The transceivers requirements are driven by telecom but even more by the big scale data centers where transceivers demand is increasing more and more together with the High-speed demand.
Nowadays, the requirements for transceivers can be decomposed into 6 main features: Low cost, High speed, high density, low power consumption, Short lifetime, and narrow temperature.
- Low cost: Who says large development says large quantity of transceivers. Taking this into account, this is obvious that transceivers need to be the cheapest possible for the datacenter to manage their development.
- High speed: Data centers need to meet the demand for 4K VR, Internet of Things (IoT), and cloud computing which significantly increase the demand for bandwidth.
- High density: The goal here is to increase the number of optical transmission channels in unit space and improve data transmission capacity.
- Low power consumption: All human developments are now adopting the Green point to protect the environment. A good point also is that going low power consumption will limit the OPEX compared to legacy High-power modules.
- Short Lifetime: It is a consequence of the rapid development and increase of data communication. Indeed, no need for the optical modules to work more than 3 to 5 years’ time.
- Narrow temperature: Who says data center says controlled environment (temperature and humidity), meaning that optical transceivers made to be working between 15 and 55 °C are fitting with the current requirement?
The above 6 features allow transceiver manufacturers to come with new technologies and ways of working fitting with the new standard and applications conditions. We will try to go trough the new technics based on the above requirements and able to ease the development of the hyper scale data centers.
A. Non-hermetic Packaging
60% of the total cost of a transceiver comes from the optical components and taking into account that getting cost reduction on optical chips is more and more difficult, the easiest way to decrease the price is to work on the packaging cost. Indeed, having a hermetic packaging is expensive and going to non-hermeticity of the package leads to a significant cost reduction while ensuring the performance and reliability of the transceiver.
Going to non-hermetic package means a non-air tightness of the optical device itself, a design optimization of the optical components, a different packaging material and a packaging process improvement.
Obviously, the most challenging part is the laser but manufacturer came with laser able to work in non-airtight applications to bypass the issue.
B. Integrated technology (Hybrid)
With the current requirements, the Transceivers need to transmit more data than before. Going to photonic integration allows to answer this evolution. When talking Photonic integration, it is integration of either silicon-based or Indium phosphide components. We speak about hybrid technology when based on different materials.
The Hybrid integration involves a construction of partially free space optics and partially integrated optics. This can be done in a very compact way and the automation process is easy to put in place for Mass production.
C. Flip Chip Technology
Flip chip is a high-density chip interconnection technology from IC packaging industry. This option meets the current trend going to chips sizes becoming smaller and smaller. The technology allows to directly weld the optical chip onto the substrate through gold-gold welding or eutectic welding, which is much better than the high frequency effect of gold wire bonding (short distance, small resistance, etc.).
Flip Chip Technology is appreciated due to its high precision, high efficiency and high quality and this is the reason why it is widely used in the datacenter optical module industry.
D. Chip On Board (COB) Technology
COB techno also comes for IC packaging industry, its principle, together with non-hermetic package, is to directly fix the chips or the optical components on the PCB, then electrical connection are gold wire bonded, and finally glue is sealing on the top.
The big advantage of this technology is that all steps can be automated and this why it is widely adopted, mainly for Short reach Application (SR4, AOC, etc..) but slowly coming in the long reach applications (LR4).
E. Silicon Photonics Technology
The silicon photonics is a technology involving the technology and technique of optoelectronic devices and silicon-based integrated circuits, integrated onto the same silicon substrate. The Silicon photonic technology can be used in many cases but from the industry point of view, the performance and the cost competitiveness are the driver of the new technologies, and this is where the challenge is.
Today, the datacenter demand in low cost and high-density products brings a lot of opportunities for the Silicon photonics technology-based applications.
What about the standards?
Whether it is MSA or IEEE, none of them defines the way of building an optical transceiver., meaning that for the same standardized transceiver, multiple solutions can be found and, with the different solution is coming the different pricing.
This is where we need to be cautious since the application for which we need to use a transceiver for is linked to the performances that needs to be achieved by this transceiver. In other terms, we cannot use the same transceiver for all applications. As an example, using non-hermetic package for telecom application is not a good solution considering that part will not necessarily be plugged into a controlled environment.
This is the everyday challenge for a Third-party transceiver company Like Skylane Optics, to convince people that price does not make everything and to help our customers to pick up the right (transceivers) solution for their application. Indeed, three of the features we spoke about in this articles (Low cost, Short lifetime, and narrow temperature) are driven by the data center world but are a real handicaps for the telecom world and this has to be taken into account.
To conclude with, the transceiver technology development direction is mainly driven by the hyper scale datacenters and the industry reacts by coming with several technologies to answer the actual and future needs of these datacenters. This leads to multiple solutions and multiple cost for the same standards.
Source: Echo Brown: The Technology Development Direction of Data Center Optical Transceivers
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