Furukawa Electric Co., Ltd. developed a very high-efficient 8-channel ELS for the realization of next-generation network switch servers employing CPO for hyperscale data centers and edge data centers.
Data traffic has been increasing to support many kinds of IT services such as cloud services and 5G mobile networks. Hyperscale data centers that process big data and edge data centers that realize the low latency for Beyond 5G are faced with the challenge of expanding bandwidth and reducing the power consumption of a network switch server.
Lower ambient temperature
Therefore, in order to save the power consumption and expand the bandwidth, it has been expected to adapt CPO as a new server architecture that performs photoelectric conversion in close proximity to an electronic device. CPO has a unique packaging structure where high-density silicon photonics transceivers are mounted together with a switch ASIC (application specific integrated circuit) on the same substrate.
A wide bandwidth switch ASIC generates a large amount of heat. Hence, it derives temperature increase of the SiPh transceivers. It is difficult for compound semiconductor lasers to realize the required characteristics and guarantee the reliability in such a high temperature. Therefore, an ELS is proposed to operate lasers at a front panel which has an environmental condition of lower ambient temperature. ELS integrates a number of lasers into a pluggable housing. And high optical output power and maximization of power conversion efficiency has been required.
Heat dissipation structure
The developed ELS consists of a QSFP housing which has been standardized for an optical transceiver
The developed ELS consists of a QSFP housing which has been standardized for an optical transceiver, an 8-channel TOSA (Transmitter Optical Sub-assembly), and electronic circuities to control TOSA. The 8-channel TOSA integrates their high-power DFB (Distributed Feedback) LDs (Laser Diodes).
In order to obtain high optical output power with an un-cooled laser structure, the optical coupling system was optimized to maximize the optical coupling efficiency and the heat dissipation structure of the TOSA was optimized to reduce an LD temperature. And This TOSA achieves a low LD bias current as low as 300 mA at a case temperature of 55 °C to realize the fiber-coupled power of 100 mW/ch with an uncooled operating condition.
Heat dissipation structure
The electronic circuities have LD driving circuitries as well as a power supply regulator, an MCU (Microcontroller Unit), and a temperature sensor. The ELS achieves fiber-coupled optical power of 100mW for all channels at a case temperature of 55°C. The total power consumption including the TOSA and the electronic circuitries was as low as 5.6 W and accordingly, a record high PCE of 14.3 % was achieved, to the best of their knowledge.
Thus, we realized a very high-efficient 8-channel ELS even with a small QSFP housing. They launched the sample delivery of the TOSA and ELS. And the commercialization has been scheduled in 2025. At ECOC 2023 scheduled on October 1-5, 2023, in Glasgow Scotland, they exhibit the TOSA and ELSs (at the FITEL-FURUKAWA ELECTRIC EUROPE booth; Booth number 230) on October 2-4, and give a talk at a technical session on October 4.
