JPH0642656B2 - Optical receiver - Google Patents
Optical receiverInfo
- Publication number
- JPH0642656B2 JPH0642656B2 JP61201080A JP20108086A JPH0642656B2 JP H0642656 B2 JPH0642656 B2 JP H0642656B2 JP 61201080 A JP61201080 A JP 61201080A JP 20108086 A JP20108086 A JP 20108086A JP H0642656 B2 JPH0642656 B2 JP H0642656B2
- Authority
- JP
- Japan
- Prior art keywords
- amplifier
- frequency
- laser diode
- optical receiver
- optical
- 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 - Lifetime
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- Semiconductor Lasers (AREA)
- Optical Communication System (AREA)
Description
【発明の詳細な説明】 〔産業上の利用分野〕 この発明は、周波数多重方式による光伝送系の光受信器
に関するものである。TECHNICAL FIELD The present invention relates to an optical receiver of an optical transmission system by a frequency multiplexing system.
第３図は従来の周波数多重方式による光伝送系の光受信
器を示すブロツク構成図、第４図は、第３図の光受信器
におけるスペクトルの関係の一例を示す図である。第１
図において、入力光１は複数の信号が別々の搬送波周波
数で多重された多重信号によつて強度変調されている。
高速フオトダイオード（以下、フオトダイオードをＰＤ
と略記する）２は上記強度変調された成分を電気信号に
変換する。従つて、高速ＰＤ出力３のスペクトルは、第
４図(a)に示す入力光１の変調周波数と同じ形をしてい
る。今、搬送波周波数1，2，3によつて多重され
た３つの信号Ｓ1，Ｓ2，Ｓ3が入力光１に含まれている
時に、搬送波周波数2を持つ信号Ｓ2のみを取り出すこ
とを考える。FIG. 3 is a block diagram showing an optical receiver of an optical transmission system according to a conventional frequency multiplexing system, and FIG. 4 is a diagram showing an example of a spectrum relationship in the optical receiver of FIG. First
In the figure, the input light 1 is intensity-modulated by a multiplexed signal in which a plurality of signals are multiplexed at different carrier frequencies.
High-speed photo diode (hereinafter referred to as PD
2) converts the intensity-modulated component into an electric signal. Therefore, the spectrum of the high speed PD output 3 has the same shape as the modulation frequency of the input light 1 shown in FIG. 4 (a). Now, when three signals S 1 , S 2 , S 3 multiplexed by carrier frequencies 1 , 2 , 3 are contained in the input light 1, it is possible to extract only the signal S 2 having the carrier frequency 2. Think
周波数a，bで変化する２つの成分の信号Ｓa，Ｓbを
加算し、入力の自乗に対応した出力を持つ素子に入力す
ると、その出力Ｓoutは、 Ｓout∝(Ｓa＋Ｓb)2 ＝▲Ｓ2 a▼＋▲Ｓ2 b▼＋２ＳaＳb ……(1) となり、信号Ｓaと信号Ｓbの積を含んでいる。信号
Ｓa，Ｓbの周波数成分には、三角関数の公式よりa＋
bとa−bの２つの周波数成分を含んでいる。この
中から低域通過フイルタ８（以下、ＬＰＦと略記する）
によりa−bの周波数成分のみを取り出すことは可能
である。従つて、局部発振器４の周波数を2に選び、
ミキサ５として、局部発振器出力６と高速ＰＤ出力３を
加算した後にその自乗に対応する素子、例えばダイオー
ドを選れば、ミキサ出力７の低周波成分のみを通過させ
るＬＰＦ８のＬＰＦ出力９は、入力光１の変調スペクト
ルの内で周波数2を搬送波とする成分の側波帯成分の
みとなる。なお、これらの技術は、ヘテロダイン検波技
術として当該分野の技術者にとつては周知の技術であ
る。When the signals S a and S b of the two components changing at the frequencies a and b are added and input to an element having an output corresponding to the square of the input, the output S out is S out ∝ (S a + S b ). 2 = ▲ S 2 a ▼ + ▲ S 2 b ▼ + 2S a S b (1), which includes the product of the signal S a and the signal S b . The frequency components of the signals S a and S b are a + from the trigonometric formula.
