201123753 六、發明說明： 【發明所屬之技術領域】 本發明係關於一種改善通信信號品質之技術， 特別係關於一種利用正交分頻多工（〇FDM)調變信 號來έ周變連續光以進行傳輸之用於光〇FDM通信系 統之信號品質改善者。 【先前技術】 OFDM調變是一種將傳輸資料利用複數次載波 (subcarder)平行傳送之方法，由於各次載波之符號 率（symbol rate)變的較低而較能抵抗符號間干擾 (intersymbol interference)，故其早已被使用於數位 地面廣播及無線區域網路（LAN)系統中，目前也正研 九將其應用於光通信系統（例如參考文獻1 )。 第4圖為光OFDM通信裝置之傳送端之略圖。 根據第4圖，光〇FDM通信裝置包含一串列平行 (serial-parallel)轉換部 11、一映射（mapping)部 I〗、 一快速傅立葉逆轉換（IFFT)部13、一循環字首 (cyclic prefix，CP)插入部M、一數位類比 (digital-analog)轉換部15及一光調變部16。 串列平行轉換部1丨以各次載波利用OFDm調變 之1個符號之傳輸位元數為單位將傳輸資料做平行 轉換’·亦即，例如次載波個數為N，若各次載波使 用QPSK調變，傳輸資料將以2N位元單位分割，則 201123753 第1輸出至第N輪屮八s，认， 翰出刀別輸出連續的2位元資料。 映射部。根據各次載波之調 山 於各次载波之輸入蟑之於次 ' 出對應 標，即複數值。IFFT部^ 2 上之座 Γ:!號。此外’1…另輸出軸= 相成分及對應虛數之疋六4 同201123753 VI. Description of the Invention: [Technical Field] The present invention relates to a technique for improving the quality of communication signals, and more particularly to a method for utilizing orthogonal frequency division multiplexing (〇FDM) modulation signals to convert continuous light Signal quality improver for optical FDM communication systems for transmission. [Prior Art] OFDM modulation is a method of transmitting transmission data in parallel using a plurality of subcarriers. Since the symbol rate of each carrier becomes lower, it is more resistant to intersymbol interference. Therefore, it has been used in digital terrestrial broadcasting and wireless local area network (LAN) systems, and is currently being applied to optical communication systems (for example, Reference 1). Figure 4 is a schematic diagram of the transmitting end of the optical OFDM communication device. According to Fig. 4, the optical FDM communication device includes a serial-parallel conversion unit 11, a mapping portion I, an inverse fast Fourier transform (IFFT) portion 13, and a cyclic prefix (cyclic). Prefix, CP) The insertion unit M, the digital-analog conversion unit 15 and the optical modulation unit 16. The serial-parallel conversion unit 1 converts the transmission data in parallel by using the number of transmission bits of one symbol of the OFDm modulation for each subcarrier, ie, for example, the number of subcarriers is N, if each subcarrier is used. QPSK modulation, the transmission data will be divided into 2N bit units, then 201123753 first output to the Nth round 屮 eight s, recognize, John will not output continuous 2-bit data. Mapping section. According to the adjustment of each carrier, the input of each carrier is the corresponding value, that is, the complex value. The seat on the IFFT section ^ 2 Γ:! In addition, '1...the other output axis = the phase component and the corresponding imaginary number 疋6 4
菩，ΓΡ杯二 成分之兩個數位信號。接 卩14於兩個數位信號中插人猶環字首。 :位類比轉換部15將各數位信號轉換為類子二 號。光調變部16根據數位類比轉換部15輪出之： 類比信號調變連續光以輸出光0FDM信號。 經過OFDM調變所得之信號具有較大的峰值對 平均功率比（PAPR: Peak t0 Average卜爾心1〇)，亦 即相對其平均功率之峰值功率之比值較大，於光纖 中傳輸時會受到較大的非線性光學效應之影響，因 而具有信號品質劣化之問題。為了避免非線性光學 效應之衫響，必須降低PAPR，例如已被提出的使用 載波（clipping)之方法（例如參考文獻2)。Bodhisattva, two cups of two components of the signal. The interface 14 is inserted into the first digit of the two digit signals. The bit analog conversion unit 15 converts each digital signal into a sub-number two. The optical modulation unit 16 rotates according to the digital analog conversion unit 15: The analog signal modulates the continuous light to output the optical OFDM signal. The signal obtained by OFDM modulation has a large peak-to-average power ratio (PAPR: Peak t0 Average), that is, the ratio of the peak power to the average power is large, and is transmitted when transmitted in the fiber. The effect of large nonlinear optical effects has a problem of signal quality degradation. In order to avoid the ringing of the nonlinear optical effect, it is necessary to reduce the PAPR, such as the proposed method of using clipping (for example, Reference 2).
