JPH03141736A - Light receiving circuit - Google Patents
Light receiving circuitInfo
- Publication number
- JPH03141736A JPH03141736A JP1278648A JP27864889A JPH03141736A JP H03141736 A JPH03141736 A JP H03141736A JP 1278648 A JP1278648 A JP 1278648A JP 27864889 A JP27864889 A JP 27864889A JP H03141736 A JPH03141736 A JP H03141736A
- Authority
- JP
- Japan
- Prior art keywords
- light receiving
- receiving circuit
- coupler
- light
- preamplifier
- 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.)
- Pending
Links
- 230000005540 biological transmission Effects 0.000 claims abstract description 17
- 238000010521 absorption reaction Methods 0.000 claims description 6
- 230000035945 sensitivity Effects 0.000 abstract description 7
- 230000000593 degrading effect Effects 0.000 abstract 1
- 230000003287 optical effect Effects 0.000 description 8
- 230000002542 deteriorative effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 230000003071 parasitic effect Effects 0.000 description 1
Landscapes
- Optical Communication System (AREA)
Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は、光波通信に用いられる受光回路に関するもの
である。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a light receiving circuit used in light wave communication.
（従来の技術）
光波通信は、現在実用化されている光通信方式に比べて
まり長距離伝送が可能であることや、光の高密度多重に
よる伝送容量の拡大などの利点を有している。光通信に
おいては、光信号を電気信号に変換するため図１に示す
ような受光回路が用いられる。図１（ａ）の従来例（１
）においては、一つの受光素子１とバイアス抵抗２及び
前置増幅器３が用いられている。４は受光素子のバイア
ス端子、７は出力端子である。また、上に述べた光波通
信方式においては、図１（ｂ）（Ｃ）の従来例（２）ま
たは従来例（３）に示すように、二つの受光素子１−１
．１２またはさらに二つの前置増幅器１１．３−２を用
いてこれらを合威部５又は結合器６で結合したバランス
形の受光回路が用いられる。これらを用いる光波通信方
式の伝送系の概略を図２に示す。ここで、１１は光源、
１２は光フプイハ、１３は局発光源、１４は光結合器で
あり、受光回路としては図１（ｂ）の例が示されている
。光波通信の場合、受光回路の直前で局発光と呼ばれる
信号光以外の強い光を出す局発光１ｉｖ１１３を使用し
ており、この局発光の持つ強度雑音が受光感度の劣化を
招く。図１ （ｂＨＣ）の従来例（２）と（３）に示さ
れるように、二つの受光素子ｌ−Ｌ １−２を用いるの
は、受光素子からの出力電気信号に含まれる局発光源１
３からの強度雑音を、位相をずらして加え合わせること
によって相殺するためである。(Prior Art) Light wave communication has advantages over optical communication systems currently in use, such as being able to transmit over longer distances and increasing transmission capacity through high-density multiplexing of light. In optical communications, a light receiving circuit as shown in FIG. 1 is used to convert optical signals into electrical signals. Conventional example (1
), one light receiving element 1, bias resistor 2, and preamplifier 3 are used. 4 is a bias terminal of the light receiving element, and 7 is an output terminal. In addition, in the light wave communication system described above, as shown in conventional example (2) or conventional example (3) in FIGS. 1(b) and (C), two light receiving elements 1-1
．． A balanced light receiving circuit is used in which 12 or two preamplifiers 11.3-2 are used and these are combined by a combiner 5 or a coupler 6. FIG. 2 shows an outline of a transmission system of a light wave communication method using these. Here, 11 is a light source,
Reference numeral 12 denotes an optical amplifier, 13 a local light source, and 14 an optical coupler. The example of the light receiving circuit is shown in FIG. 1(b). In the case of light wave communication, a local light source 1iv113 called local light source that emits strong light other than signal light is used immediately before the light receiving circuit, and the intensity noise of this local light source causes deterioration of light receiving sensitivity. As shown in conventional examples (2) and (3) of FIG.
