JP2869585B2 - Light modulator - Google Patents
Light modulatorInfo
- Publication number
- JP2869585B2 JP2869585B2 JP3046085A JP4608591A JP2869585B2 JP 2869585 B2 JP2869585 B2 JP 2869585B2 JP 3046085 A JP3046085 A JP 3046085A JP 4608591 A JP4608591 A JP 4608591A JP 2869585 B2 JP2869585 B2 JP 2869585B2
- Authority
- JP
- Japan
- Prior art keywords
- signal
- light
- optical
- optical modulator
- control
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/0121—Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
- G02F1/0123—Circuits for the control or stabilisation of the bias voltage, e.g. automatic bias control [ABC] feedback loops
Landscapes
- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Communication System (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は、高速デジタル光伝送系
において、信号光の変調に用いられる光変調装置に利用
する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an optical modulator used for modulating signal light in a high-speed digital optical transmission system.
【０００２】本発明は、特に、光変調器の動作点制御方
式に関する。[0002] The present invention particularly relates to an operating point control method for an optical modulator.
【０００３】[0003]
【従来の技術】従来の干渉型の光変調器の入出力特性例
を図５に示す。この特性は温度変化や経年変化等により
発生するＤＣドリフトのために変動する。図では入出力
特性が右にシフトしている。特性変動後に変動前と同じ
動作点で変調器を駆動すると、入出力特性のピークとボ
トムで動作しないため、消光比の劣化やアイ開口におけ
る劣化などの特性劣化を引き起こす。これを避けるため
には、変調器の特性変動に合わせて動作点を制御する必
要がある。2. Description of the Related Art FIG. 5 shows an example of input / output characteristics of a conventional interference type optical modulator. This characteristic fluctuates due to a DC drift caused by a temperature change, an aging change, or the like. In the figure, the input / output characteristics are shifted to the right. If the modulator is driven at the same operating point as before the change after the characteristic change, the modulator will not operate at the peak and bottom of the input / output characteristics, causing deterioration of characteristics such as deterioration of the extinction ratio and deterioration of the eye opening. In order to avoid this, it is necessary to control the operating point in accordance with the characteristic fluctuation of the modulator.
【０００４】従来、光変調器に加える電気変調信号に低
周波を重畳して、光を変調しその変調光の低周波成分の
絶対値と位相の変化から、特性変動を感知して制御する
低周波重畳方式がある。図６によりこれを説明する。図
６のように低周波信号ｆL で振幅変調を行ってやる。動
作点が変動した場合出力光のｆL 成分の位相が 180°異
なるため、変調信号の位相と比較することで動作点の変
動方向を知ることができる。 (桑田他、「マッハツェン
ダ型光変調器用自動バイアス制御回路の検討」、'90 電
子情報通信学会春季全国大会分冊４、B-976 参照) 。Conventionally, a low frequency is superimposed on an electric modulation signal to be applied to an optical modulator to modulate light, and a characteristic is sensed and controlled based on a change in an absolute value and a phase of a low frequency component of the modulated light. There is a frequency superposition method. This will be described with reference to FIG. The amplitude modulation is performed with the low frequency signal f L as shown in FIG. When the operating point fluctuates, the phase of the f L component of the output light differs by 180 °, so that the direction of fluctuation of the operating point can be known by comparing with the phase of the modulation signal. (See Kuwata et al., "Study of Automatic Bias Control Circuit for Mach-Zehnder Optical Modulator,"'90 IEICE Spring National Convention Volume 4, B-976).
【０００５】[0005]
【発明が解決しようとする課題】しかし、この低周波重
畳方式では信号光に本来変調すべき信号の他に変動制御
用としてさらに変調をかけることになり、信号光の劣化
(波形歪み) をきたす恐れがある欠点がある。However, in this low-frequency superposition method, the signal light is further modulated for fluctuation control in addition to the signal to be originally modulated, and the signal light is degraded.
(Waveform distortion).
