JP2679223B2 - Optical modulation method and optical modulator - Google Patents
Optical modulation method and optical modulatorInfo
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- JP2679223B2 JP2679223B2 JP1061534A JP6153489A JP2679223B2 JP 2679223 B2 JP2679223 B2 JP 2679223B2 JP 1061534 A JP1061534 A JP 1061534A JP 6153489 A JP6153489 A JP 6153489A JP 2679223 B2 JP2679223 B2 JP 2679223B2
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Description
【発明の詳細な説明】 〔概要〕 光ファイバを伝送路とする光通信システムにおいて、
高速のディジタル信号を長距離伝送する伝送装置に用い
る光変調方式に関し、数ギガビット／秒以上の伝送速度
においても，ファイバ波長分散の大きいファイバを長距
離伝送できる光変調方式を提供することを目的とし、マ
ッハツェンダ干渉計型光変調器において，二つの光導波
路を伝播する光の位相を非対称に変調することにより、
変調器出力光の立ち上がり部分の中心波長を長波長側に
動かし，立ち下がり部分の中心波長を短波長側に動かす
ものである。DETAILED DESCRIPTION [Overview] In an optical communication system using an optical fiber as a transmission line,
Regarding an optical modulation method used in a transmission device for transmitting a high-speed digital signal over a long distance, an object thereof is to provide an optical modulation method capable of transmitting a fiber having a large fiber wavelength dispersion over a long distance even at a transmission speed of several gigabits / second or more. , In a Mach-Zehnder interferometer type optical modulator, by asymmetrically modulating the phase of light propagating in two optical waveguides,
The center wavelength of the rising part of the modulator output light is moved to the long wavelength side, and the center wavelength of the falling part is moved to the short wavelength side.
本発明は、光ファイバ等を伝送路とし、高速のディジ
タル信号をのせた光信号を長距離にわたって伝送する光
通信システムにおいて、伝送路に光信号を送出する伝送
装置等に用いられるべき光変調方法及びその方法に具さ
れる光変調器に関する。The present invention relates to an optical modulation method to be used for a transmission device or the like that sends an optical signal to a transmission line in an optical communication system that uses an optical fiber or the like as a transmission line and transmits an optical signal carrying a high-speed digital signal over a long distance. And an optical modulator included in the method.
第14図は光通信システムの構成を示す図であり、従来
より良く知られた光通信システムを示している。図中、
10,20はそれぞれ送信側および受信側の光伝送装置であ
る。30は光ファイバ伝送路を示している。FIG. 14 is a diagram showing a configuration of an optical communication system, which is a well-known optical communication system. In the figure,
Reference numerals 10 and 20 denote optical transmission devices on the transmission side and the reception side, respectively. Reference numeral 30 denotes an optical fiber transmission line.
送信側の光伝送装置10は、高速のディジタル信号を乗
せた電気信号により強度変調された光信号を生成し、生
成した光信号は光ファイバ伝送路30へ導入される。光信
号は、光ファイバ伝送路30内を伝搬し、受信側の光伝送
装置20へと伝送され、光伝送装置20内の図示しない光電
変換素子等により電気信号へ変換され、当初のディジタ
ル信号が受信されるものである。The optical transmission device 10 on the transmission side generates an optical signal whose intensity is modulated by an electric signal carrying a high-speed digital signal, and the generated optical signal is introduced into the optical fiber transmission line 30. The optical signal propagates in the optical fiber transmission line 30, is transmitted to the optical transmission device 20 on the receiving side, is converted into an electric signal by a photoelectric conversion element or the like (not shown) in the optical transmission device 20, the initial digital signal It is what is received.
第15図は光ファイバ伝送路の波長分散特性を説明する
図である。なお、第15図において、横軸は波長、縦軸は
波長分散を示しており、λ０は零分散波長を示す。FIG. 15 is a diagram for explaining chromatic dispersion characteristics of an optical fiber transmission line. In FIG. 15, the horizontal axis represents wavelength, the vertical axis represents chromatic dispersion, and λ 0 represents zero-dispersion wavelength.
光ファイバ伝送路は、第15図に示すような、波長分散
特性を有している。すなわち、同一の光ファイバ伝送路
であっても、光の伝搬速度はその波長によって異なるも
のである。すなわち、零分散波長λ０より長い波長領域
では波長分散係数（ps/nm/km）は正の値をとり、短い値
では負の値をとる。The optical fiber transmission line has wavelength dispersion characteristics as shown in FIG. That is, even in the same optical fiber transmission line, the propagation speed of light varies depending on the wavelength. That is, the wavelength dispersion coefficient (ps / nm / km) takes a positive value in the wavelength region longer than the zero dispersion wavelength λ 0 , and takes a negative value in the short region.
一方、半導体レーザ素子等の光電をディジタル信号で
直接駆動する周知の直接変調方式においては、光源の物
理的特性の要因によりパルス波形内で中心波長が変動す
ることが知られている。すなわち、光源がしきい値電圧
前後で駆動される光パルスの立ち上がり部分及び立ち下
がり部分では、発光波長が所定の中心波長付近で不安定
となる現象である。このような現象は波長チャーピング
または単にチャーピングと呼ばれ、上述の伝送路の波長
分散特性との相乗作用によりパルス波形劣化を及ぼすも
のである。On the other hand, in a well-known direct modulation method in which photoelectrics such as a semiconductor laser device is directly driven by a digital signal, it is known that the center wavelength fluctuates within the pulse waveform due to the physical characteristics of the light source. That is, in the rising portion and the falling portion of the light pulse in which the light source is driven around the threshold voltage, the emission wavelength becomes unstable near the predetermined center wavelength. Such a phenomenon is called wavelength chirping or simply chirping, and causes a pulse waveform deterioration due to a synergistic effect with the wavelength dispersion characteristic of the transmission line.
第16図は光パルス波形の劣化を説明する図である。 FIG. 16 is a diagram for explaining the deterioration of the optical pulse waveform.
ここで、上記チャーピングの生じた光パルスが光ファ
イバ伝送路内をある相当の距離にわたって伝送される場
合を考えると、光パルス内には異なる波長の成分が存在
するので、これらの波長成分間に伝送遅延差が生じる。Here, considering the case where the chirped optical pulse is transmitted over a considerable distance in the optical fiber transmission line, there are different wavelength components in the optical pulse. Transmission delay difference occurs.
