I. Introduction: Parallel Coexistence, Not a Battle of Routes

As AI and data center interconnects rapidly advance toward 800G and 1.6T, LPO, LRO, and traditional DSP-based optical modules are not engaged in a “winner-takes-all” replacement battle. Instead, constrained by different system requirements, transmission distances, and levels of industry maturity, they form a long-term pattern of parallel coexistence.

Within this parallel framework, HYBRID (semi-DSP) solutions—representing a more engineering-oriented intermediate architecture—are demonstrating clear advantages over typical LRO solutions in terms of overall system and industrial value.

Based on a systematic review of the parallel evolution logic of LPO, LRO, and DSP, and combined with real-world 800G HYBRID product implementations, this paper compares the strengths and weaknesses of each approach and focuses on a key question:

Why is HYBRID more practical and advantageous than LRO in real-world deployment?

II. Review of the Three Fundamental Architectures: DSP, LPO, and LRO

1. DSP-Based Modules: The “Ballast Stone” of Performance and Ecosystem

(1)Architecture Characteristics：Full DSP on both TX and RX sides

(2)Advantages

• Strongest signal processing capability (equalization, CDR, FEC, nonlinear compensation)
• Supports medium, long, and ultra-long reach transmission
• Mature industry ecosystem, complete standards, true plug-and-play

(3)Disadvantages

• High power consumption (800G typically >14–16 W)
• Higher latency
• Highest cost

(4)Typical Applications

• Metro networks, backbone networks, DCI
• Mission-critical links with extreme reliability requirements

2. LPO: Ultimate Power Efficiency with the Deepest System Coupling

(1)Architecture Characteristics : No DSP inside the module . Signal processing fully shifted to the host SerDes

(2)Advantages

• Lowest power consumption (30–50% reduction compared to DSP)
• Ultra-low latency
• Lowest module BOM cost

(3)Disadvantages

• Extremely stringent requirements on host SerDes and channel consistency
• Limited transmission distance (typically ≤100m)
• Complex system tuning and immature ecosystem

(4)Typical Applications

Intra-rack and inter-rack ultra-short-reach interconnects in AI clusters

3. LRO: A Conceptual Compromise

(1)Architecture Characteristics : DSP retained on TX side,Linear RX architecture

(2)Advantages

• Lower power consumption than full DSP
• Better reach capability than LPO

(3)Practical Challenges

• Highly fragmented TX simplex DSP implementations
• Poor chip reusability and weak economies of scale
• Ecosystem has not reached mainstream adoption

III. HYBRID: A More Engineering-Mature “Semi-DSP” Path

1. The Essential Definition of HYBRID

HYBRID is not simply equivalent to LRO. Instead, it is a system-level DSP resource reallocation methodology:

HYBRID = Only half of the TX/RX paths inside the module pass through DSP, and for the module-level transmit/receive links, only TX or RX passes through DSP,while the remaining paths adopt linear architectures.

Conceptually, this can be understood as: HYBRID ≈ (LRO + LTO) / 2

Below is the patented HYBRID architecture description from GIGALIGHT:

HYBRID 800G Multimode Architecture Diagram (Patent Applied)

HYBRID 800G Single-Mode Architecture Diagram (Patent Applied)

HYBRID 800G Copper Cable Architecture Diagram (Patent Applied)

2. Key Differences: HYBRID vs. LRO

Dimension	LRO	HYBRID
DSP Type	TX simplex DSP	Mature duplex DSP
Chip Reusability	Very low	High, reuse of existing DSP
Market Scale	Niche, customized	Scalable, mass-producible
Supply Chain Risk	High	Low
System Consistency	Medium, one-side linear	Medium, one-side linear

Core Conclusion:
HYBRID does not introduce a new class of highly specialized DSP chips. Instead, it reuses mature duplex DSP architectures and simply reduces the number of active channels.

Furthermore, early system-level validation shows that certain LTO-based system links can even outperform LRO links, reinforcing HYBRID’s clear advantage over LRO in real industrial deployment.

IV. Comprehensive Advantages and Practical Challenges of HYBRID Key Advantages of HYBRID

1. Key Advantages of HYBRID

• Significant power reduction：~20–30% lower than full DSP solutions
• Ultra-low link latency：DSP count reduced by half; latency comparable to LRO
• Controllable signal quality：MMF 50m: PRE-FEC BER up to E-7 / E-8，SMF 500m: PRE-FEC BER up to E-10
• Clear cost optimization：~20% cost reduction versus traditional DSP solutions
• Support for higher channel density：Viable path toward 16-channel / 3.2T pluggable modules

2. Limitations and Challenges of HYBRID

• Non-DSP RX paths place slightly higher requirements on host SI tuning
• Requires system-level co-optimization rather than pure “plug-and-play”
• Still in early stages of large-scale deployment, requiring customer-side collaboration

However, compared with LPO and LRO, the engineering and deployment risks of HYBRID are significantly more controllable.

V. The Inevitability of Parallel Coexistence: Why There Is No Single Winning Route

Scenario	Optimal Solution
≤100m, ultra-low latency	LPO
100m – 2km, power/performance balance	HYBRID / LRO
≥2km, maximum reliability	DSP

These three solutions address different system constraints and optimization targets, rather than forming a simple generational replacement relationship.

VI. Conclusion: HYBRID Is the Most Realistic Intermediate Solution

• LPO is an idealized extreme solution
• DSP is an irreplaceable foundational solution
• HYBRID is currently the most engineering-feasible intermediate solution

Compared with LRO, HYBRID’s decisive advantage lies in the fact that:
It does not rely on highly specialized TX simplex DSPs with extremely limited market demand, but instead reuses mature, scalable duplex DSP architectures.

This enables HYBRID to achieve clear overall competitiveness in power consumption, cost, ecosystem maturity, supply chain stability, and system-level deployment.

In the foreseeable future, LPO, HYBRID, and DSP will continue to coexist, jointly forming the technological foundation of AI and data center interconnects.

About GIGALIGHT

As an open optical networking explorer, GIGALIGHT integrates the design, manufacturing, and sales of both active and passive optical devices and subsystems. The company’s product portfolio includes optical modules, silicon photonics modules, liquid-cooled modules, passive optical components, active optical cables, direct attach copper cables, coherent optical communication modules, and OPEN DCI BOX subsystems. GIGALIGHT focuses on serving applications such as data centers, 5G transport networks, metropolitan WDM transmission, ultra-HD broadcast and video, and more. It stands as an innovative designer of high-speed optical interconnect hardware solutions.