JPH08125605A - Optical signal transmitter and optical communication system using it - Google Patents
Optical signal transmitter and optical communication system using itInfo
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- JPH08125605A JPH08125605A JP6260712A JP26071294A JPH08125605A JP H08125605 A JPH08125605 A JP H08125605A JP 6260712 A JP6260712 A JP 6260712A JP 26071294 A JP26071294 A JP 26071294A JP H08125605 A JPH08125605 A JP H08125605A
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、光通信等に用いる光信
号送信装置とそれを用いた光通信システムに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal transmitter used for optical communication and the like and an optical communication system using the same.
【０００２】[0002]
【従来の技術】従来、光通信システムにおいて簡便かつ
高速伝送に適したものとして図４に示すような光強度変
調、直接検波方式の光通信システムが用いられている。
この光強度変調、直接検波方式の光通信システムでは、
光ファイバ伝送路１０８へ送信される信号光が、光源１
０１からの連続光を光強度変調器１０２によって２値信
号源１０３の出力に対応させて光強度変調された強度変
調光信号として生成される。そして、この強度変調光信
号は、光ファイバ伝送路１０８を介し受光器１１１によ
って受信され、電気信号に変換される。ところで、伝送
路１０８に用いられる光ファイバでは、入射光電力また
は光ファイバ長の増大にともない、その非線形性が顕著
になることが知られている。特に、光増幅器を用いた中
継伝送システムにおいては、光信号が各中継器で増幅中
継されるため、この非線形性の影響を受けやすくなる
（例えば、Journal of Lightwave Technology, vol.LT-
10, No.8, Aug, pp1117-1126参照）。2. Description of the Related Art Conventionally, an optical communication system of the optical intensity modulation and direct detection type as shown in FIG. 4 has been used as an optical communication system which is simple and suitable for high-speed transmission.
In this optical intensity modulation, direct detection type optical communication system,
The signal light transmitted to the optical fiber transmission line 108 is the light source 1
The continuous light from 01 is generated by the light intensity modulator 102 as an intensity-modulated optical signal whose light intensity is modulated corresponding to the output of the binary signal source 103. Then, the intensity-modulated optical signal is received by the light receiver 111 via the optical fiber transmission line 108 and converted into an electric signal. By the way, it is known that the non-linearity of the optical fiber used for the transmission line 108 becomes remarkable as the incident optical power or the optical fiber length increases. In particular, in a relay transmission system using an optical amplifier, an optical signal is amplified and relayed by each relay, so that it is easily affected by this nonlinearity (for example, Journal of Lightwave Technology, vol.LT-
10, No.8, Aug, pp1117-1126).
【０００３】光ファイバ非線形性の影響の一つに、ファ
イバ屈折率の光強度依存性に起因する自己位相変調効果
がある。この自己位相変調効果は、図５に示すように、
光ファイバ内を伝搬する強度変調光信号の信号光強度変
化（図５(ａ)）に応じてキャリア周波数偏移あるいは位
相偏移を引き起こし（図５(ｂ)）、その強度変調光信号
のスペクトルを伝送帯域以上に拡げる作用をする。広帯
域に拡がった光信号は、帯域が拡がる前と比べ、ファイ
バ分散の影響をより強く受けるため、結果として、受信
信号波形の劣化を生じさせる。このように自己位相変調
効果は、強度変調、直接検波方式において主要な劣化要
因となる。このため、従来の強度変調、直接検波方式の
光通信システムでは、ファイバの分散値が零付近になる
信号光波長以外の波長を有する光信号を使用することが
できなかった。ただし、ファイバの分散値が零付近にな
る零分散波長付近の光信号であっても自己位相変調効果
と高次の分散による光信号波の劣化は、問題であった。One of the effects of optical fiber nonlinearity is the self-phase modulation effect due to the light intensity dependence of the fiber refractive index. This self-phase modulation effect is as shown in FIG.