【０００６】本発明の目的は、前記の欠点を除去するこ
とにより、主信号光に波形歪を与えることなく、変調器
の特性変化による主信号光の特性の劣化を保証するため
に動作点を制御することができる光変調装置を提供する
ことにある。SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks and to set an operating point in order to guarantee the deterioration of the characteristics of the main signal light due to a change in the characteristics of the modulator without giving a waveform distortion to the main signal light. An object of the present invention is to provide a light modulation device that can be controlled.
【０００７】[0007]
【課題を解決するための手段】本発明は、入力信号光を
電気的な入力信号により変調して出力信号光を得る光変
調器と、この光変調器の動作点の制御を行うバイアス制
御手段とを備えた光変調装置において、前記光変調器
は、電気信号と信号光とが同一方向に入射される進行波
型の光変調器であり、前記バイアス制御手段は、前記信
号光とは反対方向から前記光変調器に対して低周波信号
で変調された制御信号光を入射する制御光入射手段と、
前記光変調器によって変調された前記制御信号光を取り
出す光分岐手段と、この光分岐手段からの出力信号光を
電気信号に変換する光−電気変換手段と、この光−電気
変換手段の出力を前記低周波信号により同期検波を行う
同期検波回路と、この同期検波回路の出力を入力とし前
記電気信号の平均電力に比例する第一の信号を出力する
平均電力出力手段と、前記入力信号のマーク率に比例す
る第二の信号を出力するマーク率検出手段と、前記第一
の信号と前記第二の信号とを比較しその結果に応じて前
記光変調器の動作点を制御する制御信号を出力する制御
信号生成手段と、を含むことを特徴とする。SUMMARY OF THE INVENTION The present invention provides an optical modulator for modulating an input signal light with an electrical input signal to obtain an output signal light, and a bias control means for controlling an operating point of the optical modulator. Wherein the optical modulator is a traveling wave type optical modulator in which an electric signal and a signal light are incident in the same direction, and the bias control unit is opposite to the signal light. Control light incidence means for injecting a control signal light modulated with a low frequency signal to the optical modulator from a direction,
An optical branching unit for extracting the control signal light modulated by the optical modulator, an optical-electrical conversion unit for converting an output signal light from the optical branching unit into an electric signal, and an output of the optical-electrical conversion unit. A synchronous detection circuit that performs synchronous detection using the low-frequency signal, an average power output unit that receives an output of the synchronous detection circuit as an input, and outputs a first signal proportional to an average power of the electric signal, and a mark of the input signal. A mark rate detecting means for outputting a second signal proportional to the rate, and a control signal for comparing the first signal and the second signal and controlling an operating point of the optical modulator according to the result. And a control signal generating means for outputting.
【０００８】[0008]
【作用】本発明は、変調器の特性が有限の帯域を持つこ
とに起因した平均光パワの動作点変動への依存性を利用
し、さらに、積極的に変調器の帯域を狭くするようにし
て、平均光パワの動作点変動による変化を大きくしよう
とする方式である。The present invention utilizes the dependence of the average optical power on the operating point fluctuation caused by the characteristic of the modulator having a finite band, and further actively narrows the band of the modulator. This is a method in which the change due to the fluctuation of the operating point of the average light power is increased.
【０００９】本発明の作用を図３(a) および(b) を用い
て説明する。The operation of the present invention will be described with reference to FIGS. 3 (a) and 3 (b).
【００１０】干渉型光変調器において、変調帯域が無限
大の理想的な変調器に図３(a) に示すような完全な矩形
の電圧波が印加される場合を考える。このとき、光変調
器の光出力を印加される電圧Ｖの関数としてＳ（Ｖ）と
表すと、平均光出力パワＳavは、次の［数１］で表され
る。Consider a case in which a perfect rectangular voltage wave as shown in FIG. 3A is applied to an ideal modulator having an infinite modulation band in an interferometric optical modulator. At this time, if the optical output of the optical modulator is expressed as S (V) as a function of the applied voltage V, the average optical output power S av is expressed by the following [ Equation 1].