This is to cancel out the intensity noise from 3 by shifting the phase and adding them together.
′（発明が解決しようとする課題）
光波通信において、図１ （ａ）の従来例（＋）に示し
た受光回路を用いた場合、局発光源からの強度雑音で受
光感度が劣化する。また、単一の受光素子を用いている
ため、信号成分の半分を受信できないという問題がある
。(Problem to be Solved by the Invention) In light wave communication, when the light receiving circuit shown in the conventional example (+) in FIG. 1(a) is used, the light receiving sensitivity deteriorates due to intensity noise from the local light source. Furthermore, since a single light receiving element is used, there is a problem that half of the signal components cannot be received.
受光回路の周波数帯域は、受光素子や前置増幅器の入力
容量および寄生容量などの全容量をＣ１前置増幅器の入
力抵抗をＲとして、受光素子のバイアス抵抗がＲに比べ
て十分大きい時、次式で表わされる。The frequency band of the photodetector circuit is calculated as follows when the bias resistance of the photodetector is sufficiently larger than R, where the input resistance of the C1 preamplifier is R, which is the total capacitance of the photodetector, preamplifier, input capacitance, parasitic capacitance, etc. It is expressed by the formula.
ｆ＝１／２πＲＣ
また、図１（ｂ）に示す従来例（２）の受光回路におい
ては、受光素子１−１．１−２を直接ボンディングワイ
ヤ等で接続している。従って、従来例（２）の受光回路
では受光素子を二つにすることよって、局発光源の強度
雑音を相殺することができるものの、全容量が増加し、
周波数帯域が狭くなるという問題がある。さらに、受光
回路の熱雑音は受光素子１−１．１２の容量及び前置増
幅器３の入力容量のために、高周波側で増加する。しか
も容量成分が大きい程、増加の程度も大きい。バランス
形とした場合には受光素子の容量が２倍となるので、高
周波領域における熱雑音の増加の程度は図１ （ａ）に
示す従来例（１）より大きい。従って、すべての信号成
分を受信できるため、低周波側においては従来例（］）
の２倍の受信感度が得られるが、高周波側においては受
信感度が劣化するという問題がある。f=1/2πRC Further, in the light receiving circuit of conventional example (2) shown in FIG. 1(b), the light receiving elements 1-1, 1-2 are directly connected with bonding wires or the like. Therefore, in the light receiving circuit of conventional example (2), although the intensity noise of the local light source can be canceled out by using two light receiving elements, the total capacity increases.
There is a problem that the frequency band becomes narrow. Furthermore, the thermal noise of the light receiving circuit increases on the high frequency side due to the capacitance of the light receiving element 1-1.12 and the input capacitance of the preamplifier 3. Moreover, the larger the capacitance component, the greater the degree of increase. In the case of a balanced type, the capacity of the light receiving element is doubled, so the degree of increase in thermal noise in the high frequency region is greater than in the conventional example (1) shown in FIG. 1(a). Therefore, all signal components can be received, so on the low frequency side, the conventional example (])
However, there is a problem in that the receiving sensitivity deteriorates on the high frequency side.
さらに、図１（Ｃ）に示す従来例（３）においては、周
波数帯域及び熱雑音の周波数特性は従来例（１）と同様
であり、従来例（１）に対して受光感度は２倍に改善す
ることができる。しかしながら、二つの前置増幅器３−
Ｌ ３−２が必要となるという問題がある。Furthermore, in conventional example (3) shown in Fig. 1(C), the frequency band and frequency characteristics of thermal noise are the same as conventional example (1), and the light receiving sensitivity is twice that of conventional example (1). It can be improved. However, two preamplifiers 3-
There is a problem that L 3-2 is required.
本発明の目的は、二つの受光素子を用いても受光回路の
周波数帯域を劣化させることなく一つの前置増幅器を用
いて、広帯域で高感度な受光回路を得ることにある。An object of the present invention is to obtain a wide-band, highly sensitive light-receiving circuit using one preamplifier without deteriorating the frequency band of the light-receiving circuit even when two light-receiving elements are used.