A carrier frequency shift or a phase shift is caused according to a change in signal light intensity of the intensity-modulated optical signal propagating in the optical fiber (Fig. 5 (a)) (Fig. 5 (b)), and the spectrum of the intensity-modulated optical signal is generated. Acts to extend the transmission band beyond the transmission band. The optical signal spread over a wide band is more strongly affected by fiber dispersion than before the band is spread, resulting in deterioration of the received signal waveform. In this way, the self-phase modulation effect becomes a major deterioration factor in the intensity modulation and direct detection method. Therefore, in the conventional intensity modulation and direct detection type optical communication system, it is impossible to use an optical signal having a wavelength other than the signal light wavelength at which the dispersion value of the fiber is near zero. However, the degradation of the optical signal wave due to the self-phase modulation effect and high-order dispersion was a problem even for an optical signal near the zero-dispersion wavelength where the dispersion value of the fiber is near zero.
【０００４】[0004]
【発明が解決しようとする課題】本発明の目的は、上記
自己位相変調効果による光信号波の劣化を低減する、簡
単な構成の光通信システムを提供することにある。SUMMARY OF THE INVENTION An object of the present invention is to provide an optical communication system having a simple structure, which reduces deterioration of an optical signal wave due to the self-phase modulation effect.
【０００５】[0005]
【課題を解決するための手段】請求項１記載の発明は、
２値信号データに対応して強度変調された第１の信号光
を生成する第１の光変調手段と、前記２値信号データを
反転して反転２値信号を出力する反転手段と、前記第１
の信号光の波長と異なる波長の光信号であって、前記反
転２値信号に対応して強度変調された光信号である第２
の信号光を生成する第２の光変調手段と、前記第１の信
号光及び第２の信号光を合波して該合波信号光を光ファ
イバ伝送路に送出する光合波手段を具備することを特徴
とする。According to the first aspect of the present invention,
First light modulating means for generating a first signal light intensity-modulated corresponding to binary signal data; inverting means for inverting the binary signal data and outputting an inverted binary signal; 1
Second optical signal having a wavelength different from the wavelength of the signal light, the optical signal intensity-modulated corresponding to the inverted binary signal.
Second optical modulation means for generating the signal light and the optical multiplexing means for multiplexing the first signal light and the second signal light and sending the combined signal light to the optical fiber transmission line. It is characterized by
【０００６】また、請求項２記載の発明は、請求項１記
載の光信号送信装置と、該光信号送信装置から送出され
た前記合波信号光を伝送する光ファイバ伝送路と、該光
ファイバ伝送路を介して前記合波信号光を受け、前記合
波信号光から前記第１の信号光を分離して検出する分離
手段を有する光信号受信装置を具備することを特徴とす
る。According to a second aspect of the invention, there is provided the optical signal transmitting apparatus according to the first aspect, an optical fiber transmission line for transmitting the multiplexed signal light transmitted from the optical signal transmitting apparatus, and the optical fiber. The optical signal receiving device is provided with a separating unit that receives the combined signal light via a transmission line and separates and detects the first signal light from the combined signal light.
【０００７】また、請求項３記載の発明は、請求項１記
載の光信号送信装置において、前記第１の信号光と前記
第２の信号光を、該両者の間の偏光状態を一定に保って
合波することを特徴とする。According to a third aspect of the present invention, in the optical signal transmitting apparatus according to the first aspect, the polarization state between the first signal light and the second signal light is kept constant. The feature is that they are multiplexed together.
【０００８】また、請求項４記載の発明は、請求項１記
載の光信号送信装置において、前記第１の信号光の波長
と前記第２の信号光の波長を、前記光ファイバ伝送路の
零分散波長に対して対称に配置することを特徴とする。According to a fourth aspect of the present invention, in the optical signal transmitter according to the first aspect, the wavelength of the first signal light and the wavelength of the second signal light are set to zero in the optical fiber transmission line. The feature is that they are arranged symmetrically with respect to the dispersion wavelength.
【０００９】また、請求項５記載の発明は、請求項２記
載の光通信システムにおいて、前記光信号受信装置は、
前記光ファイバ伝送路を介して受けた前記合波信号光か
ら分離された前記第１の信号光に対する前記光ファイバ
伝送路の波長分散の影響を補償する補償手段を具備する
ことを特徴とする。According to a fifth aspect of the present invention, in the optical communication system according to the second aspect, the optical signal receiving device is
Compensation means for compensating the influence of chromatic dispersion of the optical fiber transmission line on the first signal light separated from the multiplexed signal light received via the optical fiber transmission line is provided.
