The continued development of AI large-model training, high-performance computing (HPC), and cloud computing workloads is driving data center networks toward higher bandwidth, lower latency, and greater energy efficiency. As the industry moves rapidly from 400G to 800G and gradually transitions to the 1.6T era, traditional network architectures based on electronic packet switching are facing new challenges.
For a long time, data center switching networks built on Ethernet and InfiniBand have relied mainly on optical-electrical-optical (OEO) conversion for data exchange. As clusters continue to expand and the number of network devices keeps growing, every data forwarding step requires electronic processing, which not only increases system latency but also brings higher power consumption, cooling pressure, and network complexity.
Against this backdrop, Optical Circuit Switching (OCS) has once again become a key focus of the industry. As a switching technology operating at the optical layer, OCS can directly establish end-to-end optical connections, keeping optical signals in the optical domain throughout the entire transmission process without frequent optical-electrical conversion, thereby providing more efficient network interconnectivity for future ultra-large-scale AI computing centers.
Unlike traditional switching networks, OCS is not intended to replace existing packet switching systems, but serves as an important supplement at the optical layer, leveraging its advantages in stable, high-bandwidth communication scenarios and providing more flexible and efficient connection methods for next-generation data center networks.
Optical Circuit Switching (OCS) is a switching technology that establishes dedicated optical communication paths. Its core idea is to pre-establish a complete optical path between the two communicating parties, allowing data to be transmitted without passing through electronic switching throughout the entire transmission process.
Traditional switches adopt a “store—forward” mechanism, where each data packet must go through multiple steps such as parsing, route lookup, buffering, and re-transmission. OCS is completely different: it first completes optical path configuration, after which all service data is transmitted continuously along the established optical channel.
Therefore, OCS is more like establishing a high-speed dedicated fiber in the network, rather than continuously processing every data packet.
The entire switching process keeps optical signals transparent, without parsing network protocols or identifying data content, so it can support services running different communication protocols and different rates.
OCS operates at the physical layer, and its core task is to dynamically establish correspondences between input and output fibers.
A typical workflow includes the following steps:
If the communication peer changes, only the optical path needs to be reconfigured, without changing the network topology.
Currently, most large OCS systems use control software for optical path management, and can combine SDN (Software-Defined Networking) to automatically establish, adjust, and release optical connections.
Although both undertake network interconnection tasks, their working methods differ fundamentally.
The biggest feature of OCS is not fast switching, but that after an optical path is established, data can continue to be transmitted along the fixed optical path, avoiding the system overhead of massive repeated switching.
1. Reducing Network Latency
Traditional switches need to parse and forward every data packet, while after OCS establishes an optical path, optical signals can pass directly through.
Less electronic processing means:
For AI training that requires frequent parameter synchronization, network latency directly affects overall training efficiency, so OCS has clear advantages.
2. Improving Network Bandwidth Utilization
As 800G and even 1.6T optical interconnect become more common, the processing pressure on electronic switching chips continues to increase.
OCS directly uses fiber as the transmission medium and is not limited by protocols, fully leveraging the bandwidth capability of high-speed optical modules.
Especially when a large number of nodes communicate continuously, its bandwidth utilization is significantly higher than traditional networks.
3. Reducing Overall Energy Consumption
Most of the power consumption of data center network equipment comes from electronic switching chips.
OCS reduces a large amount of electronic processing, therefore:
As data centers continue to expand in scale, energy-saving advantages will become more obvious.
4. Protocol Transparency
OCS is only responsible for establishing optical connections and does not care about transmission content.
Therefore, the same optical switching platform can support:
Even if communication rates continue to upgrade in the future, there is no need to redesign the entire switching system.
5. Dynamically Reconfigurable Networks
Combined with SDN control platforms, OCS can dynamically adjust optical connections based on business needs.
For example:
This dynamic resource scheduling can further improve network utilization efficiency.
Although OCS has many advantages, it still has certain limitations at this stage.
Limited optical path reconfiguration speed
Most commercial OCS systems use MEMS micromirrors for optical path switching.
Because mechanical motion is involved, its reconfiguration time is usually on the order of milliseconds.
Compared with the nanosecond-level packet forwarding speed of traditional switching chips, there is still an order-of-magnitude difference.
Therefore, it is better suited for large-scale workloads with relatively stable connection relationships, and not for small-traffic communications that change rapidly and continuously.
Higher deployment costs
A complete OCS system includes not only switching equipment, but also involves:
Currently, overall construction costs are still higher than traditional switching networks.
Optical loss control requirements are high
Optical signals passing through multiple optical components incur a certain amount of insertion loss.
As the number of ports increases:
Therefore, large-scale deployment requires more mature optical design capability.
Software ecosystem still needs improvement
For OCS to truly deliver value, hardware alone is not enough.
