Summary and analysis of the top ten optical communication technologies in 2016

5G channel coding technology

In October 2016, Huawei announced that after completing the first phase of 5G air interface key technology verification and testing of the China IMT-2020 (5G) Promotion Group in April this year, it has made another breakthrough in the polarization code (Polar Code) technology in the field of 5G channel coding.

[Comment] The gain stability performance of the field tests in static and mobile scenarios, short and long packet scenarios is excellent, and the combined test on the high-frequency millimeter wave band has achieved a service rate of up to 27Gbps. In order for 5G to achieve a peak rate of 10Gbps or even 20Gbps, hundreds of billions of connections, and 1 millisecond latency, it is necessary to improve network performance with revolutionary basic technological innovations. Efficient channel coding technology increases the reliability of information transmission with the smallest possible service overhead, and the improvement of channel coding efficiency will directly reflect the improvement of spectrum efficiency. Constructing a channel coding method that can reach the channel capacity or approach the channel capacity (Shannon limit), and a decoding algorithm with practical linear complexity has always been the goal of channel coding technology research.

Research on increasing the bandwidth density of optical transmission on chips by 10 to 50 times

In March 2016, a paper published in Nature magazine by researchers from the University of California, Berkeley, the University of Colorado, and the Massachusetts Institute of Technology stated that they had successfully used existing CMOS standard technology to create a single chip that integrates photonics and electronic components. The bandwidth density of this new chip is 300 Gbps per square millimeter, which is 10 to 50 times that of electronic microprocessors currently on the market. Semiconductor microchips that integrate photonics and electronic components can speed up data transmission, improve performance, and reduce power consumption.

【Comment】Advances in semiconductor technology allow chips to perform more operations, but they cannot increase the bandwidth of inter-chip communication. Currently, the power consumed by chip transmission exceeds 20% of the chip power budget. This new technology improves the chip communication bandwidth by an order of magnitude under low power consumption, setting a new milestone for the current bottleneck of transistor technology. Using optical components for chip-to-memory transmission will reduce power consumption and increase the clock. In the future, it may also help achieve exascale computing.

Photonic neuromorphic chips

In November 2016, according to the website of MIT Technology Review magazine, a research team at Princeton University in the United States recently developed the world's first photonic neuromorphic chip and proved that it can calculate at ultra-fast speeds. The chip is expected to open up a new photonic computing industry. The principle of this optical device is that each node in the system uses a certain wavelength of light, a technology called wavelength division multiplexing. The light from each node is sent into the laser, and the laser output is fed back to the node, creating a feedback circuit with nonlinear characteristics. Regarding the extent to which this nonlinearity can simulate neural behavior, the study shows that its output is mathematically equivalent to a device called a "continuous time recurrent neural network (CTRNN)", which means that the programming tools of CTRNN can be applied to larger silicon photonic neural networks.

[Comment] Photons are used to solve the problem of limited speed of neural network circuits. Neural network circuits have taken the computing field by storm. Scientists hope to create more powerful neural network circuits. The key is to create circuits that work like neurons, or neuromorphic chips, but the main problem with such circuits is to increase the speed. Photonic computing is the "rising star" in the field of computing science. Compared with electrons, photons have more bandwidth and can process more data quickly. However, photonic data processing systems are expensive to manufacture, so they have not been widely adopted. This will open up a new photonic computing industry. Silicon photonic neural networks may become the "vanguard" of a larger family of silicon photonic systems for scalable information processing.

Using existing optical fibers in cities to achieve long-distance quantum transmission technology

In October 2016, according to foreign media reports, researchers from NASA recently used urban optical cables to achieve long-distance quantum transmission, transmitting laser photons 3.7 miles through "dark optical cables" in Calgary, Canada. The researchers used unused "dark optical cables" for quantum transmission and detected the transmitted photons through specially designed photon sensors.