使用截波之方法須使用將信號振幅降至一定值 以下之濾波器等來壓抑峰值振幅，藉以降低pApR 來避免非線性光學效應之影響，然而載波本身即具 有使信號品質劣化之問題。 參考文獻 1 : Arthur James Lowery et al.， 201123753 'Orthogonal-frequency-division multiplexing for dispersion compensation of long-haul optical systems,” 2006 Optical Society of America, OPTICS EXPRESS 2009, Vol. 14, No. 6, 2006 年 3 月。 參考文獻 2 : Xiaodong Li et al.，“Effects of Clipping and Filtering on the Performance of OFDM,,? IEEE COMMUNICATIONS LETTERS, Vol. 2, No. 5, 1998 年 5 月，pp. 131-133. 參考文獻 3 : Hidenori Taga, “A theoretical study of OFDM system performance with respect to subcarrier numbers,” 2009 Optical Society of America, OPTICS EXPRESS 18638, Vol. 17, No. 21， 2009年9月。 【發明内容】 因此，本發明之目的在於提供一種相較於習知 技術，不會使信號品質劣化之通信裝置及通信方法。 此外，本發明之目的在於提供一種可降低光通 信系統中，光傳輸路徑之非線性光學效應之影響之 通信裝置及通信方法。 本發明之通信裝置包含一記憶手段、一波形讀 出手段及一轉換手段。記憶手段儲存關於複數位元 之位元列之各位元模式，表示時間波形之取樣值之 一波形表。波形讀出手段從該波形表讀出對應於輸 201123753 入位元列之位it模式之時間㈣之取樣值。轉換手 段將所讀出之時間波形之取樣值轉換為類比信號。 根據本發明另一實施例之通信裝置，包含於咳 =表之對應於位元模式之時間波形，係根據該： 虞置與一對向通信裝置間之傳輸路徑之傳輸特性 所求得者，以使相對該通信裝置之對向通信裝置之 解-周4所接收信號之波形，能解調成對應於該時間 波形之位元模式之波形。 此外本發明另一實施例之通信裝置另包含一 光調變手段根據該類比信號調變連續光；該通作裝 置與對向通信裝置^傳輸純較佳為㈣輸路 徑。 此外’根據本發明另—實施例之通信裝置，包 含於該波形表之各時間波形之頻率成分較佳包含複 數次載波。 本發明之通信方法係用於儲存有關於複數位元 之位元列之各位元模式，㈣時間波形之取樣值之 一波形表之光通信萝罢 外f 丄 忒置。该通信方法包含下列步 驟：從該波形表讀出對應於輸人位元列之位元模式 之時間波形之取樣值；以及將所讀出之時間波形之 取樣值轉換為類比信號。 本發明之通k裝置是一種包含預先求得之對應 201123753 f間波形之一資料庫 於谷位元列 對應於輸入位元列之時門法开”博’以讀取並輸沒 庫之各時間波形，係考慮’傳二取樣值者。此資剩 ==讀:之時; :得:理想_波 ，:學:應=調; 1非線,光學效應之影響之分階傅 … 時間波形儲存於光 【實施方式】 了㈣更佳的效果。 以下配合所附圖㈣細朗本發明之實施例。 此外’_下列說明係根據用於光_Μ通㈣統 之光0讀通信裝置來進行，本發明亦可適用於益 =裝置或使用0聰以外的其他調變技術之通 第1圖為根據本發明之光0FDM通信裝置之略 圖。如第1圖所示，光0FDM通信裝置^一串列 平行（s/Ρ)轉換部卜—波形讀出部2、儲存有一波形 資料庫7之一記憶部3、一數位類比（d/a)轉換部$ 及一光調變部6。 、 率列平行轉換部1以OFDM調變之1個符號之 傳輸資料為單位將輸入資料做平行轉換；亦即，例 201123753 如次載波個數為Ν，μ 由於1個符萝之禮认右各-人载波使用QPSK調變， 換部1將傳二？ f料數為2N位元’並列平行轉 位元之=為 千1立輸出至波形讀出部2。 一 # M雖然被輸入至波形讀出部2之Μ位 位7"模式為，個組合其中之-，由於波形資 料庫7為包含表示分 Μ _ ^ 形資訊之資粗成兀列之時間波 吹 庫，波形讀出部2從記憶部3之波形 為料庫7 °貝出對應被輸入位元列之時間波形。The method of using the chopping method suppresses the peak amplitude by using a filter or the like that reduces the amplitude of the signal below a certain value, thereby reducing the pApR to avoid the influence of the nonlinear optical effect, but the carrier itself has a problem of deteriorating the signal quality. Reference 1: Arthur James Lowery et al., 201123753 'Orthogonal-frequency-division multiplexing for dispersion compensation of long-haul optical systems,' 2006 Optical Society of America, OPTICS EXPRESS 2009, Vol. 14, No. 6, 2006 March. Reference 2: Xiaodong Li et al., "Effects of Clipping and Filtering on the Performance of OFDM,, IEEE COMMUNICATIONS LETTERS, Vol. 2, No. 5, May 1998, pp. 131-133. Reference 3: Hidenori Taga, "A theoretical study of OFDM system performance with respect to subcarrier numbers," 2009 Optical Society of America, OPTICS EXPRESS 18638, Vol. 17, No. 21, September 2009. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a communication apparatus and communication method that do not degrade signal quality compared to the prior art. Further, it is an object of the present invention to provide a communication apparatus and communication method capable of reducing the influence of a nonlinear optical effect of an optical transmission path in an optical communication system. The communication device of the present invention comprises a memory means, a waveform reading means and a conversion means. The memory means stores a symbol pattern of the bit values of the bit rows of the complex bits, and represents a waveform table of the sample values of the time waveform. The waveform reading means