【００１０】[0010]
【作用】光信号送信装置は、２値信号データに対応して
強度変調された第１の信号光と同時に、該２値信号デー
タの反転信号に対応して強度変調された第２の信号光を
光ファイバ伝送路に送信し、第１の信号光の強度変化に
よるファイバの屈折率変化（自己位相変調効果）を、第
２の信号光の強度変化が第１の信号光にもたらす周波数
偏移で相殺する。したがって、光ファイバ伝送路を伝搬
する第１の信号光の波形劣化を解消することができる。
一方、光信号受信装置は、分離手段を用い、合波信号光
から第１の信号光のみを分離して検出する。The optical signal transmitting apparatus is configured such that, at the same time as the first signal light intensity-modulated corresponding to the binary signal data, the second signal light intensity-modulated corresponding to the inversion signal of the binary signal data. Is transmitted to the optical fiber transmission line, and a change in the refractive index of the fiber (self-phase modulation effect) due to a change in the intensity of the first signal light causes a frequency shift caused by the change in the intensity of the second signal light to the first signal light. To offset. Therefore, the waveform deterioration of the first signal light propagating through the optical fiber transmission line can be eliminated.
On the other hand, the optical signal receiving device uses the separating means to separate and detect only the first signal light from the multiplexed signal light.
【００１１】また、第１の信号光と第２の信号光の間の
偏光状態を一定に保って合波することによって、自己位
相変調効果に起因する位相偏移を相互位相変調効果に起
因する位相偏移で一定の条件で相殺することができるの
で、さらに信号光の波形劣化を低減することができる。Further, the polarization state between the first signal light and the second signal light is kept constant and multiplexed, so that the phase shift caused by the self-phase modulation effect is caused by the mutual phase modulation effect. Since the phase shift can be canceled under a certain condition, the waveform deterioration of the signal light can be further reduced.
【００１２】また、第１の信号光の波長と第２の信号光
の波長を、光ファイバ伝送路の零分散波長に対して対称
に配置することによって、両者の群遅延を等しく保つこ
とができる。Further, by arranging the wavelength of the first signal light and the wavelength of the second signal light symmetrically with respect to the zero dispersion wavelength of the optical fiber transmission line, both group delays can be kept equal. .
【００１３】また、補償手段によって、光ファイバ伝送
路の波長分散を補償することにより、さらに波形劣化を
低減することができる。Further, by compensating the chromatic dispersion of the optical fiber transmission line by the compensating means, it is possible to further reduce the waveform deterioration.
【００１４】[0014]
【実施例】以下、図面を参照して本発明による一実施例
について説明する。図１は、本発明による光通信システ
ムの一実施例を示すブロック図である。この図に示す光
通信システムは、送信器２１と、送信器２１から送信さ
れた光信号を伝送する光ファイバ伝送路８と、光ファイ
バ伝送路８を介して光信号を受信する受信器２２から構
成されている。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an optical communication system according to the present invention. The optical communication system shown in this figure includes a transmitter 21, an optical fiber transmission line 8 for transmitting the optical signal transmitted from the transmitter 21, and a receiver 22 for receiving the optical signal via the optical fiber transmission line 8. It is configured.
【００１５】この図に示す送信器２１は、波長λ１の連
続光信号を出力する光源１と、２値信号を出力する信号
源３と、光源１から出力された連続光を信号源３から出
力された２値信号に対応して強度変調する光強度変調器
２と、波長λ１と異なる波長λ２の連続光信号を出力す
る光源４と、信号源３の出力を反転して２値信号を出力
する反転回路６と、光源４から出力された連続光を反転
回路６から出力された２値信号に対応して強度変調する
光強度変調器５と、光強度変調器２および５から出力さ
れた２つの光信号を合波して、光ファイバ伝送路８へ送
出する光合波器７から構成されている。A transmitter 21 shown in this figure outputs a continuous wave light output from a light source 1 that outputs a continuous light signal of wavelength λ1, a signal source 3 that outputs a binary signal, and a continuous light output from a light source 1. Intensity modulator 2 that performs intensity modulation corresponding to the generated binary signal, light source 4 that outputs a continuous optical signal of wavelength λ2 different from wavelength λ1, and output of signal source 3 is inverted to output a binary signal. Output from the light intensity modulator 2 and 5; and the light intensity modulator 5 that intensity-modulates the continuous light output from the light source 4 in accordance with the binary signal output from the inversion circuit 6. The optical multiplexer 7 combines two optical signals and sends them to the optical fiber transmission line 8.