すると、第16図の（ａ）に示したような当初の光パル
ス波形は、異なる伝送遅延を有する成分が合成された状
態となるため伝送路内でくずれていき、最終的には同図
の（ｂ）に示すような波形劣化を生じるものである。Then, the initial optical pulse waveform as shown in (a) of FIG. 16 becomes distorted in the transmission line because the components having different transmission delays are combined, and finally in the same figure. This causes waveform deterioration as shown in (b).
一方、このときのチャーピングは、光パルス波形内の
スペクトル広がりとしてとらえることができ、このよう
なスペクトル広がりをより少なくすることにより、波形
劣化をある程度抑制することができるものと考えられ
る。すなわち、変調による波長のチャーピングを零にで
きるような変調方法を採用すれば、スペクトル広がりが
緩和されることになり、波形劣化の抑制が期待できる。On the other hand, the chirping at this time can be regarded as the spectrum spread in the optical pulse waveform, and it is considered that the waveform deterioration can be suppressed to some extent by reducing the spectrum spread. That is, if a modulation method that can eliminate the wavelength chirping due to the modulation is adopted, the spectrum spread is alleviated, and the waveform deterioration can be expected to be suppressed.
このため、光源自体を信号によって直接駆動せずに、
外部に設けた干渉型光変調器により光パルスを生成する
ことで、スペクトル広がりの小さな変調を行うことがで
きるものとして、外部変調方式による光変調方法が注目
されている。Therefore, without directly driving the light source itself with a signal,
An optical modulation method based on an external modulation method has been attracting attention as a method capable of performing modulation with a small spectrum spread by generating an optical pulse by an interferometric optical modulator provided outside.
スペクトル広がりが最も小さく、したがって光ファイ
バの波長分散の影響を受けにくい光変調方式の一つに、
光の干渉を応用したマッハツェンダ干渉計型光変調器等
の光変調器（以下、干渉型光変調器）による外部変調方
式がある。One of the optical modulation methods that has the smallest spectral spread and is therefore less susceptible to the chromatic dispersion of optical fibers.
There is an external modulation method using an optical modulator (hereinafter referred to as an interferometric optical modulator) such as a Mach-Zehnder interferometer type optical modulator to which optical interference is applied.
良く知られる一般的な干渉型変調器では、光源から導
入される光を分岐し、制御電極を設けた２つの光導波路
内を伝搬させて各々の光の位相を逆方向に同じ量だけ増
減させることによって０又はπの位相差を与え、互いに
干渉させることで波長チャーピングの少ない、強度変調
された光パルスが生成される。In a well-known general interferometric modulator, light introduced from a light source is branched and propagated in two optical waveguides provided with control electrodes to increase or decrease the phase of each light by the same amount in opposite directions. As a result, a phase difference of 0 or π is given, and by making them interfere with each other, an intensity-modulated optical pulse with little wavelength chirping is generated.
すなわち、干渉型変調器は、変調波形のフーリエ成分
である変調側波帯による広がりまで波長チャーピングを
小さくすることができる（F.KOYAMA et al.,JOURNAL OF
LIGHTWAVE TECHNOLOGY,VOL.6,NO.1,1988,PP.87−9
3）。That is, the interferometric modulator can reduce the wavelength chirping up to the spread due to the modulation sideband that is the Fourier component of the modulation waveform (F.KOYAMA et al., JOURNAL OF
LIGHTWAVE TECHNOLOGY, VOL.6, NO.1,1988, PP.87-9
3).
ところが、数ギガビット／秒以上の伝送速度において
は、たとえ波長チャーピングを零にしても、変調側波帯
によるスペクトル広がりが本質的に存在するため、光フ
ァイバ伝送路の波長分散特性による光パルス波形の劣化
を完全に無視することはできない。However, at a transmission speed of several gigabits / second or more, even if the wavelength chirping is set to zero, the spectrum spread due to the modulation sideband is essentially present, so the optical pulse waveform due to the chromatic dispersion characteristic of the optical fiber transmission line is present. Can not be completely ignored.
したがって、上述のような外部変調方式を採用するこ
とによって光パルスのスペクトル広がりを変調側波帯に
よるものにまで低減しても、数ギガビット／秒以上とい
った高速な伝送速度の領域では、例えば、使用する光源
の中心波長に対して零分散とならない光ファイバ伝送路
を用いた光伝送システムでは長距離伝送ができないとい
う問題があった。Therefore, even if the spectral spread of the optical pulse is reduced to that due to the modulation sideband by adopting the external modulation method as described above, it is used in a high transmission rate region of several gigabits per second or more, for example. There is a problem that long-distance transmission cannot be performed in an optical transmission system using an optical fiber transmission line that does not exhibit zero dispersion with respect to the center wavelength of the light source.
本発明は、数ギガビット／秒以上の伝送速度であっ
て、波長分散の大きい光ファイバ伝送路においても長距
離伝送可能な光伝送方法を提供することを目的とする。An object of the present invention is to provide an optical transmission method capable of long-distance transmission even in an optical fiber transmission line having a transmission speed of several gigabits / second or more and having a large wavelength dispersion.
第１図および第２図は本発明の原理説明図である。第
１図は，マッハツェンダ干渉計型光変調器の各部の光の
電界を表している。図中E0は入力光の電界の振幅，ω０
は電界の角周波数,tは時間，φA,φＢはそれぞれ光導波
路ＡおよびＢにおいて変調された位相を表す。Eout
（ｔ）は出力光の電界であり，詳細を（１）式に示す。1 and 2 are explanatory views of the principle of the present invention. FIG. 1 shows the electric field of light at each part of the Mach-Zehnder interferometer type optical modulator. In the figure, E 0 is the amplitude of the electric field of the input light, ω 0
Is the angular frequency of the electric field, t is the time, and φ A and φ B are the phases modulated in the optical waveguides A and B, respectively. Eout
(T) is the electric field of the output light, details of which are shown in equation (1).
Eout（ｔ） ＝E0/2（COS（ω0t＋φＡ）＋COS（ω0t＋φＢ）） ＝E0/2（X2＋Y2）1/2COS（ω0t−tan-1（Y/X）） …（１） ただし Ｘ＝COS（φＡ）＋COS（φＢ） Ｙ＝SIN（φＡ）＋SIN（φＢ） （１）式からわかる様にEout（ｔ）にはtan-1（Y/X）
の位相変調がかかっている。これは以下に示す様に波長
チャーピングとなる。 Eout (t) = E 0/ 2 (COS (ω 0 t + φ A) + COS (ω 0 t + φ B)) = E 0/2 (X 2 + Y 2) 1/2 COS (ω 0 t-tan -1 (Y / X)) (1) where X = COS (φ A ) + COS (φ B ) Y = SIN (φ A ) + SIN (φ B ) (1) Eout (t) has tan -1 (Y / X)
Is subject to phase modulation. This is wavelength chirping as shown below.
