What is the LPO Transceiver?
May 14, 20241 min read
The optical communications industry has achieved significant advances in recent years, fueled by 5G and HPC, resulting in a rapid growth of optical infrastructure. The data center network speed is gradually developing from 400G to 800G and 1.6T, and will even reach 3.2T in the near future. The rapid development of data center networks has spurred continuous advancements in the speed of optical modules. However, to meet the demands of modern high-performance networks, optical transceivers need to evolve in various aspects beyond just speed, including power consumption, packaging, and more. This has led to the emergence of various new technologies.
Challenges in Transceiver Development
Technology iteration involves more than just doubling numbers. After getting to the 400G stage, it becomes imperative to address not only the enhancement of data transmission speed but also the challenges associated with increased power consumption and costs.
In the early days, a 10G transceiver used just about 1W of power. Until 400G and 800G, transceiver power usage surged, reaching 30W, accounting for 40% or more of the machine's total power consumption. Compared to 2010, total power in 2022 has increased by 22 times. The increase in energy consumption of optical communication devices puts a major burden on the overall use of energy and costs for the whole data center. To address these challenges, the industry explored two main solutions, Conventional Pluggable Optics (CPO) and Linear-Drive Pluggable Optics (LPO).
The Introduction of LPO Transceiver
What is LPO Technology?
LPO (Linear-drive Pluggable Optics) is a transceiver packaging technology. It uses a linear drive strategy to replace DSPs with a Transimpedance Amplifier (TIA) and Driver Chip (DRIVER) with excellent linearity and EQ capabilities. It utilizes specialized components, including ASIC substrates, ASIC (Retimer), and ASIC die, to optimize signal processing and enable efficient plug-and-play functionality in optical communication systems.
LPO Transceiver: Innovative Modules with Linear-Drive Technology
The LPO transceiver uses linear analog components in its data communication, eliminating the need for complex CDR or DSP systems. Compared to DSP solutions, LPO transceiver exhibits major savings in power consumption and latency, making them suitable for the needs of short-range, high-bandwidth, low-power, and low-latency data communication in HPC centers.
What are DSP and CDR?
Not all traditional transceivers incorporate Digital Signal Processing (DSP). However, in high-speed transceivers where stringent signal requirements prevail, DSP becomes essential. DSP is a chip-running algorithm that proves crucial in meeting the demanding signal processing needs of high-speed transceivers. It has a digital clock recovery function, and dispersion compensation function, which can reduce distortion on the system BER impact. However, it also has high power consumption and costs. For example, in the 400G transceiver, the 7nm DSP used, the power consumption is about 4W, accounting for about 50% of the power consumption of the entire module.
Clock Data Recovery (CDR) is also used for data restoration. It extracts the data sequence from the received signal and recovers the clock timing signal corresponding to the data sequence, thus restoring the specific information received.
Understanding Linear-Drive Technology
The linear-drive technology of LPO solution is to remove the DSP/CDR chip in the transceiver and integrate the related functions into the switching chip on the device side. In the transceiver, only the Driver Chip (DRIVER) and Trans-Impedance Amplifier (TIA) with high linearity are left, while Continuous Time Linear Equalization (CTLE) and Equalization (EQ) functions are integrated, respectively, for compensating high-speed signals to a certain extent.
The Advantages of LPO Transceiver
Compared with traditional transceivers, the advantages of LPO transceiver are mainly reflected in the four aspects of power consumption, cost, latency, and maintenance.
Low Power Consumption
The absence of DSP undoubtedly results in a significant reduction in power consumption. As indicated by Macom's data, an 800G transceiver incorporating DSP functionality can surpass 16W in power consumption. In contrast, an 800G LPO transceiver leveraging linear-drive technology exhibits remarkably lower power consumption, measuring less than 8.5W.
Low Cost
As previously highlighted, the Bill of Materials (BOM) cost attributed to DSP constitutes a significant portion, ranging from 20-40%, and this cost is effectively eliminated with the removal of DSP. The integration of EQ functionality in both the driver and TIA does introduce a slight incremental cost. However, the overall expenditure experiences a net reduction. According to industry analyses, in the context of an 800G transceiver, the BOM cost is estimated at approximately 600-700 dollars, with the DSP chip alone accounting for a cost range of 50-70 dollars. The inclusion of EQ functionality in the driver and TIA results in a marginal cost increase, ranging from 3-5 dollars. Through this calculated approach, the overall system cost realizes a reduction of approximately 8%, translating to a savings of around 50-60 dollars.
Low Latency
The elimination of DSP results in a reduction of one processing step, consequently decreasing data transmission latency. This advantage holds particular significance in HPC scenarios, where minimized latency is a crucial factor for optimal performance.
Easy Maintenance
Within the CPO framework, the need to power off and replace the entire board in the event of a system device malfunction presents a considerable inconvenience for maintenance tasks. In contrast, the pluggable nature of LPO transceivers allows for efficient replacement without the need to power down the entire system, further enhancing the overall convenience of the LPO solution. This not only simplifies fiber cabling but also streamlines equipment maintenance.
Pluggable Module | LPO | CPO |
Power consumption | High | Fairly low | Low |
Cost | High | Fairly low | Low |
Latency | Fairly High | Fairly low | Low |
Product Maturity | High | Fairly low | Fairly low |
Maintainability | Good | Good | Poor |
Link Performance | Good | Average | Good |
Interconnection Ecology | Good | Poor | Poor |
FS 800G LPO Transceiver Solution
Building on the advantages of LPO technology, FS has introduced its 800G OSFP finned top LPO module (OSFP-DR8-800G-LPO), designed to provide highly efficient solutions for AI/HPC data centers with ultra-low power consumption, latency optimization, and proven reliability：
Power Reduction: With a maximum power consumption of just 8.5W, the module consumes about 50% less energy than traditional 800G DSP-based modules, significantly reducing the energy and cooling burden on data centers.
Latency Optimization: With a DSP-free architecture, the module effectively reduces processing latency and is highly suitable for application scenarios with high real-time requirements, such as AI training and financial transactions.
Proven Reliability: The FS 800G LPO module has undergone rigorous testing, including traffic tests, bit error rate (BER) tests, and optical spectrum evaluation, confirming exceptional performance stability and transmission reliability. Field deployment validation with FS LPO switches confirmed the module's error-free operation under real-world workload conditions.
Operational Flexibility: Designed with hot-pluggable modularity, it simplifies on-site replacement and maintenance while ensuring both flexibility and reliability.
Application Scenarios: The FS 800G LPO module is well-suited for AI clusters and power-sensitive, high-bandwidth interconnect applications, and should be used in conjunction with LPO switches to achieve optimal performance.
Conclusion
Moving forward, LPO will unlock new possibilities for AI, cloud computing, and supercomputing networks as large-scale deployments accelerate. FS’s 800G LPO module offers cutting-edge performance and supports seamless data transmission in modern data centers and high-performance computing environments.
By choosing FS, you gain access to fast delivery, a diverse product portfolio, and tailored services, unlocking the full potential of high-speed, energy-efficient optical solutions.