【数１】 ここで、Ｓ(Ｖ)＝ cos2(Ｖ／２）、｜Ｖ1−Ｖ0｜＝π という条件で変調器を用いていたと仮定する。経年変化
などでＳ（Ｖ）からＳ（Ｖ＋ΔＶ）と変動したとき平均
光出力パワＳav1 は、 Ｓav1＝0.5Ｓ(Ｖ1＋ΔＶ)＋0.5Ｓ(Ｖ0＋ΔＶ） ＝0.5Ｓ(Ｖ1＋ΔＶ)＋0.5Ｓ(Ｖ1＋ΔＶ＋π） ＝0.5 と変わらない。(Equation 1) Here, it is assumed that the modulator is used under the condition that S (V) = cos 2 (V / 2) and | V 1 −V 0 | = π. When it changes from S (V) to S (V + ΔV) due to aging or the like, the average light output power S av1 is: S av1 = 0.5 S (V 1 + ΔV) +0.5 S (V 0 + ΔV) = 0.5 S (V 1 + ΔV) ) + 0.5S (V 1 + ΔV + π) = 0.5
【００１１】次に、より現実的な系として有限な帯域を
持つ系を考える。変調器に図３(b) に示す電圧波が印加
されると考える。系の状態を印加電圧により次の二つに
区別する。(1) Ｖ1 、Ｖ0 である状態、(2) Ｖ1 →
Ｖ0 、Ｖ0 →Ｖ1 と変化する状態、(1) である確率を
Ｘ、(2) である確率を（１−Ｘ）とすると平均光出力パ
ワＳavは、次の［数２］で表される。Next, a system having a finite band is considered as a more realistic system. It is assumed that the voltage wave shown in FIG. 3B is applied to the modulator. The state of the system is classified into the following two by the applied voltage. (1) V 1 , V 0 state, (2) V 1 →
Assuming that V 0 , V 0 → V 1 , the probability of (1) is X, and the probability of (2) is (1−X), the average light output power S av is given by the following [ Equation 2]. It is represented by
【数２】 (Equation 2)
【００１２】Ｓ（Ｖ）がＳ（Ｖ＋ΔＶ）に変動したとき
第１項は変わらないが、第２項の積分値は積分区間がπ
であるため変化する。このことにより、（１−Ｘ）が０
とならない帯域が有限な現実的な変調器に、立ち上が
り、立ち下がり時間が０でない電圧パルスを印加するこ
とで光を変調する場合、平均光出力パワの変動を識別す
ることで電圧−光出力特性の変動をとらえることができ
る。When S (V) changes to S (V + ΔV), the first term does not change, but the integral value of the second term is π
Because it changes. As a result, (1-X) becomes 0
In the case where light is modulated by applying a voltage pulse whose rise and fall times are not 0 to a realistic modulator having a finite band that cannot be obtained, the voltage-light output characteristic is identified by identifying the fluctuation of the average light output power. Can be captured.
【００１３】従って、変調された光信号を光−電気変換
手段で電気信号に変換して、さらに平均化して、その値
を動作点が最適動作点であると仮定したときに予想され
る値と比較して、その差が最小となるように動作点を変
えることで常に動作点を最適な値にすることができる。Therefore, the modulated optical signal is converted into an electric signal by the optical-electrical conversion means, further averaged, and the value is compared with the value expected when the operating point is the optimum operating point. In comparison, by changing the operating point so as to minimize the difference, the operating point can always be set to an optimum value.
【００１４】電圧−光出力特性の変化率にたいして平均
光出力の変化率を大きくとるためには［数２］で（１−
Ｘ）を大きくするようにすればよい。つまり変調器の帯
域を狭くすればよい。電気信号線路と光導波路が平行に
配置されるような高速光伝送用進行波型光変調器におい
て、電気信号の進行方向と反対の方向から入射された制
御用の連続光は電気信号により変調光となるが、光の進
行方向と電気信号の進行方向が逆であるため、帯域は光
の進行方向と電気の進行方向が同じ場合に比べて狭い。In order to increase the change rate of the average light output with respect to the change rate of the voltage-light output characteristic, (1−
X) may be increased. That is, the band of the modulator may be narrowed. In a traveling-wave optical modulator for high-speed optical transmission in which an electric signal line and an optical waveguide are arranged in parallel, a control continuous light incident from a direction opposite to the traveling direction of the electric signal is modulated by the electric signal. However, since the traveling direction of light and the traveling direction of the electric signal are opposite, the band is narrower than when the traveling direction of light and the traveling direction of electricity are the same.