【００１６】このような構成によって送信器２１は、強
度変調器２によって光源１から出力された波長λ１の連
続光を２値信号源３の出力に対応したキャリア波長λ１
の強度変調光信号（以下、信号光と呼ぶ。）に変換する
とともに、光強度変調器５を用いて光源４から出力され
た波長λ２の連続光を反転回路６の出力信号に応じて光
強度変調することによって、キャリア波長λ２の強度変
調光信号（以下、反転信号光と呼ぶ。）を生成し、光合
波器７で光ファイバ伝送路８に結合する。With such a configuration, the transmitter 21 transmits the continuous light of the wavelength λ1 output from the light source 1 by the intensity modulator 2 to the carrier wavelength λ1 corresponding to the output of the binary signal source 3.
Of the intensity modulated optical signal (hereinafter referred to as signal light), and the continuous light of the wavelength λ2 output from the light source 4 using the optical intensity modulator 5 is converted into the optical intensity according to the output signal of the inverting circuit 6. By modulating, an intensity-modulated optical signal having a carrier wavelength λ2 (hereinafter referred to as inverted signal light) is generated and coupled to the optical fiber transmission line 8 by the optical multiplexer 7.
【００１７】一方、受信器２２は、波長λ１に近い帯域
の光フィルタ透過特性を持つ光フイルタ９（図３(ｂ)参
照。）と、光ファイバ伝送路８の光ファイバの分散値と
逆の分散値をもつ分散補償用光ファイバ１０と、光信号
を電気信号に変換する受光器１１を直列に接続すること
によって構成されている。On the other hand, the receiver 22 has an optical filter 9 (see FIG. 3B) having an optical filter transmission characteristic in a band close to the wavelength λ1 and a dispersion value of the optical fiber of the optical fiber transmission line 8 which is opposite to the dispersion value. It is configured by connecting in series a dispersion compensating optical fiber 10 having a dispersion value and a photodetector 11 for converting an optical signal into an electric signal.
【００１８】このように構成された受信器２２におい
て、光ファイバ伝送路８を伝搬してきた信号光および反
転信号光は、光フィルタ９に導かれ、波長λ１の信号光
が波長λ２の反転信号光から分離され、波長λ１の信号
光のみが検出される。次いで、この波長λ１の信号光が
分散補償用光ファイバ１０へ入力され、分散補償用光フ
ァイバ１０において、信号光に対する光ファイバ伝送路
８の波長分散の影響が相殺される。そして、受光器１１
において、この第１の信号光が電気信号に変換される。In the receiver 22 configured as described above, the signal light and the inverted signal light propagating through the optical fiber transmission line 8 are guided to the optical filter 9, and the signal light of the wavelength λ1 is the inverted signal light of the wavelength λ2. And the signal light of wavelength λ1 is detected. Next, the signal light of the wavelength λ1 is input to the dispersion compensating optical fiber 10, and the influence of the chromatic dispersion of the optical fiber transmission line 8 on the signal light is canceled in the dispersion compensating optical fiber 10. And the light receiver 11
At, the first signal light is converted into an electric signal.
