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JP4864910B2 - Optical communication apparatus, system, and optical communication method - Google Patents

Optical communication apparatus, system, and optical communication method Download PDF

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JP4864910B2
JP4864910B2 JP2008023887A JP2008023887A JP4864910B2 JP 4864910 B2 JP4864910 B2 JP 4864910B2 JP 2008023887 A JP2008023887 A JP 2008023887A JP 2008023887 A JP2008023887 A JP 2008023887A JP 4864910 B2 JP4864910 B2 JP 4864910B2
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ラース ヤンセン サンダー
逸郎 森田
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本発明は、直交周波数分割多重（ＯＦＤＭ）伝送技術を適用した直接検波光通信システムに関する。   The present invention relates to a direct detection optical communication system to which orthogonal frequency division multiplexing (OFDM) transmission technology is applied.

非特許文献１には、受信側にて直接検波を行う光ＯＦＤＭ通信システムが記載されている。図２は、非特許文献１に記載の光ＯＦＤＭ通信システムにおける、送信側光通信装置の構成を示す図である。図２によると、光通信装置は、レーザダイオード１と、光変調器１２と、ＯＦＤＭベースバンド信号処理部１４とを備え、光変調器１２は、２つのマッハツェンダ光変調器１２１及び１２２と、移相器１２３を含んでいる。   Non-Patent Document 1 describes an optical OFDM communication system that performs direct detection on the receiving side. FIG. 2 is a diagram illustrating a configuration of a transmission-side optical communication device in the optical OFDM communication system described in Non-Patent Document 1. According to FIG. 2, the optical communication device includes a laser diode 1, an optical modulator 12, and an OFDM baseband signal processing unit 14. The optical modulator 12 includes two Mach-Zehnder optical modulators 121 and 122, and a shifter. A phaser 123 is included.

ＯＦＤＭベースバンド信号処理部１４は、離散フーリエ逆変換処理を行うＩＦＦＴ（Ｉｎｖｅｒｓｅ Ｆａｓｔ Ｆｏｕｒｉｅｒ Ｔｒａｎｓｆｏｒｍ）回路を含み、ＩＦＦＴ回路が出力するサンプル値の実部をアナログ変換した同相ベースバンド信号１７と、同じく虚部をアナログ変換した直交ベースバンド信号１８を出力し、マッハツェンダ光変調器１２１は、レーザダイオード１が出力する連続光の振幅又は強度を、同相ベースバンド信号１７により変調し、マッハツェンダ光変調器１２２は、レーザダイオード１が出力する連続光の振幅又は強度を、直交ベースバンド信号１８により変調する。   The OFDM baseband signal processing unit 14 includes an IFFT (Inverse Fast Fourier Transform) circuit that performs discrete Fourier inverse transform processing, and is similar to the in-phase baseband signal 17 obtained by analog conversion of the real part of the sample value output from the IFFT circuit. The Mach-Zehnder optical modulator 121 modulates the amplitude or intensity of continuous light output from the laser diode 1 with the in-phase baseband signal 17, and the Mach-Zehnder optical modulator 122 The amplitude or intensity of the continuous light output from the laser diode 1 is modulated by the orthogonal baseband signal 18.

非特許文献１においては、受信側にて直接検波を行うため、負の周波数に対応するサブキャリアは未使用としている。つまり、ＩＦＦＴ回路がポート番号−Ｎ／２＋１〜Ｎ／２のＮ個のポートを持ち、各ポート番号にサブキャリ間の周波数間隔を乗じたものを、対応するサブキャリの周波数とした場合、−Ｎ／２〜−１のポートは未使用であり、“０”が入力されたものとして離散フーリエ逆変換処理を行っている。よって、直交ベースバンド信号１８の正の周波数成分は、同相ベースバンド信号１７の正の周波数成分より位相がπ／２進み、直交ベースバンド信号１８の負の周波数成分は、同相ベースバンド信号１７の負の周波数成分より位相がπ／２遅れたもの、つまり、直交ベースバンド信号１８は、同相ベースバンド信号１７をヒルベルト変換したものとなっている。よって、移相器１２３により、マッハツェンダ光変調器１２２の出力光信号の位相をπ／２遅らせて、マッハツェンダ光変調器１２１の出力光信号と合波することで、ＯＦＤＭ信号の負の周波数成分が打ち消され、正の周波数成分のみを持つ信号が送信される。   In Non-Patent Document 1, since direct detection is performed on the receiving side, subcarriers corresponding to negative frequencies are unused. In other words, if the IFFT circuit has N ports with port numbers -N / 2 + 1 to N / 2, and each port number multiplied by the frequency interval between sub-carriers is the frequency of the corresponding sub-carrier, -N / Ports 2 to -1 are unused, and discrete Fourier inverse transform processing is performed assuming that "0" is input. Therefore, the phase of the positive frequency component of the quadrature baseband signal 18 is advanced by π / 2 from the positive frequency component of the in-phase baseband signal 17, and the negative frequency component of the quadrature baseband signal 18 is the same as that of the in-phase baseband signal 17. The phase whose phase is delayed by π / 2 from the negative frequency component, that is, the quadrature baseband signal 18 is obtained by Hilbert transform of the in-phase baseband signal 17. Therefore, the phase shifter 123 delays the phase of the output optical signal of the Mach-Zehnder optical modulator 122 by π / 2 and combines it with the output optical signal of the Mach-Zehnder optical modulator 121, so that the negative frequency component of the OFDM signal is reduced. The signal is canceled and has only a positive frequency component.