reads out the sample value corresponding to the time (four) of the bit it mode of the input bit sequence of 201123753 from the waveform table. The conversion means converts the sampled value of the time waveform read out into an analog signal. A communication device according to another embodiment of the present invention is included in a time waveform corresponding to a bit pattern of a cough table according to the transmission characteristics of the transmission path between the device and the pair of communication devices, The waveform of the received signal of the solution-week 4 of the opposite communication device of the communication device can be demodulated into a waveform corresponding to the bit pattern of the time waveform. In addition, the communication device according to another embodiment of the present invention further includes a light modulation means for modulating the continuous light according to the analog signal; and the communication device and the opposite communication device are preferably transmitted as a (four) transmission path. Further, in the communication device according to another embodiment of the present invention, the frequency component of each time waveform included in the waveform table preferably includes a plurality of subcarriers. The communication method of the present invention is for storing a symbol pattern of a bit column of a plurality of bits, and (4) a waveform table of a time waveform of a waveform of the optical communication. The communication method includes the steps of: reading a sample value of a time waveform corresponding to a bit pattern of the input bit column from the waveform table; and converting the sampled value of the read time waveform into an analog signal. The device of the present invention is a method comprising a pre-determined waveform corresponding to the 201123753 f waveform, wherein the valley bit column corresponds to the input bit column, and the gate method is opened to read and input the library. The time waveform is considered as 'passing the two sample values. This is the remaining == reading: when: : get: ideal _ wave,: learning: should = adjust; 1 non-linear, the effect of optical effects of the step Fu... Time The waveform is stored in the light [Embodiment] (4) The effect is better. The following is a brief description of the embodiment of the present invention in conjunction with the drawings (4). Further, the following description is based on the optical 0-read communication device for the optical _ Μ (4) system. The present invention can also be applied to a device or a modulation technique other than 0. Figure 1 is a schematic diagram of an optical OFDM communication device according to the present invention. As shown in Fig. 1, the optical OFDM communication device ^A series of parallel (s/Ρ) conversion sections - a waveform reading section 2, a memory section 3 storing a waveform database 7, a digital analogy (d/a) conversion section $, and a light modulation section 6 The parallel-parallel conversion unit 1 performs parallel conversion of input data in units of transmission data of one symbol of OFDM modulation. That is, for example, 201123753, if the number of subcarriers is Ν, μ is determined by the use of QPSK for the right-person carrier, and the change for part 1 is 2N bits. The bit = is output to the waveform readout section 2. The #M is input to the waveform readout section 2, and the mode is the combination of the waveform database 7 The time 波 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