Also requires:
The relevant ecosystem is currently being continuously improved.
The industry currently mainly has four technology routes.
1. MEMS Micro-Electro-Mechanical Systems
MEMS is currently the most mature OCS technology in application.
Its core consists of a large number of independently controllable micromirrors.
Each micromirror can precisely change its reflection angle, thereby directing the beam to different output ports.
According to different structures, they can be divided into:
Micromirrors switch only at fixed positions.
Features:
Each micromirror can rotate in multiple directions.
Advantages include:
Currently, large AI clusters mainly adopt 3D MEMS solutions.
2. Digital Liquid Crystal (DLC)
DLC uses the alignment direction of liquid crystal molecules to change the polarization state of light.
The entire process involves no mechanical motion.
Main features:
However, its reconfiguration speed usually reaches hundreds of milliseconds, making it more suitable for applications with low real-time requirements, such as network protection and backup links.
3. Piezoelectric Optical Switches
Piezoelectric solutions use piezoelectric materials that produce tiny displacements when driven by voltage.
By changing the position of collimators, the beam can be realigned.
Advantages include:
The limitations are:
As port scale increases, mechanical structure complexity rises significantly, and scalability is somewhat limited.
4. Silicon Photonics Waveguide Technology
Silicon photonics technology has developed rapidly in recent years and is considered an important direction for future highly integrated optical switching.
Its basic principle is to build waveguide networks inside silicon chips, controlling optical propagation paths by changing the refractive index.
Common implementation methods include:
Compared with mechanical solutions, it has:
However, it still faces issues such as insertion loss, crosstalk, scalable manufacturing, and long-term reliability.
1. AI Training Clusters
This is currently the most important application area of OCS.
In large-scale training clusters composed of thousands or even tens of thousands of GPUs and TPUs, a large number of compute nodes need to continuously exchange gradients and model parameters.
OCS can establish stable high-bandwidth optical connections, effectively improving overall communication efficiency.
2. High-Performance Computing (HPC)
Scientific computing usually has fixed communication patterns.
For example:
These tasks are well suited to long-term stable optical connections, so OCS has high application value.
3. Data Center Backbone Networks
For persistent high-traffic workloads, OCS can handle optical connection tasks at the backbone layer.
By reducing the number of electronic switching steps, overall network efficiency is improved.
4. Data Center Interconnect (DCI)
Massive data synchronization is required between multiple data centers.
OCS can establish high-speed optical paths to achieve:
Compared with traditional solutions, network complexity can be further reduced.
5. Network Protection and Backup
When the primary link fails, OCS can reconfigure a backup optical path to achieve link switching.
This capability can improve network reliability and business continuity.
OCS is not suitable for all networks.
For the following scenarios, its advantages are not obvious:
For example, very short-cycle small-scale communications between GPUs usually still rely on traditional switching networks.
Therefore, the current mainstream approach generally adopts a collaborative “electrical switching + optical circuit switching” architecture, allowing the two types of technologies to leverage their respective strengths.
As AI computing scale continues to grow, OCS is gradually moving from research exploration to actual deployment.
In the short term, applications are mainly concentrated in ultra-large-scale AI training networks, where high-port-count MEMS solutions still dominate; meanwhile, new technologies such as digital liquid crystal and silicon photonics continue to make breakthroughs, offering more options for diverse future deployments.
From a long-term perspective, as high-speed optical modules, silicon photonics chips, and intelligent network control platforms mature, OCS applications are expected to expand further into more scenarios, including data center backbone networks, campus interconnect, storage networks, and data center interconnect (DCI). In the future, the deep integration of optical and electrical switching will become an important direction for building high-performance data center networks.
At the same time, the industrial ecosystem around optical switching equipment, optical components, control software, and network orchestration platforms is being continuously improved. The advancement of standardization and coordinated development across the upstream and downstream supply chain will further enhance the compatibility, scalability, and deployment efficiency of OCS systems, laying the foundation for large-scale commercial applications.
Optical circuit switching is not a replacement for traditional switching technologies, but an important complement for the era of high-speed optical interconnect. By establishing dedicated communication paths at the optical layer and reducing optical-electrical conversion and electronic processing steps, it delivers significant advantages in reducing latency, improving bandwidth utilization, optimizing energy consumption, and enhancing network scalability.
As AI training clusters, high-performance computing platforms, and next-generation data center networks continue to evolve, network communications are gradually moving from a model that relies solely on electronic switching toward opto-electronic collaboration. In the future, optical circuit switching and traditional packet switching will jointly build more efficient, flexible, and scalable network infrastructure, providing more stable and reliable interconnectivity for ultra-large-scale computing and driving data center network architecture toward higher performance and energy efficiency.
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