更に、非特許文献１に記載の構成においては、受信側にて直接検波を行うことにより、各サブキャリアの周波数差の位置に発生する相互変調（ＩｎｔｅｒＭｏｄｕｌａｔｉｏｎ）ノイズの影響を避けるために、正の低域側半分のサブキャリも未使用としている。つまり、ＩＦＦＴ回路のポート番号０〜Ｎ／４−１も未使用としている。この様にすることで、図４にそのスペクトラムを示す光信号１９が光変調器１２から送信される。図４において、符号６０は、レーザダイオード１が送信する光信号に基づくキャリア成分であり、符号６１がＯＦＤＭ信号成分である。なお、各信号の下の数字は、ＩＦＦＴ回路のポート番号に対応している。直接検波による相互変調ノイズは、ＩＦＦＴ回路のポート番号で換算すると、１〜Ｎ／４−１の位置に発生するため、この構成によりＯＦＤＭ信号成分６１は、相互変調ノイズによる影響を避けることができる。   Furthermore, in the configuration described in Non-Patent Document 1, positive detection is performed on the reception side in order to avoid the influence of intermodulation noise generated at the position of the frequency difference of each subcarrier. The subcarrier on the lower half is also unused. That is, the port numbers 0 to N / 4-1 of the IFFT circuit are not used. By doing so, an optical signal 19 whose spectrum is shown in FIG. 4 is transmitted from the optical modulator 12. In FIG. 4, reference numeral 60 denotes a carrier component based on the optical signal transmitted by the laser diode 1, and reference numeral 61 denotes an OFDM signal component. The number below each signal corresponds to the port number of the IFFT circuit. Intermodulation noise due to direct detection is generated at a position of 1 to N / 4-1 when converted by the port number of the IFFT circuit. Therefore, this configuration can avoid the influence of the intermodulation noise on the OFDM signal component 61. .

Ｂｒｅｎｄｏｎ．Ｊ．Ｃ．Ｓｃｈｍｉｄｔ、ｅｔ ａｌ.、“Ｅｘｐｅｒｉｍｅｎｔａｌ Ｄｅｍｏｎｓｔｒａｔｉｏｎｓ ｏｆ ２０ Ｇｂｉｔ／ｓ Ｄｉｒｅｃｔ−Ｄｅｔｅｃｔｉｏｎ Ｏｐｔｉｃａｌ ＯＦＤＭ ａｎｄ １２ Ｇｂｉｔ／ｓ ｗｉｔｈ ａ ｃｏｌｏｒｌｅｓｓ ｔｒａｎｓｍｉｔｔｅｒ”、２００７ Ｏｐｔｉｃａｌ Ｓｏｃｉｅｔｙ ｏｆ Ａｍｅｒｉｃａ、ＰＤＰ１８、２００７年Brendon. J. et al. C. Schmidt, et al., “Experimental Demonstrations of 20 Gbit / s Direct-Detection Optical OFDM and 12 Gbit / s with a colorPet 7”

上述した様に、従来技術においては、ＩＦＦＴ回路のポート数の１／４未満のサブキャリアしか使用できないという問題がある。   As described above, the conventional technique has a problem that only subcarriers less than ¼ of the number of ports of the IFFT circuit can be used.

