JPH08213956A - Optical signal transmission method - Google Patents
Optical signal transmission methodInfo
- Publication number
- JPH08213956A JPH08213956A JP7041445A JP4144595A JPH08213956A JP H08213956 A JPH08213956 A JP H08213956A JP 7041445 A JP7041445 A JP 7041445A JP 4144595 A JP4144595 A JP 4144595A JP H08213956 A JPH08213956 A JP H08213956A
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- Prior art keywords
- optical
- optical signal
- transmitting station
- transmission method
- station
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Abstract
Description
【0001】[0001]
【産業上の利用分野】本発明は光CATVシステム、光
ITVシステム等における光信号伝送方法に関するもの
である。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal transmission method in an optical CATV system, an optical ITV system or the like.
【0002】[0002]
【従来の技術】光CATVシステム、光ITVシステム
等における光信号伝送方法には従来より各種方法があ
り、その一つとして図7に示す光伝送装置を利用する方
法があった。図7に示す光伝送装置は数100mから数
kmの距離で配置された複数(n箇所)の送信局31か
らの映像を光伝送路26により受信局23に伝送し、受
信局23の一つの受光器24で受光して一括監視できる
ようにしたものである。図7の各送信局31には映像撮
影用カメラ等の信号源21、変調器27、光源(E/O
変換器)22、光合波器(光カプラ)25が設置され、
各送信局31からの光信号は光ファイバ(光伝送路)2
6により受信局23へ送られるようにしてある。2. Description of the Related Art Conventionally, there are various methods for transmitting an optical signal in an optical CATV system, an optical ITV system, etc., and one of them is a method using an optical transmission device shown in FIG. The optical transmission device shown in FIG. 7 transmits images from a plurality (n places) of transmission stations 31 arranged at a distance of several hundreds of meters to several kilometers to the reception station 23 through the optical transmission path 26, and one of the reception stations 23 is transmitted. The light receiver 24 receives the light so that it can be collectively monitored. Each transmitting station 31 in FIG. 7 has a signal source 21, such as a video camera, a modulator 27, a light source (E / O).
A converter) 22 and an optical multiplexer (optical coupler) 25 are installed,
The optical signal from each transmitting station 31 is an optical fiber (optical transmission line) 2
6 to the receiving station 23.
【0003】図7では各送信局31の信号源21からの
信号(例えば映像信号)は各送信局31の変調器27に
より特定周波数の搬送波(サブキャリア)に乗せられ、
この搬送波により変調された光信号が光源22の半導体
レーザ(例えばLD)から発生する。搬送波の周波数帯
域は光伝送方法によって異なるが図7の光伝送装置では
0.4から2GHzの範囲としてある。図7の各送信局
31からの光信号は光合波器25を通して光伝送路26
に導かれて多重化され、一括して受信局23の受光器
(例えばフォトダイオード:PD)24で受光されて検
波され、分配器28により分配され、復調器29により
前記搬送波の周波数別に復調され、送信局31別に監視
機器(例えばモニタテレビ)40により受像されて映像
の監視が行なわれる。In FIG. 7, a signal (for example, a video signal) from the signal source 21 of each transmitting station 31 is put on a carrier (subcarrier) of a specific frequency by a modulator 27 of each transmitting station 31,
The optical signal modulated by this carrier wave is generated from the semiconductor laser (for example, LD) of the light source 22. The frequency band of the carrier wave varies depending on the optical transmission method, but is in the range of 0.4 to 2 GHz in the optical transmission device of FIG. The optical signal from each transmitting station 31 in FIG.
To be multiplexed and received at a light receiving device (eg, photodiode: PD) 24 of the receiving station 23 for detection, distributed by a distributor 28, and demodulated by a demodulator 29 for each frequency of the carrier wave. The image is received by the monitoring device (for example, monitor TV) 40 for each transmitting station 31 and the image is monitored.
【0004】図7の様に複数の光信号を合波して多重伝
送する場合、各送信極31から送られて受信局23で受
信される搬送波の大きさが同一になることが雑音特性上
望ましい。そのため従来は図6に示す様に光源(E/O
変換器)22と光合波器(光カプラ)25との間に光減
衰器(アッテネータ)30を挿入し、夫々の光アッテネ
ータ30により光伝送路26に送り出される光信号のレ
ベルを調節して、受信局23における搬送波の大きさが
同一になるようにしてある。In the case of multiplexing a plurality of optical signals for multiplex transmission as shown in FIG. 7, the carrier waves sent from the respective transmission poles 31 and received by the receiving station 23 have the same size, which is a noise characteristic. desirable. Therefore, conventionally, as shown in FIG. 6, a light source (E / O
The optical attenuator (attenuator) 30 is inserted between the converter 22 and the optical multiplexer (optical coupler) 25, and the level of the optical signal sent to the optical transmission line 26 by each optical attenuator 30 is adjusted, The sizes of the carrier waves in the receiving station 23 are set to be the same.
【0005】[0005]
【発明が解決しようとする課題】図6に示す従来方法の
光信号伝送方法では次の様な問題があった。 .受信局23において各送信局31からの搬送波の強
度を測定しながら、光信号の強度を送信局31の光アッ
テネータ30で調節しなければならず、作業が面倒であ
った。 .送信局の増設時には増設される送信局の光アッテネ
ータ30だけでなく、既設の送信局23の光アッテネー
タ30の減衰量をも再調整しなければならず、調整作業
がより一層面倒であった。The conventional optical signal transmission method shown in FIG. 6 has the following problems. . The intensity of the optical signal must be adjusted by the optical attenuator 30 of the transmitting station 31 while measuring the intensity of the carrier wave from each transmitting station 31 at the receiving station 23, which is troublesome. . When the number of transmitting stations is increased, it is necessary to readjust not only the optical attenuator 30 of the transmitting station to be added but also the attenuation amount of the optical attenuator 30 of the existing transmitting station 23, which makes the adjustment work even more troublesome.