—第2圖顯示波形資料庫7之示意圖。第2圖中， 位兀列編號為賦予2μ個位元模式之識別碼，例如將 De Bmjin；^式中所切割出之標頭位置作為識別碼。 例如，當被輸入之M位元的列為位元列編號丨之位 元模式時，波形讀出部2依序輸出取樣值相當於 20 172 72 ·· PAM k號之同相成分之數位信號並 依序輸出取樣值相當於58、200、62…PAM信號之 正交成分之數位信號。 此時’儲存於波形資料庫7中對應於各位元模 式之時間波形之取樣值，是以一對向光OFDM裝置 之接收端之解調部被輸入理想信號為條件，根據該 光OFDM裝置之傳送端之光處理回路、該光〇fdm 裝置所使用光傳輸路徑之光放大器及光纖、甚至該 對向光OFDM通信裝置之接收端之光處理回路之光 201123753 傳輸特性，利用八κ比鹿 备 者。 刀心傅立茱逆轉換法所預先求得- Figure 2 shows a schematic diagram of the waveform database 7. In Fig. 2, the bit array number is an identification code assigned to the 2 μ bit pattern, for example, the header position cut in the De Bmjin; ^ equation is used as the identification code. For example, when the input M-bit column is the bit pattern of the bit column number 丨, the waveform reading unit 2 sequentially outputs the digital signal of the in-phase component of the sample value corresponding to 20 172 72 ·· PAM k The digital signals whose sampling values correspond to the orthogonal components of the 58,200, 62, ... PAM signals are sequentially output. At this time, the sample value of the time waveform corresponding to the bit pattern stored in the waveform database 7 is based on the condition that the demodulation unit at the receiving end of the pair of optical OFDM devices is input with an ideal signal, according to the optical OFDM device. The optical processing circuit of the transmitting end, the optical amplifier of the optical transmission path used by the optical fdm device, and the optical fiber, and even the light of the optical processing circuit of the receiving end of the optical OFDM communication device, 201123753, use the eight-kappa ratio By. The knife-edge Fourier transform method is pre-determined
者亦即，同時考慮光0FD 等線性特性，，效== 於㈣等非線性綱 波开… 2 計算使接收端能夠得到理想時間 =之傳輸波形’並將其預先儲存於記憶部3 為波形資料庫7。 此外，本實施例中，波形資料庫7所包含之 ^皮形亦可包含循環字首部分，藉此，數位類比轉 換部5將波形讀出部2之各輸出轉換為類比信號。 光調變部6根據數位類比轉換部15輸出之類比信號 ，變連續光以輸出光0FDM信號。此外，關於循環 广百部分亦可不包含於波形資料庫7中，而由波形 5貝出部2來附加〇 此外，儲存於波形資料庫7之資料量，會隨著 次載波個數而增加。因此，降低次载波個數可降低 儲存波形資料庫7之記憶部3的記憶容量，而易於 實現本發明。再者，由於〇FDM信號之pApR如參 考文獻3所記載，具有與次載波個數一起減少的傾 向，亦可提升降低非線性光學效應之影響的效果。 如前所述’本發明之光OFDM通信裝置，為包 含預先求得之對應於各位元列之時間信號波形之一 資料庫，讀取並輸出對應於輸入位元列之時間波形 201123753 者。此資料庫之各時間波形係根據考慮了非線性光 學效應之影響之分階傅立葉逆轉換法所求得者。將 以此時間波形調變之光OFDM信號於作為計算基礎 之光傳輸路徑傳輸時，光OFDM裝置之接收端之解 调部可得到理想的信號波形，因此可改善信號品質。 第3圖顯示習知光〇FDM通信裝置及適用本發 明之光OFDM通信裝置之傳輸特性。此外，第3圖 :i橫軸為各光中繼器及光〇FDM通信裝置所實際 設定之光輸出功率，縱軸則顯示誤碼率（BER)。此 外，標號50為習知技術之光〇FDM通信裝置之傳 輸特性，標號51及52為本發明之光〇FDM通信裝 置之傳輸特性。此外，標號51為使用各光中繼器及 光OFDM通信裝置之光輸出功率為_6咖時求得之 ::形資料庫7之傳輸特性;標號5 2為使用光輸出功 率為_5dBm時求得之波形資料庫7之傳輸特性。 接从由第3圖可知’透過使用以適#光輸出功率建 ;形貝料庫7之本發明之光OFDM通信裝置，可 明顯改善職，亦即可顯著改善信號品質。 201123753 【圖式簡單說明】 第1圖為本發明之光OFDM通信裝置之略圖。 第2圖為波形資料庫之示意圖。 第3圖為本發明之效果之示意圖。 第4圖為習知技術之光OFDM通信裝置之略圖。 【主要元件符號說明】 1、11 串列平行轉換部 2 波形讀出部 3 記憶部 4 循環字首插入部 5 > 15 數位類比轉換部 6、16 光調變部 7 波形資料庫 12 映射部 13 快速傅立葉逆轉換部50 習知技術之傳輸特性 51、52本發明之傳輸特性That is to say, considering linear characteristics such as light 0FD, the effect == in (4), etc. The nonlinear wave is opened... 2 The calculation enables the receiving end to obtain the ideal time = the transmitted waveform 'and stores it in the memory unit 3 in advance. Database 7. Further, in the present embodiment, the shape of the waveform included in the waveform database 7 may include a cyclic prefix portion, whereby the digital analog converting portion 5 converts the respective outputs of the waveform reading portion 2 into analog signals. The optical modulation unit 6 converts the continuous light to output the optical OFDM signal based on the analog signal output from the digital analog conversion unit 15. In addition, the