したがって、本発明は、上述した問題を解決した、ＯＦＤＭ光通信用の光通信装置、システム及び光通信方法を提供することを目的とする。   Accordingly, an object of the present invention is to provide an optical communication apparatus, system, and optical communication method for OFDM optical communication that solve the above-described problems.

本発明における光通信装置によれば、
直交周波数分割多重光信号を送信する光通信装置であって、負の周波数に対応するサブキャリアを総て未使用として行う離散フーリエ逆変換処理の出力の実部に基づく同相ベースバンド信号と、虚部に基づく直交ベースバンド信号を出力する手段と、同相ベースバンド信号及び直交ベースバンド信号の最高周波数より高い周波数の第１の正弦波信号と、第１の正弦波信号と同一周波数で、位相がπ／２だけ遅れた第２の正弦波信号を発生する手段と、同相ベースバンド信号と第１の正弦波信号を加算する第１の加算手段と、直交ベースバンド信号と第２の正弦波信号を加算する第２の加算手段と、光信号を、第１の加算手段の出力信号でキャリア抑圧変調する第１の変調手段と、該光信号を、第２の加算手段の出力信号でキャリア抑圧変調する第２の変調手段と、第１の変調手段の出力光信号と、第２の変調手段の出力光信号を、一方の出力光信号の位相をπ／２だけ遅らせた上で合波する手段とを備えている。 According to the optical communication device of the present invention,
An optical communication device that transmits an orthogonal frequency division multiplexed optical signal, an in-phase baseband signal based on the real part of the output of the inverse discrete Fourier transform processing in which all subcarriers corresponding to negative frequencies are unused, and imaginary Means for outputting a quadrature baseband signal based on the first part, a first sine wave signal having a frequency higher than the highest frequency of the in-phase baseband signal and the quadrature baseband signal, and the same frequency as the first sine wave signal, the phase means for generating a second sine wave signal delayed by π / 2, first addition means for adding the in-phase baseband signal and the first sine wave signal, quadrature baseband signal and second sine wave signal , A first modulation means for carrier suppressing modulation of the optical signal with the output signal of the first adding means, and carrier suppression of the optical signal with the output signal of the second adding means. Modulate Means for combining the second modulation means, the output optical signal of the first modulation means, and the output optical signal of the second modulation means after delaying the phase of one of the output optical signals by π / 2; It has.

本発明の通信装置における他の実施形態によれば、
直交周波数分割多重光信号を送信する光通信装置であって、正の周波数に対応するサブキャリアを総て未使用として行う離散フーリエ逆変換処理の出力の実部に基づく同相ベースバンド信号と、虚部に基づく直交ベースバンド信号を出力する手段と、同相ベースバンド信号及び直交ベースバンド信号の最高周波数より高い周波数の第１の正弦波信号と、第１の正弦波信号と同一周波数で、位相がπ／２だけ進んだ第２の正弦波信号を発生する手段と、同相ベースバンド信号と第１の正弦波信号を加算する第１の加算手段と、直交ベースバンド信号と第２の正弦波信号を加算する第２の加算手段と、光信号を、第１の加算手段の出力信号でキャリア抑圧変調する第１の変調手段と、該光信号を、第２の加算手段の出力信号でキャリア抑圧変調する第２の変調手段と、第１の変調手段の出力光信号と、第２の変調手段の出力光信号を、一方の出力光信号の位相をπ／２だけ遅らせた上で合波する手段とを備えている。 According to another embodiment of the communication device of the present invention,
An optical communication apparatus for transmitting an orthogonal frequency division multiplexed optical signal, an in-phase baseband signal based on a real part of an output of a discrete Fourier inverse transform process in which all subcarriers corresponding to positive frequencies are unused, and an imaginary Means for outputting a quadrature baseband signal based on the first part, a first sine wave signal having a frequency higher than the highest frequency of the in-phase baseband signal and the quadrature baseband signal, and the same frequency as the first sine wave signal, the phase means for generating a second sine wave signal advanced by π / 2, first addition means for adding the in-phase baseband signal and the first sine wave signal, quadrature baseband signal and second sine wave signal , A first modulation means for carrier suppressing modulation of the optical signal with the output signal of the first adding means, and carrier suppression of the optical signal with the output signal of the second adding means. Modulate Means for combining the second modulation means, the output optical signal of the first modulation means, and the output optical signal of the second modulation means after delaying the phase of one of the output optical signals by π / 2; It has.