【００１９】次に、上述した送信器２１、光ファイバ伝
送路８および受信器２２からなる光通信システムにおけ
る、強度変調光信号の自己位相変調効果について説明す
る。まず、自己位相変調効果による周波数偏移に関して
説明する。上記光通信システムにおいて、波長λ１の信
号光の光強度が図２(ａ)に実線で示すように変化したと
する。この波長λ１の信号光自身の強度変化は、自己位
相変調効果によって、図２(ｂ)に実線で示すような周波
数偏移を起こす。一方、波長λ１の信号光を反転した図
２(ａ)に破線で示す波長λ２の反転信号光は、相互位相
変調効果によって、図２(ｂ)に破線で示すような周波数
偏移を起こす。この反転信号光の強度変化と相互位相変
調効果によって発生した周波数偏移は、信号光の強度変
化と自己位相変調効果によって生じた周波数偏移を相殺
するように変化する。Next, the self-phase modulation effect of the intensity-modulated optical signal in the optical communication system including the transmitter 21, the optical fiber transmission line 8 and the receiver 22 described above will be described. First, the frequency shift due to the self-phase modulation effect will be described. In the above optical communication system, it is assumed that the light intensity of the signal light of wavelength λ1 changes as shown by the solid line in FIG. The intensity change of the signal light of the wavelength λ1 itself causes a frequency shift as shown by the solid line in FIG. 2B due to the self-phase modulation effect. On the other hand, the inverted signal light of the wavelength λ2, which is the signal light of the wavelength λ1 inverted and is shown by the broken line in FIG. 2A, causes the frequency shift as shown by the broken line in FIG. The frequency shift generated by the intensity change of the inverted signal light and the cross phase modulation effect changes so as to cancel the frequency shift generated by the intensity change of the signal light and the self phase modulation effect.
【００２０】したがって、結果として光ファイバ伝送路
８内を伝搬する信号光は、自己位相変調効果の影響を受
けなくなる。即ち、光ファイバ伝送路８内を伝搬する信
号光に過剰なスペクトル拡がりが生じなくなり、自己位
相変調効果による信号波形劣化が低減される（図２
(ｂ)）。Therefore, as a result, the signal light propagating in the optical fiber transmission line 8 is not affected by the self-phase modulation effect. That is, excessive spread of the spectrum does not occur in the signal light propagating in the optical fiber transmission line 8, and the signal waveform deterioration due to the self-phase modulation effect is reduced (FIG. 2).
(b)).
【００２１】次に、光合波器７へ入力される波長λ１の
信号光の電界をＥ１、波長λ２の反転信号光の電界をＥ
２として、自己位相変調効果による位相偏移について説
明する。信号光電界Ｅ１による自己位相変調効果および
反転信号光電界Ｅ２による相互位相変調効果に起因する
信号光の位相変化φは、次式によって表される。 φ＝ｋ2Ｌ（｜Ｅ1｜2 ＋ａ｜Ｅ2｜2）……………（１） ただし、Ｌはファイバ長、ｋ2は非線形定数を表してい
る。また、ａは、信号光電界Ｅ１と反転信号光電界Ｅ２
間の偏光状態に依存する係数で、両者間の偏光角をθと
すると次式によって表され、２／３から２の間の値をと
る。 ａ＝２（１＋sin2θ）／（２＋cos2θ）…………（２）Next, the electric field of the signal light of wavelength λ1 input to the optical multiplexer 7 is E1, and the electric field of the inverted signal light of wavelength λ2 is E.
2, the phase shift due to the self-phase modulation effect will be described. The phase change φ of the signal light caused by the self-phase modulation effect by the signal light electric field E1 and the cross phase modulation effect by the inversion signal light electric field E2 is represented by the following equation. φ = k 2 L (| E 1 | 2 + a | E 2 | 2 ) ... (1) where L represents the fiber length and k 2 represents the nonlinear constant. Further, a is the signal light electric field E1 and the inverted signal light electric field E2.
It is a coefficient depending on the polarization state between, and is represented by the following equation when the polarization angle between them is θ, and takes a value between 2/3 and 2. a = 2 (1 + sin 2 θ) / (2 + cos 2 θ) ………… (2)
【００２２】（２）式から、sin2θ＝１／３すなわち偏
光角θが約±３５度のときに、ａ＝１となる。したがっ
て、信号光電界Ｅ１および反転信号光電界Ｅ２を、両者
の偏光角が３５度になるような一定の条件で、光合波器
７において合成することによって、信号光電界Ｅ１の自
己位相変調効果による位相偏移を、反転信号光電界Ｅ２
による相互位相変調効果による位相偏移によって打ち消
すことができる。From the equation (2), when sin 2 θ = 1/3, that is, when the polarization angle θ is about ± 35 degrees, a = 1. Therefore, by combining the signal light electric field E1 and the inverted signal light electric field E2 in the optical multiplexer 7 under a constant condition such that the polarization angles of both are 35 degrees, the self-phase modulation effect of the signal light electric field E1 is produced. The phase shift is converted into the inverted signal light electric field E2.
