Analysis of Key Technology of 100G and Above Ultra High Speed Optical Communication System

With the continuous advancement of social informationization, the demand for bandwidth for the sprout and development of emerging businesses such as ultra-high definition video, cloud computing and the Internet of Things grows rapidly. Business demand-driven technology advances. The single-channel transmission rate of optical transmission systems has gone from 2.5Gbit / s → 10Gbit / s → 40Gbit / s → 100Gbit / s. The next generation of ultra-100G optical transmission systems are also making breakthroughs.

100G and above ultra-high-speed optical communication system is how to get the transfer rate greatly improved? Where is the innovation of a 100G optical system relative to a low-rate optical communication system? This article tries to explain for you one by one.

The traditional optical communication system uses intensity modulation / direct detection (IM / DD), that is, the transmitting end modulates the optical carrier intensity, and the receiver performs envelope detection on the optical carrier. The system is simple in structure, easy to integrate and low in cost, but it can only use amplitude modulation, low band utilization, and the system transmission capacity and relay distance are greatly limited. Draw lessons from wireless communication system for a variety of ways to modulate the electromagnetic spectrum to improve the utilization of the spectrum of ideas, we can also carry out the optical carrier frequency and phase modulation it? The answer is yes, but only if the optical carrier must have a defined frequency and phase (without the same fixed frequency and phase as natural light). As a result, researchers have turned their attention to coherent light. Coherent light refers to the same frequency, the vibration direction is not vertical, and the phase difference constant light. Use this feature, you can send the end through AM, FM, phase modulation using external light modulation technology to send the signal modulated onto the optical carrier. At the receiving end, a laser generated by a local oscillator is mixed with the input signal light in an optical mixer to obtain an intermediate frequency signal that changes in frequency, phase and amplitude with the same regularity of signal light. This is the key technology behind coherent optical communication technology, that is, the 100G and above ultra-high

Due to taking full advantage of the modularization dimension (amplitude, phase and polarization state) of the optical signal to carry the data and replacing the normal light source with coherent light, the spectral efficiency can be greatly improved, and the single optical fiber can be further promoted when the available frequency band resource is unchanged Transmission capacity. In conclusion, the main advantages of coherent optical communication technology are as follows: PSK, DPSK, QAM and other modulation formats can be used, which is conducive to flexible engineering applications; under the same communication conditions, coherent detection receiver than ordinary receiver sensitivity The coherent receiver can greatly reduce the frequency separation of the frequency division multiplexing system, that is, dense wavelength division multiplexing (DWDM), wavelength division multiplexing Replacing the high frequency spacing of traditional optical multiplexing technology has the potential advantage of achieving higher transmission rates with frequency division multiplexing.

In practice, based on the considerations of cost and compatibility, the optical fiber cables already laid can be fully utilized, and the existing optical transmission systems can be upgraded by upgrading and modifying the optical transceiver units to increase the transmission data rate of a single wavelength channel System capacity. The 100G optical communication system transformed by the above method has the best cost performance and feasibility.

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