【００１５】図４(a) および(b) は実際に光を順方向
（電気信号と同じ方向）から入射した場合と、逆方向
（電気信号とは反対の方向）から入射した場合の動作点
を変えたとき出力する平均光パワをグラフにした実験結
果である。電気信号は10Gb/s,NRZ(Non-Return-to-Zero)
信号、変調器の帯域は信号の変調に十分な帯域 (ただし
順方向の場合) を持っている。実験の結果たしかに、動
作点の変動を平均光パワを測定することで認識できるこ
とと、光の進行方向と電気信号の進行方向が逆にすると
進行方向が同じ場合に比べて平均光パワの変動が大きい
ことが確認できた。FIGS. 4A and 4B show operating points when light is actually incident from a forward direction (the same direction as an electric signal) and when light is incident from a reverse direction (a direction opposite to an electric signal). FIG. 9 is an experimental result in which the average light power output when changing is plotted. Electrical signal is 10Gb / s, NRZ (Non-Return-to-Zero)
The signal and modulator bandwidths have enough bandwidth to modulate the signal (but in the forward direction). It is clear from the results of the experiment that the fluctuation of the operating point can be recognized by measuring the average optical power, and that if the traveling direction of the light and the electric signal is reversed, the fluctuation of the average optical power will be smaller than when the traveling direction is the same. It was confirmed that it was large.
【００１６】なお、以上の方式では平均光パワーの変動
のみを見るために、光変調器端面での反射戻り光の影響
により制御の精度に問題が生じる恐れがある。しかしこ
の問題は、入射する制御信号光を低周波信号で変調し、
分岐された制御信号光を同期検波することで、本来の制
御信号光のみを取り出すことができ、解決することがで
きる。In the above system, since only the fluctuation of the average light power is observed, there is a possibility that a problem may occur in the control accuracy due to the influence of the reflected return light at the end face of the optical modulator. However, this problem is that the incoming control signal light is modulated with a low frequency signal,
By performing synchronous detection of the branched control signal light, only the original control signal light can be extracted, and this can be solved.
【００１７】[0017]
【実施例】以下、本発明の実施例について図面を参照し
て説明する。Embodiments of the present invention will be described below with reference to the drawings.
【００１８】図１は本発明の第一実施例を示すブロック
構成図で、本発明の基本構成を示す。FIG. 1 is a block diagram showing a first embodiment of the present invention, and shows a basic structure of the present invention.
【００１９】本第一実施例は、入力信号光１を主電気信
号３により変調して出力信号光２を得る光変調器10a
と、この光変調器10a の動作点の制御を行うバイアス制
御手段とを備えた光変調装置において、本発明の特徴と
するところの、光変調器10a は、電気信号と信号光とが
同一方向に入射される進行波型の光変調器であり、前記
バイアス制御手段は、入力信号光１とは反対方向から光
変調器10a に対して低周波信号で変調された制御信号光
８を入射する制御光入射手段としての、低周波信号９を
発生する低周波発振回路61、低周波信号９により変調さ
れた制御信号光８を出力する電気−光変換手段42、およ
び制御信号光８を光変調器10a に入射する光分岐手段
(2)32 と、光変調器10a によって変調された制御信号光
８を取り出す光分岐手段(1)31 と、この光分岐手段(1)3
1により分岐された制御信号光８を電気信号に変換する
光−電気変換手段15と、この光−電気変換手段15の出力
を低周波発振回路61の発生する低周波信号９により同期
検波を行う同期検波回路62と、この同期検波回路62の出
力を入力とし十分に長い単位時間に対する入力信号の平
均電力に比例する第一の信号としての平均電力信号４を
出力する平均電力出力手段としての平滑化手段16と、光
変調器10a に変調を行うことを目的とした主信号である
主電気信号３のマーク率に対応する第二の信号としての
定格信号５を出力するマーク率検出手段としてのマーク
率検出回路14と、平均電力信号４と定格信号５とを比較
しその結果に応じて光変調器10a の動作点を制御する制
御信号６を出力する制御信号生成手段としての、平均電
力信号４と定格信号５との差分に比例した信号を増幅出
力する差分増幅手段13、この差分増幅手段13の出力を入
力とし入力の値が常に一定になるように出力電圧を変動
する入力電圧制御回路12、およびこの入力電圧制御回路
12の出力を一つの入力として主電気信号３をもう一つの
入力として２入力の加算値に比例する制御信号６を出力
する直流電圧印加回路11とを含んでいる。In the first embodiment, an optical modulator 10a for modulating an input signal light 1 with a main electric signal 3 to obtain an output signal light 2