【0006】本発明の目的は二以上の送信局の光源から
発光される光信号の強度、変調度が自動的に調整され
て、各送信局からの光信号が受信局で同一強度で受信さ
れるようにし、送信局の新設や増設が容易で、信頼性の
高い光信号伝送方法を提供することにある。An object of the present invention is to automatically adjust the intensity and modulation degree of optical signals emitted from the light sources of two or more transmitting stations so that the optical signals from each transmitting station are received by the receiving station with the same intensity. Thus, it is an object of the present invention to provide a highly reliable optical signal transmission method that facilitates new installation or extension of a transmission station.
【0007】[0007]
【課題を解決するための手段】本発明のうち請求項1の
光信号伝送方法は図1〜4に示すように、二以上の送信
局2の光源3から、各送信局2の変調器1の周波数の異
なる搬送波により変調された波長の異なる光信号を送り
出し、それらの光信号を光合波器4により光伝送路5に
合波して多重化し、多重化された光信号を受信局6の一
つの受光器7により同時に受光して復調するようにした
光信号伝送方法において、各送信局2の光合波器4の一
端に受光部8を設け、光伝送路5の上流から送られる光
信号を下流の送信局2の受光部8で受けて光/電気変換
し、その電気信号に応じて送信局1から光合波器4に送
り出される光信号レベルを制御するようにしたものであ
る。The optical signal transmission method according to claim 1 of the present invention is, as shown in FIGS. 1 to 4, from the light sources 3 of two or more transmitting stations 2 to the modulator 1 of each transmitting station 2. Optical signals of different wavelengths modulated by carrier waves of different frequencies are sent out, these optical signals are multiplexed by the optical multiplexer 4 into the optical transmission line 5, and the multiplexed optical signals are received by the receiving station 6. In the optical signal transmission method in which one light receiving device 7 simultaneously receives and demodulates, a light receiving portion 8 is provided at one end of the optical multiplexer 4 of each transmitting station 2, and an optical signal sent from the upstream of the optical transmission path 5 is provided. Is received by the light receiving section 8 of the downstream transmitting station 2 and converted into light / electricity, and the optical signal level sent from the transmitting station 1 to the optical multiplexer 4 is controlled according to the electric signal.
【0008】本発明のうち請求項2の光信号伝送方法は
請求項1記載の光信号伝送方法において、図1〜3に示
すように光伝送路5の上流から送られる光信号を、光伝
送路5の上流に設けた基準光信号発生部9から発生され
る基準光信号としたものである。According to a second aspect of the present invention, in the optical signal transmission method according to the first aspect, the optical signal transmitted from the upstream side of the optical transmission line 5 as shown in FIGS. This is a reference optical signal generated from a reference optical signal generator 9 provided upstream of the path 5.
【0009】本発明のうち請求項3の光信号伝送方法は
請求項1記載の光信号伝送方法において、図4に示すよ
うに光伝送路5の上流から送られる光信号が光伝送路5
の上流の送信局2からの光信号であり、下流の送信局2
の受光部8ではその光信号を光/電気変換し且つその電
気信号から所望周波数の電気信号を取り出し、その電気
信号に応じて送信局2から光合波器4に送り出される光
信号レベルを制御するようにしたものである。In the optical signal transmission method according to claim 3 of the present invention, in the optical signal transmission method according to claim 1, the optical signal sent from the upstream of the optical transmission line 5 as shown in FIG.
Optical signal from the upstream transmission station 2 of the
In the light receiving section 8 of the optical signal, the optical signal is converted into an electric signal, an electric signal of a desired frequency is extracted from the electric signal, and the optical signal level sent from the transmitting station 2 to the optical multiplexer 4 is controlled according to the electric signal. It was done like this.
【0010】本発明のうち請求項4の光信号伝送方法は
請求項1乃至請求項3記載のいずれかの光信号伝送方法
において、図1に示すように送信局2の受光部8から出
力される電気信号に応じて送信局2の出力側に設けた光
アッテネータ10の減衰量を制御して、送信局2から光
合波器4に送り出される光信号レベルを制御するように
したものである。An optical signal transmission method according to a fourth aspect of the present invention is the optical signal transmission method according to any one of the first to third aspects, in which the optical signal is output from the light receiving section 8 of the transmitting station 2 as shown in FIG. The optical attenuator 10 provided on the output side of the transmission station 2 is controlled according to the electric signal to control the optical signal level sent from the transmission station 2 to the optical multiplexer 4.
【0011】本発明のうち請求項5の光信号伝送方法は
請求項1乃至請求項3記載のいずれかの光信号伝送方法
において、図2に示すように送信局2の受光部8から出
力される電気信号に応じて送信局2の光源3の駆動電流
を制御して、送信局2から光合波器4に送り出される光
信号レベルを制御するようにしたものである。The optical signal transmission method according to a fifth aspect of the present invention is the optical signal transmission method according to any one of the first to third aspects, wherein the optical signal is output from the light receiving section 8 of the transmitting station 2 as shown in FIG. The drive current of the light source 3 of the transmitting station 2 is controlled according to the electric signal to control the optical signal level sent from the transmitting station 2 to the optical multiplexer 4.
【0012】本発明のうち請求項6の光信号伝送方法は
請求項1乃至請求項3記載のいずれかの光信号伝送方法
において、図3に示すように送信局2の受光部8から出
力される電気信号に応じて送信局2の変調器1の変調度
を制御して、送信局2から光合波器4に送り出される光
信号レベルを制御するようにしたものである。The optical signal transmission method according to a sixth aspect of the present invention is the optical signal transmission method according to any one of the first to third aspects, wherein the optical signal is output from the light receiving section 8 of the transmission station 2 as shown in FIG. The modulation degree of the modulator 1 of the transmitting station 2 is controlled according to the electric signal to control the optical signal level sent from the transmitting station 2 to the optical multiplexer 4.