It contains two frequency components, b and a - b . From this, the low-pass filter 8 (hereinafter abbreviated as LPF)
Thus, it is possible to extract only the a – b frequency components. Therefore, select the frequency of the local oscillator 4 as 2 ,
As the mixer 5, if the element corresponding to the square of the local oscillator output 6 and the high speed PD output 3 is added and then a diode, for example, is selected, the LPF output 9 of the LPF 8 that passes only the low frequency component of the mixer output 7 is input. In the modulation spectrum of the light 1, only the sideband component of the component having the frequency 2 as the carrier wave becomes. Note that these techniques are known to those skilled in the art as heterodyne detection techniques.
上記従来の光受信器は以上のように構成されているの
で、入力光１を電気信号に変換する高速ＰＤ２として
は、搬送波周波数に対して十分に応答するものが必要で
ある。ところが、１つの信号の周波数帯域を広くとる
か、もしくは多重数を大きくとる場合には、搬送波の最
大周波数は高くなり、場合によつては数ＧHzに及ぶ場合
もある。このような高周波に対して応答できるＰＤの入
手は困難であり、このことは周波数多重方式による光伝
送系の性能を制限する要因になるという問題点があつ
た。Since the above conventional optical receiver is configured as described above, it is necessary that the high-speed PD 2 that converts the input light 1 into an electric signal is one that responds sufficiently to the carrier frequency. However, when the frequency band of one signal is wide or the number of multiplexed signals is large, the maximum frequency of the carrier wave becomes high, and in some cases, it may reach several GHz. It is difficult to obtain a PD capable of responding to such a high frequency, which causes a problem of limiting the performance of the optical transmission system based on the frequency multiplexing method.
この発明は、かかる問題点を解決するためになされたも
ので、ＰＤに対して高速の応答性を必要としない周波数
多重方式による光伝送系の光受信器を得ることを目的と
する。The present invention has been made to solve such a problem, and an object thereof is to obtain an optical receiver of an optical transmission system by a frequency multiplexing system which does not require high-speed response to PD.
この発明に係る光受信器は、入力光を、局部発振器の周
波数で利得の変化するレーザダイオード増幅器で増幅し
た後、その出力光をＰＤで電気信号に変換し、その出力
する電気信号の内で低周波成分だけを通過させるように
したものである。An optical receiver according to the present invention amplifies input light by a laser diode amplifier whose gain changes at the frequency of a local oscillator, converts the output light into an electric signal by a PD, and outputs the electric signal among the output electric signals. It is designed to pass only low frequency components.
この発明の光受信器においては、レーザダイオード増幅
器により入力光の変調周波数が周波数変換されるため
に、ＰＤは変換された低い周波数成分のみを電気信号に
変換すれば良い。In the optical receiver of the present invention, since the modulation frequency of the input light is frequency-converted by the laser diode amplifier, the PD only needs to convert the converted low frequency component into an electric signal.
第１図はこの発明の一実施例である光受信器を示すブロ
ツク構成図である。図に示すように、入力光１はレーザ
ダイオード（以下、ＬＤと略記する）増幅器１０に入射
するが、ＬＤ増幅器１０の注入電流は局部発振器４によ
つて変調されている。FIG. 1 is a block diagram showing an optical receiver according to an embodiment of the present invention. As shown in the figure, the input light 1 is incident on a laser diode (hereinafter abbreviated as LD) amplifier 10, and an injection current of the LD amplifier 10 is modulated by a local oscillator 4.
一般に、ＬＤの活性層における利得係数ｇは、 ただし、β，Ｊ０：半導体材料によつて決まる定数 ｄ：活性層の厚さ Ｊ：注入電流の密度 で表わされる。従つて、ＬＤの構造によつて決まる定数
ξを用いることにより、ＬＤ増幅器１０の利得Ｇと流入
電流ＩLDの間には、 ただし、 なる関係がある。Generally, the gain coefficient g in the active layer of LD is However, β, J 0 is a constant determined by the semiconductor material, d is the thickness of the active layer, and J is the density of the injection current. Therefore, by using the constant ξ determined by the structure of the LD , between the gain G of the LD amplifier 10 and the inflow current I LD , However, There is a relationship.
