相干檢測中的DSP算法和仿真研究
發(fā)布時間：2019-05-14 19:28
【摘要】：相干檢測是一種全息檢測技術(shù),它可以允許信息被編碼在光纖的所有自由度上,包括幅度,相位以及偏振。因此,它可以提高信號功率以及系統(tǒng)的頻譜效率。近年來,由于高清電視、視頻會議等新業(yè)務(wù)的驅(qū)動,網(wǎng)絡(luò)容量迅速增長,之前的帶寬已經(jīng)不夠使用,具有高頻譜效率的相干檢測技術(shù)開始受到人們的廣泛關(guān)注。 同時,高速率模數(shù)轉(zhuǎn)換器(ADC)的實(shí)現(xiàn)以及大規(guī)模集成電路(VLSI)的發(fā)展使得對光纖傳輸損傷在GHz波特速率上進(jìn)行數(shù)字補(bǔ)償成為可能。因此,與數(shù)字信號處理(DSP)技術(shù)的結(jié)合將使相干檢測技術(shù)更加具有吸引力。對于相干檢測后的信號,DSP算法可以對光纖信道的線性效應(yīng)做到無損補(bǔ)償,例如色散效應(yīng)和偏振模色散效應(yīng)。此外,DSP算法也可以實(shí)現(xiàn)發(fā)射端激光器與本地激光器的載波同步�；谝陨显�,對于相干檢測技術(shù)中DSP算法的研究非常火熱。 本文首先介紹了基于DSP的相干光系統(tǒng)的基礎(chǔ)知識,然后介紹了目前應(yīng)用在相干光通信中的DSP算法,包括色散補(bǔ)償、解偏振串?dāng)_、非線性補(bǔ)償、頻率估計以及相位估計算法五個方面。這些算法普遍存在著復(fù)雜度大的缺點(diǎn),為了降低硬件功耗,復(fù)雜度必須要降低。作者在相位估計和頻率估計這兩個方面做出了改進(jìn)。對于頻率估計中的共軛M次方算法,它需要采用復(fù)數(shù)乘法器來去除調(diào)制相位信息,這會帶來硬件功耗的增大。基于此,作者提出了一種低復(fù)雜度的M次方算法,這種算法采用查表器件來去除調(diào)制相位信息。與傳統(tǒng)的共軛M次方算法的性能一樣的同時,這個算法不需要采用復(fù)數(shù)乘法器,因而使復(fù)雜度大大降低。此外,作者還在相位估計算法方面做出了創(chuàng)新。盲相位搜索算法是目前相位估計中精度最高的算法之一,它首先假設(shè)出所有可能的相位噪聲值,然后再借助歐式距離最短原則選出最接近于真實(shí)相位噪聲的測試相位。為了保證盲相位搜索算法的高精度,在盲相位搜索算法中一般采用逐符號估計,同時測試相位個數(shù)也要求很多,這會帶來很大的復(fù)雜度。在本文中,基于相位噪聲慢變的特性,作者提出了粗估計和細(xì)估計相結(jié)合的兩步法以及滑動塊的思想,降低了測試相位的個數(shù)以及每個符號重復(fù)計算的次數(shù)。通過采用兩步法以及滑動塊的思想,原始的盲相位搜索算法的復(fù)雜度大大降低。仿真結(jié)果表明,在激光器線寬容忍度降低11%的同時,算法復(fù)雜度至少可降低一半。
[Abstract]:Coherent detection is a holographic detection technique, which allows information to be encoded on all degrees of freedom of optical fiber, including amplitude, phase and polarization. Therefore, it can improve the signal power and the spectral efficiency of the system. In recent years, due to the drive of high-definition television, video conferencing and other new services, the network capacity has increased rapidly, and the bandwidth has not been used enough. the coherence detection technology with high spectral efficiency has been paid more and more attention. At the same time, the implementation of high rate analog-to-digital converter (ADC) and the development of large-scale integrated circuit (VLSI) make it possible to digitally compensate the optical fiber transmission damage at GHz port rate. Therefore, the combination with digital signal processing (DSP) technology will make coherent detection technology more attractive. For coherent signals, DSP algorithm can compensate the linear effect of fiber channel nondestructive, such as dispersion effect and polarization mode dispersion effect. In addition, DSP algorithm can also realize carrier synchronization between emitter laser and local laser. For the above reasons, the research on DSP algorithm in coherent detection technology is very hot. In this paper, the basic knowledge of coherent optical system based on DSP is introduced, and then the DSP algorithm used in coherent optical communication is introduced, including dispersion compensation, depolarization crosstalk, nonlinear compensation. There are five aspects of frequency estimation and phase estimation algorithm. These algorithms generally have the disadvantage of large complexity. In order to reduce the hardware power consumption, the complexity must be reduced. The author has made improvements in phase estimation and frequency estimation. For the conjugated M-th power algorithm in frequency estimation, it needs to use the complex multiplier to remove the modulation phase information, which will lead to the increase of hardware power consumption. Based on this, a low complexity M-power algorithm is proposed, which uses look-up table devices to remove modulation phase information. The performance of this algorithm is the same as that of the traditional conjugated M-th power algorithm, at the same time, this algorithm does not need to use complex multiplier, so the complexity is greatly reduced. In addition, the author also makes an innovation in the phase estimation algorithm. Blind phase search algorithm is one of the most accurate algorithms in phase estimation at present. It first assumes all possible phase noise values, and then selects the test phase which is closest to the real phase noise with the help of the principle of shortest Euclidean distance. In order to ensure the high accuracy of blind phase search algorithm, symbol by symbol estimation is generally used in blind phase search algorithm, and the number of test phases is also required, which will bring great complexity. In this paper, based on the slow change of phase noise, the author proposes a two-step method combining rough estimation with fine estimation and the idea of sliding block, which reduces the number of test phases and the number of repeated calculations per symbol. By using the two-step method and the idea of sliding block, the complexity of the original blind phase search algorithm is greatly reduced. The simulation results show that the complexity of the algorithm can be reduced by at least half while the tolerance of laser line is reduced by 11%.
