This technology enables high-speed, high-bandwidth data communication between CPUs on a server, and between CPUs and peripheral devices.
Background:
Advances in CPU processing have exponentially increased the data management capabilities of servers. Now, improved virtualization technology allows a single CPU to perform multiple processes. The volume of data passing through CPUs or from CPUs to peripherals is increasing dramatically. While today's servers use optical interconnects capable of data rates of 10 Gbps per channel, future servers are expected to be even faster, at 25 Gbps. Furthermore, as shown in Figure 1, optical interconnects are also expected to be used not only to communicate data between servers, but also between tables within a server, given the difficulty of achieving high data rates using electrical communications.
Technological Challenges:
Implementing interconnects on a server requires an optical transceiver to convert electrical signals into optical signals. Current optical transceivers have achieved data rates between 10 and 14 Gbps, so speed has become a barrier to reaching the desired rates of 25 Gbps. Furthermore, current optical transceivers are physically very bulky, making it difficult to place them near a CPU or other devices. This is a problem because the electrical signal traveling between the device and the optical transceiver encounters losses and interference in the transmission line, which are greater the longer the circuit. This degrades signal quality and makes it more difficult to increase speed.
Newly Developed Transceiver:
To successfully produce a compact optical transceiver with the necessary optical interconnects for high-speed, high-bandwidth data transmissions within servers, Fujitsu Laboratories has developed an opto-electrical converter to transform electrical signals into optical signals using an optical device. In more detail:
1. High-Speed Circuit Technology:
Fujitsu Laboratories was able to increase speeds through circuit technology in the IC that runs optical devices, making the rise and fall of the optical signal more pronounced. This was achieved even in low-cost optical devices with insufficiently fast response times by implementing circuit technology that suppresses the multiple reflections that degrade the signal's waveform. The result is an increase in data rates from the current 10-14 Gbps to 25 Gbps per channel.
2. Compact Optical Coupling Technology
: Conventionally, efficient transmission of an optical signal between opto-electrical converters and optical fiber required an optical coupling unit. This consisted of a lens component and an optical connector (Figure 3). However, the lens component was large and expensive. This new design consists of an opto-electrical converter with a flexible printed circuit board equipped with optical devices and integrated circuits, enabling a compact optical transceiver. Furthermore, Fujitsu Laboratories has also developed an effective film-type lens that is stacked on the underside of the flexible printed circuit board, thus resolving the aforementioned problems.
Figure 3: Structure of a conventional opto-electrical converter.
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