Introducing Linear Pluggable Optics (LPO)
Linear Pluggable Optics (LPO) are a new optical transceiver technology. The idea is simple: instead of a DSP (digital signal processor) inside the module – replacing it with transimpedance amplifier (TIA) and a driver chip with high linearity and EQ capability – LPO shifts signal processing into the host device. This makes the module simpler, more efficient, and lower in latency than traditional optics. A new technology built for the demands of modern data centers and AI clusters.
This article gives a short insight into how LPO technology works, how it differs from DSP-based optics, the scenarios where it offers the most advantages, and the standards that enable its deployment.
What is LPO and How is it Different?
Today's high-speed optical transceivers use a DSP to handle tasks like retiming, equalization, and forward error correction (FEC). This ensures reliable signal-processing under many link conditions, but also adds significant power consumption and latency.
LPO technology removes the DSP with complex CDR functionality and keeps only high-linearity analog components such as drivers, lasers, photodiodes, and TIAs (transimpedance amplifiers). The host ASIC in the switch or NIC then takes care of the digital processing that would normally happen inside the module.
By shifting these functions from the module to the host, LPO achieves lower power consumption and latency while staying fully compatible with modern high-speed data center architectures.
LPO vs DSP-Based Modules at a Glance
| Feature | DSP-Based Transceiver | LPO Transceiver |
|---|---|---|
| Architecture | DSP inside the module for retiming, equalization and FEC | No DSP – only linear analog components |
| Power Usage | Higher due to DSP power draw | Up to 50% lower power consumption |
| Latency | Higher latency (DSP processing adds delay) | Lower latency (no DSP processing in module) |
| Host Dependency | Self-contained, works with almost any host | Relies on the host ASIC to handle signal processing |
| Tolerance to Impairments | High | Low |
| Reach | Handles longer and more variable links |
Limited to short-reach links (currently < 500 m) |
| Cost | More expensive (DSP is a costly component) | Lower cost potential with simpler design |
Where LPO Fits Best
LPO modules are built for short-reach, high-density connections where efficiency and low latency matter most. In AI/ML clusters and GPU fabrics, removing DSP delays improves synchronization during training, while reduced power and cost per link make it easier to scale massive deployments. Hyperscale data centers benefit as well, as higher port density and lower total cost make LPO attractive for leaf–spine networks inside or between racks, where host ASICs manage signal conditioning. For longer or less predictable links, however, DSP-based optics remain the preferred option.
Because LPO shifts signal processing to the host, compatibility depends not only on form factor or EEPROM data but also on the specific hardware implementation of the switch or NIC. LPO modules must therefore be qualified for use with supported platforms to ensure proper performance and stability.
Built on Open Standards
Interoperability is key for LPO, which is why it is based on open standards:
- The LPO MSA (Multi-Source Agreement) defines the overall architecture — modules without DSPs, host-managed equalization, and monitoring features along the signal path.
- The OIF CEI-112G Linear PAM4 specification defines the electrical signaling between host and module at 112 Gb/s per lane.
- The CMIS (Common Management Interface Specification) with Versatile Control Set (VCS) expands management functions so hosts can identify LPO modules and exchange configuration parameters consistently across vendors.
Together, these standards create a broad, interoperable ecosystem of hosts and modules.
FLEXOPTIX LPO Modules
At FLEXOPTIX, we’re excited to offer this technology in our portfolio. Our LPO transceivers support 400G and 800G applications in QSFP and OSFP form factors. They bring all the efficiency and performance benefits of LPO to data center operators, while integrating seamlessly with supported switches and NICs.
LPO makes high-speed optics simpler, faster, and greener. For data centers aiming to cut power, latency, and TCO, it’s the natural next step, and FLEXOPTIX has the modules to get you there.
What comes after LPO?
Looking ahead, Linear Receiver Optics (LRO) refine the LPO concept by integrating a transmitter-side DSP to improve signal integrity, while keeping the receive path fully analog. Co-Packaged Optics (CPO) take integration even further by bringing optics and compute onto a shared platform. Together, they point toward a future of increasingly seamless and efficient optical connectivity.