【0013】本発明のうち請求項7の光信号伝送方法は
請求項1乃至請求項6記載のいずれかの光信号伝送方法
において、図1〜4に示すように送信局2の受光部8が
受光器11と所定信号を取り出すフィルタ12とから構
成され、同フィルタ12から出力される電気信号により
送信局2から光合波器4に送り出される光信号レベルを
制御するようにしたものである。The optical signal transmitting method according to claim 7 of the present invention is the optical signal transmitting method according to any one of claims 1 to 6, in which the light receiving portion 8 of the transmitting station 2 is provided as shown in FIGS. The optical receiver is composed of a photodetector 11 and a filter 12 for extracting a predetermined signal, and an electric signal output from the filter 12 controls the optical signal level sent from the transmitting station 2 to the optical multiplexer 4.
【0014】本発明のうち請求項8の光信号伝送方法は
請求項7記載の光信号伝送方法において、送信局2の受
光部8のフィルタ12が、同受光部8で電気変換された
基準光信号の強度を取り出すようにしたものである。The optical signal transmitting method according to claim 8 of the present invention is the optical signal transmitting method according to claim 7, wherein the filter 12 of the light receiving portion 8 of the transmitting station 2 is electrically converted by the light receiving portion 8. The signal strength is taken out.
【0015】本発明のうち請求項9の光信号伝送方法は
請求項7記載の光信号伝送方法において、送信局2の受
光部8のフィルタ12が、同受光部8で電気変換された
自局より上流の送信局2からの光信号のうち所望周波数
の信号を取り出すようにしたものである。The optical signal transmitting method according to claim 9 of the present invention is the optical signal transmitting method according to claim 7, wherein the filter 12 of the light receiving portion 8 of the transmitting station 2 is electrically converted by the light receiving portion 8. A signal of a desired frequency is extracted from the optical signal from the upstream transmitting station 2.
【0016】[0016]
【作用】本発明のうち請求項1の光信号伝送方法では、
光伝送路5中を伝送される上流からの光信号を二以上の
送信局2の夫々の光合波器4の一端に設けた受光部8で
光/電気変換し、その電気信号に応じて送信局1から光
合波器4に送り出される光信号レベルを制御するので、
二以上の送信局2から送り出されて受信局6の一つの受
光器7で受信される光信号レベルが同一になるように前
記制御を行えば受光器7での受信時の雑音特性が劣化し
にくくなる。In the optical signal transmission method according to claim 1 of the present invention,
An optical signal from the upstream transmitted through the optical transmission line 5 is optically / electrically converted by the light receiving unit 8 provided at one end of each optical multiplexer 4 of the two or more transmitting stations 2, and is transmitted according to the electrical signal. Since the optical signal level sent from the station 1 to the optical multiplexer 4 is controlled,
If the above control is performed so that the optical signal levels sent from two or more transmitting stations 2 and received by one photoreceiver 7 of the receiving station 6 are the same, the noise characteristic at the time of reception by the photoreceiver 7 is deteriorated. It gets harder.
【0017】本発明のうち請求項2の光信号伝送方法で
は、光伝送路5の上流から送られる光信号を光伝送路5
の上流に設けた基準光信号発生部9から発生される基準
光信号としたので、その基準光信号を送信局2の受光部
8で受け、夫々の受光部8から出力される電気信号に応
じて各送信局1から光合波器4に送り出される光信号レ
ベルを制御するので、二以上の送信局2から送り出され
て受信局6の一つの受光器7で受信される光信号レベル
が同一になるように前記制御を行えば受光器7での受信
時の雑音特性が劣化しにくくなる。In the optical signal transmission method according to the second aspect of the present invention, the optical signal transmitted from the upstream of the optical transmission line 5 is transmitted.
Since the reference optical signal is generated from the reference optical signal generator 9 provided upstream of the optical receiver, the reference optical signal is received by the light receiving unit 8 of the transmitting station 2 and the electric signal output from each light receiving unit 8 is received. Since the optical signal level sent from each transmitting station 1 to the optical multiplexer 4 is controlled, the optical signal levels sent from two or more transmitting stations 2 and received by one photoreceiver 7 of the receiving station 6 are the same. If the above control is performed so that the noise characteristic at the time of reception by the light receiver 7 is less likely to deteriorate.
【0018】本発明のうち請求項3の光信号伝送方法で
は、光伝送路5の上流から送られる光信号が光伝送路5
の上流の送信局2からの光信号であり、下流の送信局2
の受光部8ではその光信号を光/電気変換し且つその電
気信号から所望周波数の電気信号を取り出し、その電気
信号に応じて送信局2から光合波器4に送り出される光
信号レベルを制御するようにしたので、二以上の送信局
2から送り出されて受信局6の一つの受光器7で受信さ
れる光信号レベルが同一になるように前記制御を行えば
受光器7での受信時の雑音特性が劣化しにくくなる。In the optical signal transmission method according to the third aspect of the present invention, the optical signal sent from the upstream of the optical transmission line 5 is the optical transmission line 5.
Optical signal from the upstream transmission station 2 of the
In the light receiving section 8 of the optical signal, the optical signal is converted into an electric signal, an electric signal of a desired frequency is extracted from the electric signal, and the optical signal level sent from the transmitting station 2 to the optical multiplexer 4 is controlled according to the electric signal. Therefore, if the above-mentioned control is performed so that the optical signal levels sent from two or more transmitting stations 2 and received by one light receiver 7 of the receiving station 6 are the same, the light receiving device 7 receives Noise characteristics are less likely to deteriorate.
