and NIC behavior.

Review the Optical Transceiver Failure Analysis Guide for the broader troubleshooting process.

A Marginal Link Can Have Multiple Causes
Firmware
→
SerDes
→
Equalization
→
LPO
→
Fiber
→
FEC / NIC
Bottom Line

LPO removes processing from the optical module. It does not remove the need for engineering.

The headline advantage is lower module power and heat. The more important architectural change is that signal-integrity responsibility shifts toward the switch, SerDes, electrical channel, firmware and NIC.

The right question is therefore not simply whether LPO uses less power than DSP-based optics. It is whether the complete system has been designed and validated to operate without the retiming DSP.

Planning an 800G AI Fabric?

Evaluate the Switch, SerDes and Optics Together

Talk with Axiom about 800G switching, Linear Pluggable Optics, host SerDes requirements, RoCEv2, interoperability and system-level qualification.

Talk to a Networking Specialist

About the Author

Carlos Berto
VP of Engineering

Dr. Carlos Berto leads Axiom’s Network Engineering team, working directly with enterprise and hyperscale data centers on real-world deployment challenges across optical, memory, and interconnect infrastructure.

With over 25 years in telecommunications and data infrastructure, he has been involved in the design, validation, and troubleshooting of high-speed systems from early 10G networks through today’s 400G, 800G, and emerging 1.6T environments.

His work focuses on where systems fail outside controlled lab conditions signal integrity breakdowns, thermal constraints, and power delivery instability in production environments particularly in AI and HPC deployments.

Dr. Berto holds a Ph.D. in Engineering and contributes technical insights that translate field experience into practical guidance for engineering teams responsible for performance and reliability.

Focus Areas

  • Optical and Interconnect Systems (400G / 800G / 1.6T)
  • AI and HPC Infrastructure
  • Signal Integrity, Thermals, and Power Delivery

Connect

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