English (UK) 
简体中文(中国) Acacia Communications recently announced the first 400G single carrier DWDM transmission on the 6,600 km Marea submarine cable between Virginia Beach, Virginia and Bilbao, Spain. The field demonstration was conducted by Acacia in collaboration with Microsoft and Facebook, and helped to demonstrate that improvements in capacity and spectral efficiency can enable increased utilization of deployed fiber and improved network capacity. The 400G single carrier transmission was achieved with baud rate of around 70Gbaud using Acacia’s AC1200 module.
The growth of cloud and internet services are driving the need for increasing subsea network capacity. Meeting these demands requires advanced coherent transmission systems that support higher data rates that weren’t possible in prior transatlantic systems. The Marea submarine cable, a joint project between Microsoft, Facebook, and global telecommunications infrastructure company Telxius, features an “open” design that allows it to evolve with technology and enables adoption of new technologies, such as the Acacia AC1200 coherent module.
The field demonstration was performed with Acacia’s AC1200 coherent module, which is powered by its Pico digital signal processor. Acacia’s AC1200 supports a combination of high baud rate, flexible modulation formats and enhanced performance features that enable improvements in capacity and reach. Utilizing Acacia’s patented Fractional QAM modulation, the field demonstration achieved 400G transmission using approximately 4 bits/symbol, with a baud rate of nearly 70Gbaud. Additionally, modulation formats greater than 4 bits/symbol were utilized to achieve a spectral efficiency of 6.41 bits per second per Hz (b/s/Hz) on the same 6,600 km cable.
“Transmission of 400G over 6,600 km is a significant milestone and demonstrates what can be achieved with higher performance transmission optics combined with a well-designed line system,” said Mark Filer, Principle Optical Engineer, Azure Networking, Microsoft Corp. “This field demonstration of an advanced solution that is just becoming commercially available highlights the value of Marea’s open architecture to evolve with the latest technology. By allowing early adoption of new technologies such as Acacia’s AC1200, we are able to increase the utilization of our deployed fiber, maximize our investment and improve network capacity.”
“We are excited to have completed this field demonstration on the Marea cable, with the first transmission of 400G on a single carrier, highlighting the performance and features of our AC1200 coherent module,” said Christian Rasmussen, Founder and Vice President of Digital Signal Processing and Optics at Acacia Communications, “We believe the benefits of our AC1200 module will help network operators improve their network utilization in a range of applications from edge DCI to submarine.”
Earlier in October, Infinera had a trial with Telxius to use Infinera’s fourth-generation Infinite Capacity Engine (ICE4) advanced coherent technology, transmitting 26.2Tbps capacity over a fiber pair across the 6644km MAREA cable, achieving a spectral efficiency of 6.21 bits per second per (b/s/Hz) over the 6644 km trans-atlantic cable, and upgrading system capacity of MAREA to more than 200Tbps over 8 fiber pairs.
Using 400G technology, it won't significantly upgrade the total capacity of MAREA cable system further than above 200Tbps at this moment. And there is no announcement of the achievement on capacity per fiber pair from the stakeholders. But it demonstrates further the success of MAREA's OPEN Cable strucutre.
The MAREA cable system is supplied by SubCom and equipped with SubCom's SLTE when it was ready for service. The trials by Infinera and Acacia demonstrate that SLTEs from multiple suppliers can work well in this OPEN cable system.