（課題を解決するための手段）
本発明における回路構成を図３に示す。本発明では、互
いに逆バイアスした二つの受光素子１１．１−２と、結
合器６と、前置増幅器３及びそれらを結ぶ伝送線路Ｌ−
１，８−２からなる受光回路を提案している。結合器６
のポート１ （６−１）、 ２（６−２）、３（６−
３）からの入力インピーダンス、伝送線路８−１．８−
２の特性インピーダンス及び、用いられる前置増幅器３
の入力インピーダンスはそれぞれ相等しいとする。(Means for Solving the Problems) A circuit configuration in the present invention is shown in FIG. In the present invention, two light-receiving elements 11.1-2 with opposite biases, a coupler 6, a preamplifier 3, and a transmission line L-
We have proposed a light receiving circuit consisting of 1 and 8-2. Combiner 6
Ports 1 (6-1), 2 (6-2), 3 (6-
3) Input impedance from transmission line 8-1.8-
2 and the preamplifier 3 used.
The input impedances of are assumed to be equal.
（作用及び実施例）
本発明で用いている結合器６は、ポート１（６１）とポ
ート２ （６−２）より入力した信号を合或しボー ）
３ （６−３）より出力するものであり、一つのポー
１〜からの入力インピーダンスは他の２つのポートに接
続したインピーダンスの影響を受けないものである。こ
のような結合器６を一つの前置増幅器３の直前に用いる
。この点が従来のバランス形の受光回路と異なる。本発
明で用いる結合器の一例を図４に示す。(Operations and Examples) The coupler 6 used in the present invention combines or bauds signals input from port 1 (61) and port 2 (6-2).
3 (6-3), and the input impedance from one port 1 to is not affected by the impedance connected to the other two ports. Such a coupler 6 is used immediately before one preamplifier 3. This point differs from conventional balanced light receiving circuits. An example of a coupler used in the present invention is shown in FIG.
この結合器６では、６個の伝送線路６−４が用いられて
おり、２個の伝送線路６−４の各一端を開放端とし各他
端を吸収抵抗６−５で相互接続した単位回路が２段縦続
に配置され、初段の単位回路の開放端はポート１（６−
１）、ポート２（６−２）にそれぞれ接続されており、
２段目の単位回路の開放端は初段の吸収抵抗６−５の両
端に接続されている。さらに２段目の単位回路の吸収抵
抗６−５の両端には３段目の伝送線路６−４の各一端が
接続され、その３段目の伝送線路の他端を相互接続して
ポート３ （６−３）を形成している。すなわち、ポー
ト１（６−１）とポート３（６−３）との間及びポート
２（６−２）とポート３（６−３）との間に同数の伝送
線路６−４の区間が設けられ、各区間の対応する接続点
相互間に吸収抵抗６−５が配置された構成となっている
。This coupler 6 uses six transmission lines 6-4, and a unit circuit in which one end of each of the two transmission lines 6-4 is an open end and each other end is interconnected with an absorption resistor 6-5. are arranged in cascade in two stages, and the open end of the first stage unit circuit is connected to port 1 (6-
1) and port 2 (6-2), respectively.
The open end of the second stage unit circuit is connected to both ends of the first stage absorption resistor 6-5. Further, one end of each third-stage transmission line 6-4 is connected to both ends of the absorption resistor 6-5 of the second-stage unit circuit, and the other ends of the third-stage transmission line are interconnected to connect the ports 3 to 3. (6-3) is formed. In other words, there are the same number of transmission line sections 6-4 between port 1 (6-1) and port 3 (6-3) and between port 2 (6-2) and port 3 (6-3). Absorption resistors 6-5 are arranged between corresponding connection points in each section.