今、流入電流ＩLDがlの周波数で、また、ＬＤ増幅器
１０への入力光強度Ｐinがsの周波数でそれぞれ変化
している状態を考えると、ＬＤ増幅器１０の出力光強度
Ｐoutは、 ただし、Ｐino：Ｐinの振幅 ＩLDO：ＩLDの振幅 となり、s−lの周波数成分を含む。以上の現象は、
先に示した従来の光受信器におけるミキサ５により周波
数変換が行われることと同じ効果を持つ。局部発振器４
の周波数lを選択したい信号の搬送波周波数に等しく
すれば、（例えば第４図に示す関係において周波数2
とすれば）上記のs−lの周波数成分は搬送波に乗せ
られた所望の信号成分そのものであり、一般的には搬送
波周波数よりも十分に低い周波数成分のみを含んでい
る。従つて、ＬＤ増幅器出力１１を電気信号に変換する
ＰＤ１２としては、所望の信号成分に応答できるだけの
応答速度を持てば良い。また、一般にはＰＤ１２の出力
としては、上記第(4)式中に示されるような所望の信号
以外の高周波成分、及び雑音成分が含まれるので、ＰＤ
出力１３は所望の信号成分以外の周波数成分を除去する
ＬＰＦ８を通過した後、受信信号１４として取り出され
る。Now, at the frequency of the inflow current I LD is l, also considering the state of the input light intensity P in to the LD amplifier 10 is changed each at the frequency of s, the output light intensity P out of the LD amplifier 10, However, the amplitude of P ino : P in becomes the amplitude of I LDO : I LD , and the frequency component of s − l is included. The above phenomenon is
This has the same effect as the frequency conversion performed by the mixer 5 in the conventional optical receiver shown above. Local oscillator 4
If equal to the carrier frequency of the signal to be selected frequency l, the frequency 2 in the relationship shown in (e.g. Figure 4
If so, the frequency component of s - 1 is the desired signal component itself carried on the carrier, and generally includes only the frequency component sufficiently lower than the carrier frequency. Therefore, the PD 12 for converting the LD amplifier output 11 into an electric signal may have a response speed capable of responding to a desired signal component. Further, since the output of the PD 12 generally includes a high frequency component and a noise component other than the desired signal as shown in the equation (4), the PD
The output 13 passes through the LPF 8 that removes frequency components other than the desired signal component, and is then extracted as a reception signal 14.
第２図はこの発明の他の実施例である光受信器を示すブ
ロツク構成図である。先に述べたＬＤ活性層の利得は、
活性層を構成している半導体のバンドギヤツプ等によつ
て決まる特定の波長領域のみで生じ、その波長領域より
わずかに短波長側では吸収が生じることが知られてい
る。この吸収を生じる波長領域の光をＬＤの活性層に注
入すると、活性層にキヤリアが発生し、電流を注入した
のと同様の効果を生じる。第２図の実施例は、このよう
な効果を利用したものである。図において、注入用ＬＤ
１５の放射波長はＬＤ増幅器１０の活性層が吸収を生じ
る波長領域に設定されている。注入用ＬＤ１５の注入用
ＬＤ出力１６は局部発振器出力６によつて変化し、これ
に応じてＬＤ増幅器１０の活性層のキヤリア密度が変化
する。この変化によつて入力光１の変調周波数成分の内
で特定の周波数成分のみがＰＤ１２で電気信号に変換さ
れ、受信信号１４として取り出される過程は、上記第１
図に示した例の場合と同一である。FIG. 2 is a block diagram showing an optical receiver according to another embodiment of the present invention. The gain of the LD active layer described above is
It is known that it occurs only in a specific wavelength region determined by the band gap of the semiconductor that constitutes the active layer, etc., and absorption occurs in a wavelength range slightly shorter than the wavelength region. When light in the wavelength region that causes this absorption is injected into the active layer of the LD, carriers are generated in the active layer, and the same effect as when current is injected is produced. The embodiment shown in FIG. 2 utilizes such an effect. In the figure, LD for injection
The radiation wavelength of 15 is set to a wavelength region where the active layer of the LD amplifier 10 causes absorption. The injection LD output 16 of the injection LD 15 is changed by the local oscillator output 6, and the carrier density of the active layer of the LD amplifier 10 is changed accordingly. Due to this change, only a specific frequency component of the modulation frequency component of the input light 1 is converted into an electric signal by the PD 12 and is taken out as the reception signal 14.