It can be canceled by the phase shift due to the mutual phase modulation effect.
【００２３】なお、信号光の波長λ１および反転信号光
の波長λ２を、図３（ａ）に示すように、光ファイバ伝
送路８の零分散波長に対して対称に配置した場合、両者
の群遅延を等しくすることが可能となり、光ファイバ伝
送路８を伝搬中の両信号間の関係を一定に保つことがで
きる。When the wavelength λ1 of the signal light and the wavelength λ2 of the inverted signal light are symmetrically arranged with respect to the zero dispersion wavelength of the optical fiber transmission line 8 as shown in FIG. The delays can be made equal, and the relationship between both signals propagating through the optical fiber transmission line 8 can be kept constant.
【００２４】[0024]
【発明の効果】以上説明したように、請求項１記載の発
明によれば、２値信号データに対応して強度変調された
第１の信号光を生成する第１の光変調手段と、その２値
信号データを反転して反転２値信号を出力する反転手段
と、第１の信号光の波長と異なる波長の光信号であっ
て、反転２値信号に対応して強度変調された光信号であ
る第２の信号光を生成する第２の光変調手段と、第１の
信号光及び第２の信号光を合波して該合波信号光を光フ
ァイバ伝送路に送出する光合波手段を設けたので、光フ
ァイバ伝送路を伝送する第１の信号光の自己位相変調効
果を第２の信号光の相互位相変調効果によって相殺する
ことができる。As described above, according to the first aspect of the present invention, the first light modulating means for generating the first signal light intensity-modulated corresponding to the binary signal data, and the first light modulating means are provided. Inversion means for inverting binary signal data and outputting an inverted binary signal, and an optical signal having a wavelength different from the wavelength of the first signal light, the optical signal being intensity-modulated corresponding to the inverted binary signal. Second optical modulating means for generating the second signal light, and optical combining means for multiplexing the first signal light and the second signal light and sending the combined signal light to the optical fiber transmission line. Since the above is provided, the self-phase modulation effect of the first signal light transmitted through the optical fiber transmission line can be canceled by the mutual phase modulation effect of the second signal light.
【００２５】また、第１の信号光と第２の信号光の波長
が異なるため、合波信号光から第１の信号光を簡単に分
離することができる。この結果、従来に比べ信号波形劣
化を低減することができる光通信のシステムを容易に構
築することができる。また、請求項２記載の発明によれ
ば、請求項１記載の発明による光信号装置を用いた光通
信システムを構築することができる。これらによって、
信号光波長に対するファイバ分散値を必ずしも零付近に
する必要がなくなる。また、零分散波長付近における高
次分散と自己位相変調効果による波形劣化の低減に対し
ても有効である。したがって、特に光増幅中継システム
等において、高性能化と同時にファイバ分散値のばらつ
きに対する要求条件を大幅に緩和することが可能とな
り、低コスト化も図ることが可能であるという大きな効
果を奏する。Since the first signal light and the second signal light have different wavelengths, it is possible to easily separate the first signal light from the combined signal light. As a result, it is possible to easily construct an optical communication system capable of reducing signal waveform deterioration as compared with the related art. Further, according to the invention of claim 2, it is possible to construct an optical communication system using the optical signal device according to the invention of claim 1. By these,
The fiber dispersion value for the signal light wavelength does not necessarily have to be near zero. It is also effective for reducing higher-order dispersion near the zero-dispersion wavelength and waveform deterioration due to the self-phase modulation effect. Therefore, particularly in an optical amplification repeater system and the like, it is possible to significantly reduce the requirements for the dispersion of the fiber dispersion value at the same time as the performance is improved, and it is possible to achieve the cost reduction.