図３で用いられている伝送線路などの特性インピーダン
スをＺ。とする。このとき、受光素子１１から前置増幅
器３側を見たときの入カインピダンスはＺ。となる。す
なわち、受光素子１−１からはもう一つの受光素子１−
２のもつ容量成分は見えない。これは、もう一方の受光
素子においても同様である。ポート１ （６−１）にお
ける受光素子１−１からの信号成分の持つ周波数帯域と
、結合器６の出力ポート３ （６−３）での受光素子■
ｌからの信号成分の周波数帯域は等しく、その振幅はｌ
／花となる。これは、受光素子１−２からポート６ （
６−３）への信号成分についても同様である。ところで
、図３に示した二つの受光素子１１．１−２からの信号
成分は光結合器６の特性により、互いに位相がπだけず
れている。従って、この二つの受光素子１−１．１−２
を予め、一方はプラスで他方はマイナスというように、
互いに逆にバイアスしておけば、ボー１−３ （６−３
）においては二つの受光素子１−Ｌ １−２からの信号
成分が加え合わされ、単体の受光素子のときと比べて拒
倍の振幅と、等しい周波数帯域を持つ信号が出力される
。Z is the characteristic impedance of the transmission line used in Figure 3. shall be. At this time, the input impedance when looking from the light receiving element 11 to the preamplifier 3 side is Z. becomes. That is, from the light receiving element 1-1 to the other light receiving element 1-
The capacitive component of 2 cannot be seen. This also applies to the other light receiving element. The frequency band of the signal component from the light receiving element 1-1 at port 1 (6-1) and the light receiving element at the output port 3 (6-3) of the coupler 6
The frequency bands of the signal components from l are equal and their amplitudes are l
/becomes a flower. This is from light receiving element 1-2 to port 6 (
The same applies to the signal component to 6-3). By the way, the signal components from the two light receiving elements 11.1-2 shown in FIG. 3 are out of phase with each other by π due to the characteristics of the optical coupler 6. Therefore, these two light receiving elements 1-1.1-2
In advance, one is positive and the other is negative, etc.
If the biases are opposite to each other, baud 1-3 (6-3
), the signal components from the two light-receiving elements 1-L 1-2 are added together, and a signal having an amplitude that is less than that of a single light-receiving element and a frequency band that is equal to that of a single light-receiving element is output.
すなわち、受光素子が一つから二つとなっても、周波数
帯域が狭くなることはなく、その周波数帯域は単一の受
光素子を用いた場合と同様である。That is, even if the number of light receiving elements changes from one to two, the frequency band does not become narrower, and the frequency band is the same as when a single light receiving element is used.
次に、雑音特性について述べる。本発明の場合、周波数
帯域の説明について述べたように、二つの受光素子があ
るにもかかわらず周波数特性に対しては単一の場合と同
様である。従って、高周波数領域における熱雑音の増加
分は単一の場合と等しい。さらに、バランス形とするこ
とによって、強度雑音を相殺することができるばかりで
なく信号成分も元倍となる。Next, the noise characteristics will be described. In the case of the present invention, as described regarding the frequency band, although there are two light receiving elements, the frequency characteristics are the same as in the case of a single light receiving element. Therefore, the increase in thermal noise in the high frequency region is equal to that in the single case. Furthermore, by using a balanced type, not only can intensity noise be canceled out, but also signal components can be doubled.
（発明の効果）
以上述べたように、本発明により周波数帯域および受光
感度の劣化を招くことなく、一つの前置増幅器のみで、
バランス形の受光回路を構成することができる。(Effects of the Invention) As described above, according to the present invention, only one preamplifier can be used without deteriorating the frequency band and light receiving sensitivity.
A balanced light receiving circuit can be constructed.