This is the same as in the example shown in the figure.
上記第２図に示す実施例のように、いつたん局部発振器
４の周波数成分を光に変換するものでは、光増幅器が近
接して配置されていて、互いの電気的干渉が問題になる
場合に適応している。In the case where the frequency component of the local oscillator 4 is converted to light as in the embodiment shown in FIG. 2, when the optical amplifiers are arranged close to each other and mutual electrical interference becomes a problem. Adapted.
なお、上記実施例では、光電変換素子としてフオトダイ
オードを用いた例について述べたが、フオトダイオード
の代わりにアバランシエフオトダイオードを用いても同
様の効果が得られることは明らかである。In the above-mentioned embodiment, an example in which a photodiode is used as the photoelectric conversion element has been described, but it is clear that the same effect can be obtained by using an avalanche photodiode instead of the photodiode.
また、上記実施例では、光増幅器としてレーザダイオー
ド増幅器を用いた例について説明したが、レーザダイオ
ードに無反射コートを施す等の手段により共振効果を低
減した半導体素子、及び光で励起されるＹＡＧ等のレー
ザ用媒質を光増幅器として用いたものについても同じ効
果が得られる。Further, in the above-mentioned embodiment, an example in which a laser diode amplifier is used as an optical amplifier has been described, but a semiconductor element in which the resonance effect is reduced by means such as applying a non-reflective coating to the laser diode, YAG excited by light, etc. The same effect can be obtained by using the above laser medium as an optical amplifier.
この発明は以上説明したとおり、光受信器において、入
力光を、局部発振器の周波数で利得の変化するＬＤ増幅
器で増幅した後、その出力光をＰＤで電気信号に変換
し、その出力する電気信号の内で低周波成分だけを通過
させるようにしたので、ＰＤに対して高速の応答性を必
要としない光受信器が得られるという優れた効果を奏す
るものである。As described above, according to the present invention, in the optical receiver, after the input light is amplified by the LD amplifier whose gain changes at the frequency of the local oscillator, the output light is converted into the electric signal by the PD and the electric signal output by the PD is converted. Since only the low frequency component is allowed to pass through the optical receiver, it is possible to obtain an excellent effect that an optical receiver that does not require high-speed response to the PD can be obtained.
第１図はこの発明の一実施例である光受信器を示すブロ
ツク構成図、第２図はこの発明の他の実施例である光受
信器を示すブロツク構成図、第３図は従来の周波数多重
方式による光伝送系の光受信器を示すブロツク構成図、
第４図は、第３図の光受信器におけるスペクトルの関係
の一例を示す図である。 図において、１……入力光、２……高速フオトダイオー
ド（高速ＰＤ）、３……高速ＰＤ出力、４……局部発振
器、５……ミキサ、６……局部発振器出力、７……ミキ
サ出力、８……低域通過フイルタ（ＬＰＦ）、９……Ｌ
ＰＦ出力、１０……レーザダイオード増幅器（ＬＤ増幅
器）、１１……ＬＤ増幅器出力、１２……フオトダイオ
ード（ＰＤ）、１３……ＰＤ出力、14……受信信号、１
５……注入用レーザダイオード（注入用ＬＤ）、１６…
…注入用ＬＤ出力である。 なお、各図中、同一符号は同一、又は相当部分を示す。FIG. 1 is a block diagram showing an optical receiver according to an embodiment of the present invention, FIG. 2 is a block diagram showing an optical receiver according to another embodiment of the present invention, and FIG. 3 is a conventional frequency. Block configuration diagram showing an optical receiver of an optical transmission system by a multiplexing system,
FIG. 4 is a diagram showing an example of the relationship of spectra in the optical receiver of FIG. In the figure, 1 ... Input light, 2 ... High-speed photodiode (high-speed PD), 3 ... High-speed PD output, 4 ... Local oscillator, 5 ... Mixer, 6 ... Local oscillator output, 7 ... Mixer output , 8 ...... Low pass filter (LPF), 9 ...... L
PF output, 10 ... Laser diode amplifier (LD amplifier), 11 ... LD amplifier output, 12 ... Photodiode (PD), 13 ... PD output, 14 ... Received signal, 1
5 ... Laser diode for injection (LD for injection), 16 ...