【００２６】また、請求項３記載の発明によれば、第１
の信号光と第２の信号光の間の偏光状態を一定に保って
合波するので、自己位相変調効果に起因する位相偏移を
相互位相変調効果に起因する位相偏移によって一定の条
件で相殺することができ、波形劣化を低減することがで
きる。According to the invention described in claim 3, the first
Since the polarization state between the signal light and the second signal light is kept constant, the phase shift caused by the self-phase modulation effect is caused by the phase shift caused by the mutual phase modulation effect under constant conditions. They can be canceled out, and waveform deterioration can be reduced.
【００２７】また、請求項４記載の発明によれば、第１
の信号光の波長と第２の信号光の波長を、光ファイバ伝
送路の零分散波長に対して対称に配置するので、両者の
群遅延を等しく保つことができ、光ファイバ伝送路を伝
搬中の両光信号間の関係が一定に保たれるので、さらに
波形劣化の低減を図ることができる。According to the invention described in claim 4, the first
Since the wavelength of the signal light and the wavelength of the second signal light are symmetrically arranged with respect to the zero-dispersion wavelength of the optical fiber transmission line, the group delays of the both can be kept equal, and the signal is propagated through the optical fiber transmission line. Since the relationship between the two optical signals is kept constant, it is possible to further reduce the waveform deterioration.
【００２８】また、請求項５記載の発明によれば、光信
号受信装置において、第１の信号光を分離した後、光フ
ァイバ伝送路の波長分散を補償する補償手段を具備する
ので、光ファイバ伝送路の波長分散を、補償手段によっ
て相殺し、波長分散による波形劣化を低減することがで
きる。According to the invention described in claim 5, the optical signal receiving device is provided with a compensating means for compensating the chromatic dispersion of the optical fiber transmission line after separating the first signal light. The wavelength dispersion of the transmission line can be canceled by the compensating means, and the waveform deterioration due to the wavelength dispersion can be reduced.
【図１】本発明に係る光通信システムの一実施例を示し
たブロック図である。FIG. 1 is a block diagram showing an embodiment of an optical communication system according to the present invention.
【図２】（ａ）横軸に時間、縦軸に光強度をとり、信号
光強度変化および反転信号光強度変化を表した波形図で
ある。 （ｂ）横軸に図２（ａ）と共通の時間、縦軸に周波数偏
移をとり、信号光強度変化と自己位相変調効果による周
波数偏移および反転信号光強度変化と相互位相変調効果
による周波数偏移を表した波形図である。FIG. 2 (a) is a waveform diagram showing a change in signal light intensity and a change in inverted signal light intensity, with the horizontal axis representing time and the vertical axis representing light intensity. (B) The horizontal axis represents time common to FIG. 2 (a), and the vertical axis represents frequency shift. Frequency shift due to signal light intensity change and self-phase modulation effect and due to inversion signal light intensity change and cross phase modulation effect. It is a wave form diagram showing a frequency shift.
【図３】横軸に光信号の波長、縦軸にパワー密度をと
り、（ａ）信号光および反転信号光の波長配置と光ファ
イバの群遅延特性、（ｂ）光フィルタ９の透過帯域特性
を示す特性図である。FIG. 3 shows the wavelength of the optical signal on the horizontal axis and the power density on the vertical axis, where (a) the wavelength arrangement of the signal light and inverted signal light and the group delay characteristics of the optical fiber, and (b) the transmission band characteristic of the optical filter 9. FIG.
【図４】従来の強度変調、直接検波方式による光通信シ
ステムの構成を示すブロック図。FIG. 4 is a block diagram showing the configuration of a conventional optical communication system using intensity modulation and direct detection.
【図５】（ａ）横軸に時間、縦軸に光強度をとり、信号
光強度変化を表した波形図である。 （ｂ）横軸に図５（ａ）と共通の時間、縦軸に周波数偏
移量をとり、図５（ａ）に示す信号光強度変化の自己位
相変調効果による周波数偏移を表した波形図である。FIG. 5A is a waveform diagram showing a change in signal light intensity, where the horizontal axis represents time and the vertical axis represents light intensity. (B) Waveform showing the frequency shift due to the self-phase modulation effect of the signal light intensity change shown in FIG. 5A, where the horizontal axis shows the time common to FIG. 5A and the vertical axis shows the frequency shift amount. It is a figure.
