Abstract
In 1966, Dr. Charles K. Kao’s group showed that it would be possible to purify silica sufficiently to make signal transmission over glass fibers in communication area. Four years later, Corning Inc. successfully fabricated that first ultrapure fiber. Through fifty years of development, hundreds of millions of people or computers exchange information through the Internet which is connected by optic fiber nowadays. If internet technology is the basis of human society nowadays, optical fiber communication technology is the basis of the internet.
In the past forty years, optical fiber communication technology has formed a global industry that is worth hundreds of billions of dollars a year. Chinese manufacturers occupy an increasingly important position in this industry chain. There are three Chinese companies in the top ten of the world’s optical communication equipment suppliers. Fiberhome Technology Group (Wuhan Research Institute of Posts and Telecommunications, WRI) is one of the three Chinese companies, and this group is also the only one that has a complete industry chain of optical fiber communication from optoelectronic devices to optical fiber cables and optical communication systems. Specifically, the first optical fiber in China was designed and fabricated by WRI in 1976.
How to improve the transmission capacity, transmission distance, and single-channel transmission rate are the three hot research topics in the optical fiber communication area. The explosive growth of internet data services promote the development of a highspeed dense wavelength division multiplexing (DWDM) transmission system. With the great demands for communication bandwidth by data center, cloud computing, and other emerging industries, the existing backbone networks will not be able to meet the bandwidth demands in the near future. Since 2010, we started to undertake the national key basic research development program project ‘ultra-high speed, ultra-large capacity ultra-long distance (3U) optical transmission based research’ as the leading agency. Under the support of this project, we have obtained a series of achievements in scientific research. The representative achievements are briefly introduced in this Review below.
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In the past ten years, the demand of channel capacity in optical fiber transmission systems has increased dramatically due to ever-increasing data traffic. In order to meet this demand, the most practical solution is to combine the technologies of high spectral efficiency (SE) modulation formats, coherent optical detection, digital signal processing, and wideband low noise optical amplification. Therefore, several optical transport systems with total capacities of 10 to 100 Tb/s have been demonstrated. In 2010, Zhou
Before 2010, due to the limitation of the experimental equipment and the technical issues, China obviously lagged behind the developed countries in the field of ultra-high capacity optical fiber transmission. In the past 5 years, WRI as the main force of China in this field gradually approached or reached the international leading level. Table
Total Capacity | Modulation Format | Bands | Channel | Distance | Fiber | Application | Year |
---|---|---|---|---|---|---|---|
30.7 | PDM-16QAM-OFDM | C, L | 25 | 80 | SSMF | EDFA | 2011 |
16.7[ | DFT-S PDM-8PSK OFDM | C, L | 25 | 2240 | SSMF | Raman | 2012 |
63[ | PDM-16QAM-OFDM | C, L | 25 | 160 | SSMF | Raman | 2013 |
100.3[ | DFT-S PDM-128QAM OFDM | C, L | 25 | 80 | SSMF | Raman | 2014 |
Table 1. Our Work in Ultra-high Capacity SMF Transmission
Specifically, in 2014, we also realized optical fiber transmission at a capacity of 100 Tb/s. In the experimental demonstration, the coherent optical orthogonal frequency division multiplexing (CO-OFDM) with discrete Fourier transform spreading (DFT-S) and 128-QAM format was applied. It is noted that DFT-S can reduce the peak-to-average power ratio (PAPR) and mitigate the fiber nonlinearity[
Figure
Figure 1.(a) Experimental setup for a
In SMF transmission systems, 100 Tb/s is considered as the capacity upper bound, which is constrained by the optical signal-to-noise ratio (OSNR) and fiber nonlinear noise. Recently, researchers around world have turned their attention to space division multiplexing optical technology to explore other dimensions in optical transmission, including few mode fiber (FMF) transmission, multi core fiber (MCF) transmission, and optical angular momentum (OAM) transmission.
In the past two years, we have made some breakthroughs in the field of space division multiplexing optical transmission technology. In 2014, we collaborated with Huazhong University of Science and Technology (HUST) and completed a free-space data transmission with an aggregate transmission capacity of 1.036 Pb/s and a high SE of 112.6 bit/s/Hz[
In the field of high-speed real-time transmission, we also has done a lot of works, some of these results have been used in the real commercial systems. In 2015, we experimentally demonstrated a 200 Tb/s (
Figure 2.BER performances of all 375 channels after a 1 km FMF transmission. Inset: received optical spectrum and received constellations of the recovered OFDM signal.
100 G polarization-multiplexed quadrature phase shift keying (PM-QPSK) coherent optical single-carrier transmission technology has been widely used in commercial optical networks. How to maximize the use of limited spectrum resources and enhance the spectrum utilization of 100 G commercial systems is a hot topic for researchers. In 2013, we demonstrated a real-time 3.2 Tb/s (
Figure
Figure 3.Experimental setup and optical spectra.
Figure 4.(a) BER performance for the 32 WDM channels after a 2080 km transmission; (b) Q factor versus distance for the
Recently, we proposed a novel polarization switched (PS) QPSK technique called manipulated rotating (MR) PS-QPSK. The corresponding correlated constant modulus algorithm (CMA) is also proposed for recovering the signal[
Figure 5.Experimental setup for the real-time evaluation of the MR-PS-QPSK transmission system.
The BER versus OSNR in the back-to-back case is shown in Fig.
Figure 6.(a) Back-to-back performance of DP-QPSK and MR-PS-QPSK at the same baud rate; (b) the unrepeated transmission performance of DP-QPSK and MR-PS-QPSK at the same baud rate.
In the past 5 years, Wuhan Research Institute of Posts and Telecommunications obtained a series of achievements in the field of “3U” optical transmission. Some techniques have been used in actual commercial systems. In the future, we will conduct a more in-depth research in the field of low cost IM-DD transmission, low cost coherent PON, and silicon-based optoelectronic integration, making more contributions to the optical communication industry of China.
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