本発明における光通信システムによれば、
上記光通信装置と、該光通信装置が送信した光信号を直接検波する光通信装置とを含むことを特徴とする。 According to the optical communication system of the present invention,
The optical communication device includes an optical communication device that directly detects an optical signal transmitted by the optical communication device.

本発明における光通信方法によれば、
直交周波数分割多重光通信方法であって、正又は負の周波数に対応するサブキャリアを未使用として行う離散フーリエ逆変換処理の出力の実部及び虚部に基づき第１のベースバンド信号と、第１のベースバンド信号をヒルベルト変換した第２のベースバンド信号を生成するステップと、第１及び第２のベースバンド信号の最高周波数より高い周波数の第２の正弦波信号と、第２の正弦波信号をヒルベルト変換した第１の正弦波信号を発生するステップと、第１のベースバンド信号と第１の正弦波信号を加算して第１の加算信号を生成し、第２のベースバンド信号と第２の正弦波信号を加算して第２の加算信号を生成するステップと、光信号を、第１の加算信号でキャリア抑圧変調して第１の変調光信号を生成し、該光信号を、第２の加算信号でキャリア抑圧変調して第２の変調光信号を生成するステップと、第１の変調光信号と、第２の変調光信号を、一方の変調光信号の位相をπ／２だけ遅らせた上で合波するステップとを備えている。 According to the optical communication method of the present invention,
An orthogonal frequency division multiplexing optical communication method, comprising: a first baseband signal based on a real part and an imaginary part of an output of an inverse discrete Fourier transform process in which a subcarrier corresponding to a positive or negative frequency is unused; Generating a second baseband signal obtained by Hilbert transforming one baseband signal, a second sine wave signal having a frequency higher than the highest frequency of the first and second baseband signals, and a second sine wave Generating a first sine wave signal obtained by converting the signal into a Hilbert transform; adding the first baseband signal and the first sine wave signal to generate a first addition signal; Adding a second sine wave signal to generate a second addition signal; generating a first modulated optical signal by subjecting the optical signal to carrier suppression modulation with the first addition signal; , The second addition signal The step of generating the second modulated optical signal by carrier suppression modulation, the first modulated optical signal, and the second modulated optical signal are delayed after the phase of one modulated optical signal is delayed by π / 2. And a wave step.

離散フーリエ逆変換処理において、データ通信に利用できないポート数を減少させることができる。   In the discrete Fourier inverse transform process, the number of ports that cannot be used for data communication can be reduced.

本発明を実施するための最良の実施形態について、以下では図面を用いて詳細に説明する。   The best mode for carrying out the present invention will be described in detail below with reference to the drawings.

図１は、本発明による光ＯＦＤＭ通信システムにおける、送信側の光通信装置の構成を示す図である。図１によると、光通信装置は、レーザダイオード１と、光変調器２と、発振器３と、ＯＦＤＭベースバンド信号処理部４と、加算器５及び６とを備え、光変調器２は、２つのマッハツェンダ光変調器２１及び２２と、移相器２３を含んでいる。   FIG. 1 is a diagram showing a configuration of an optical communication apparatus on a transmission side in an optical OFDM communication system according to the present invention. According to FIG. 1, the optical communication apparatus includes a laser diode 1, an optical modulator 2, an oscillator 3, an OFDM baseband signal processing unit 4 and adders 5 and 6. Two Mach-Zehnder optical modulators 21 and 22 and a phase shifter 23 are included.

ＯＦＤＭベースバンド信号処理部４は、離散フーリエ逆変換処理を行うＩＦＦＴ回路を含み、ＩＦＦＴ回路が出力するサンプル値の実部をアナログ変換した同相ベースバンド信号７と、同じく虚部をアナログ変換した直交ベースバンド信号８を出力する。なお、以下の説明において、ＩＦＦＴ回路は、ポート番号−Ｎ／２＋１〜Ｎ／２のＮ個のポートを持ち、各ポート番号にサブキャリ間の周波数間隔を乗じたものが、ベースバンドにおける、対応するサブキャリの周波数であるものとする。本実施形態において、負のサブキャリアは未使用とする。つまり、ＩＦＦＴ回路のポート番号−Ｎ／２＋１〜−１には、データ入力をせず、“０”が入力されたものとして離散フーリエ逆変換処理を行う。   The OFDM baseband signal processing unit 4 includes an IFFT circuit that performs inverse discrete Fourier transform processing, and an in-phase baseband signal 7 obtained by analog conversion of the real part of the sample value output from the IFFT circuit, and an orthogonal form obtained by analog conversion of the imaginary part. A baseband signal 8 is output. In the following description, the IFFT circuit has N ports of port numbers -N / 2 + 1 to N / 2, and each port number multiplied by the frequency interval between subcarriers corresponds to the baseband. It is assumed that it is the frequency of the subcarrier. In this embodiment, the negative subcarrier is unused. That is, the inverse Fourier transform processing is performed on the assumption that “0” is input without inputting data to the port numbers −N / 2 + 1 to −1 of the IFFT circuit.