[Comment] This is the first time that quantum transmission has been experimented in existing urban optical cables. Previously, researchers were only able to achieve quantum transmission over this distance in a laboratory environment. Quantum transmission can achieve absolutely secure transmission of encrypted information, allowing the sender to send "invisible information" to the receiver, and information interception cannot be achieved on the quantum network. Quantum transmission outside the laboratory involves a series of problems and is a new challenge. This experiment overcomes these problems and is an important milestone in the development of the future quantum Internet. "

Fiber optic transmission technology (supports calls for 4.8 billion people worldwide)

In August 2016, Wuhan Institute of Post and Telecommunications revealed at the provincial science and technology conference that the institute's laboratory had recently broken the world record for optical transmission, reaching 400T per second. An optical fiber as thin as a hair can accommodate 4.8 billion people around the world to talk online at the same time. This is the fifth time that the Institute of Post and Telecommunications has successfully hit the world record in three years. According to calculations, the data size of an ordinary high-definition movie is about 2G, and a Blu-ray high-definition movie is about 10G. With the latest optical transmission speed of the Institute of Post and Telecommunications, 40,000 Blu-ray high-definition movies can be transmitted in 1 second.

【Comment】 With the continuous emergence of technologies such as AR/VR and 4K HD, many industries such as Internet+, Internet of Things, big data, cloud computing, and smart cities rely on the high-speed transmission of massive data, which requires the underlying information highway to be as wide as possible. Multi-core single-mode technology is like opening up multiple parallel roads in one optical fiber, greatly improving the total transportation capacity.

Chip-to-chip communication technology

In July 2016, it was reported that the European Union had launched the ICT-STREAMS project to develop transceivers and routing technologies for high-speed chip-to-chip communications at the circuit board level, with the goal of increasing the density of advanced blade servers by 4 times, increasing throughput by 16 times, and reducing power consumption to 1/10 of the original. The ICT-STREAMS project plans to use silicon photonics technology, compact dense wavelength division multiplexing (DWDM) systems, high channel counts, and dense embedded optical engines to enable total data throughput at the circuit board level to exceed 25Tb/s. The project includes: 50Gb/s high-efficiency optoelectronic and electronic transceiver devices, silicon-based III-V silicon-based lasers and nano-amplifiers that support DWDM optical interconnects, thermal offset compensation subsystems with non-invasive integrated monitors, low-loss and low-cost single-mode optoelectronic printed circuit boards, low-cost optoelectronic integration processes, software-controlled, energy-efficient WDM embedded optical engines, and 16×16 WDM master platforms using EOPCB mounting.

【Comments】 The project introduces silicon photonics technology and WDM as a routing mechanism to increase capacity and reduce power consumption, and will achieve 1.6Tb/s and 25.6Tb/s throughput at the optical engine level and board level respectively. The use of chip-to-chip communication in server rack design is a hot topic in the development of the high-end server industry, which can effectively increase data throughput and reduce physical space, network complexity, switch and cable usage and energy consumption.

Highest density fiber transmission technology (capacity increased 100 times)

In May 2016, NTT, Fujikura and Hokkaido University announced that they had developed the world's highest density optical fiber, achieving a diameter of less than 250 microns. 19 optical fiber channels for simultaneous transmission of 6 types of light are configured, and there are 114 information paths on one line. In order to achieve more than 100 tunnel multiplexing for optical fiber diameters below 250 microns, NTT and Hokkaido University optimized the bending distribution rate of the core wires that can be transported by 3 or 6 modules and used the most suitable core wire structure. The results proved that the cores of the 6 modules that can guide waves are arranged in 19 honeycomb shapes, and the world's largest 114 channels are multiplexed on an optical fiber diameter of less than 25 microns.

【Comment】 This research and development breaks the transmission capacity limit of optical fiber cores and is being carried out globally. However, if we consider the upper limit of the actual usable optical fiber diameter and the controllability of the core curvature distribution, not only will the number of cores increase, but if the number of modules increases, it will be difficult for one optical fiber to exceed 50 tunnels. Through this research, NTT and other companies will be able to open roads with more reliable optical fibers that can meet the 1,000 times Exa bit requirements as the amount of data communication increases in the future. The optical fiber developed this time will be put into practical use in 2020, and it is expected to continue to meet the basics of optical fiber transmission in terms of the ever-increasing demand for data communication.

