High-Speed Coherent Modules - DCO vs ACO

Posted on Feb 2, 2024 by

In the ever-evolving landscape of optical communication, high-speed coherent modules showcasing vital performance capabilities to meet the escalating demands of data transmission in today's rapidly advancing digital era. Specifically, we delve into two key players in this domain: DCO (Digital Coherent Optics) and ACO (Analog Coherent Optics) modules, which encapsulate the core of advanced optical communication. To truly grasp the significance of these technologies, this article will explore the nuanced distinctions between them.

What Are DCO & ACO ?

Digital Coherent Optics (DCO)

Digital Coherent Optics (DCO) stands at the forefront of cutting-edge optical communication technology. Leveraging sophisticated digital signal processing, DCO excels in coherent modulation and demodulation. This involves the meticulous handling of phase and amplitude information within optical waves through advanced digital techniques. The utilization of digital methods not only ensures precise adjustments but also opens avenues for seamless optimizations.

Analog Coherent Optics (ACO)

ACO employs analog signal processing techniques to carry out coherent modulation and demodulation. Diverging from the reliance on discrete signals seen in digital methods, ACO embraces a continuous signal processing approach. This analog methodology enables ACO to seamlessly align with the inherent characteristics of analog optical signals, providing benefits in terms of signal fidelity and resilience. The continuous processing employed by ACO facilitates precise manipulation of phase and amplitude information within optical waves, contributing to robust and reliable performance within optical communication systems.

DCO Coherent Module vs ACO Coherent Module

In the early days, coherent transceivers leaned heavily on robust high-power DSP for the intricate task of optical signal processing. This reliance led to analog communication between modules and systems, a strategic move to avert overheating concerns related to both optical devices and the DSP itself. However, as technology advanced and DSP seamlessly integrated with optical components, the landscape shifted. Analog communication stepped aside, making room for the era of digital communication, heralding the advent of the Coherent Optical Module Array - DCO.

DCO and ACO Technologies in Coherent Modules

Technologies of DCO

  • Integration Method

DCO coherent module integrates the DSP chip directly onto the optical device, enabling digital communication between the module and the host system. This approach facilitates communication between heterogeneous switch/router vendors.

  • Signal Processing Method

DCO utilizes digital signal processing (DSP) for coherent modulation and demodulation, manipulating the phase and amplitude of optical waves through digital techniques. By adjusting the phase and amplitude, DCO can encode highly complex digital signals into the optical waves, representing the data to be transmitted. Moreover, the application of digital technology allows the DCO system to monitor and adjust signals in real-time during the transmission process. DSP can dynamically detect and correct changes and interference in the optical waves, enhancing the stability and reliability of the system.


Figure 1: Integration Approach for DCO Modules

Technologies of ACO

  • Integration Method

The key distinction between DCO and ACO modules lies in their communication approach. Unlike DCO, which integrates the DSP chip directly into the optical device, ACO opts for analog communication between the module and the host system.

  • Signal Processing Method

The ACO Coherent Module employs sophisticated analog signal processing techniques for coherent modulation and demodulation. In contrast to digital methods, the analog approach seamlessly interacts with continuous signals, allowing for a natural alignment with the inherent characteristics of optical waves.


Figure 2: Integration Approach for ACO Modules

DCO and ACO Applications in Coherent Modules

Applications of DCO

  • Long-Haul Communication

DCO modules are particularly well-suited for long-distance communication. The advanced digital signal processing capabilities enable efficient signal modulation and demodulation, ensuring reliable data transmission over extended distances.

  • Data Center Interconnects

Within data centers, where high-speed and high-capacity connectivity is crucial, DCO modules play a vital role in enabling the efficient transmission of substantial data volumes between servers and data storage units.

  • Telecommunication Networks

Telecommunication networks benefit from DCO technology, especially in the core backbone infrastructure. The ability to maintain signal quality over extended optical links makes DCO modules valuable in telecommunication applications.

  • Metro Networks

DCO modules are deployed to establish high-speed connections within metropolitan area networks (metro networks), linking diverse locations like corporate offices, data centers, academic institutions, or other critical facilities. By enabling rapid data transmission, DCO modules contribute to supporting fast and reliable communication between various locations within a metropolitan area network, addressing the demands for high-capacity and efficient communication in urban environments.

Applications of ACO

  • Short to Medium-Haul Communication

ACO technology is crucial for simplifying connectivity between end-users and the network infrastructure. With continuous signal processing, ACO seamlessly integrates into access networks, providing reliable connections to homes and businesses with minimal signal degradation.

  • Access Networks

ACO technology can simplify connectivity between end-users and the network infrastructure. With continuous signal processing, ACO seamlessly integrates into access networks, providing reliable connections to homes and businesses with minimal signal degradation.

  • Enterprise Networks

In enterprise networks, where high-speed connectivity is vital but distances are relatively short, ACO modules play a key role. The analog approach ensures precise signal handling, making them suitable for stable and high-speed connections within a limited range, essential for enterprise operations.

  • Cloud Computing Infrastructure

ACO modules find practical applications in cloud computing infrastructure, primarily due to their efficiency in handling data transfers within confined spaces like data centers. The analog nature of ACO allows for reliable performance in the dense and dynamic environment of cloud computing.


The competition between DCO and ACO highlights their respective technical advantages. DCO stands out with its mastery of digital signal processing, especially in coherent modulation and demodulation. Meanwhile, ACO, utilizing analog signal processing, demonstrates unique strengths in signal fidelity and resilience. This ongoing technological rivalry propels advancements in optical communication, opening up broader possibilities in our digital era.

You might be interested in

See profile for George.
FS 200G/400G CFP2-DCO Transceivers Overview
Jun 23, 2022
See profile for Sheldon.
Decoding OLT, ONU, ONT, and ODN in PON Network
Mar 14, 2023
See profile for Irving.
What's the Difference? Hub vs Switch vs Router
Dec 17, 2021
See profile for Sheldon.
What Is SFP Port of Gigabit Switch?
Jan 6, 2023
See profile for Migelle.
PoE vs PoE+ vs PoE++ Switch: How to Choose?
Mar 16, 2023