【0019】本発明のうち請求項4の光信号伝送方法で
は、送信局2の受光部8から出力される電気信号に応じ
て送信局2の出力側に設けた光アッテネータ10の減衰
量を制御して、送信局2から光合波器4に送り出される
光信号レベルを制御するので、二以上の送信局2から送
り出されて受信局6の一つの受光器7で受信される光信
号レベルが同一になるように前記光アッテネータ10の
減衰量を制御すれば受光器7での受信時の雑音特性が劣
化しにくくなる。In the optical signal transmitting method according to the fourth aspect of the present invention, the attenuation amount of the optical attenuator 10 provided on the output side of the transmitting station 2 is controlled according to the electric signal output from the light receiving section 8 of the transmitting station 2. Then, since the optical signal level sent from the transmitting station 2 to the optical multiplexer 4 is controlled, the optical signal level sent from two or more transmitting stations 2 and received by one light receiver 7 of the receiving station 6 is the same. If the attenuation amount of the optical attenuator 10 is controlled so that the noise characteristic at the time of reception by the light receiver 7 is less likely to deteriorate.
【0020】本発明のうち請求項5の光信号伝送方法で
は、送信局2の受光部8から出力される電気信号に応じ
て送信局2の光源3の駆動電流を制御して、送信局2か
ら光合波器4に送り出される光信号レベルを制御するの
で、二以上の送信局2から送り出されて受信局6の一つ
の受光器7で受信される光信号レベルが同一になるよう
に前記駆動電流の減衰量を制御すれば受光器7での受信
時の雑音特性が劣化しにくくなる。In the optical signal transmitting method according to the fifth aspect of the present invention, the driving current of the light source 3 of the transmitting station 2 is controlled in accordance with the electric signal output from the light receiving portion 8 of the transmitting station 2 to transmit the transmitting station 2. The optical signal level sent from the optical multiplexer 4 to the optical multiplexer 4 is controlled so that the optical signal levels sent from two or more transmitting stations 2 and received by one light receiver 7 of the receiving station 6 become the same. By controlling the amount of attenuation of the current, the noise characteristic at the time of reception by the light receiver 7 is less likely to deteriorate.
【0021】本発明のうち請求項6の光信号伝送方法で
は、送信局2の受光部8から出力される電気信号に応じ
て送信局2の変調器1の変調度を制御して、送信局2か
ら光合波器4に送り出される光信号レベルを制御するの
で、二以上の送信局2から送り出されて受信局6の一つ
の受光器7で受信される光信号レベルが同一になるよう
に前記変調度を制御すれば受光器7での受信時の雑音特
性が劣化しにくくなる。In the optical signal transmitting method according to claim 6 of the present invention, the modulation degree of the modulator 1 of the transmitting station 2 is controlled in accordance with the electric signal output from the light receiving section 8 of the transmitting station 2 and the transmitting station is controlled. Since the optical signal level sent from 2 to the optical multiplexer 4 is controlled, the optical signal level sent from two or more transmitting stations 2 and received by one light receiving device 7 of the receiving station 6 becomes the same. If the modulation degree is controlled, the noise characteristic at the time of reception at the light receiver 7 is less likely to deteriorate.
【0022】本発明のうち請求項7の光信号伝送方法で
は、送信局2の受光部8が受光器11と所定信号を取り
出すフィルタ12とから構成され、同フィルタ12から
出力される電気信号により送信局2から光合波器4に送
り出される光信号レベルを制御するので、フィルタ12
の通過周波数を選択することにより、上流から送られて
くる光信号から所望周波数の信号を取り出し、取り出さ
れた信号に合わせて送信局2のアッテネータ10の減衰
量、送信局2の光源3の駆動電流、送信局2の変調器1
の変調度を制御して、受信局6の一つの受光器7で受信
される光信号レベルが同一になる様にすることができ、
受光器7での受信時の雑音特性が劣化しにくくなる。In the optical signal transmitting method according to claim 7 of the present invention, the light receiving portion 8 of the transmitting station 2 comprises a light receiving device 11 and a filter 12 for taking out a predetermined signal, and an electric signal output from the filter 12 is used. Since the optical signal level sent from the transmitting station 2 to the optical multiplexer 4 is controlled, the filter 12
Of the desired frequency from the optical signal sent from the upstream side by selecting the passing frequency of, the attenuation amount of the attenuator 10 of the transmitting station 2 and the driving of the light source 3 of the transmitting station 2 in accordance with the extracted signal. Current, modulator 1 of transmitter station 2
By controlling the modulation degree of, the optical signal level received by one optical receiver 7 of the receiving station 6 can be made the same,
Noise characteristics at the time of reception at the light receiver 7 are less likely to deteriorate.
【0023】本発明のうち請求項8の光信号伝送方法で
は、送信局2の受光部8のフィルタ12が、同受光部8
で電気変換された基準光信号の強度を取り出すようにし
たものであるため、基準光信号の強度に合わせて送信局
2のアッテネータ10の減衰量、送信局2の光源3の駆
動電流、送信局2の変調器1の変調度を制御して、受信
局6の一つの受光器7で受信される光信号レベルが均等
化されるようにすることができ、受光器7での受信時の
雑音特性が劣化しにくくなる。In the optical signal transmission method according to claim 8 of the present invention, the filter 12 of the light receiving portion 8 of the transmitting station 2 is the same as the light receiving portion 8 of the same.
Since the intensity of the reference optical signal electrically converted by is extracted, the attenuation amount of the attenuator 10 of the transmitting station 2, the drive current of the light source 3 of the transmitting station 2, the transmitting station, and the transmitting station according to the intensity of the reference optical signal. It is possible to control the modulation degree of the second modulator 1 so that the optical signal level received by one light receiver 7 of the receiving station 6 is equalized, and noise at the time of reception by the light receiver 7 is generated. The characteristics are less likely to deteriorate.