And an optical modulator including bias control means for controlling the operating point of the optical modulator 10a. The optical modulator 10a, which is a feature of the present invention, is characterized in that the electric signal and the signal light are in the same direction. The bias control means makes the control signal light 8 modulated by the low frequency signal incident on the optical modulator 10a from the opposite direction to the input signal light 1. A low-frequency oscillation circuit 61 for generating a low-frequency signal 9 as control light-injecting means, an electro-optical converter 42 for outputting a control signal light 8 modulated by the low-frequency signal 9, and an optical modulator for modulating the control signal light 8 Light splitting means incident on the vessel 10a
(2) 32, an optical branching means (1) 31 for extracting the control signal light 8 modulated by the optical modulator 10a, and the optical branching means (1) 3
The optical-to-electrical conversion means 15 for converting the control signal light 8 branched by 1 into an electric signal and the output of the optical-to-electrical conversion means 15 are synchronously detected by the low frequency signal 9 generated by the low frequency oscillation circuit 61. Synchronous detection circuit 62 and smoothing as average power output means for receiving the output of synchronous detection circuit 62 as input and outputting average power signal 4 as a first signal proportional to the average power of the input signal for a sufficiently long unit time. And a mark rate detecting means for outputting a rated signal 5 as a second signal corresponding to the mark rate of the main electric signal 3 which is a main signal for the purpose of modulating the optical modulator 10a. An average power signal as control signal generation means for comparing the mark rate detection circuit with the average power signal and the rated signal and outputting a control signal for controlling an operating point of the optical modulator in accordance with the result; 4 and the rated signal 5 A differential amplifying means 13 for amplifying and outputting a signal proportional to the minute, an input voltage control circuit 12 for receiving an output of the differential amplifying means 13 and varying an output voltage so that an input value is always constant; circuit
And a DC voltage application circuit 11 that outputs a control signal 6 proportional to the sum of the two inputs with the output of 12 as one input and the main electrical signal 3 as another input.
【００２０】なお、図１において、低周波発振回路61お
よび同期検波回路62を除いた回路は、既に本発明者を含
む発明者らによって提案されたものであり（特願平２−
２３８０６６号明細書および図面参照、本願出願時にお
いて未公開）、特に、本発明の特徴とするところは、前
記提案の回路に対して、光変調器端面での反射戻り光の
影響を取り除くために、低周波発振回路61および同期検
波回路62を設けたことにある。In FIG. 1, the circuit excluding the low-frequency oscillation circuit 61 and the synchronous detection circuit 62 has already been proposed by the present inventors including the present inventors (Japanese Patent Application No. Hei.
(See 238066 and drawings, unpublished at the time of filing the present application.) In particular, the feature of the present invention is to remove the influence of reflected return light at the end face of the optical modulator on the proposed circuit. , A low-frequency oscillation circuit 61 and a synchronous detection circuit 62.
【００２１】図２は本発明の第二実施例を示すブロック
構成図で、図１の本発明の基本構成の具体的構成例を示
す。FIG. 2 is a block diagram showing a second embodiment of the present invention, and shows a specific example of the basic structure of the present invention shown in FIG.