発振器３は、例えば、同相ベースバンド信号７及び直交ベースバンド信号８の最高周波数成分より高い、例えば、ＩＦＦＴ回路のポート番号Ｎ番に対応するナイキスト周波数と同じ周波数の正弦波信号１０及び１１を生成し、加算器５は、同相ベースバンド信号７と正弦波信号１０を加算し、加算器６は、直交ベースバンド信号８と正弦波信号１１を加算する。ここで、発振器３が発生する正弦波信号１０及び１１は同一周波数であり、正弦波信号１１は、正弦波信号１０より位相がπ／２だけ遅れたものとする。   For example, the oscillator 3 generates sine wave signals 10 and 11 having higher frequency components than the highest frequency components of the in-phase baseband signal 7 and the quadrature baseband signal 8, for example, the same frequency as the Nyquist frequency corresponding to the port number N of the IFFT circuit. The adder 5 adds the in-phase baseband signal 7 and the sine wave signal 10, and the adder 6 adds the quadrature baseband signal 8 and the sine wave signal 11. Here, it is assumed that the sine wave signals 10 and 11 generated by the oscillator 3 have the same frequency, and the phase of the sine wave signal 11 is delayed by π / 2 from the sine wave signal 10.

マッハツェンダ光変調器２１は、レーザダイオード１が出力する連続光の振幅又は強度を、同相ベースバンド信号７と正弦波信号１０とを加算した信号により変調し、マッハツェンダ光変調器２２は、レーザダイオード１が出力する連続光の振幅又は強度を、直交ベースバンド信号８と正弦波信号１１とを加算した信号により変調する。ここで、本発明においては、マッハツェンダ光変調器２１及び２２がキャリア抑圧光信号を送信する様に、そのバイアスレベルを調整する。つまり、電気信号の入力が０のときに、レーザダイード１からの光信号が送信されない様にバイアスレベルを調整する。マッハツェンダ光変調器２１及び２２の後段にキャリア成分抑圧のフィルタを挿しても良い。   The Mach-Zehnder optical modulator 21 modulates the amplitude or intensity of the continuous light output from the laser diode 1 with a signal obtained by adding the in-phase baseband signal 7 and the sine wave signal 10. The Mach-Zehnder optical modulator 22 Is modulated by a signal obtained by adding the orthogonal baseband signal 8 and the sine wave signal 11. Here, in the present invention, the bias level is adjusted so that the Mach-Zehnder optical modulators 21 and 22 transmit the carrier-suppressed optical signal. That is, the bias level is adjusted so that the optical signal from the laser diode 1 is not transmitted when the electric signal input is zero. A filter for suppressing the carrier component may be inserted after the Mach-Zehnder optical modulators 21 and 22.

本発明の光変調器２は、更に、マッハツェンダ光変調器２２の出力光信号を、移相器２３において、位相をπ／２だけ遅らせ、マッハツェンダ光変調器２１の出力光信号と合波し、光信号９として送信する。   The optical modulator 2 of the present invention further combines the output optical signal of the Mach-Zehnder optical modulator 22 with the output optical signal of the Mach-Zehnder optical modulator 21 by delaying the phase by π / 2 in the phase shifter 23. Transmit as an optical signal 9.

図３は、本発明の光通信装置が出力する光信号９の概略的なスペクトラムを示す図である。なお、各信号の下に示す数字は、ＩＦＦＴ回路のポート番号に対応している。   FIG. 3 is a diagram showing a schematic spectrum of the optical signal 9 output from the optical communication apparatus of the present invention. The numbers below each signal correspond to the port number of the IFFT circuit.