【0024】本発明のうち請求項9の光信号伝送方法で
は、送信局2の受光部8のフィルタ12が、自局より上
流の送信局2から伝送された光信号のうち所望周波数の
信号を取り出すようにしたものであるため、その信号の
強度に合わせて送信局2のアッテネータ10の減衰量、
送信局2の光源3の駆動電流、送信局2の変調器1の変
調度を制御して、受信局6の一つの受光器7で受信され
る光信号レベルが均等化されるようにすることができ、
受光器7での受信時の雑音特性が劣化しにくくなる。In the optical signal transmitting method according to claim 9 of the present invention, the filter 12 of the light receiving portion 8 of the transmitting station 2 transmits a signal of a desired frequency among the optical signals transmitted from the transmitting station 2 upstream from the own station. Since the signal is taken out, the attenuation amount of the attenuator 10 of the transmitting station 2 is adjusted according to the strength of the signal,
To control the drive current of the light source 3 of the transmitting station 2 and the modulation degree of the modulator 1 of the transmitting station 2 so that the optical signal level received by one of the light receivers 7 of the receiving station 6 is equalized. Can
Noise characteristics at the time of reception at the light receiver 7 are less likely to deteriorate.
【0025】[0025]
【実施例1】本発明の光信号伝送方法の第1の実施例を
図1に基づいて詳細に説明する。図1に示す光伝送装置
は数100mから数kmの距離で配置された複数(n箇
所)の送信局1に映像撮影用カメラ等の信号源13、変
調器(MOD)1、光源(E/O変換器)3、光合波器
4設置され、各送信局2からの光信号は変調器1からの
搬送波(サブキャリア)によって変調され、光合波器4
を介して光ファイバ(光伝送路)5に送り込まれて合波
され、多重化されて受信局6へ送られ、受信局6におい
て一つの受光器(O/E変換器:例えばフォトダイオー
ド:PD)7により同時に受光されるようにしてある。First Embodiment A first embodiment of the optical signal transmission method of the present invention will be described in detail with reference to FIG. The optical transmission device shown in FIG. 1 includes a signal source 13 such as a video camera, a modulator (MOD) 1 and a light source (E / E) in a plurality (n locations) of transmission stations 1 arranged at a distance of several 100 m to several km. O converter) 3 and optical multiplexer 4 are installed, the optical signal from each transmitting station 2 is modulated by the carrier wave (subcarrier) from modulator 1, and optical multiplexer 4
Is transmitted to the optical fiber (optical transmission line) 5 via the optical fiber, multiplexed, multiplexed, and transmitted to the receiving station 6, where one optical receiver (O / E converter: eg photodiode: PD) ) 7 to receive light at the same time.
【0026】図1では従来の構成に加え、送信局1側の
光伝送路5の上流に発振器14とE/O変換器15とか
ら構成される基準光信号発生部9を設置し、夫々の送信
局2では光合波器4の一端に受光器(O/E変換器)1
1と前記基準光信号発生部9からの基準光信号の強度の
みを取り出すフィルタ12とから構成される受光部8を
設け、このフィルタ12から出力される電気信号を光ア
ッテネータ10に入力して光アッテネータ10の減衰量
を制御するようにしてある。この場合、受光される基準
光信号のレベルが小さいときは光アッテネータ10の減
衰量の低減を少なくして光アッテネータ10の減衰量を
大きくし、その送信局から送り出される光信号のレベル
が弱まるようにする。逆に、受光される基準信号のレベ
ルが大きいときは光アッテネータ10の減衰量の低減を
大きくして光アッテネータ10の減衰量を小さくし、そ
の送信局から送り出される光信号のレベルの弱まりを少
なくする。これにより各送信局2から伝送されて受信局
6で受光される光信号強度は同一となる。In FIG. 1, in addition to the conventional configuration, a reference optical signal generator 9 comprising an oscillator 14 and an E / O converter 15 is installed upstream of the optical transmission line 5 on the transmitter station 1 side, and each of them is provided with a reference optical signal generator 9. At the transmitting station 2, a light receiver (O / E converter) 1 is provided at one end of the optical multiplexer 4.
1 and a filter 12 for extracting only the intensity of the reference optical signal from the reference optical signal generator 9 is provided, and the electric signal output from the filter 12 is input to the optical attenuator 10 to generate an optical signal. The attenuation amount of the attenuator 10 is controlled. In this case, when the level of the received reference optical signal is low, the reduction of the attenuation amount of the optical attenuator 10 is reduced to increase the attenuation amount of the optical attenuator 10 so that the level of the optical signal transmitted from the transmitting station is weakened. To On the contrary, when the level of the received reference signal is high, the attenuation of the optical attenuator 10 is greatly reduced to reduce the attenuation of the optical attenuator 10 to reduce the weakening of the level of the optical signal sent from the transmitting station. To do. As a result, the optical signal intensity transmitted from each transmitting station 2 and received by the receiving station 6 becomes the same.
【0027】図1において光合波器4の分岐損失を図5
に示す様に1dBと10dB、隣接する光合波器4間の
伝送路損失を5dBとすると、各送信局2からの出力信
号が受信局6においてほぼ同一になるように調整するた
めには、図1において隣接する2つの送信局2のうち、
下流側の送信局2の光アッテネータ10はそれより一つ
上流側の送信局2の光アッテネータ10より6dB大き
くする必要がある。一方、下流側の送信局2で受光され
る基準信号のレベルは一つ上流側の送信局2で受光され
る信号のレベルより6dB小さくなり、この値は光アッ
テネータ10の損失差と一致する。このため両送信局2
で受光される基準信号のレベルに応じて各送信局2の光
アッテネータ10を自動的に調整すると、下流側の送信
局2の光アッテネータ10の減衰量の低減が少なく、上
流側の送信局2の光アッテネータ10の減衰量の低減が
多くなる。このため、下流側の送信局2から送信される
光信号の減衰量は多くなるが、上流側の送信局2から送
信される光信号の減衰量はが少なくなり、受信局6で受
信される各送信局2からの光信号強度がほぼ同一にな
る。The branch loss of the optical multiplexer 4 in FIG. 1 is shown in FIG.