【００２２】本第二実施例は、図１の第一実施例におい
て、光分岐手段(1)31 として光分岐カップラ(1)31aを、
光分岐手段(2)32 として光分岐カップラ(2)32aを、光−
電気変換手段15として pin形のホトダイオード（ＰＤ）
15a を、平滑化手段16として低域通過ろ波器を含む平滑
化回路16a を、差分増幅手段13として差動増幅器13a
を、入力電圧制御回路12および直流電圧印加回路11とし
て直流レベル制御回路11a を、電気−光変換手段42とし
て制御用光源42a をそれぞれ設け、さらに入力信号光１
および制御信号光８をそれぞれ入力するためのアイソレ
ータ20および41を設けたものである。また、17は終端抵
抗である。そして、アイソレータ20は光分岐カプラー
(1)31aのポートに、アイソレータ41は光分岐カップラ
(2)32aのポートにそれぞれ接続される。In the second embodiment, an optical branching coupler (1) 31a is used as the optical branching means (1) 31 in the first embodiment of FIG.
The light branching coupler (2) 32a is used as the light branching means (2) 32,
Pin type photodiode (PD) as electric conversion means 15
15a, a smoothing circuit 16a including a low-pass filter as the smoothing means 16, and a differential amplifier 13a as the differential amplifying means 13.
A DC level control circuit 11a is provided as an input voltage control circuit 12 and a DC voltage application circuit 11, and a control light source 42a is provided as an electric-optical conversion means 42.
And isolator 20 and 41 for inputting the control signal light 8 respectively. Reference numeral 17 denotes a terminating resistor. And, the isolator 20 is an optical branching coupler.
(1) The isolator 41 is connected to the port 31a by the optical branching coupler.
(2) Each is connected to the port of 32a.
【００２３】なお、ここで pin形のホトダイオード15a
はアバランシェ形のホトダイオードでもよく、光分岐カ
ップラ31a および32a の代わりにハーフミラーを用いて
もよい。また、制御用光源42a としてはレーザダイオー
ドまたは発光ダイオードが用いられる。Here, the pin type photodiode 15a
May be an avalanche photodiode, and a half mirror may be used instead of the optical branching couplers 31a and 32a. Further, a laser diode or a light emitting diode is used as the control light source 42a.
【００２４】次に、本第二実施例の動作について説明す
る。Next, the operation of the second embodiment will be described.
【００２５】低周波発振回路61は低周波信号９を発生し
制御用光源42a および同期検波回路62に入力する。制御
用光源42a は低周波信号９で変調された制御信号光８を
発光する。そして、光分岐カップラ(2)32aは、制御用光
源42a からの制御信号光８をアイソレータ41を介してそ
のポートから取り入れ光変調器10a に出力信号光２と
は反対方向にそのポートに入力する。この光変調器10
a に入力された制御信号光８は光変調器10a で変調を受
けそのポートから出力される。The low frequency oscillation circuit 61 generates a low frequency signal 9 and inputs it to the control light source 42a and the synchronous detection circuit 62. The control light source 42a emits the control signal light 8 modulated by the low frequency signal 9. Then, the optical branching coupler (2) 32a takes in the control signal light 8 from the control light source 42a from its port via the isolator 41 and inputs it to the optical modulator 10a in the direction opposite to the output signal light 2 to that port. . This optical modulator 10
The control signal light 8 input to a is modulated by the optical modulator 10a and output from the port.
【００２６】そして、この変調を受けた制御信号光８
は、光分岐カップラ(1)31aによりそのポートから取り
出されホトダイオード15a に入力される。The modulated control signal light 8
Is extracted from the port by the optical branching coupler (1) 31a and input to the photodiode 15a.
【００２７】ホトダイオード15a は入力された信号光を
電気信号に変換し、同期検波回路62に入力する。同期検
波回路62は低周波発振回路61からの低周波信号９に従い
入力された電気信号を同期検波し平滑化回路16a に入力
する。平滑化回路16a は入力された電気信号を平滑化し
て低周波電圧としての平均電力信号４を出力する。The photodiode 15a converts the input signal light into an electric signal and inputs the electric signal to the synchronous detection circuit 62. The synchronous detection circuit 62 synchronously detects the electric signal input according to the low frequency signal 9 from the low frequency oscillation circuit 61 and inputs the electric signal to the smoothing circuit 16a. The smoothing circuit 16a smoothes the input electric signal and outputs an average power signal 4 as a low frequency voltage.