circulation of a plurality of parts may not be included in the waveform database 7, but is added by the waveform 5 output unit 2. In addition, the amount of data stored in the waveform database 7 increases with the number of subcarriers. Therefore, reducing the number of subcarriers can reduce the memory capacity of the memory unit 3 of the stored waveform database 7, and the present invention can be easily implemented. Further, since the pApR of the 〇FDM signal is as described in Reference 3, it has an effect of reducing the influence of the nonlinear optical effect by reducing the inclination with the number of subcarriers. As described above, the optical OFDM communication apparatus of the present invention reads and outputs a time waveform corresponding to the input bit column 201123753, which includes a data bank of a time signal waveform corresponding to each of the element columns which is obtained in advance. The time waveforms of this database are obtained from a stepwise Fourier transform method that takes into account the effects of nonlinear optical effects. When the optical OFDM signal modulated by this time waveform is transmitted on the optical transmission path which is the basis of calculation, the demodulation section of the receiving end of the optical OFDM apparatus can obtain an ideal signal waveform, thereby improving signal quality. Figure 3 shows the transmission characteristics of a conventional optical fiber FDM communication device and an optical OFDM communication device to which the present invention is applied. In addition, Fig. 3 shows that the horizontal axis represents the optical output power actually set by each optical repeater and the optical FDM communication device, and the vertical axis shows the error rate (BER). Further, reference numeral 50 is a transmission characteristic of a conventional optical fiber FDM communication apparatus, and reference numerals 51 and 52 are transmission characteristics of the aperture FDM communication apparatus of the present invention. In addition, reference numeral 51 is obtained when the optical output power of each optical repeater and the optical OFDM communication device is _6 coffee: the transmission characteristic of the shape database 7; and the reference 52 is when the optical output power is _5 dBm. The transmission characteristics of the obtained waveform database 7 are obtained. As can be seen from Fig. 3, by using the optical OFDM communication device of the present invention which is constructed by using the optical output power, the optical OFDM communication device of the present invention can be significantly improved, and the signal quality can be remarkably improved. 201123753 [Simplified description of the drawings] Fig. 1 is a schematic diagram of an optical OFDM communication apparatus of the present invention. Figure 2 is a schematic diagram of the waveform database. Fig. 3 is a schematic view showing the effect of the present invention. Figure 4 is a schematic diagram of an optical OFDM communication device of the prior art. [Description of main component symbols] 1, 11 serial parallel conversion unit 2 waveform reading unit 3 memory unit 4 cyclic prefix insertion unit 5 > 15 digital analog conversion unit 6, 16 optical modulation unit 7 waveform database 12 mapping unit 13 Fast Fourier Transform Section 50 Transmission Characteristics of Conventional Techniques 51, 52 Transmission Characteristics of the Present Invention
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