As shown in FIG. 3, assuming that the transmission line loss between the adjacent optical multiplexers 4 is 5 dB and 1 dB and 10 dB, in order to adjust the output signals from the respective transmitting stations 2 to be substantially the same at the receiving station 6, Of the two transmitting stations 2 adjacent in 1,
The optical attenuator 10 of the transmitting station 2 on the downstream side needs to be 6 dB larger than the optical attenuator 10 of the transmitting station 2 on the upstream side. On the other hand, the level of the reference signal received by the transmitting station 2 on the downstream side is 6 dB lower than the level of the signal received by the transmitting station 2 on the upstream side, and this value matches the loss difference of the optical attenuator 10. Therefore, both transmitting stations 2
When the optical attenuator 10 of each transmitting station 2 is automatically adjusted in accordance with the level of the reference signal received by the optical transmitting device 2, the amount of attenuation of the optical attenuator 10 of the transmitting station 2 on the downstream side is small, and the transmitting station 2 on the upstream side is reduced. The reduction of the attenuation amount of the optical attenuator 10 is increased. Therefore, the attenuation amount of the optical signal transmitted from the transmission station 2 on the downstream side increases, but the attenuation amount of the optical signal transmitted from the transmission station 2 on the upstream side decreases, and the optical signal is received by the reception station 6. The optical signal intensity from each transmitting station 2 becomes substantially the same.
【0028】図1の受信局6には図示されていないが、
この受信局6には図7の受信局3と同様に分配器、復調
器、モニタテレビ等の端末装置が設置されており、多重
化されて光伝送路を伝送されてくる光信号は受光器で同
時に受光されて検波された後、分配器により復調器へ分
配され、復調器において搬送周波数別に復調され、送信
局別にモニタテレビ等の受信装置により映像の監視が行
なわれるようにしてある。Although not shown in the receiving station 6 of FIG.
Similar to the receiving station 3 of FIG. 7, the receiving station 6 is provided with a terminal device such as a distributor, a demodulator, and a monitor TV, and the optical signal transmitted through the optical transmission line after being multiplexed is received by the optical receiver. At the same time, the light is received and detected at the same time, and then distributed to the demodulator by the distributor, demodulated for each carrier frequency in the demodulator, and the image is monitored by the receiving device such as a monitor television for each transmitting station.
【0029】[0029]
【実施例2】本発明の光信号伝送方法の第2の実施例を
図2に基づいて詳細に説明する。図2に示すものは基本
的構成は図1に示すものと同じであり、異なるのは図1
の光アッテネータ10を取外し、フィルタ12からの出
力を光源3に入力するようにしたことである。そして図
2では受光部8のフィルタ12を基準光信号発生部9か
らの基準光信号の強度のみを取り出すものとし、このフ
ィルタ12で取り出された基準光信号に基づいて光源3
の駆動電流を制御するようにしてある。Second Embodiment A second embodiment of the optical signal transmission method of the present invention will be described in detail with reference to FIG. The structure shown in FIG. 2 is the same as that shown in FIG.
The optical attenuator 10 is removed and the output from the filter 12 is input to the light source 3. In FIG. 2, the filter 12 of the light receiving unit 8 extracts only the intensity of the reference optical signal from the reference optical signal generating unit 9, and the light source 3 is extracted based on the reference optical signal extracted by the filter 12.
The drive current of is controlled.
【0030】図2においても光合波器4の分岐損失を図
5に示す様に1dBと10dB、隣接する光合波器4間
の伝送路損失を5dBとすると、下流側の送信局2の受
光部6で受光される基準光信号のレベルが小さく、上流
側の送信局2の受光部6で受光される基準光信号のレベ
ルが大きくなる。この場合、受光される基準光信号のレ
ベルが小さいときは送信局2の光源3の駆動電流を小さ
くして光源3から発光される光量を少なくし、受光され
る基準光信号のレベルが大きいときは光源3の駆動電流
を大きくして光源3から発光される光量を多くすると、
受信局6で受信される各送信局2からの光信号強度がほ
ぼ同一になる。Also in FIG. 2, assuming that the branch loss of the optical multiplexer 4 is 1 dB and 10 dB as shown in FIG. 5 and the transmission line loss between the adjacent optical multiplexers 4 is 5 dB, the light receiving portion of the transmitting station 2 on the downstream side. The level of the reference optical signal received by 6 is low, and the level of the reference optical signal received by the light receiving unit 6 of the upstream transmission station 2 is high. In this case, when the level of the received reference optical signal is low, the drive current of the light source 3 of the transmitting station 2 is reduced to reduce the amount of light emitted from the light source 3, and when the level of the received reference optical signal is high. Increases the drive current of the light source 3 to increase the amount of light emitted from the light source 3,
The optical signal intensities from the respective transmitting stations 2 received by the receiving station 6 become substantially the same.
【0031】[0031]
【実施例3】本発明の光信号伝送方法の第3の実施例を
図2に基づいて詳細に説明する。図3に示すものは基本
的には図2に示すものと同じ構成であり、異なるのはフ
ィルタ12から出力される基準光信号の電気信号を変調
器1に入力し、その電気信号に基づいて変調器7の変調
度を制御するようにしたことである。Third Embodiment A third embodiment of the optical signal transmission method of the present invention will be described in detail with reference to FIG. The configuration shown in FIG. 3 is basically the same as that shown in FIG. 2, except that the electrical signal of the reference optical signal output from the filter 12 is input to the modulator 1 and based on the electrical signal. That is, the modulation degree of the modulator 7 is controlled.