【００２８】一方、マーク率検出回路14は入力された主
電気信号３のマーク率を検出し出力する。そして定格信
号発生回路14a はマーク率検出回路14で検出されたマー
ク率に比例した定格信号５を生成出力する。On the other hand, the mark ratio detection circuit 14 detects and outputs the mark ratio of the input main electric signal 3. The rating signal generating circuit 14a generates and outputs a rating signal 5 proportional to the mark rate detected by the mark rate detecting circuit 14.
【００２９】差動増幅器13a は、平均電力信号４と定格
信号５との差電圧を増幅して制御電圧７を直流レベル制
御回路11a に入力する。The differential amplifier 13a amplifies the difference voltage between the average power signal 4 and the rated signal 5 and inputs the control voltage 7 to the DC level control circuit 11a.
【００３０】直流レベル制御回路11a は、制御電圧７と
主電気信号３とを入力して、制御電圧７が常に一定値と
なるように制御信号６を生成し、光変調器10の動作点を
制御する。The DC level control circuit 11a receives the control voltage 7 and the main electric signal 3 and generates the control signal 6 so that the control voltage 7 always has a constant value, and determines the operating point of the optical modulator 10. Control.
【００３１】従って、光変調器10a 端面での反射戻り光
があったとしても、同期検波回路62により除かれるの
で、精度の高い動作点制御を行うことができる。Therefore, even if there is reflected light returning from the end face of the optical modulator 10a, the reflected light is removed by the synchronous detection circuit 62, so that highly accurate operating point control can be performed.
【００３２】[0032]
【発明の効果】以上説明したように、本発明を用いるこ
とで干渉型の変調器の入出力特性の変動による消光比の
劣化、およびアイ開口における劣化などの特性劣化なら
びに制御信号光の光変調器端面による反射戻り光の影響
も除去して、動作点を常に最適な状態に制御することが
できる効果がある。また従来の制御法と異なり信号光に
は波形歪みなどの影響を与えることがない。As described above, by using the present invention, deterioration of the extinction ratio due to fluctuation of input / output characteristics of the interference type modulator, deterioration of characteristics such as deterioration in the eye opening, and optical modulation of control signal light can be achieved. There is an effect that the operating point can always be controlled to an optimum state by removing the influence of the reflected return light due to the container end face. Unlike the conventional control method, the signal light has no influence such as waveform distortion.
【図面の簡単な説明】[Brief description of the drawings]
【図１】 本発明の第一実施例を示すブロック構成図。FIG. 1 is a block diagram showing a first embodiment of the present invention.
【図２】 本発明の第二実施例を示すブロック構成図。FIG. 2 is a block diagram showing a second embodiment of the present invention.
【図３】 本発明の作用の説明図。FIG. 3 is an explanatory diagram of the operation of the present invention.
【図４】 動作点の変動と平均光パワの関係を示す図。FIG. 4 is a diagram showing a relationship between fluctuation of an operating point and average light power.
【図５】 従来例の入出力特性図。FIG. 5 is an input / output characteristic diagram of a conventional example.
【図６】 従来の低周波重畳方式の入出力特性図。FIG. 6 is an input / output characteristic diagram of a conventional low-frequency superposition method.
