News Release

Furukawa Electric Co., Ltd. (Head Office: 2-2-3 Marunouchi, Chiyoda-ku, Tokyo; President: Keiichi Kobayashi) presents and exhibits the technologies of ELS to be adopted to CPO at 11th IEEE (The Institute of Electrical and Electronics Engineers) CPMT Symposium Japan (ICSJ2022) which is only sponsored by IEEE EPS (Electronics Packaging Society) in Japan. ICSJ2022 is held at Kyoto University, Japan, on November 9th to 11th as a hybrid event of onsite and online meetings.

There has been a strong demand to expand the bandwidths for both hyperscale data centers that process big data and edge data centers that realize low latency for Beyond 5G. In accordance with these market trends, power saving has been a challenge for network switch servers.
Hence, a new server architecture employing CPO has been expected. CPO has a unique packaging structure where high-density silicon photonics transceivers are mounted together with a switch ASIC on the same substrate. As the bandwidth of switch ASIC is expanded, the power consumption is increased, and then higher heat is generated. If a compound semiconductor laser is integrated in the optical transceiver, it will be operated in a high temperature environment, which will deteriorate its characteristics and also affect to its reliability.
Therefore, ELS is placed on the front panel, which is outside the housing with a low ambient temperature, and the laser beam is supplied to the optical transceiver via a multi-lane polarization-maintaining fiber cable. (Fig. 1)
In order to operate ELS with high optical output and low power consumption, we optimized the design of ELS to achieve a high optical coupling efficiency and suppress the temperature increase in an uncooled condition.

Furukawa Electric presents and exhibits an 8-channel CWDM TOSA and a pigtailed-QSFP ELS employing the TOSA at ICSJ2022. We utilize the high-power and wavelength-selected compound semiconductor laser technologies and optical packaging technologies that we have been building over the past 20 years.
We optimized the structural design of the TOSA to suppress the temperature increase of a high optical power distributed feedback (DFB) laser diode (LD). We also realized a high optical coupling efficiency between the high optical power DFB LD and the PMF cable. These attributes contribute to realize a high fiber-coupled power in an uncooled condition. At a case temperature of 55℃, an optical output power of >100mW can be obtained with an LD bias current of 350mA or higher. (Fig. 2)
The mechanical size of the TOSA is as small as 23.5 mm × 13.0 mm × 4.0 mm, which enables it to be built in a QSFP housing with other components. (Fig. 3)
In addition, the optimization of the heat dissipation structure enables to suppress the temperature difference between the housing of the pigtail-QSFP ELS and the case of the TOSA as low as 0.7℃. Therefore, the pigtailed-QSFP ELS can keep the same optical output power characteristics as well as the TOSA.