ZTE achieves ‘world first’

ZTE Corporation has demonstrated what is said to be the first ever real-time transport and coherent detection of an ultra-100G orthogonal frequency division multiplexing (OFDM) signal. ZTE successfully transmitted the signal over a long distance in standard single mode fibre without optical dispersion compensation, setting a world first for the coherent detection of an OFDM optical signal, and laying a solid foundation for the long-distance transmission and coherent detection of OFDM signals.

The demonstration’s results were presented at the Optical Fiber Communication (OFC) Conference on 14 March 2014 and have been accepted by the OFC as a post-deadline paper.

Having the advantages of spectrum efficiency, dynamic distribution of spectrum resource and being an effective solution to dispersion in fiber transmission, OFDM transmission has, for a long time, been the subject of investigation for use as the modulation code signal. Compared to an offline coherent optical OFDM transmission system, a real-time coherent detection of OFDM transmission system resolves the problems of limited hardware resources and improves signal precision.

In this demonstration, ZTE used time-domain synchronisation and a frequency offset estimation algorithm. This algorithm optimises complex floating-point multiplication into a simple sign shift operation by only comparing the signature of the signal. At the same time the high power peak-to-average ratio in the OFDM signal transmission was reduced using distortion reduction technology, and the moving average of frequencies was used to estimate channel demand to eliminate the noise in the fiber channel and thus reduce errors in the system’s performance.

Since ZTE’s Optical Wave Institute was founded in New Jersey, USA in 2010, it has focused on the research and development of cutting-edge technologies such as high speed 100G and ultra-100G signal transmission. Working closely with the company’s China-based R&D teams, it has solved several key challenges in 100G technologies and has become the company’s “engine” for global high-speed optical communication transmission developments.

In recent years ZTE has focused on real-time high bit-rate optical OFDM signal transmission research with the aim of both solving technical challenges and developing applications of the technology. By focusing on advanced technologies such as high speed 100G and ultra-100G signal transmission and receiving, ZTE has solved many key challenges in the field and released major new products.

In September 2013, ZTE was the first in the world to implement single-channel direct detection of 50Gbps optical 64QAM-OFDM (quadrature amplitude modulation-OFDM) signal real-time transmission (generation and receiving), and successfully achieved fiber transmission of the signal, breaking the previous world record of 10Gbps. In March 2014, ZTE became the first in the world to realise dual-carrier real-time 100Gbps transmission direct detection for a 16QAM-OFDM signal and to implement the transmission of the signal.