Photon integration of multi-photon entangled quantum states and on-chip optical frequency comb research

In March 2016, Science magazine published a research paper titled Generation of multiphoton entangled quantum states by means of integrated frequency combs, which was published by Brent E. Little, a researcher at the Xi'an Institute of Optics and Precision Mechanics of the Chinese Academy of Sciences, in collaboration with the National Institute of Scientific Research of Quebec, Canada, and other institutions. In this paper, the spontaneous four-wave mixing effect in the microring resonator was used, and a time-domain separated and phase-adjustable optical pulse pair was used as the pump source to obtain entangled photon pairs with a frequency interval of 200GHz across the three communication bands of SCL. Multiphoton entangled states are the cornerstone of quantum communication, quantum computing, and ultra-high-resolution sensing and imaging technologies that transcend the classical limit. At the same time, they have extremely important applications in exploring basic problems in quantum physics. This entangled photon source is the quantum frequency comb with the widest bandwidth to date, and its quantum interference fringe visibility reaches 93.2%. By extracting two pairs of photons simultaneously at two different resonant wavelengths, a four-photon entangled state is obtained, and its quantum interference fringe visibility reaches 89%.

[Comment] This study successfully realized the visible light optical frequency comb in the Si3N4 microring, and obtained entangled photon pairs with a frequency interval of 200GHz across the three communication bands of SCL. This has become an urgent need for the development of quantum application technology in large-scale integrated on-chip entangled photon sources. This research has ushered in an era of on-chip generation and control of complex quantum states, and provided a scalable integrated optical quantum information processing platform. This work is another important progress in the research of photon integrated on-chip quantum optics by the Xi'an Institute of Optics and Precision Mechanics after the on-chip parallel heralded single photon source and on-chip cross-polarization entangled photon pairs.

Fiber transmission rate exceeds 1Tb/s

In October 2016, Nokia Bell Labs, Deutsche Telekom's T-Lab and the Technical University of Munich (TUM) achieved unprecedented transmission capacity and spectral efficiency through a new modulation technology in a field test of optical fiber communications. When the adjustable transmission rate is dynamically adapted to the channel conditions and traffic demand, the flexibility and performance of the optical network can be maximized. As part of the Safe and Secure European Routing (SASER) project, this experiment on Deutsche Telekom's deployed optical fiber network reached a transmission rate of 1Tb/s.

【Comment】 The trial of the new modulation method of PCS has achieved higher transmission capacity on a given channel and significantly improved the spectral efficiency of optical communications. PCS intelligently uses constellation points with large amplitudes to transmit signals at a lower frequency than constellation points with small amplitudes, which, on average, has better adaptability to noise and other impairments. This enables the transmission rate to be adjusted to perfectly adapt to the transmission channel, resulting in a 30% capacity increase. Deutsche Telekom provides a unique network infrastructure to evaluate and demonstrate highly innovative transmission technologies like this. In the future, it will also support higher-level test scenarios and technologies, and increase capacity, coverage distance and flexibility on the already laid fiber optic infrastructure.

Realizing 610Mbps single-channel real-time transmission based on LED

In January 2016, the Beijing Science and Technology Project "Indoor High-speed Visible Light Communication System Transceiver and Handover Technology Research and Development" (execution period from January 2014 to December 2015) chaired by Chen Xiongbin, a researcher at the State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, was announced to have been completed as planned. The research team commissioned the China Telecommunication Technology Laboratory of the Ministry of Industry and Information Technology to conduct a third-party test on the single-channel real-time 610Mbps visible light communication, and the results were good. Based on a 1-watt fluorescent white light LED and a PIN detector, the average single-channel real-time transmission rate under OOK modulation was 610Mbps. At a transmission distance of 6.2 meters, the average bit error rate was 3.5e-5, which is much lower than the upper limit of the bit error rate of forward error correction of 3.8e-3.

【Comment】 Visible light communication, a new wireless optical communication technology, is more in line with the development direction of wireless communication technology (high speed, large capacity, and security) than traditional radio communication technology, and will give rise to many innovative applications in the future. China has many LED companies and a vast semiconductor lighting market, and this basic advantage is difficult for other countries to achieve. The practical research of visible light communication technology should attract everyone's attention.