【0032】図3においても光合波器4の分岐損失を図
5に示す様に1dBと10dB、隣接する光合波器4間
の伝送路損失を5dBとすると、下流側の送信局2の受
光部6で受光される基準光信号のレベルが小さく、上流
側の送信局2の受光部6で受光される基準光信号のレベ
ルが大きくなる。受光される基準光信号のレベルが小さ
いときは変調度を弱め、基準光信号のレベルが大きいと
きは変調度を高めると受信局6で受信される各送信局2
からの光信号の送信強度がほぼ同一になる。Also in FIG. 3, assuming that the branch loss of the optical multiplexer 4 is 1 dB and 10 dB as shown in FIG. 5 and the transmission line loss between the adjacent optical multiplexers 4 is 5 dB, the light receiving portion of the transmitting station 2 on the downstream side. The level of the reference optical signal received by 6 is low, and the level of the reference optical signal received by the light receiving unit 6 of the upstream transmission station 2 is high. When the level of the received reference optical signal is low, the degree of modulation is weakened, and when the level of the reference optical signal is high, the degree of modulation is increased.
The transmission intensities of the optical signals from are almost the same.
【0033】[0033]
【実施例4】本発明の光信号伝送方法の第4の実施例を
図4に基づいて詳細に説明する。図4に示すものは基本
的には図1に示すものと同じ構成であり、異なるのは図
4における基準光信号発生部9を除去し、光伝送路5の
上流の送信局2からの光信号を下流の送信局2の受光部
8で受光し、その受光信号のレベルに基づいて送信局2
の光アッテネータ10の減衰量を制御するようにしたも
のである。この場合、各送信局2の受光部8のフィルタ
12は上流の多くの送信局2から光伝送路5に送り出さ
れる光信号のうち、所望とする送信局2からの光信号を
取り出すことができるように通過周波数帯を決めてあ
る。Fourth Embodiment A fourth embodiment of the optical signal transmission method of the present invention will be described in detail with reference to FIG. The configuration shown in FIG. 4 is basically the same as that shown in FIG. 1, except that the reference optical signal generator 9 in FIG. 4 is removed and the light from the transmitting station 2 upstream of the optical transmission line 5 is removed. The signal is received by the light receiving unit 8 of the downstream transmitting station 2, and the transmitting station 2
The attenuation amount of the optical attenuator 10 is controlled. In this case, the filter 12 of the light receiving unit 8 of each transmitting station 2 can extract a desired optical signal from the transmitting station 2 among the optical signals transmitted from many upstream transmitting stations 2 to the optical transmission path 5. The passing frequency band is decided like this.
【0034】図4においても光合波器4の分岐損失を図
5に示す様に1dBと10dB、隣接する光合波器4間
の伝送路損失を5dBとすると、下流側の送信局2の受
光部8で受光される上流の送信局2からの光信号のレベ
ルが小さく、上流側の送信局2の受光部8で受光される
上流の送信局2からの光信号のレベルが大きくなる。受
光される光信号のレベルが小さいときは光アッテネータ
10の減衰量の低減が少なく、レベルが大きいときは光
アッテネータ10の減衰量の低減が多くなる。即ち、下
流側の送信局2の光アッテネータ10の減衰量の低減は
少なく、上流側の送信局2の光アッテネータ10の減衰
量の低減は多くなる。このため上流からの光信号を受け
た送信局2から送信される光信号は、受けた光信号のレ
ベルに合ったレベルの光信号となって光伝送路5に送り
出され、受信局6で受信される各送信局2からの光信号
強度がほぼ均一になる。Also in FIG. 4, assuming that the branch loss of the optical multiplexer 4 is 1 dB and 10 dB as shown in FIG. 5 and the transmission line loss between the adjacent optical multiplexers 4 is 5 dB, the light receiving section of the transmitting station 2 on the downstream side. The level of the optical signal from the upstream transmitting station 2 received at 8 is low, and the level of the optical signal from the upstream transmitting station 2 received at the light receiving unit 8 of the upstream transmitting station 2 is high. When the level of the received optical signal is low, the attenuation of the optical attenuator 10 is small, and when the level of the received optical signal is high, the attenuation of the optical attenuator 10 is large. That is, the reduction of the attenuation amount of the optical attenuator 10 of the downstream transmitting station 2 is small, and the reduction of the attenuation amount of the optical attenuator 10 of the upstream transmitting station 2 is large. Therefore, the optical signal transmitted from the transmitting station 2 that receives the optical signal from the upstream becomes an optical signal having a level matching the level of the received optical signal, is sent to the optical transmission line 5, and is received by the receiving station 6. The optical signal intensities from the respective transmitting stations 2 are substantially uniform.
【0035】[0035]
【その他の実施例】本発明の光信号伝送方法は光信号が
多重化され、それらが一つの受光器で同時に受光される
ような光信号方式であれば光信号伝送装置の形態は問わ
ない。図1〜4に示すものはバス型システムであるが、
この他にも図示されていないスター型、ループ型、ツリ
ー型の装置、或はそれら以外のいずれの型の装置であっ
てもよい。Other Embodiments In the optical signal transmission method of the present invention, the optical signal transmission device may take any form as long as it is an optical signal system in which optical signals are multiplexed and simultaneously received by one light receiver. Although the one shown in FIGS. 1 to 4 is a bus type system,
Other than these, a star-type, loop-type, tree-type device, or any other type device not shown may be used.
【0036】[0036]
【発明の効果】本発明の請求項1〜請求項9の光信号伝
送方法は次の様な効果がある。 .光信号伝送装置の設置時や増設時に各送信器の出力
信号のレベルを手動操作して調整する必要がなく、光伝
送装置の設置時や増設時に出力信号のレベルが自動的に
調節され、各送信局からの光信号が受信局で同一強度と
なるため、受光時の雑音特性が改善される。 .経時変化や、他の原因により光伝送路に損失の変動
が発生した場合も、送信局2から出力される光信号のレ
ベルが自動的に補正されるため光伝送の信頼性が向上す
る。The optical signal transmission methods according to claims 1 to 9 of the present invention have the following effects. . There is no need to manually adjust the output signal level of each transmitter when installing or adding an optical signal transmission device, and the output signal level is automatically adjusted when installing or adding an optical transmission device. Since the optical signal from the transmitting station has the same intensity at the receiving station, the noise characteristic at the time of receiving light is improved. . Even if the loss changes in the optical transmission line due to changes over time or other causes, the level of the optical signal output from the transmitting station 2 is automatically corrected, and the reliability of optical transmission is improved.