... This is the LD output for injection. In the drawings, the same reference numerals indicate the same or corresponding parts.
Claims (3)
つて得られる多重信号により光を強度変調し、この強度
変調された光を伝送し、この伝送された光を受光して前
記複数の入力信号の内の特定の入力信号のみを出力する
光伝送系の光受信器において、入力光を増幅する光増幅
器と、この光増幅器の利得を特定の周波数で変化させる
手段と、前記光増幅器の出力光を受光するフオトダイオ
ードと、このフオトダイオードの出力する電気信号の内
で、低周波成分だけを通過させる帯域通過フイルタとを
備えたことを特徴とする光受信器。1. A plurality of input signals are frequency-multiplexed, the light is intensity-modulated by a multiplexed signal, the intensity-modulated light is transmitted, the transmitted light is received, and the plurality of the plurality of input signals are received. In an optical receiver of an optical transmission system that outputs only a specific input signal of input signals, an optical amplifier that amplifies the input light, a means that changes the gain of the optical amplifier at a specific frequency, and the optical amplifier An optical receiver comprising: a photo diode for receiving output light; and a band pass filter for passing only a low frequency component in an electric signal output by the photo diode.
器を用い、このレーザダイオード増幅器の利得を特定の
周波数で変化させる手段として、前記レーザダイオード
増幅器の注入電流を変化させる発振器を設けたことを特
徴とする特許請求の範囲第１項記載の光受信器。2. A laser diode amplifier is used as the optical amplifier, and an oscillator for changing the injection current of the laser diode amplifier is provided as means for changing the gain of the laser diode amplifier at a specific frequency. The optical receiver according to claim 1.
器を用い、このレーザダイオード増幅器の利得を特定の
周波数で変化させる手段として、前記レーザダイオード
増幅器を励起させるレーザダイオード光源と、このレー
ザダイオード光源の注入電流を変化させる発振器を設け
たことを特徴とする特許請求の範囲第１項記載の光受信
器。3. A laser diode amplifier is used as the optical amplifier, and as a means for changing the gain of the laser diode amplifier at a specific frequency, a laser diode light source for exciting the laser diode amplifier and an injection current of the laser diode light source. The optical receiver according to claim 1, further comprising an oscillator that changes the frequency.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61201080A JPH0642656B2 (en) | 1986-08-27 | 1986-08-27 | Optical receiver |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61201080A JPH0642656B2 (en) | 1986-08-27 | 1986-08-27 | Optical receiver |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6359030A JPS6359030A (en) | 1988-03-14 |
| JPH0642656B2 true JPH0642656B2 (en) | 1994-06-01 |
Family
ID=16435059
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61201080A Expired - Lifetime JPH0642656B2 (en) | 1986-08-27 | 1986-08-27 | Optical receiver |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0642656B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4794351A (en) * | 1986-09-29 | 1988-12-27 | American Telephone And Telegraph Company, At&T Bell Laboratories | Optical mixer for upconverting or downconverting an optical signal |
| JP2824875B2 (en) * | 1991-07-16 | 1998-11-18 | 科学技術振興事業団 | Optical demodulator |
| JPH06334607A (en) * | 1993-05-24 | 1994-12-02 | Nec Corp | Selective optical receiving circuit |
-
1986
- 1986-08-27 JP JP61201080A patent/JPH0642656B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6359030A (en) | 1988-03-14 |
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