２、５ 光強度変調器 ３ 信号源 ６ 反転回路 ７ 光合波器 ８ 光ファイバ伝送路 ９ 光フイルタ １０ 分散補償用光ファイバ ２１ 送信器 ２２ 受信器 2, 5 Optical intensity modulator 3 Signal source 6 Inversion circuit 7 Optical multiplexer 8 Optical fiber transmission line 9 Optical filter 10 Dispersion compensation optical fiber 21 Transmitter 22 Receiver
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｈ０４Ｂ 10/26 10/14 10/04 10/06 ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification code Internal reference number FI Technical indication H04B 10/26 10/14 10/04 10/06
Claims (5)
た第１の信号光を生成する第１の光変調手段と、 前記２値信号データを反転して反転２値信号を出力する
反転手段と、 前記第１の信号光の波長と異なる波長の光信号であっ
て、前記反転２値信号に対応して強度変調された光信号
である第２の信号光を生成する第２の光変調手段と、 前記第１の信号光及び第２の信号光を合波して該合波信
号光を光ファイバ伝送路に送出する光合波手段を具備す
ることを特徴とする光信号送信装置。1. A first optical modulator for generating a first signal light intensity-modulated corresponding to binary signal data, and an inversion device for inverting the binary signal data and outputting an inverted binary signal. Means for generating a second signal light, which is an optical signal having a wavelength different from the wavelength of the first signal light, the optical signal being an intensity-modulated optical signal corresponding to the inverted binary signal. An optical signal transmitting apparatus comprising: a modulating unit; and an optical combining unit that combines the first signal light and the second signal light and sends the combined signal light to an optical fiber transmission line.
する光ファイバ伝送路と、 該光ファイバ伝送路を介して前記合波信号光を受け、前
記合波信号光から前記第１の信号光を分離して検出する
分離手段を有する光信号受信装置を具備することを特徴
とする光通信システム。2. The optical signal transmitting device according to claim 1, an optical fiber transmission line for transmitting the multiplexed signal light sent from the optical signal transmitting device, and the optical coupling device via the optical fiber transmission line. An optical communication system comprising: an optical signal receiving device having a separating unit that receives signal light and separates and detects the first signal light from the multiplexed signal light.
を、該両者の間の偏光状態を一定に保って合波すること
を特徴とする請求項１記載の光信号送信装置。3. The optical signal transmitting apparatus according to claim 1, wherein the first signal light and the second signal light are multiplexed while maintaining a constant polarization state between them.
号光の波長を、前記光ファイバ伝送路の零分散波長に対
して対称に配置することを特徴とする請求項１記載の光
信号送信装置。4. The wavelength of the first signal light and the wavelength of the second signal light are symmetrically arranged with respect to the zero-dispersion wavelength of the optical fiber transmission line. Optical signal transmitter.
伝送路を介して受けた前記合波信号光から分離された前
記第１の信号光に対する前記光ファイバ伝送路の波長分
散の影響を補償する補償手段を具備することを特徴とす
る請求項２記載の光通信システム。5. The optical signal receiving device compensates for the influence of chromatic dispersion of the optical fiber transmission line on the first signal light separated from the multiplexed signal light received via the optical fiber transmission line. The optical communication system according to claim 2, further comprising:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6260712A JPH08125605A (en) | 1994-10-25 | 1994-10-25 | Optical signal transmitter and optical communication system using it |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6260712A JPH08125605A (en) | 1994-10-25 | 1994-10-25 | Optical signal transmitter and optical communication system using it |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH08125605A true JPH08125605A (en) | 1996-05-17 |
Family
ID=17351716
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6260712A Pending JPH08125605A (en) | 1994-10-25 | 1994-10-25 | Optical signal transmitter and optical communication system using it |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH08125605A (en) |
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-
1994
- 1994-10-25 JP JP6260712A patent/JPH08125605A/en active Pending
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| WO2009013795A1 (en) * | 2007-07-20 | 2009-01-29 | Fujitsu Limited | Optical transmission device, wavelength multiplexing optical communication system, and optical transmission method |
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| WO2015145984A1 (en) * | 2014-03-27 | 2015-10-01 | 日本電気株式会社 | Optical transmission device, optical communication system, optical transmission method, and storage medium |
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