本実施形態においては、負のサブキャリは未使用、つまり、ＩＦＦＴ回路の負のサブキャリアに対応するポートには総て“０”が入力されたものとするため、直交ベースバンド信号８は、同相ベースバンド信号をヒルベルト変換したものとなる。また、正弦波信号１０は、正弦波信号１１をヒルベルト変換したものである。したがって、移相器２３で位相をπ／２だけ遅らせることにより、ＯＦＤＭ信号成分５１については、負の周波数成分が打ち消され、正弦波信号１０及び１１については、正の周波数成分が打ち消され、負の周波数成分のみが残ることになる。図３の符号５０は、正弦波信号１０及び１１の負の周波数成分に対応する信号成分を示している。なお、図３においては、正弦波信号１０及び１１の周波数を、ＩＦＦＴのナイキスト周波数としている。   In this embodiment, since the negative subcarrier is not used, that is, all “0” s are input to the ports corresponding to the negative subcarriers of the IFFT circuit, the quadrature baseband signal 8 has the same phase. This is a Hilbert transform of the baseband signal. The sine wave signal 10 is a signal obtained by converting the sine wave signal 11 into a Hilbert transform. Therefore, by delaying the phase by π / 2 by the phase shifter 23, the negative frequency component is canceled for the OFDM signal component 51, the positive frequency component is canceled for the sine wave signals 10 and 11, and the negative frequency component is canceled. Only the frequency component of is left. Reference numeral 50 in FIG. 3 indicates a signal component corresponding to the negative frequency component of the sine wave signals 10 and 11. In FIG. 3, the frequencies of the sine wave signals 10 and 11 are the Nyquist frequency of IFFT.

本発明による光通信システムにおいて、受信側の光通信装置は、従来通り、図３に示す光信号９を直接検波する。ここで、図３の符号５０で示す信号成分は、受信側の光通信装置にとってのキャリア成分となり、このキャリア成分５０と、ＯＦＤＭ信号成分５１の間には、ＯＦＤＭ信号成分５１の帯域より大きい空き帯域が存在するため、受信側の光通信装置は、相互変調ノイズによる影響を受けることなく復調処理を行うことができる。   In the optical communication system according to the present invention, the receiving side optical communication apparatus directly detects the optical signal 9 shown in FIG. Here, the signal component indicated by reference numeral 50 in FIG. 3 is a carrier component for the optical communication apparatus on the receiving side, and a space larger than the band of the OFDM signal component 51 is between the carrier component 50 and the OFDM signal component 51. Since there is a band, the optical communication device on the receiving side can perform demodulation processing without being affected by intermodulation noise.

以上、本実施形態においては、従来技術と異なり、ＩＦＦＴ回路の正の周波数に対応するサブキャリアを総て使用することができる。   As described above, in this embodiment, unlike the prior art, all subcarriers corresponding to the positive frequency of the IFFT circuit can be used.

なお、正の周波数に対応するサブキャリアを総て未使用とし、負の周波数に対応するサブキャリアのみを使用する形態であっても良い。この場合、ＯＦＤＭベースバンド信号処理部４が出力する同相ベースバンド信号７は、直交ベースバンド信号８をヒルベルト変換したものとなるため、正弦波信号１１の位相は、正弦波信号１０の位相をπ／２だけ進めたものとする。つまり、正弦波信号１１は、正弦波信号１０をヒルベルト変換したものとする。これにより、ＯＦＤＭ信号成分５１の高周波側にキャリア成分５０が位置し、ＯＦＤＭ信号成分５１とキャリア成分５０間の空き帯域が、ＯＦＤＭ信号成分５１の帯域より大きいスペクトラムを持つ光信号９が生成される。   Note that a configuration may be adopted in which all subcarriers corresponding to positive frequencies are unused and only subcarriers corresponding to negative frequencies are used. In this case, since the in-phase baseband signal 7 output from the OFDM baseband signal processing unit 4 is obtained by performing a Hilbert transform on the quadrature baseband signal 8, the phase of the sine wave signal 11 is equal to the phase of the sine wave signal 10 by π. It is assumed that / 2 is advanced. That is, the sine wave signal 11 is obtained by performing a Hilbert transform on the sine wave signal 10. As a result, an optical signal 9 is generated in which the carrier component 50 is located on the high frequency side of the OFDM signal component 51 and the spectrum between the OFDM signal component 51 and the carrier component 50 is larger than that of the OFDM signal component 51. .

