Overcoming Linear Pluggable Optics (LPO) deployment challenges: From standards to scale
By Mark Kimber / Semtech
The data center industry is reaching a critical juncture with the adoption of Linear Pluggable Optics (LPO) technology. As bandwidth demand surges and power consumption concerns intensify, the industry is moving beyond asking "What is LPO?" to tackling the more complex question: "How do we successfully deploy LPO at scale while maintaining operational reliability?"
This evolution represents a maturation of LPO technology, with hyperscalers and data center operators now focusing on overcoming operational concerns and ensuring seamless deployment across diverse infrastructure environments.
The foundation of standards: Building industry confidence
Successful deployment of any emerging technology depends on robust standards that ensure interoperability and reliability. Comprehensive LPO standards development advances the technology from laboratory concept to deployment-ready solution.
Industry standards leadership has focused on two critical areas: 1) electrical interface standards and testing, and 2) optical link performance and deployment. The Optical Internetworking Forum (OIF) concentrates on electrical interface standards, particularly around the following test points:
· TP1: Tests a module's input, simulating the host's output signal as it arrives at the module connector.
· TP1a: Tests the host’s ASIC transmitter output after passing through the host board and card edge connector.
· TP4: Verifies the module's electrical output signal and calibrates the signals used to test host input compliance.
· TP4a: Tests the host's input.
This work established crucial testing methodologies, including the Electrical Eye Closure Quaternary (EECQ) metric for measuring transmit port quality, and sophisticated port equalization methodologies to ensure optimal signal-to-noise ratios.
Complementing this work, the LPO Multi-Source Agreement (LPO MSA) is addressing optical link performance and deployment challenges, producing end-to-end link optimization methodologies and stress signal testing protocols that reflect real-world deployment scenarios.
Achieving true plug-and-play operation
Early LPO implementations often required manual tuning between modules and ports, resulting in operational overhead that negated many of the efficiency benefits. The development of a standards-based approach fundamentally changed this paradigm.
True plug-and-play operation centers on several key innovations. Pre-calibrated ports and modules now work together without manual adjustment, while Common Management Interface Specification (CMIS) functionality enables automatic module configuration to match port characteristics. Deterministic Continuous Time Linear Equalizer (CTLE) settings, based on port loss characteristics, ensure optimal performance without requiring manual intervention.
This approach facilitates seamless integration across different vendor ecosystems, addressing the primary concern of data center operators who work with equipment from multiple suppliers.
Optical power requirements and signal quality
Meeting TP2 specifications for optical power and extinction ratio proved challenging for many early implementations. Investigation reveals that insufficient equalization at the electrical interface and inadequate driver gain are often the causes of these issues.
The solution involves comprehensive driver equalization to ensure complete equalization of the host port when using Transmit Finite Impulse Response (TxFIR) filters and driver input CTLE. Additionally, modulator-specific equalization provided independent capabilities, while features such as Transmit Loss of Signal (TX LOS) detection and Automatic Gain Control (AGC) ensured robust operation across varying conditions.
Modern LPO drivers incorporate these features, providing the complete equalization capabilities needed to meet TP2 requirements while maintaining consistent simplicity in deployment.
High-Loss host port performance
Data centers with very high-loss host ports present particular challenges for maintaining acceptable Bit Error Rate (BER) performance. The solution involves implementing receiver-side equalization capabilities in the Trans-Impedance Amplifier (TIA), enabling optimum link equalization across different port loss characteristics while maintaining optimized signal-to-noise ratios throughout the link.
Diagnostic and troubleshooting capabilities
Hyperscalers express significant concern about reduced diagnostic visibility compared to Digital Signal Processing (DSP)-based retimed modules. The response involves comprehensive diagnostic implementations on both transmit and receive sides.
Transmit-side diagnostics include TX LOS detection, input signal level measurement and transmit power monitoring. Receive-side diagnostics encompass Loss of Signal (LOS) detection, Loss of Modulation (LOM) monitoring and eye monitoring capabilities at the switch receiver. These capabilities, combined with proper integration into network management systems, provide operators with the visibility needed to maintain and troubleshoot LPO deployments effectively.
Enhanced CMIS integration
CMIS extension proved crucial for enabling intelligent LPO deployment. Enhanced capabilities include automatic data polarity setup when modules are inserted, automatic input equalizer configuration based on port characteristics and linearity adjustment between modules and switches.
Port loss notification for optimized output equalization settings creates a comprehensive automation framework. These enhancements represent the final piece of the plug-and-play ecosystem, enabling truly seamless LPO deployment across diverse infrastructure environments.
Proven interoperability success
The LPO Multi-Source Agreement represents a collaborative effort involving more than 49 companies committed to developing interoperability specifications. Comprehensive interoperability testing conducted in early 2025 with approximately 90 participants from member companies achieved a significant milestone.
The testing demonstrated impressive results, with a high success rate and nearly all test links functioning immediately upon connection. Multiple module vendors successfully interoperated with various switch platforms, and validation was achieved across diverse implementation approaches. These results effectively counter early criticism about LPO robustness, providing concrete evidence that the technology is ready for large-scale deployment.
Future development and 200G evolution
Success with current LPO implementations establishes a foundation for continued innovation. Development efforts advance next-generation 200 Gbps per lane capabilities, utilizing advanced simulation models for high-speed performance prediction and enhanced equalization techniques for extreme data rates.
Collaborative development through industry forums ensures future standards will maintain the interoperability and plug-and-play characteristics that make current implementations successful. The expectation is that 200G-capable products will be available by the end of 2025, maintaining the technology's position at the forefront of optical networking innovation.
Strategic deployment considerations
For organizations evaluating LPO deployment, several key success factors emerge from industry experience. Standards compliance remains fundamental, as both electrical and optical interfaces must meet established specifications to ensure interoperability and reliable operation.
Comprehensive equalization capabilities are essential, requiring full-featured drivers with complete equalization, gain and diagnostic capabilities. The complexity of modern data center environments demands solutions that can adapt to varying conditions while maintaining optimal performance.
Intelligent management capabilities, particularly leveraging enhanced CMIS features for seamless plug-and-play operation, are crucial for achieving operational efficiency benefits. The automation capabilities reduce both deployment complexity and ongoing operational overhead.
Finally, working with suppliers who demonstrate interoperability and leadership in standards assures that implementations will integrate successfully with existing infrastructure and support future technology evolution.
The path forward
Linear Pluggable Optics technology has successfully evolved from a promising approach to building low-power, high-performance optical networks into a deployment-ready solution. The industry is effectively addressing real-world challenges that initially created hesitation for deployment, establishing a clear path for large-scale adoption.
The comprehensive standards frameworks from OIF and LPO MSA provide the foundation for reliable interoperability across vendor ecosystems. Proven diagnostic capabilities ensure operational visibility requirements are met, while accurate plug-and-play operation eliminates complexity barriers that could hinder large-scale deployment.
The focus now shifts from proving the technology works to optimizing deployment processes and scaling operations efficiently. With proper implementation of standards-compliant solutions featuring comprehensive equalization and intelligent management capabilities, LPO can deliver on its promise of reduced power consumption and complexity while maintaining the reliability and performance standards that modern data centers demand.
The foundation for successful LPO deployment is firmly established. Data center operators can now confidently evaluate and implement LPO solutions, knowing that technical challenges are addressed and the industry ecosystem supports reliable, scalable deployment. The next phase will focus on making operations smoother and gaining the efficiency benefits that first sparked industry interest in this technology.
Mark Kimber is a senior principal product definition specialist for Semtech.