ω0t−tan-1（Y/X）をΦとおくと，角周波数は ω（ｔ）＝ｄΦ/dt＝ω０−ｄ（tan-1（Y/X））/dt,ま
た波長はλ＝２πc/ω（ｔ）（ｃは光速）より，Δω＝
−ｄ（tan-1（Y/X））/dtが波長チャーピングを引き起
こす。If ω 0 t−tan −1 (Y / X) is Φ, the angular frequency is ω (t) = dΦ / dt = ω 0 −d (tan −1 (Y / X)) / dt, and the wavelength is From λ = 2πc / ω (t) (c is the speed of light), Δω =
−d (tan −1 (Y / X)) / dt causes wavelength chirping.
ここで位相の変調を以下のようにおこなう。 Here, the phase modulation is performed as follows.
φＡ＞0,φＢ＜0,ABS（φＡ）＞ABS（φＢ） ABS（φＢ−φＡ）≒０（光出力High）， ABS（φＢ−φＡ）≒π（光出力Low） ただしABS（φ）はφの絶対値を表す。φ A > 0, φ B <0, ABS (φ A )> ABS (φ B ) ABS (φ B −φ A ) ≈0 (optical output High), ABS (φ B −φ A ) ≈π (optical output Low) However, ABS (φ) represents the absolute value of φ.
この時の各部の動作波形を図２に示す。 The operation waveforms of each part at this time are shown in FIG.
ｆに示す様に出力光強度が立ち上がる部分で出力光の
位相が遅れ，立ち下がる部分では位相が進む。これに対
応して中心波長がｇに示す様に立ち上がり部分で長波長
側に，立ち下がり部分で短波長側に動く。As shown in f, the phase of the output light is delayed in the part where the output light intensity rises, and the phase advances in the part where the output light intensity falls. Corresponding to this, the center wavelength moves to the long wavelength side at the rising portion and to the short wavelength side at the falling portion as shown by g.
従来はφＡ＝−φＢという条件で変調をおこなってい
た。この場合Eout（ｔ）は（２）式となる。Conventionally, modulation was performed under the condition of φ A = −φ B. In this case, Eout (t) is given by equation (2).
Eout（ｔ）＝E0COS（φ）COS（ω0t） …（２） ただしφ＝φＡ＝−φＢ この場合φの変調により光電界の振幅が変調されるだ
けで変調に伴う波長変動は生じない。Eout (t) = E 0 COS (φ) COS (ω 0 t) (2) where φ = φ A = −φ B In this case, the amplitude of the optical electric field is only modulated by the modulation of φ, and the wavelength accompanying the modulation is obtained. No change occurs.
本発明では、変調器の各導波路の位相を非対称に変調
することにより、出力光の中心波長を図２の（ｇ）に示
すように、立ち上がり部分で長波長側に、また、立ち下
がり部分で短波長側に動くようにした。In the present invention, by modulating the phase of each waveguide of the modulator asymmetrically, the center wavelength of the output light is increased toward the long wavelength side and decreased toward the long wavelength side as shown in (g) of FIG. So that it moves to the short wavelength side.
一方、光ファイバ伝送路の波長分散係数は、第15図に
示すように、光伝送路に例えば、1.3μｍ帯で零分散波
長を示すシングルモードファイバを用い、信号光波長と
して、波長分散係数の正の領域、例えば損失の少ない1.
55μｍ帯で使用した場合等に大きな値となる。On the other hand, the chromatic dispersion coefficient of the optical fiber transmission line is, as shown in FIG. 15, a single mode fiber showing a zero dispersion wavelength in the 1.3 μm band is used in the optical transmission line, and Positive area, e.g. less loss 1.
It is a large value when used in the 55 μm band.
このときの波長分散係数は例えば最大20ps/nm/kmであ
り、波長が長くなるほど光ファイバ内を伝搬する速度が
遅くなる。The wavelength dispersion coefficient at this time is, for example, 20 ps / nm / km at maximum, and the longer the wavelength, the slower the speed of propagation in the optical fiber.
したがって、上述のように非対称に位相を変調したこ
とにより生成された波長チャーピングと、光ファイバ伝
送路の正の波長分散の効果とにより、光パルスの立ち上
がり部分では波長が長くなるため相対的に伝搬速度が遅
れ、立ち下がり部分では波長が短くなるため逆に相対的
に伝搬速度は早まることとなる。以上のような作用によ
れば、本発明によって生成された光パルスは光ファイバ
伝送路を伝搬する間にパルス圧縮を生じる。Therefore, due to the wavelength chirping generated by asymmetrically modulating the phase as described above and the effect of positive chromatic dispersion in the optical fiber transmission line, the wavelength becomes longer at the rising portion of the optical pulse, so that the wavelength becomes relatively long. Since the propagation speed is delayed and the wavelength is shortened at the falling portion, the propagation speed is relatively increased on the contrary. According to the above operation, the optical pulse generated by the present invention causes pulse compression while propagating through the optical fiber transmission line.
このパルス圧縮は、変調側波帯と光ファイバ伝送路の
波長分散によって生じる波形広がりを補償する方向に働
くことになり、したがって伝送可能な光ファイバ長を改
善する作用をする。This pulse compression acts in the direction of compensating for the waveform broadening caused by the modulation sidebands and the chromatic dispersion of the optical fiber transmission line, and therefore has the effect of improving the transmittable optical fiber length.
〔実施例〕 マッハツェンダ干渉計型光変調器において，光の位相
変調には電気光学効果を用いる。すなわち電気光学効果
を持つ物質の屈折率を電界により変化させることによ
り，光の位相を変化させる。[Embodiment] In the Mach-Zehnder interferometer type optical modulator, the electro-optical effect is used for phase modulation of light. That is, the phase of light is changed by changing the refractive index of the substance having the electro-optical effect by the electric field.
