22 April 2021
POET enters telecom market with 100G LR4 optical engines
POET Technologies Inc of Toronto, Ontario, Canada — a designer and developer of the POET Optical Interposer and photonic integrated circuits (PICs) for the data-center and telecom markets — has completed design of a 100G LR4 (four-channel long reach) optical engine with a reach of 10km for client-side interconnects to data centers, enterprises and edge computing networks.
Of the five common types of 100G transceiver modules found within the data center, two types — CWDM4 and PSM4 — are targeted at data communications up to 2km. SR4 (500m), LR4 (10km) and ER4 (40km) are the other types typically specified for 100G datacoms. POET’s focus on CWDM4 and LR4 designs is based on what it claims is a unique capability to integrate fully monolithic 4-channel multiplexing and demultiplexing functionality directly into its waveguides, avoiding the costly requirement to align and couple additional devices into a transceiver module.
POET’s LR4 design converts four input channels of 25Gb/s electrical data into four LAN WDM (wavelength division multiplexing) optical signals and then multiplexes them into a single channel for 100Gb/s optical transmission along a single fiber. PSM4 and SR4 transceivers are not multiplexed and hence require four parallel fibers, which are especially costly over distances of 2-10km. Despite completing separate designs for TX (transmit), RX (receive) and combination TX-RX optical engines, POET intends to focus first on the TX design, which offers significant cost and performance advantages, and represents a fast go-to-market approach for the firm.
“A 100G LR4 transceiver sells for about 2-3x the price of a 100G CWDM4 module, due to its higher complexity and performance requirements,” notes president & general manager Vivek Rajgarhia. “POET’s integrated monolithic multiplexer significantly reduces the cost of the optical engine, allowing us to provide a savings to customers in the range of 25%. By flip-chipping four DML [directly modulated laser] lasers onto an Optical Interposer with inherently superior thermal management and the ability to tune the waveguides to specific center wavelengths, we are able to design an optical engine that uses 10-15% less power to deliver data at the same speed and over the same distance as comparable modules. Further, because of the small size of the optical engine, we anticipate seeing potential novel applications of this technology from customers,” he adds. “Since we have had the LR4 Optical Interposer wafers in fabrication since December, we expect to be able to deliver alpha samples to customers in the third quarter of 2021. Deploying an LR4 design in a short time after the CWDM design exemplifies the power of our platform approach, as major elements of the CWDM interposer design are reused in the LR4 derivative.”
As the standard for interconnects to long-haul networks, 100G LR4 transceivers are purchased in high volumes by telecom equipment providers and are not being replaced by 400G transceivers even as speeds in long-haul networks increase, notes POET. In a client webinar by LightCounting in April, shipments in 100G LR4 modules were forecasted to be essentially stable at about 4 million units annually from 2021 through 2026, with prices having stabilized as a result of there being no room left for cost reductions using the traditional manufacturing approach for these devices. This cost barrier and the high power consumption of existing transceiver designs allows POET to provide competitive designs for this segment, which represents a second large market opportunity for POET, complementing its previously announced 100G CWDM designs, says the firm.
Powering these optical engines will be 25Gb/s DMLs from Sanan Integrated Circuits (SAIC), which has incorporated POET’s interposer compatibility requirements into its line of LR4 DML lasers. These lasers have been independently tested and validated to operate to LR4 specifications and are already in their qualification phase. SAIC will also be sourcing the monitor photodiodes and high-speed photodiodes, which rounds out the bill of materials for the optical engine.
Assembly, manufacture and sales of these optical engines will be accomplished through POET’s joint venture with SAIC, Super Photonics Xiamen (SPX). SPX has accepted delivery of the first-of-a-kind equipment set for the assembly of optical engines based on POET’s Optical Interposer and will be actively engaged in the assembly of POET’s alpha optical engine prototypes later this quarter. POET and SPX are currently working with two alpha customers, and the design-win funnel has been active with increasing demand for both standard and custom designs for LR4 optical engines.