また、上述した実施形態においては、マッハツェンダ光変調器２２の出力光信号の位相を移相器２３によりπ／２だけ遅らせた上で、マッハツェンダ光変調器２１の出力光信号と合波していたが、マッハツェンダ光変調器２１の出力光信号の位相をπ／２だけ遅らせた上で、マッハツェンダ光変調器２１の出力光信号と合波する構成であっても良い。   In the above-described embodiment, the phase of the output optical signal of the Mach-Zehnder optical modulator 22 is delayed by π / 2 by the phase shifter 23 and then combined with the output optical signal of the Mach-Zehnder optical modulator 21. However, the output optical signal of the Mach-Zehnder optical modulator 21 may be combined with the output optical signal of the Mach-Zehnder optical modulator 21 after delaying the phase of the output optical signal by π / 2.

本発明の光ＯＦＤＭ通信システムにおける、送信側の光通信装置の構成を示す図である。It is a figure which shows the structure of the optical communication apparatus of the transmission side in the optical OFDM communication system of this invention. 従来技術による光ＯＦＤＭ通信システムにおける、送信側の光通信装置の構成を示す図である。It is a figure which shows the structure of the optical communication apparatus of the transmission side in the optical OFDM communication system by a prior art. 本発明の光通信装置が出力する光信号スペクトラムの概略を示す図である。It is a figure which shows the outline of the optical signal spectrum which the optical communication apparatus of this invention outputs. 従来技術による光送信信号のスペクトラムの概略を示す図である。It is a figure which shows the outline of the spectrum of the optical transmission signal by a prior art.

符号の説明Explanation of symbols

１ レーザダイオード
２、１２ 光変調器
３ 発振器
４、１４ ＯＦＤＭベースバンド信号処理部
５、６ 加算器
７、１７ 同相ベースバンド信号
８、１８ 直交ベースバンド信号
１０、１１ 正弦波信号
９、１９ 送信光信号
２１、２２、１２１、１２２ マッハツェンダ光変調器
２３、１２３ 移相器
５０、６０ キャリア成分
５１、６１ ＯＦＤＭ信号成分 DESCRIPTION OF SYMBOLS 1 Laser diode 2, 12 Optical modulator 3 Oscillator 4, 14 OFDM baseband signal processing part 5, 6 Adder 7, 17 In-phase baseband signal 8, 18 Quadrature baseband signal 10, 11 Sine wave signal 9, 19 Transmitted light Signal 21, 22, 121, 122 Mach-Zehnder optical modulator 23, 123 Phase shifter 50, 60 Carrier component 51, 61 OFDM signal component

Claims (4)