従って，マッハツェンダ干渉計型光変調器において，
二つの光導波路を伝播する光の位相を非対称に変調する
方法としていくつかの方法が考えられる。一つは，各導
波路をそれぞれ異なる駆動電圧で変調する方法である，
二つ目は駆動電圧は同じであるが電極の断面構造を非対
称にすることにより，光導波路への変調電界のかかり方
を非対称にする方法がある。三つ目は各導波路でそれぞ
れ電極長を変えて光が屈折率変化を感じる導波路長を変
える方法である。Therefore, in the Mach-Zehnder interferometer type optical modulator,
There are several possible methods for asymmetrically modulating the phase of light propagating through the two optical waveguides. One is a method of modulating each waveguide with different drive voltage.
The second method is to make the modulation electric field applied to the optical waveguide asymmetric by making the cross-sectional structure of the electrodes asymmetric, although the drive voltage is the same. The third method is to change the electrode length in each waveguide to change the waveguide length at which light senses a change in the refractive index.
図３に第１の実施例を示す。これは，駆動電圧振幅を
非対称にかける例であり,Z板電気光学結晶を想定してい
る。Ｘ板およびＹ板電気光学結晶でも同様に実施でき
る。図中,1は位相変調を大きくかける方の光導波路であ
り,2は位相変調を小さくかける方の光導波路である。３
は変調用電極であり,4はアース電極である。３と４で進
行波型電極を構成している。５は終端抵抗であり，進行
波型電極の特性インピーダンスと整合している。６は光
導波路１の位相変調を行うための駆動回路,7は光導波路
２の位相変調を行うための駆動回路である。FIG. 3 shows a first embodiment. This is an example of applying the drive voltage amplitude asymmetrically, assuming a Z-plate electro-optic crystal. The same can be done with X-plate and Y-plate electro-optic crystals. In the figure, 1 is an optical waveguide for which the phase modulation is largely applied, and 2 is an optical waveguide for which the phase modulation is small. 3
Is a modulation electrode and 4 is a ground electrode. 3 and 4 form a traveling wave type electrode. Reference numeral 5 denotes a terminating resistor, which matches the characteristic impedance of the traveling wave electrode. Reference numeral 6 is a drive circuit for performing phase modulation of the optical waveguide 1, and 7 is a drive circuit for performing phase modulation of the optical waveguide 2.
第４図は第１の実施例の動作を示すタイムチャート図
である。V1は光導波路１の位相変調を行う駆動波形であ
り,V2は光導波路２の位相変調を行う駆動波形である。V
1とV2で極性を逆にし，駆動電圧振幅はV1の方を大きく
ことにより位相変調を非対称にかける。FIG. 4 is a time chart showing the operation of the first embodiment. V1 is a drive waveform for performing phase modulation of the optical waveguide 1, and V2 is a drive waveform for performing phase modulation of the optical waveguide 2. V
The polarities are reversed between 1 and V2, and the drive voltage amplitude is made larger at V1 to apply phase modulation asymmetrically.
第５図に第２の実施例を示す。これは，電極長を非対
称にして位相変調を非対称にかけるものであり,Z板電気
光学結晶を想定している。第５図〜第11図まで図中の１
〜４の記号の意味は図３の記号の意味と同じである。FIG. 5 shows a second embodiment. In this method, the electrode length is made asymmetric and the phase modulation is made asymmetric, and a Z-plate electro-optic crystal is assumed. 1 to 5 in FIG. 5 to FIG.
The symbols ~ 4 have the same meanings as the symbols in FIG.
第６図に第３の実施例を示す。これは，電極長を非対
称にして位相変調を非対称にかけるものであり,X板また
はＹ板電気光学結晶を想定している。FIG. 6 shows a third embodiment. This is to make the electrode length asymmetric and apply the phase modulation asymmetrically, and assumes an X-plate or Y-plate electro-optic crystal.
第７図に第４の実施例を示す。図７は，変調器の断面
構造を示している。本実施例は，電極の断面構造を非対
称にすることにより位相変調を非対称にかけるものであ
り,Z板電気光学結晶を想定している。本例では，光導波
路２から少し位置をずらして電極を配置している。FIG. 7 shows a fourth embodiment. FIG. 7 shows a sectional structure of the modulator. In the present embodiment, the phase modulation is applied asymmetrically by making the sectional structure of the electrode asymmetrical, and a Z-plate electro-optic crystal is assumed. In this example, the electrodes are arranged with a slight shift from the optical waveguide 2.
第８図に第５の実施例を示す。本実施例は電極の断面
構造を非対称にすることにより位相変調を非対称にかけ
るものであり,X板またはＹ板電気光学結晶を想定してい
る。本例では，光導波路２と電極間の距離を大きくして
いる。FIG. 8 shows a fifth embodiment. In this embodiment, phase modulation is applied asymmetrically by making the sectional structure of the electrode asymmetrical, and an X-plate or Y-plate electro-optic crystal is assumed. In this example, the distance between the optical waveguide 2 and the electrode is increased.
第９図に第６の実施例を示す。本実施例は電極の断面
構造を非対称にすることにより位相変調を非対称にかけ
るものであり,X板またはＹ板電気光学結晶を想定してい
る。一つの変調用電極で光導波路1,2を変調しており，
光導波路２と電極間の距離を大きくしている。FIG. 9 shows a sixth embodiment. In this embodiment, phase modulation is applied asymmetrically by making the sectional structure of the electrode asymmetrical, and an X-plate or Y-plate electro-optic crystal is assumed. The optical waveguides 1 and 2 are modulated by one modulation electrode.
The distance between the optical waveguide 2 and the electrode is increased.
第10図に第７の実施例を示す。これは，光導波路１だ
けを変調するものであり,Z板電気光学結晶を想定してい
る。FIG. 10 shows a seventh embodiment. This modulates only the optical waveguide 1, and assumes a Z-plate electro-optic crystal.
第11図に第８の実施例を示す。これは，光導波路１だ
けを変調するものであり,X板またはＹ板電気光学結晶を
想定している。FIG. 11 shows the eighth embodiment. This modulates only the optical waveguide 1, and assumes an X-plate or Y-plate electro-optic crystal.
第12図は波長分散によって生じる最小受光電力の劣
化，すなわちパワーペナルティの計算結果である。ファ
イバ伝送によって生じるパワーペナルティの許容値を0.
5dBとした場合，従来の変調方法では許容できる波長分
散値が500〜700ps/nmであるのに対し，位相変調比を5:1
にした場合には1500ps/nm以上と改善される。第13図は
異なる位相変調比で同様の計算をおこなったものであ
り，変調比が2:1以上あれば良いことがわかる。Figure 12 shows the calculation result of the power penalty, that is, the deterioration of the minimum received power caused by chromatic dispersion. The allowable power penalty caused by fiber transmission is 0.