【學(xué)位授予單位】：北京郵電大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2012
【分類號】：TN26;TP368.1
本文編號：2476987
[Abstract]:Coherent detection is a holographic detection technique, which allows information to be encoded on all degrees of freedom of optical fiber, including amplitude, phase and polarization. Therefore, it can improve the signal power and the spectral efficiency of the system. In recent years, due to the drive of high-definition television, video conferencing and other new services, the network capacity has increased rapidly, and the bandwidth has not been used enough. the coherence detection technology with high spectral efficiency has been paid more and more attention. At the same time, the implementation of high rate analog-to-digital converter (ADC) and the development of large-scale integrated circuit (VLSI) make it possible to digitally compensate the optical fiber transmission damage at GHz port rate. Therefore, the combination with digital signal processing (DSP) technology will make coherent detection technology more attractive. For coherent signals, DSP algorithm can compensate the linear effect of fiber channel nondestructive, such as dispersion effect and polarization mode dispersion effect. In addition, DSP algorithm can also realize carrier synchronization between emitter laser and local laser. For the above reasons, the research on DSP algorithm in coherent detection technology is very hot. In this paper, the basic knowledge of coherent optical system based on DSP is introduced, and then the DSP algorithm used in coherent optical communication is introduced, including dispersion compensation, depolarization crosstalk, nonlinear compensation. There are five aspects of frequency estimation and phase estimation algorithm. These algorithms generally have the disadvantage of large complexity. In order to reduce the hardware power consumption, the complexity must be reduced. The author has made improvements in phase estimation and frequency estimation. For the conjugated M-th power algorithm in frequency estimation, it needs to use the complex multiplier to remove the modulation phase information, which will lead to the increase of hardware power consumption. Based on this, a low complexity M-power algorithm is proposed, which uses look-up table devices to remove modulation phase information. The performance of this algorithm is the same as that of the traditional conjugated M-th power algorithm, at the same time, this algorithm does not need to use complex multiplier, so the complexity is greatly reduced. In addition, the author also makes an innovation in the phase estimation algorithm. Blind phase search algorithm is one of the most accurate algorithms in phase estimation at present. It first assumes all possible phase noise values, and then selects the test phase which is closest to the real phase noise with the help of the principle of shortest Euclidean distance. In order to ensure the high accuracy of blind phase search algorithm, symbol by symbol estimation is generally used in blind phase search algorithm, and the number of test phases is also required, which will bring great complexity. In this paper, based on the slow change of phase noise, the author proposes a two-step method combining rough estimation with fine estimation and the idea of sliding block, which reduces the number of test phases and the number of repeated calculations per symbol. By using the two-step method and the idea of sliding block, the complexity of the original blind phase search algorithm is greatly reduced. The simulation results show that the complexity of the algorithm can be reduced by at least half while the tolerance of laser line is reduced by 11%.
【學(xué)位授予單位】：北京郵電大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2012
【分類號】：TN26;TP368.1
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