九州大学学術情報リポジトリ
Kyushu University Institutional Repository
Behavior Modeling and Characteristic
Measurement of Key Impairments in Optical Transceivers
陳, 浩
https://doi.org/10.15017/2534464
出版情報：九州大学, 2019, 博士（学術）, 課程博士 バージョン：
権利関係：
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氏 名 ：陳 浩
論文題名 ：
Behavior Modeling and Characteristic Measurement of Key Impairments in Optical Transceivers
（ 光 ト ラ ン シ ー バ に お け る 特 性 劣 化 主 要 因 の 動 作 モ デ ル と 性 能 評 価 に 関する研究）
区 分 ：甲
論 文 内 容 の 要 旨
As optical communication system develops to require high speed, low latency, small size, low power consumption and low cost, both direct-detection system and coherent-detection system are widely developed and utilized in recent decades in various application scenarios. To improve the transmission capacity, advanced signal processing technique to mitigate the impairments of optical transceivers is as the potential solution. The basis of the efficient signal processing is the deep understanding, the accurate behavior modeling and the efficient measurement and extraction for the key distortions and impairments in the optical transceiver modules. In this thesis, we focus on the behavior modeling and characteristic measurement of wideband electrical amplitude, in-phase and quadrature-phase (IQ) modulator, digital-to-analog convertor (DAC) and analog-to-digital convertor (ADC) in the coherent and direct-detection optical transceivers.
For the nonlinearity in the wideband electrical amplifier in the optical coherent transceiver, this thesis proposes a gain-isolated nonlinear model based on Volterra series. It improves the estimation accuracy of the conventional Volterra model in estimating the nonlinear waveform as well as the nonlinear bit error rate (BER) penalty. The proposed nonlinear model is experimentally validated under various conditions (48 cases in total) including dual polarization Nyquist/non-return-to-zero (NRZ) pulse amplitude modulation (PAM)2/4/8 signals corresponding to 4/16/64 quadrature amplitude modulation (QAM) and 8 different amplifier gain conditions. The estimated nonlinearity penalty in all validated cases have small errors of less than 0.5 dB. Based on this model, nonlinearity penalty of amplifier and Mach-Zehnder modulator in dual polarization coherent optical system are further investigated by simulation.
For the IQ skew in the coherent optical transmitter, this thesis proposes a measurement method based on analyzing the shape of image spectrum when sending single sideband signal. It solves the problem of measuring the transmitter IQ skew by the transmitter itself. Experiments demonstrate that the proposed IQ skew measure method has as high as sub-picosecond accuracy and is quite robust under various configuration conditions including deviated child and parent Mach-Zehnder modulator bias and test signal magnitudes. Multiple phase average method is proposed and experimentally validated to further reduce the measurement error fluctuations possibly interfered from the DAC imperfections.
For the optical discrete multi tone (DMT) transceiver, the hardware efficient channel probing scheme based on training sequence is proposed. Based on the investigations on the performance dependence of the modulation randomness of training sequence, the proposed training sequence scheme has the repeated short
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pseudorandom binary sequence (PRBS) on the probing subcarrier in order to reduce the hardware complexity and meanwhile the long PRBS on the interfering subcarriers to generate the correct level of inter-subcarrier interference. Experiment has validated that the proposed training sequence scheme has high accuracy considering the probing performance in both channel equalization estimation and subcarrier signal to noise ratio (SNR) measurement in the DMT probing stage. With the proposed training sequence scheme, an efficient and accurate DMT probing scheme with realizable and low hardware complexity enables the 100Gbps experiment transmission over 500m standard single-mode fiber.
For the distortions of DAC and ADC in optical transceiver, the measurement and behavior modeling method is proposed. Missing-tone method is proposed to measure the signal-dependent distortions in DAC and ADC.
From the measured total noise and distortion spectrum, white noise, colored noise and strong narrowband interference are observed, extracted and separated. Based on these distortion results, sophisticated DAC and ADC model are built and the simulation platforms of two promising candidates, DMT and PAM modulation for 100Gbps optical direct-detection systems are established. Finally the tolerance of DAC and ADC distortions in the optical DMT and PAM system is investigated and compared.