図１ （ａ）（ｂ） （Ｃ）は従来光通信で用いられる
受光回路の構成例を示す回路図、図２は本発明の受光回
路が用いられる光波通信方式の伝送系の概略を示す系統
図、図３は本発明で提案する受光回路の構成例図、図４
は本発明で用いる結合器の一例を示す回路図である。
１ １−１．Ｌ−１・・・受光素子、 ２．２−Ｌ ２
２・・・バイアス抵抗、 ３．３−Ｌ １２・・・前置
増幅器、 ４．４−１．４−２・・・バイアス端子、５
・・・合成部、 ６・・・結合器、６−１．６−２．６
３・・・ポート、６−４・・・伝送線路、６−５・・・
吸収抵抗、 ７・・・出力端子、８−１．８−２・・・
伝送線路、 １１・・・光源１． １２・・・光ファイ
バ、 １３・・・局発光源、 １４・・・光結合器。
図
４−２（バーＩηｉ＃、’））
（６）
（ｂ）
７万クー
図３Figures 1 (a), (b), and (C) are circuit diagrams showing configuration examples of light receiving circuits used in conventional optical communications, and Figure 2 is a system schematically showing a transmission system of a light wave communication system in which the light receiving circuit of the present invention is used. Figures 3 and 3 are configuration examples of the light receiving circuit proposed in the present invention, and Figure 4
1 is a circuit diagram showing an example of a coupler used in the present invention. 1 1-1. L-1... Light receiving element, 2.2-L2
2... Bias resistor, 3.3-L 12... Preamplifier, 4.4-1.4-2... Bias terminal, 5
...Synthesizer, 6...Coupler, 6-1.6-2.6
3...Port, 6-4...Transmission line, 6-5...
Absorption resistor, 7... Output terminal, 8-1.8-2...
Transmission line, 11... light source 1. 12... Optical fiber, 13... Local light source, 14... Optical coupler. Figure 4-2 (bar Iηi#,')) (6) (b) 70,000 ku Figure 3
Claims (2)
合成する２入力１出力の結合器と、該結合器の出力側に
配置された前置増幅器とを備え、前記結合器の２入力の
各インピーダンスは前記二つの伝送線路のインピーダン
スにそれぞれ整合し、前記１出力のインピーダンスは前
記前置増幅器の入力インピーダンスに整合するように構
成された受光回路。(1) comprising two light receiving elements, a 2-input 1-output coupler for combining the respective outputs of the two light-receiving elements, and a preamplifier disposed on the output side of the coupler; The light receiving circuit is configured such that the impedance of each of the two inputs is matched to the impedance of the two transmission lines, and the impedance of the one output is matched to the input impedance of the preamplifier.
及び前記２入力の他方と前記１出力間に同数の伝送線路
区間が設けられ、該区間の相対応する相互接続点間に吸
収抵抗が配置された構成を有することを特徴とする特許
請求の範囲第１項記載の受光回路。(2) The coupler is provided with the same number of transmission line sections between one of the two inputs and the one output and between the other of the two inputs and the one output, and between corresponding interconnection points of the sections. The light receiving circuit according to claim 1, characterized in that the light receiving circuit has a configuration in which an absorption resistor is arranged.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1278648A JPH03141736A (en) | 1989-10-27 | 1989-10-27 | Light receiving circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1278648A JPH03141736A (en) | 1989-10-27 | 1989-10-27 | Light receiving circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH03141736A true JPH03141736A (en) | 1991-06-17 |
Family
ID=17600211
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1278648A Pending JPH03141736A (en) | 1989-10-27 | 1989-10-27 | Light receiving circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH03141736A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010035662A1 (en) * | 2008-09-29 | 2010-04-01 | 日本電気株式会社 | Optical transmitter, optical receiver, and optical communication system |
-
1989
- 1989-10-27 JP JP1278648A patent/JPH03141736A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010035662A1 (en) * | 2008-09-29 | 2010-04-01 | 日本電気株式会社 | Optical transmitter, optical receiver, and optical communication system |
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| JPS62241439A (en) | Two-wire and four-wire converting circuit | |
| JPH077953B2 (en) | Shared signal line for digital signals |