負の周波数に対応するサブキャリアを総て未使用として行う離散フーリエ逆変換処理の出力の実部に基づく同相ベースバンド信号と、虚部に基づく直交ベースバンド信号を出力する手段と、
同相ベースバンド信号及び直交ベースバンド信号の最高周波数より高い周波数の第１の正弦波信号と、第１の正弦波信号と同一周波数で、位相がπ／２だけ遅れた第２の正弦波信号を発生する手段と、
同相ベースバンド信号と第１の正弦波信号を加算する第１の加算手段と、
直交ベースバンド信号と第２の正弦波信号を加算する第２の加算手段と、
光信号を、第１の加算手段の出力信号でキャリア抑圧変調する第１の変調手段と、
該光信号を、第２の加算手段の出力信号でキャリア抑圧変調する第２の変調手段と、
第１の変調手段の出力光信号と、第２の変調手段の出力光信号を、一方の出力光信号の位相をπ／２だけ遅らせた上で合波する手段と、
を備えている直交周波数分割多重光信号を送信する光通信装置。 Means for outputting an in-phase baseband signal based on the real part of the output of the inverse discrete Fourier transform processing performed by using all subcarriers corresponding to negative frequencies as unused, and an orthogonal baseband signal based on the imaginary part;
A first sine wave signal having a frequency higher than the highest frequency of the in-phase baseband signal and the quadrature baseband signal, and a second sine wave signal having the same frequency as the first sine wave signal and a phase delayed by π / 2. Means to generate;
First addition means for adding the in-phase baseband signal and the first sine wave signal;
Second addition means for adding the orthogonal baseband signal and the second sine wave signal;
First modulation means for carrier-suppressing the optical signal with the output signal of the first addition means;
Second modulation means for carrier-suppressing the optical signal with the output signal of the second addition means;
Means for combining the output optical signal of the first modulation means and the output optical signal of the second modulation means after delaying the phase of one of the output optical signals by π / 2;
An optical communication apparatus that transmits an orthogonal frequency division multiplexed optical signal. 正の周波数に対応するサブキャリアを総て未使用として行う離散フーリエ逆変換処理の出力の実部に基づく同相ベースバンド信号と、虚部に基づく直交ベースバンド信号を出力する手段と、
同相ベースバンド信号及び直交ベースバンド信号の最高周波数より高い周波数の第１の正弦波信号と、第１の正弦波信号と同一周波数で、位相がπ／２だけ進んだ第２の正弦波信号を発生する手段と、
同相ベースバンド信号と第１の正弦波信号を加算する第１の加算手段と、
直交ベースバンド信号と第２の正弦波信号を加算する第２の加算手段と、
光信号を、第１の加算手段の出力信号でキャリア抑圧変調する第１の変調手段と、
該光信号を、第２の加算手段の出力信号でキャリア抑圧変調する第２の変調手段と、
第１の変調手段の出力光信号と、第２の変調手段の出力光信号を、一方の出力光信号の位相をπ／２だけ遅らせた上で合波する手段と、
を備えている直交周波数分割多重光信号を送信する光通信装置。 Means for outputting an in-phase baseband signal based on the real part of the output of the inverse discrete Fourier transform processing in which all subcarriers corresponding to positive frequencies are unused, and an orthogonal baseband signal based on the imaginary part;
A first sine wave signal having a frequency higher than the highest frequency of the in-phase baseband signal and the quadrature baseband signal, and a second sine wave signal having the same frequency as the first sine wave signal and a phase advanced by π / 2. Means to generate;
First addition means for adding the in-phase baseband signal and the first sine wave signal;
Second addition means for adding the orthogonal baseband signal and the second sine wave signal;
First modulation means for carrier-suppressing the optical signal with the output signal of the first addition means;
Second modulation means for carrier-suppressing the optical signal with the output signal of the second addition means;
Means for combining the output optical signal of the first modulation means and the output optical signal of the second modulation means after delaying the phase of one of the output optical signals by π / 2;
An optical communication apparatus that transmits an orthogonal frequency division multiplexed optical signal. 請求項１又は２に記載の光通信装置と、該光通信装置が送信した光信号を直接検波する光通信装置とを含む光通信システム。   An optical communication system comprising the optical communication device according to claim 1 and an optical communication device that directly detects an optical signal transmitted by the optical communication device. 直交周波数分割多重光通信方法であって、
正又は負の周波数に対応するサブキャリアを未使用として行う離散フーリエ逆変換処理の出力の実部及び虚部に基づき第１のベースバンド信号と、第１のベースバンド信号をヒルベルト変換した第２のベースバンド信号を生成するステップと、
第１及び第２のベースバンド信号の最高周波数より高い周波数の第２の正弦波信号と、第２の正弦波信号をヒルベルト変換した第１の正弦波信号を発生するステップと、
第１のベースバンド信号と第１の正弦波信号を加算して第１の加算信号を生成し、第２のベースバンド信号と第２の正弦波信号を加算して第２の加算信号を生成するステップと、
光信号を、第１の加算信号でキャリア抑圧変調して第１の変調光信号を生成し、該光信号を、第２の加算信号でキャリア抑圧変調して第２の変調光信号を生成するステップと、
第１の変調光信号と、第２の変調光信号を、一方の変調光信号の位相をπ／２だけ遅らせた上で合波するステップと、
を備えている光通信方法。 An orthogonal frequency division multiplexing optical communication method comprising:
A first baseband signal based on the real part and the imaginary part of the output of the inverse discrete Fourier transform process in which the subcarrier corresponding to the positive or negative frequency is unused, and the second obtained by Hilbert transform of the first baseband signal Generating a baseband signal of
Generating a second sine wave signal having a frequency higher than the highest frequency of the first and second baseband signals, and a first sine wave signal obtained by Hilbert transforming the second sine wave signal;
The first baseband signal and the first sine wave signal are added to generate a first addition signal, and the second baseband signal and the second sine wave signal are added to generate a second addition signal. And steps to
The optical signal is subjected to carrier suppression modulation with the first addition signal to generate a first modulated optical signal, and the optical signal is subjected to carrier suppression modulation with the second addition signal to generate a second modulated optical signal. Steps,
Combining the first modulated optical signal and the second modulated optical signal after delaying the phase of one modulated optical signal by π / 2;
An optical communication method comprising:
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