In a large data center like Facebook and Google, there are many high-speed servers that are processing as well as exchanging much data at extremely high speeds. It was reported according to Facebook’s Dunn Lee that the peak pipe speed required for Facebook data center server communications have reached 4 terabits/second. Currently the company is using 40Gb/s interfaces to interconnect these high-speed servers. Even though 100G Ethernet technology has been recently commercially available, the technology is however still not widely deployed. Different from the backbone high-speed transmission technology, the communications within data centers are generally based on short-reach technologies, which do not require a tight design on the transmission distances as in the long-distance fiber transmission technologies. For related news please see here.
With the 100G Ethernet commercially available, now people are aiming at the next generation Ethernet technology. In OFC/NFOEC 2008, people considered one terabit Ethernet. After that, some initial investigations were booming in academy. For example, some researchers are using optical coherent-OFDM technology to carry one terabit per second data rate over a single channel over 600 km over SSMF fibers. In this year’s OFC/NFOEC, there is a special panel session on terabit technology. However, recently some voice is up asking if Terabit is practical and can be supported by today’s or next following years’ technology. People think 400Gb/s technology can be more practical based on today’s technology. For example, by combining 25 Gb/s substreams, it is possible to generate a 400Gb/s single channel. We are not sure whether we will leap forward by factors of 10 or 4. Let us wait and see. But the final destination that we can believe in is Shannon’s capacity limit. Yah, that is the truth! For the details on the above debate, please read an article in lightreading.com.
Orthogonal frequency division multiplexing (OFDM), which was original developed for wireless communication technique for efficient spectrum utilization, has been successfully extended to optical transmission systems. One of key advantages is the OFDM-based technology has better tolerance to fiber dispersion and is expected to support high data-rate over a single channel through modulating multiple low-rate data streams on thousands of subcarriers. Many breakthroughs of the optical-coherent OFDM transmission technique have been reported. It has been able to support 100 Gb/s per channel data rate. Recently, there is another new breakthrough to transmit one terabit per second data rate on a single channel over 600 km SSMF fiber. Here is the link to access this technical paper from Optics Express.
Currently, most of the reported OFDM transmission experiments are using Matlab-based technique to generate multiple sub-stream data rates modulating on the subcarriers. Though the ASIC chips supporting OFDM are very mature in wireless communications, it is still challenging to extend the chip manufacturing technology to OFDM-based optical communications since the latter has much higher (x1000 times) transmission data rate than the former.
In this year’s OFC/NFOEC there is a special panel session on Terabit Ethernet organized by Andrew Ellis, Seb Savory respectively from Tyndall Natl. Inst., Ireland, and Univ. College London, UK. Viewing the fact of increasing bandwidth requirement and the success of 100G Ethernet commercial deployment, people are more and more interested in the next generation Ethernet technology, Terabit Ethernet. As highlighted on the OFC/NFOEC website, “this workshop will examine the motivation behind such predictions and discuss the potential requirements for transponders offering such capacities.” It is expected that many attendees would participate in this session and many insightful discussions would be carried out. So far, there is no commercial technology that supports 1 terabit Ethernet and no industrial companies claim to commercialize this type of technology. However, much research in this direction has been started since year 2008 mainly in academy.
We have seen 100G Ethernet commercially available in year 2009. In year 2008, people were talking about Terabit Ethernet on OFC/NFOEC. It was predicted that the technology would be commercially deployed in year 2015, according to the father of Ethernet, Bob Metcalfe. Please the interesting video show below from lightreading.com