When set to 5 dB, the chromatic dispersion value allowed by the conventional modulation method is 500 to 700 ps / nm, whereas the phase modulation ratio is 5: 1.
When set to 1,500ps / nm or more is improved. Figure 13 shows the same calculation with different phase modulation ratios, and it can be seen that the modulation ratio should be 2: 1 or more.
以上の計算結果からわかる様に，本発明によれば従来
の変調方式に較べて，ファイバ伝送特性が改善され，高
速光通信装置の性能向上に寄与するところが大きい。As can be seen from the above calculation results, according to the present invention, the fiber transmission characteristics are improved as compared with the conventional modulation method, which largely contributes to the performance improvement of the high-speed optical communication device.
第１図および第２図は本発明の原理を示す図， 第３図は本発明の第１の実施例の構成図， 第４図は第１の実施例の動作を示すタイムチャート図， 第５図は本発明の第２の実施例を示す図， 第６図は本発明の第３の実施例を示す図， 第７図は本発明の第４の実施例を示す図， 第８図は本発明の第５の実施例を示す図， 第９図は本発明の第６の実施例を示す図， 第10図は本発明の第７の実施例を示す図， 第11図は本発明の第８の実施例を示す図， 第12図および第13図は本発明によるファイバ伝送特性改
善の計算結果を示す図， 第14図は光通信システムの構成図， 第15図は伝送路の波長分散特性を説明する図， 第16図はパルス波形の劣化を説明する図である。 図中， 1:位相変調を大きくかける方の光導波路， 2:位相変調を小さくかける方の光導波路， 3:変調用電極， 4:アース電極， 5:終端抵抗， 6:光導波路１の位相変調を行うための駆動回路， 7:光導波路２の位相変調を行うための駆動駆回路であ
る。1 and 2 are diagrams showing the principle of the present invention, FIG. 3 is a block diagram of the first embodiment of the present invention, and FIG. 4 is a time chart diagram showing the operation of the first embodiment. 5 is a diagram showing a second embodiment of the present invention, FIG. 6 is a diagram showing a third embodiment of the present invention, FIG. 7 is a diagram showing a fourth embodiment of the present invention, and FIG. Shows a fifth embodiment of the present invention, FIG. 9 shows a sixth embodiment of the present invention, FIG. 10 shows a seventh embodiment of the present invention, and FIG. 11 shows a book. 8 is a diagram showing an eighth embodiment of the invention, FIGS. 12 and 13 are diagrams showing calculation results of fiber transmission characteristic improvement according to the present invention, FIG. 14 is a configuration diagram of an optical communication system, and FIG. 15 is a transmission line. Fig. 16 is a diagram for explaining the wavelength dispersion characteristics of Fig. 16, and Fig. 16 is a diagram for explaining the deterioration of the pulse waveform. In the figure, 1: Optical waveguide with large phase modulation, 2: Optical waveguide with small phase modulation, 3: Modulation electrode, 4: Ground electrode, 5: Termination resistance, 6: Phase of optical waveguide 1 A drive circuit for performing modulation, and 7: a drive circuit for performing phase modulation of the optical waveguide 2.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 沖山 正 神奈川県川崎市中原区上小田中1015番地 富士通株式会社内 (72)発明者 清野 實 神奈川県川崎市中原区上小田中1015番地 富士通株式会社内 (56)参考文献 特開 昭61−212125（ＪＰ，Ａ) 特開 昭62−63917（ＪＰ，Ａ) 特開 昭63−261220（ＪＰ，Ａ) 特開 昭64−91111（ＪＰ，Ａ) ＩＥＥＥ Ｊｏｕｒｎａｌ ｏｆ Ｌ ｉｇｈｔｗａｖｅ Ｔｅｃｈｎｏｌｏｇ ｙ Ｖｏｌ．６ Ｎｏ．１ ｐ．87〜 ｐ．93 電子通信学会論文誌 Ｖｏｌ．Ｊ59− Ｃ Ｎｏ．３ ｐ．155−ｐ．162 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masaru Okiyama 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Minoru Seino 1015, Kamiodanaka, Nakahara-ku, Kawasaki, Kanagawa Prefecture, Fujitsu Limited ( 56) References JP-A-61-212125 (JP, A) JP-A-62-63917 (JP, A) JP-A-63-261220 (JP, A) JP-A-64-91111 (JP, A) IEEE Journal of Lightwave Technology Vol. 6 No. 1 p. 87-p. 93 IEICE Transactions Vol. J59-C No. 3 p. 155-p. 162
Claims (8)
波路の屈折率を電気的に制御する制御手段とを有し、入
力光をそれぞれ各光導波路に入力し、各光導波路を伝搬
したそれぞれの光を合波して変調器出力光を出力する光
変調器の光変調方法において、 前記制御手段により、 前記各光導波路を伝搬する光の位相変化量の絶対値がそ
れぞれ異なり、 且つ、入力信号に応じて、伝搬する各光の位相変化量の
差の絶対値が０又はπとなるように、 且つ、前記変調器出力光の立ち上がり部分の中心波長を
長波長側に動かし、立ち下がり部分の中心波長を短波長
側に動かすように少なくとも１つの光導波路の屈折率を
制御することを特徴とする光変調方法。1. An optical waveguide having two optical waveguides and a control means for electrically controlling the refractive index of at least one optical waveguide, wherein input light is input to each optical waveguide and propagated through each optical waveguide. In the optical modulation method of an optical modulator that multiplexes the light and outputs the modulator output light, the control means causes the absolute values of the phase change amounts of the light propagating through the optical waveguides to be different from each other, and Depending on the signal, the absolute value of the difference in the amount of phase change of each propagating light becomes 0 or π, and the center wavelength of the rising part of the modulator output light is moved to the long wavelength side, and the falling part An optical modulation method characterized in that the refractive index of at least one optical waveguide is controlled so as to move the central wavelength of the optical waveguide to the short wavelength side.
