1. Why high-power laser arrays suddenly matter
AI clusters are becoming interconnect-bound. A modern training or inference cluster is not simply a pile of GPUs; it is a machine for moving tensors, gradients, KV-cache fragments, model shards, checkpoint data, and synchronization traffic across a fabric.
For a long time, the front-panel optical transceiver model worked well enough: the switch ASIC sent electrical signals across a board to pluggable optics at the faceplate. But as lane speeds climb and switch radix explodes, those board traces become expensive in power, signal integrity, and routing density.
Co-packaged optics shortens the electrical path. Laser arrays solve the optical carrier problem. Packaging companies solve the reality problem.
2. The CPO architectural shift
Traditional pluggable optics
The switch ASIC drives high-speed electrical signals across the PCB to pluggable optical modules at the front panel. This is operationally familiar and field-serviceable, but the electrical path is long, power-hungry, and difficult to scale as lane speed rises.
- Longer electrical reach
- More retiming/equalization
- Front-panel congestion
- Higher board-routing complexity
Co-packaged optics
The optical engines move next to the switch ASIC on or near the package substrate. The high-speed electrical path shrinks from centimeters to millimeters, reducing electrical loss and power.
- Short electrical traces
- Lower SerDes power pressure
- Higher faceplate bandwidth density
- New thermal/serviceability challenges
Figure 1 — CPO is fundamentally a packaging move: shorten the electrical path and move the optical conversion closer to the switch ASIC.
3. What a high-power laser array actually does
In many silicon photonics systems, the laser is not used to encode data directly. The laser provides a clean continuous-wave optical carrier. A modulator then imprints electrical data onto that optical carrier.
Laser
Creates stable optical carrier power at one or more wavelengths.
Modulator
Turns the carrier into a data signal using electrical drive from the switch/PHY.
Receiver
Photodiode and TIA recover the optical signal as an electrical signal.
A laser array places multiple laser emitters in one assembly. Each emitter may provide one wavelength, and the wavelengths can be combined using wavelength-division multiplexing. In a CPO system, this allows a compact module to feed many optical lanes.
4. Why external laser sources are becoming the CPO default
Lasers are hot, aging-prone, and service-sensitive. Putting them directly inside a tightly integrated switch package can make thermal design and field replacement difficult. External laser source architecture separates the laser power plant from the optical engine.
External Laser Source (ELS): a module that provides continuous-wave optical power to co-packaged optical engines. The optical engine uses that light and modulates it locally near the ASIC.
| Design choice | Benefit | Tradeoff |
|---|---|---|
| Laser inside optical engine | Compact optical path; fewer external fiber routes. | Harder cooling and replacement; laser aging may affect the whole assembly. |
| External laser source | Better serviceability, centralized cooling, easier laser monitoring. | Requires fiber routing, blind-mate connectors, eye-safety design, and optical distribution management. |
| Comb laser / multi-λ source | Many wavelengths from one source; elegant WDM scaling. | More complex control, stabilization, qualification, and ecosystem maturity questions. |
OIF standardized the External Laser Small Form Factor Pluggable (ELSFP) form factor for external laser modules used with CPO systems, including pluggability and management interfaces. This is important because CPO must become manufacturable and serviceable, not just technically elegant.
5. The optical power budget: why “high-power” is not hype
A laser array must overcome every loss between the laser and receiver while leaving enough signal margin for modulation quality, aging, temperature, and manufacturing variation.
| Loss / margin source | Why it matters | Design response |
|---|---|---|
| Fiber coupling loss | Small alignment errors can consume precious optical margin. | Precision attach, active alignment, lens arrays, low-loss connectors. |
| Modulator insertion loss | Silicon photonics modulators reduce carrier power before transmission. | More efficient modulators, stronger laser source, optimized bias/control loops. |
| Connector loss | CPO systems may involve dense fiber breakouts and blind-mate interfaces. | Connector qualification, cleaning process, factory automation. |
| Aging | Laser output declines over lifetime. | Operating margin, monitoring photodiodes, redundancy, replaceable ELS. |
| Temperature drift | Wavelength shifts can break WDM spacing and filter alignment. | Thermoelectric control, wavelength lockers, feedback loops. |
6. Where Jabil fits: turning photonics into a product
Jabil is not usually the name people associate with the “invention” of CPO. But in a real supply chain, companies like Jabil are often the difference between a lab demo and high-volume manufacturing.
Jabil’s photonics business describes capabilities in optical manufacturing services, advanced photonics packaging, design services, and co-packaged optics. Ranovus announced a collaboration with Jabil for mass production of the ODIN optical engine, with Ranovus describing ODIN as integrating lasers, modulators, photodetectors, drivers, TIAs, and control loops into a compact electro-photonic integrated circuit.
Why Jabil-style integration matters
- Optical alignment is far more sensitive than normal board assembly.
- Fiber attach and connector cleanliness directly affect link margin.
- Production test must validate optical, electrical, thermal, and firmware-control behavior.