１ 入力信号光 ２ 出力信号光 ３ 主電気信号 ４ 平均電力信号 ５ 定格信号 ６ 制御信号 ７ 制御電圧 ８ 制御信号光 ９ 低周波信号 10a 光変調器 11 直流電圧印加回路 11a 直流レベル制御回路 12 入力電圧制御回路 13 差分増幅手段 13a 差動増幅器 14 マーク率検出回路 14a 定格信号発生回路 15 光−電気変換手段 15a ホトダイオード（ＰＤ） 16 平滑化手段 16a 平滑化回路 17 終端抵抗 20、41 アイソレータ 31 光分岐手段(1) 31a 光分岐カップラ(1) 32 光分岐手段(2) 32a 光分岐カップラ(2) 42 電気−光変換手段 42a 制御用光源 61 低周波発振回路 62 同期検波回路 Reference Signs List 1 input signal light 2 output signal light 3 main electric signal 4 average power signal 5 rated signal 6 control signal 7 control voltage 8 control signal light 9 low frequency signal 10a optical modulator 11 DC voltage application circuit 11a DC level control circuit 12 input voltage Control circuit 13 Differential amplification means 13a Differential amplifier 14 Mark ratio detection circuit 14a Rated signal generation circuit 15 Opto-electric conversion means 15a Photodiode (PD) 16 Smoothing means 16a Smoothing circuit 17 Terminating resistor 20, 41 Isolator 31 Optical branching means (1) 31a Optical branching coupler (1) 32 Optical branching means (2) 32a Optical branching coupler (2) 42 Electric-optical conversion means 42a Control light source 61 Low frequency oscillation circuit 62 Synchronous detection circuit
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.6，ＤＢ名) H04B 10/00 - 10/24 G02F 1/01 - 1/05 502 ──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. 6 , DB name) H04B 10/00-10/24 G02F 1/01-1/05 502
Claims (1)
調して出力信号光を得る光変調器と、この光変調器の動
作点の制御を行うバイアス制御手段とを備えた光変調装
置において、前記光変調器は、電気信号と信号光とが同
一方向に入射される進行波型の光変調器であり、前記バ
イアス制御手段は、前記信号光とは反対方向から前記光
変調器に対して低周波信号で変調された制御信号光を入
射する制御光入射手段と、前記光変調器によって変調さ
れた前記制御信号光を取り出す光分岐手段と、この光分
岐手段からの出力信号光を電気信号に変換する光−電気
変換手段と、この光−電気変換手段の出力を前記低周波
信号により同期検波を行う同期検波回路と、この同期検
波回路の出力を入力とし前記電気信号の平均電力に比例
する第一の信号を出力する平均電力出力手段と、前記入
力信号のマーク率に比例する第二の信号を出力するマー
ク率検出手段と、前記第一の信号と前記第二の信号とを
比較しその結果に応じて前記光変調器の動作点を制御す
る制御信号を出力する制御信号生成手段と、を含むこと
を特徴とする光変調装置。An optical modulator comprising: an optical modulator that modulates an input signal light with an electrical input signal to obtain an output signal light; and a bias control unit that controls an operating point of the optical modulator. The optical modulator is a traveling-wave optical modulator in which an electric signal and a signal light are incident in the same direction, and the bias control unit controls the optical modulator from a direction opposite to the signal light. Control light incidence means for receiving a control signal light modulated by a low-frequency signal, an optical branching means for extracting the control signal light modulated by the optical modulator, and an output signal light from the optical branching means for electrically transmitting the control signal light. Optical-electrical conversion means for converting the signal into a signal, a synchronous detection circuit for performing synchronous detection of the output of the optical-electrical conversion means with the low-frequency signal, and an output of the synchronous detection circuit as an input to the average power of the electric signal. Emits a proportional first signal Average power output means for applying, a mark rate detection means for outputting a second signal proportional to the mark rate of the input signal, and comparing the first signal and the second signal and according to the result. Control signal generating means for outputting a control signal for controlling an operating point of the light modulator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3046085A JP2869585B2 (en) | 1991-02-18 | 1991-02-18 | Light modulator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3046085A JP2869585B2 (en) | 1991-02-18 | 1991-02-18 | Light modulator |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04263525A JPH04263525A (en) | 1992-09-18 |
| JP2869585B2 true JP2869585B2 (en) | 1999-03-10 |
Family
ID=12737152
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3046085A Expired - Fee Related JP2869585B2 (en) | 1991-02-18 | 1991-02-18 | Light modulator |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2869585B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6983085B2 (en) | 2002-02-07 | 2006-01-03 | Nippon Telegraph And Telephone Corporation | Optical transmission circuit |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4934557B2 (en) * | 2007-09-27 | 2012-05-16 | 株式会社日立製作所 | 4-level phase modulator |
| JP5001245B2 (en) * | 2008-09-25 | 2012-08-15 | 住友大阪セメント株式会社 | Bias control device for light intensity modulator |
-
1991
- 1991-02-18 JP JP3046085A patent/JP2869585B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6983085B2 (en) | 2002-02-07 | 2006-01-03 | Nippon Telegraph And Telephone Corporation | Optical transmission circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04263525A (en) | 1992-09-18 |
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