波路の屈折率を電気的に制御する制御手段とを有し、入
力光をそれぞれ各光導波路に入力し、各光導波路を伝搬
したそれぞれの光を合波して変調器出力光を出力する光
変調器において、 前記制御手段は、 前記各光導波路を伝搬する光の位相変化量の絶対値がそ
れぞれ異なり、 且つ、入力信号に応じて、伝搬する各光の位相変化量の
差の絶対値が０又はπとなるように、 且つ、前記変調器出力光の立ち上がり部分の中心波長を
長波長側に動かし、立ち下がり部分の中心波長を短波長
側に動かすように少なくとも１つの光導波路の屈折率を
制御することを特徴とする光変調器。2. An optical waveguide having two optical waveguides and a control means for electrically controlling the refractive index of at least one optical waveguide, wherein input light is input to each optical waveguide and propagated through each optical waveguide. In the optical modulator that multiplexes the light and outputs the modulator output light, the control means has different absolute values of the phase change amount of the light propagating through the respective optical waveguides, and according to the input signal. , The absolute value of the difference between the phase changes of the propagating lights is 0 or π, and the central wavelength of the rising part of the modulator output light is moved to the long wavelength side, and the central wavelength of the falling part is changed. An optical modulator characterized in that the refractive index of at least one optical waveguide is controlled so as to move to the short wavelength side.
が形成された基板と、前記光導波路の一部を並列に進行
する第１及び第２の並列進行部に分岐する分岐部及び、
該第１及び第２の並列進行部を集束する集束部を有する
前記光導波路と、前記基板上であって前記光導波路の各
々の並列進行部の近傍に沿ってそれぞれ一対に形成され
た第１及び第２の進行波型電極と、前記第１と第２の進
行波型電極を制御する制御手段を具備した干渉型光変調
器において、 前記第１の進行波型電極は、前記第２の進行波型電極と
は異なる電極長を有し、 前記制御手段は、 前記各光導波路を伝搬する光の位相変化量の絶対値がそ
れぞれ異なり、 且つ、入力信号に応じて、伝搬する各光の位相変化量の
差の絶対値が０又はπとなるように、 且つ、前記変調器出力光の立ち上がり部分の中心波長を
長波長側に動かし、立ち下がり部分の中心波長を短波長
側に動かすように前記各光導波路の屈折率を制御するこ
とを特徴とする干渉型光変調器。3. A substrate made of an electro-optic crystal having an optical waveguide formed on one surface thereof, and a branching portion for branching a part of the optical waveguide into first and second parallel advancing portions advancing in parallel.
The optical waveguide having a converging portion for converging the first and second parallel advancing portions, and a pair of first optical waveguides formed on the substrate near the parallel advancing portions of the optical waveguide. And a second traveling wave type electrode, and an interferometric optical modulator comprising control means for controlling the first and second traveling wave type electrodes, wherein the first traveling wave type electrode is the second traveling wave type electrode. The traveling means has an electrode length different from that of the traveling-wave electrode, and the control means has different absolute values of the phase change amount of the light propagating through the respective optical waveguides, and, according to the input signal, The absolute value of the difference in the amount of phase change is 0 or π, and the center wavelength of the rising portion of the modulator output light is moved to the long wavelength side, and the center wavelength of the falling portion is moved to the short wavelength side. And controlling the refractive index of each of the optical waveguides. Watari optical modulator.
が形成された基板と、前記光導波路の一部を並列に進行
する第１及び第２の並列進行部に分岐する分岐部及び、
該第１及び第２の並列進行部を集束する集束部を有する
前記光導波路と、前記基板上であって前記光導波路の各
々の並列進行部の近傍に沿ってそれぞれ一対に形成され
た第１及び第２の進行波型電極と、前記第１と第２の進
行波型電極を制御する制御手段を具備した干渉型光変調
器において、 前記第１の進行波型電極は、前記第１の並列進行部上で
あって、前記第１の並列進行部の中心線と異なる位置に
中心線を有し、 前記第２の進行波型電極は、前記第２の並列進行部上で
あって、前記第２の並列進行部の中心線と同じ位置に中
心線を有し、 前記制御手段は、 前記各光導波路を伝搬する光の位相変化量の絶対値がそ
れぞれ異なり、 且つ、入力信号に応じて、伝搬する各光の位相変化量の
差の絶対値が０又はπとなるように、 且つ、前記変調器出力光の立ち上がり部分の中心波長を
長波長側に動かし、立ち下がり部分の中心波長を短波長
側に動かすように前記各光導波路の屈折率を制御するこ
とを特徴とする干渉型光変調器。4. A substrate made of an electro-optic crystal having an optical waveguide formed on one surface thereof, and a branching portion for branching a part of the optical waveguide into first and second parallel advancing portions advancing in parallel.
The optical waveguide having a converging portion for converging the first and second parallel advancing portions, and a pair of first optical waveguides formed on the substrate near the parallel advancing portions of the optical waveguide. And a second traveling wave type electrode, and an interferometric optical modulator comprising control means for controlling the first and second traveling wave type electrodes, wherein the first traveling wave type electrode is the first On the parallel traveling part, having a centerline at a position different from the centerline of the first parallel traveling part, the second traveling wave electrode is on the second parallel traveling part, A centerline is provided at the same position as the centerline of the second parallel traveling section, and the control means has different absolute values of the phase change amounts of the light propagating through the optical waveguides, and the control means is responsive to an input signal. So that the absolute value of the difference in the amount of phase change of each propagating light is 0 or π, and Interferometric optical modulation characterized in that the refractive index of each optical waveguide is controlled so that the center wavelength of the rising part of the modulator output light is moved to the long wavelength side and the center wavelength of the falling part is moved to the short wavelength side. vessel.
が形成された基板と、前記光導波路の一部を並列に進行
する第１及び第２の並列進行部に分岐する分岐部及び、
該第１及び第２の並列進行部を集束する集束部を有する
前記光導波路と、前記基板上であって前記光導波路の各
々の並列進行部の近傍に沿ってそれぞれ一対に形成され
た第１及び第２の進行波型電極と、前記第１と第２の進
行波型電極を制御する制御手段を具備した干渉型光変調
器において、 前記第１及び第２の進行波型電極はその長さは同じ長さ
で、対応する前記第１と第２の並列進行部との配置関係
が対称となるように配置し、 前記制御手段は、 前記各光導波路を伝搬する光の位相変化量の絶対値がそ
れぞれ異なり、 且つ、入力信号に応じて、伝搬する各光の位相変化量の
差の絶対値が０又はπとなるように、 且つ、前記変調器出力光の立ち上がり部分の中心波長を
長波長側に動かし、立ち下がり部分の中心波長を短波長
側に動かすように第１の電極と第２の電極に異なる電圧
を与え前記各光導波路の屈折率を制御することを特徴と
する干渉型光変調器。5. A substrate made of an electro-optic crystal and having an optical waveguide formed on one surface thereof, and a branching portion for branching a part of the optical waveguide into first and second parallel advancing portions advancing in parallel.
