Research On Transmission Performance Effects Of Modulation Based On Optical Communications

With the rapid development of modern high-teches, we have entered a new era full of information. So it puts high demands on the transmission network system performance, not just the ultra-high-speed, ultra-long-range and high-capacity basic transmission network, but also the short haul communication which is the most closely in touch with users.Orthogonal frequency-division multiplexingtechnology has high spectrum efficiency, good resistance to channel impairments, etc., so it has been widely applied for not only long-distance basic transmission network, but also short-distance network. Orthogonal Frequency Division Multiplexing contains several modem technologies applied to different systems:coherent reception and direct detection, asymmetrically and symmetrically clipped Optical technology, DHT, DCT, etc.. Different modulation techniques can be applied to adapt to different performance requirements. We study in detail the optical OFDM transmission performance based on IM/DD system different modulation and demodulation techniques by a series of theoretical verification, simulation and experimental studies in this paper. The specific research contents and relevant outcomes are shown as follows:(1) By doing a serial of reading, the paper presents the characteristics of the Orthogonal frequency-division multiplexing system. Meanwhile it describes application scenarios and development status of IM/DD system, respectively, from the visible light technology and PON technology to illustrate. (2) Then, we introduce the basic theory of IM/DD optical OFDM system. Mainly the basic principle, achievement, the reception method(coherent detection and direct detection) and the modulation method(asymmetrically and symmetrically clipped optical technology) in the OFDM system. And we explore the IM/DD optical OFDM system offline experiment and concern the system components for the experiment and algorithm simulation tools.(3) Research and simulation system based on ACO-OFDM modulation techniques. First we studied the IM/DD optical sideband modulation system technology, exploring traditional methods compatible single sideband modulation. Then we introduced an asymmetric clipped optical OFDM technology, the new optical single sideband modulation technique, we verified the correctness of the system, followed by building simulation system. With comparison of the traditional single-sideband modulation system, the new system can save resources and reduce bit error rate which can improve system performance. Thus, the method will play an important role in the study of future IM/DD system modulation and demodulation schemes.(4) The research and realization of optical OFDM system based on DHT modulation. We introduced the traditional OFDM scheme based on FFT implementation in IM/DD system, and then proposed a new OFDM system based on DHT. So we verified the feasibility of DHT implementation based on OFDM theory and compared two kinds of schemes calculate complexity. By contrasting the traditional scheme and the new scheme with estimation and experiment, we put forward the complexity of the new method can be reduced to half when got the same performance requirements. So the new DHT scheme is very attractive in the future short distance IM/DD system.