The manufacturing bottleneck
- Scaling CPO requires yield, not just bandwidth.
- High-volume optical test time can become expensive.
- Thermal fixtures, automation, and calibration loops become part of the product.
7. Vendor and ecosystem map
The laser-array/CPO ecosystem is not one market. It is a stack: materials, laser chips, photonic ICs, optical engines, switch ASICs, connectors, packaging, and system manufacturing.
| Company / group | Likely role in the stack | Why it matters |
|---|---|---|
| Coherent | High-power CW lasers, InP photonics, ELS modules, CPO demonstrations. | Coherent has shown CPO-related demonstrations including a 6.4T socketed CPO paired with an ELS module powered by high-power InP CW lasers. |
| Lumentum | Datacenter and telecom optical components, laser sources, WDM heritage. | Laser reliability and high-volume optical component experience are central to ELS/CPO scaling. |
| Broadcom | Switch ASICs and CPO platforms. | Broadcom’s Bailly 51.2T CPO switch announcement claimed major optical interconnect power improvement versus conventional approaches. |
| Marvell | DSP, PAM4 PHY, optical interconnect silicon. | Important for the electrical/optical boundary: retiming, modulation, signal recovery, and PHY integration. |
| Ranovus | ODIN CPO/NPO optical engine platform. | Ranovus describes ODIN as integrating lasers, modulators, photodetectors, drivers, TIAs, and control loops into an EPIC. |
| Jabil | Photonics manufacturing and advanced packaging. | Provides the production bridge: optical packaging, assembly, and scaling optical engines to high volume. |
| Ayar Labs | Optical I/O chiplets and external laser architecture. | Represents the chiplet-style future where optical I/O is treated as a package-level interface. |
| OIF | Standards and implementation agreements. | ELSFP standardization gives the ecosystem a serviceable, multi-vendor external laser module path. |
8. Full AI data path: from GPU tensor to photons
The laser array is not isolated. It participates in a larger AI data path that starts with GPU memory traffic and ends with remote accelerators receiving usable data.
9. The hard problems most articles skip
Thermal drift
Laser wavelength shifts with temperature. WDM systems rely on precise wavelength spacing, so thermal control and feedback loops become mandatory.
Reliability and aging
Lasers can degrade faster than passive optical components. This is why external, field-replaceable laser modules are attractive.
Power integrity
Laser drivers need clean rails. Digital switch ASIC noise, regulator ripple, and package coupling can show up as optical noise or instability.
Fiber management
CPO reduces electrical cable complexity but increases fiber density, routing, bend-radius, service, and cleaning requirements.
Testing economics
Every lane needs optical validation: output power, extinction ratio, eye quality, BER, thermal sweep, and aging margin.
Operational blast radius
If one shared laser source feeds multiple optical engines, redundancy and fault isolation must be carefully designed.
The most important operational question: when a laser drifts, degrades, or fails, does the cluster lose one lane, one optical engine, one switch, one rack, or a whole fabric partition?
10. The forward thesis: optical power becomes schedulable infrastructure
The deeper shift is that optics becomes part of the AI platform control plane. Today we schedule GPUs, CPU cores, memory, NICs, and storage. Tomorrow, the optical layer may expose capacity, wavelength health, laser margin, thermal headroom, and fault domains to the scheduler.
| Today | Future direction |
|---|---|
| GPU-aware scheduling | GPU + optical-fabric-aware scheduling |
| Static network topology | Dynamic optical circuit or wavelength allocation |
| Optics hidden behind Ethernet | Telemetry-rich optical layer exposed to orchestration |
| Laser treated as a component | Laser treated like shared power/cooling infrastructure |
The real CPO story is not “replace copper with fiber.” It is “make light a controlled, monitored, serviceable resource inside the AI data center.”
References and source notes
- OIF Implementation Agreements — includes ELSFP 01.0/02.0 and CPO module implementation agreements.
- OIF ELSFP Implementation Agreement — defines the external laser source pluggable form factor for CPO systems.
- OIF ELSFP CMIS Implementation Agreement — management interface extension for ELSFP modules.
- Broadcom Bailly 51.2T CPO switch release — 51.2T StrataXGS Tomahawk 5 Bailly CPO switch announcement.
- Broadcom CPO overview — Broadcom’s co-packaged optics positioning.
- Ranovus collaborates with Jabil — ODIN optical engine mass-production collaboration.
- Jabil Photonics — optical manufacturing services and advanced photonics packaging capabilities.
- Coherent CPO technologies at OFC 2026 — 6.4T CPO demonstration with ELS and high-power InP CW lasers.
- Co-packaged optics: status, challenges, and solutions — technical review discussing ELS as a promising CPO light-source approach.
Numbers in this article are intentionally presented as system-level ranges or directional design constraints unless tied to a cited vendor announcement. Exact CPO optical budgets vary by wavelength plan, modulation format, connector stack, reach, receiver sensitivity, and product generation.