The optical waveguide having a converging portion for converging the first and second parallel advancing portions, and a pair of first optical waveguides formed on the substrate near the parallel advancing portions of the optical waveguide. And a second traveling wave electrode, and a control means for controlling the first and second traveling wave electrodes, wherein the first and second traveling wave electrodes are long The lengths are the same, and the corresponding first and second parallel advancing portions are arranged so that the positional relationship is symmetrical, and the control means controls the phase change amount of the light propagating through the respective optical waveguides. The absolute values are different from each other, and the absolute value of the difference in the amount of phase change of each propagating light is 0 or π according to the input signal, and the center wavelength of the rising portion of the modulator output light is set to Move to the long wavelength side and move the center wavelength of the falling part to the short wavelength side. As described above, the interferometric optical modulator, wherein different voltages are applied to the first electrode and the second electrode to control the refractive index of each of the optical waveguides.
が形成された基板と、前記光導波路の一部を並列に進行
する第１及び第２の並列進行部に分岐する分岐部及び、
該第１及び第２の並列進行部を集束する集束部を有する
前記光導波路と、前記基板上であって前記光導波路の各
々の並列進行部の近傍に沿ってそれぞれ一対に形成され
た第１及び第２の進行波型電極と、前記第１と第２の進
行波型電極を制御する制御手段を具備した干渉型光変調
器において、 前記第１及び第２の進行波型電極間の中心線と、前記第
１及び第２の光導波路間の中心線とが異なるように前記
第１及び第２の進行波型電極を形成し、 且つ、前記第１及び第２の進行波型電極の電極間隔が、
それぞれ異なるように形成し、 前記制御手段は、 前記各光導波路を伝搬する光の位相変化量の絶対値がそ
れぞれ異なり、 且つ、入力信号に応じて、伝搬する各光の位相変化量の
差の絶対値が０又はπとなるように、 且つ、前記変調器出力光の立ち上がり部分の中心波長を
長波長側に動かし、立ち下がり部分の中心波長を短波長
に動かすように前記各光導波路の屈折率を制御すること
を特徴とする干渉型光変調器。6. A substrate made of an electro-optic crystal and having an optical waveguide formed on one surface thereof, and a branching portion for branching a part of the optical waveguide into first and second parallel advancing portions advancing in parallel.
The optical waveguide having a converging portion for converging the first and second parallel advancing portions, and a pair of first optical waveguides formed on the substrate near the parallel advancing portions of the optical waveguide. And an interferometric optical modulator comprising a second traveling wave type electrode and a control means for controlling the first and second traveling wave type electrodes, wherein a center between the first and second traveling wave type electrodes A line and a center line between the first and second optical waveguides are different from each other, and the first and second traveling wave type electrodes are formed, and the first and second traveling wave type electrodes are formed. The electrode spacing is
Formed differently, the control means is different in absolute value of the phase change amount of the light propagating through each of the optical waveguides, and, in accordance with the input signal, the difference in the phase change amount of the propagating light. Refraction of each of the optical waveguides such that the absolute value is 0 or π, and the center wavelength of the rising portion of the modulator output light is moved to the long wavelength side and the center wavelength of the falling portion is moved to the short wavelength side. An interferometric optical modulator characterized by controlling the rate.
が形成された基板と、前記光導波路の一部を並列に進行
する第１及び第２の並列進行部に分岐する分岐部及び、
該第１及び第２の並列進行部を集束する集束部を有する
前記光導波路と、前記基板上であって前記光導波路の各
々の並列進行部の近傍に沿って形成された電極と、前４
記電極を制御する制御手段を具備した干渉型光変調器に
おいて、 前記電極は、信号電極と第１のアース電極と第２のアー
ス電極を有し、前記信号電極と前記第１のアース電極と
の間に前記第１の並列進行部を前記信号電極と前記第２
のアース電極との間に前記第２の並列進行部を設け、前
記信号電極から前記第１のアース電極までの距離と前記
信号電極から前記第２のアース電極までの距離を非対称
に構成し、 前記制御手段は、 前記各光導波路を伝搬する光の位相変化量の絶対値がそ
れぞれ異なり、 且つ、入力信号に応じて、伝搬する各光の位相変化量の
差の絶対値が０又はπとなるように、 且つ、前記変調器出力光の立ち上がり部分の中心波長を
長波長側に動かし、立ち下がり部分の中心波長を短波長
に動かすように前記各光導波路の屈折率を制御すること
を特徴とする干渉型光変調器。7. A substrate made of an electro-optic crystal having an optical waveguide formed on one surface thereof, and a branching portion for branching a part of the optical waveguide into first and second parallel advancing portions advancing in parallel.
The optical waveguide having a converging portion for converging the first and second parallel advancing portions, an electrode formed on the substrate in the vicinity of the parallel advancing portions of the optical waveguides, and
In the interferometric optical modulator including control means for controlling the electrode, the electrode includes a signal electrode, a first ground electrode, and a second ground electrode, and the signal electrode, the first ground electrode, and The first parallel advancing portion between the signal electrode and the second electrode.
The second parallel advancing portion is provided between the signal electrode and the first ground electrode, and the distance from the signal electrode to the second ground electrode is asymmetrical. The control means has different absolute values of the phase change amounts of the lights propagating through the respective optical waveguides, and the absolute value of the difference of the phase change amounts of the propagating lights is 0 or π depending on the input signal. In addition, the refractive index of each of the optical waveguides is controlled so that the center wavelength of the rising part of the modulator output light is moved to the long wavelength side and the center wavelength of the falling part is moved to the short wavelength. And an interferometric optical modulator.
