ZTE: Leading R&D on 100G and Beyond

LR’s Todd Townsend recently interviewed Dr. Jia Zhensheng, assistant director and senior member of technical staff (SMTS) of Optical Labs, ZTE USA. Dr. Jia introduced the technical advantages of 100G products, especially the DSP and SD-FEC modules. He also talked about field deployments worldwide and pioneering achievements in 400G and 1T research.

LR: What are the technical advantages of 100G over 40G, and what possibilities does 100G open up for operators?

Dr. Jia: The 40G ecosystem is not that healthy as a result of frequent changes in technology. Take modulation formats for example. We have everything from PSBT, DPSK, and DQPSK all the way up to coherent QPSK. Standardization has also been missing from the beginning, and the supply chain is unstable. By contrast, 100G is a single technology directly aimed at PM-QPSK and all the 100G standards are ready for mass deployment. We know that 100G provides much higher capacity than 40G and significantly reduces operational cost for carriers if they scale up their infrastructure. More and more operators have already decided to skip over 40G and deploy 100G. We believe that 100G era is coming and is going to take off.

LR: What advantages does ZTE have in 100G?

Dr. Jia: ZTE has always been at the forefront of optical transmission technology. After the release of sample 100G products at the end of 2009, ZTE launched the first commercial products in 2011. We think ZTE has been influential in three key areas. The first area is coherent detection with DSP capability. ZTE pioneered the use of a 40 nm process for excellent channel equalization and longer transmission distance. The second area is soft-decision forward-error correction (SD-FEC). ZTE implemented 15% turbo-product code (TPC) SD-FEC on the 100G MSA transponder to achieve 1500 km or more transmission distance. This can result in 11.1 dB net coding gain. The third area is flexible aggregation and large cross-connect. We can cross connect and aggregate 3.2 Tbit client signals of any granularity, from ODU0, ODU1 all the way up to ODU4 ODU flex signals.

LR: What R&D is ZTE doing on beyond 100G?

Dr. Jia: ZTE has put great effort into 400G and 1T R&D. In September last year, we released the news at the European Conference on Optical Communication that we had succeeded with single-carrier PM-QPSK, which makes 400G single-carrier ultralong-haul transmission possible. With Deutsche Telecom, we transmitted 2450 km of mixed 100G, 400G, and 1 terabit signals over the optical infrastructure in Germany, which includes eight nodes. We also transmitted 24 Tbit DWDM signals and achieved the highest single channel rate (11.2 Tbit/s) using superchannel technology. These achievements were the first of their kind in the industry.

We have released seven practical 400G and 1T prototypes aimed at different application areas for customers. As the leading industry innovator, we have filed patents on optical modules, algorithms, framing, and system optimization.

LR: How will ZTE products be used in 100G and beyond?

Dr. Jia: ZTE has completed dozens of tests on 100G and has commercially deployed 100G products for operators such as China Telecom, China Unicom, China Mobile, China Education Network, TATA Communications, and Hong Kong PCCW. ZTE has achieved the longest transmission distance, highest receiver sensitivity, and fastest provisioning time in recent tests with China Telecom and China Mobile. In October 2012, ZTE and T-Mobile finished deploying 100G on T-Mobile’s existing 10G backbone network in Austria. ZTE has also started deploying 100G on the China Education Network.

In our field trials with DT, we acquired quantitative knowledge about the trade-off between data rate and transmission distance. We also acquired knowledge about the trade-off between implementation complexity and spectrum efficiency. We think these experiences have been critical for allowing operators to strategically scale their networks into future backbones.