IN Brief:
- The ELSFP module generates eight simultaneous DWDM wavelengths across two four-channel bands centred near 1311nm and 1331nm.
- Lumentum specifies up to 24dBm optical output per wavelength with approximately 12W total module power consumption.
- Initial availability with an OCI MSA-aligned optical interface is expected during the first half of 2027.
Lumentum has developed an eight-wavelength dense wavelength division multiplexing external laser module for co-packaged and near-packaged optical systems. The ELSFP-format device keeps the laser source physically separate from switching or accelerator silicon while delivering multiple high-power wavelengths to optical engines elsewhere in the system.
The module generates eight simultaneous DWDM wavelengths across two four-channel bands centred near 1311nm and 1331nm. Lumentum specifies wavelength accuracy of ±0.2nm and optical output of up to 24dBm, approximately 250mW, per wavelength at the fibre. Total module power consumption is around 12W.
External laser sources address one of the thermal and serviceability problems created by co-packaged optics. Moving optical engines close to a switch ASIC shortens the highest-speed electrical connections and can reduce SerDes power, but the immediate environment around large switching devices is difficult for temperature-sensitive laser components.
Separating the light source allows the lasers to remain at an accessible point in the chassis while optical power is routed towards the co-packaged engine. A degraded source can then be replaced without removing the switching package or the photonic devices mounted alongside it. That service model is one reason external-laser development is advancing in parallel with CPO.
The use of eight DWDM wavelengths increases the amount of optical capacity available through a single source module. Multiple wavelengths can share fibre infrastructure rather than requiring a separate physical path for every channel, easing pressure on connector and fibre counts around high-radix switching packages.
Wavelength stability becomes critical in such an architecture because the channels must remain separated across temperature and operating conditions. Lumentum’s quoted ±0.2nm accuracy therefore matters alongside raw optical output. A source that drifts substantially from its assigned wavelength can compromise multiplexing performance even if its output power remains high.
The 24dBm-per-wavelength figure provides additional system margin for splitting, coupling and routing losses between the ELSFP and the optical engines it illuminates. High source power is useful where one laser module feeds several photonic paths, but the overall electrical-to-optical efficiency remains important because datacentre systems are already operating under increasingly severe rack-power constraints.
Lumentum’s module builds on its Ultra High Power laser platform. At OFC 2026 the company demonstrated a 16-channel DWDM configuration assembled from two ELSFP modules, producing channels on a 200GHz grid around 1310nm. The latest development integrates eight wavelengths into one pluggable source while aligning the optical interface with work being carried out through the Optical Compute Interconnect Multi-Source Agreement.
Standardisation is likely to determine whether external lasers become genuinely serviceable components rather than proprietary parts tied to a particular switch architecture. Co-packaged optics already brings together semiconductor packaging, photonic engines, fibre interfaces, laser sources, thermal control and system monitoring. Agreed mechanical and optical interfaces would allow individual elements to evolve without requiring the complete system to be redesigned each time.
The module also sits within a wider change in optical-system architecture. Conventional pluggable transceivers are moving to higher lane speeds, while linear-drive and near-packaged approaches reduce portions of the electrical path without placing the optics directly beside the ASIC. CPO goes further, but the resulting system has to recover some of the serviceability lost when conventional optical modules disappear from the front panel.
Lumentum expects initial availability of the OCI-aligned ELSFP during the first half of 2027. The immediate engineering task is now less about proving that eight high-power wavelengths can be produced in one module and more about integrating those sources into complete optical systems with controlled fibre routing, monitoring, redundancy and replacement procedures.