が形成された基板と、前記光導波路の一部を並列に進行
する第１及び第２の並列進行部に分岐する分岐部及び、
該第１及び第２の並列進行部を集束する集束部を有する
前記光導波路と、前記基板上であって前記光導波路の並
列進行部の近傍に沿って形成された電極と、前記電極を
制御する制御手段を具備した干渉型光変調器において、 前記電極は、 前記光導波路の第１の並列進行部の近傍に設けられた変
調用電極と、 前記第１の並列進行部を軸とし前記第２の並列進行部の
形成された基板表面とは反対側の基板表面に設けられた
アース電極とからなり、 前記制御手段は、 前記各光導波路を伝搬する光の位相変化量の絶対値がそ
れぞれ異なり、 且つ、入力信号に応じて、伝搬する各光の位相変化量の
差の絶対値が０又はπとなるように、 且つ、前記変調器出力光の立ち上がり部分の中心波長を
長波長側に動かし、立ち下がり部分の中心波長を短波長
側に動かすように前記各光導波路の屈折率を制御するこ
とを特徴とする干渉型光変調器。8. A substrate made of an electro-optic crystal having an optical waveguide formed on one surface thereof, and a branching portion for branching a part of the optical waveguide into first and second parallel advancing portions advancing in parallel.
The optical waveguide having a converging portion for converging the first and second parallel advancing portions, an electrode formed on the substrate in the vicinity of the parallel advancing portion of the optical waveguide, and controlling the electrode. In the interferometric optical modulator having a control means, the electrode is a modulation electrode provided in the vicinity of the first parallel traveling portion of the optical waveguide, and the first parallel traveling portion serves as an axis. And a ground electrode provided on the surface of the substrate opposite to the surface of the substrate on which the parallel advancing portions are formed, wherein the control unit determines the absolute value of the phase change amount of the light propagating through each of the optical waveguides. Differently, and according to the input signal, the absolute value of the difference in the amount of phase change of each propagating light is 0 or π, and the center wavelength of the rising portion of the modulator output light is set to the long wavelength side. Move the center wavelength of the falling part to the shorter wavelength side. Interferometric light modulator and controlling the refractive index of the respective optical waveguide to move.
Priority Applications (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1061534A JP2679223B2 (en) | 1989-03-14 | 1989-03-14 | Optical modulation method and optical modulator |
| CA002011954A CA2011954C (en) | 1989-03-14 | 1990-03-12 | Optical modulator |
| US07/492,129 US5074631A (en) | 1989-03-14 | 1990-03-13 | Optical modulator |
| DE69033696T DE69033696T2 (en) | 1989-03-14 | 1990-03-14 | Optical modulator |
| DE69025481T DE69025481T2 (en) | 1989-03-14 | 1990-03-14 | Optical modulator |
| EP95109629A EP0674210B1 (en) | 1989-03-14 | 1990-03-14 | Optical modulator |
| EP90104811A EP0387832B1 (en) | 1989-03-14 | 1990-03-14 | Optical modulator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1061534A JP2679223B2 (en) | 1989-03-14 | 1989-03-14 | Optical modulation method and optical modulator |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7261891A Division JPH0886991A (en) | 1995-10-09 | 1995-10-09 | Method and device for transmitting light and light transmission system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02269309A JPH02269309A (en) | 1990-11-02 |
| JP2679223B2 true JP2679223B2 (en) | 1997-11-19 |
Family
ID=13173867
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1061534A Expired - Lifetime JP2679223B2 (en) | 1989-03-14 | 1989-03-14 | Optical modulation method and optical modulator |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2679223B2 (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2685835A1 (en) * | 1991-12-31 | 1993-07-02 | France Telecom | VERY LONG DISTANCE TRANSMISSION SYSTEM ON OPTICAL FIBER COMPENSATED FOR DISTORTIONS AT RECEPTION. |
| FR2685834B1 (en) * | 1991-12-31 | 1995-03-31 | France Telecom | LONG DISTANCE DIGITAL TRANSMISSION SYSTEM ON OPTICAL FIBER WITH DISTORTION COMPENSATION. |
| JP3490486B2 (en) * | 1993-12-28 | 2004-01-26 | 富士通株式会社 | Light modulator |
| JPH08316909A (en) * | 1995-05-16 | 1996-11-29 | Toshiba Corp | Optical transmission system and module and driving method for optical modulator |
| GB9510051D0 (en) * | 1995-05-18 | 1995-07-12 | Integrated Optical Components | Integrated optical modulators |
| JP2792482B2 (en) * | 1995-09-28 | 1998-09-03 | 日本電気株式会社 | Semiconductor Mach-Zehnder modulator |
| JPH0886991A (en) * | 1995-10-09 | 1996-04-02 | Fujitsu Ltd | Method and device for transmitting light and light transmission system |
| JP3913856B2 (en) * | 1997-08-28 | 2007-05-09 | 富士通株式会社 | Optical pulse generation device, dispersion measurement device, dispersion compensation device, and dispersion measurement method |
| US6831774B2 (en) | 2000-07-07 | 2004-12-14 | Nippon Telegraph And Telephone Corporation | Multi-wavelength generating method and apparatus based on flattening of optical spectrum |
| EP2116889B1 (en) | 2007-03-06 | 2014-08-06 | NGK Insulators, Ltd. | Optical phase modulator |
| JP5267105B2 (en) * | 2008-12-22 | 2013-08-21 | 富士通株式会社 | Optical module, method for manufacturing the same, and optical transmitter |
| JP6503900B2 (en) * | 2015-06-01 | 2019-04-24 | 住友大阪セメント株式会社 | Method of driving waveguide type optical device, and waveguide type optical device used in the driving method |
| JP2017083608A (en) * | 2015-10-27 | 2017-05-18 | 住友大阪セメント株式会社 | Optical modulator |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61212125A (en) * | 1985-03-15 | 1986-09-20 | Nec Corp | Method and device for transmitting optical pulse |
| JPS6263917A (en) * | 1985-09-17 | 1987-03-20 | Fujitsu Ltd | Optical modulator |
| JPS63261220A (en) * | 1987-04-20 | 1988-10-27 | Fujitsu Ltd | Light modulating element |
| JPS63292110A (en) * | 1987-05-26 | 1988-11-29 | Asahi Glass Co Ltd | Waveguide type optical frequency shifter |
-
1989
- 1989-03-14 JP JP1061534A patent/JP2679223B2/en not_active Expired - Lifetime
Non-Patent Citations (2)
| Title |
|---|
| ＩＥＥＥ Ｊｏｕｒｎａｌ ｏｆ Ｌｉｇｈｔｗａｖｅ Ｔｅｃｈｎｏｌｏｇｙ Ｖｏｌ．６ Ｎｏ．１ ｐ．８７〜ｐ．９３ |
| 電子通信学会論文誌 Ｖｏｌ．Ｊ５９−Ｃ Ｎｏ．３ ｐ．１５５−ｐ．１６２ |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02269309A (en) | 1990-11-02 |
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