【図1】本発明の光信号通信方法の第1の実施例を示す
説明図。FIG. 1 is an explanatory diagram showing a first embodiment of an optical signal communication method of the present invention.
【図2】本発明の光信号通信方法の第2の実施例を示す
説明図。FIG. 2 is an explanatory diagram showing a second embodiment of the optical signal communication method of the present invention.
【図3】本発明の光信号通信方法の第3の実施例を示す
説明図。FIG. 3 is an explanatory diagram showing a third embodiment of the optical signal communication method of the present invention.
【図4】本発明の光信号通信方法の第4の実施例を示す
説明図。FIG. 4 is an explanatory diagram showing a fourth embodiment of the optical signal communication method of the present invention.
【図5】光合波器の分岐損失と、光合波器間の伝送路損
失の説明図。FIG. 5 is an explanatory diagram of branch loss of the optical multiplexer and transmission line loss between the optical multiplexers.
【図6】従来の光通信方法において送信局からの光信号
を光アッテネータで調節する場合の説明図。FIG. 6 is an explanatory diagram of a case where an optical signal from a transmitting station is adjusted by an optical attenuator in a conventional optical communication method.
【図7】従来の光通信方法の説明図。FIG. 7 is an explanatory diagram of a conventional optical communication method.
1は変調器 2は送信局 3は光源 4は光合波器 5は光伝送路 6は受信局 7は受光器 8は受光部 9は基準光信号発生部 10は光アッテネータ 11は受光器 12はフィルタ 1 is a modulator 2 is a transmitting station 3 is a light source 4 is an optical multiplexer 5 is an optical transmission line 6 is a receiving station 7 is a light receiving device 8 is a light receiving part 9 is a reference optical signal generating part 10 is an optical attenuator 11 is a light receiving device 12 filter
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 FI 技術表示箇所 H04J 14/00 14/02 H04B 10/02 10/18 H04B 9/00 M ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification code Internal reference number FI Technical display location H04J 14/00 14/02 H04B 10/02 10/18 H04B 9/00 M
Claims (9)
各送信局(2)の変調器(1)の周波数の異なる搬送波
により変調された波長の異なる光信号を送り出し、それ
らの光信号を光合波器(4)により光伝送路(5)に合
波し、合波された光信号を受信局(6)の一つの受光器
(7)で同時に受光して復調するようにした光信号伝送
方法において、各送信局(2)の光合波器(4)の一端
に受光部(8)を設け、光伝送路(5)の上流から送ら
れる光信号を下流の送信局(2)の受光部(8)で受け
て光/電気変換し、その電気信号に応じて送信局(1)
から光合波器(4)に送り出される光信号レベルを制御
するようにしたことを特徴とする光信号伝送方法。1. From the light sources (3) of two or more transmitting stations (2),
Optical signals of different wavelengths, which are modulated by carrier waves of different frequencies of the modulator (1) of each transmitting station (2), are sent out, and these optical signals are multiplexed by the optical multiplexer (4) into the optical transmission line (5). Then, in the optical signal transmission method in which the combined optical signal is simultaneously received by one light receiver (7) of the receiving station (6) and demodulated, the optical multiplexer (4) of each transmitting station (2) ) Is provided at one end thereof, and an optical signal sent from the upstream side of the optical transmission line (5) is received by the light receiving section (8) of the downstream transmitting station (2) to be converted into an electrical signal. Transmitting station according to the signal (1)
An optical signal transmission method characterized in that the optical signal level sent from the optical multiplexer to the optical multiplexer (4) is controlled.
光伝送路(5)の上流から送られる光信号が光伝送路
(5)の上流に設けた基準光信号発生部(9)からの基
準光信号であることを特徴とする光信号伝送方法。2. The optical signal transmission method according to claim 1,
An optical signal transmission method, wherein the optical signal sent from the upstream of the optical transmission line (5) is a reference optical signal from a reference optical signal generation unit (9) provided upstream of the optical transmission line (5).
光伝送路(5)の上流から送られる光信号が光伝送路
(5)の上流の送信局(2)からの光信号であり、下流
の送信局(2)の受光部(8)ではその光信号を光/電
気変換し且つその電気信号から所望周波数の電気信号を
取り出し、その電気信号に応じて送信局(2)から光合
波器(4)に送り出される光信号レベルを制御するよう
にしたことを特徴とする光信号伝送方法。3. The optical signal transmission method according to claim 1,
The optical signal sent from the upstream of the optical transmission line (5) is the optical signal from the transmission station (2) upstream of the optical transmission line (5), and the optical signal is received by the light receiving unit (8) of the downstream transmission station (2). An optical signal is converted into an electric signal, an electric signal of a desired frequency is extracted from the electric signal, and the optical signal level sent from the transmitting station (2) to the optical multiplexer (4) is controlled according to the electric signal. An optical signal transmission method characterized by the above.
信号伝送方法において、送信局(2)の受光部(8)か
ら出力される電気信号に応じて送信局(2)の出力側に
設けた光アッテネータ(10)の減衰量を制御して、送
信局(2)から光合波器(4)に送り出される光信号レ
ベルを制御するようにしたことを特徴とする光信号伝送
方法。4. The optical signal transmission method according to any one of claims 1 to 3, wherein the output of the transmitting station (2) is output according to the electric signal output from the light receiving section (8) of the transmitting station (2). An optical signal transmission method, characterized in that the amount of attenuation of the optical attenuator (10) provided on the side is controlled to control the optical signal level sent from the transmitting station (2) to the optical multiplexer (4). .
信号伝送方法において、送信局(2)の受光部(8)か
ら出力される電気信号に応じて送信局(2)の光源
(3)の駆動電流を制御して、送信局(2)から光合波
器(4)に送り出される光信号レベルを制御するように
したことを特徴とする光信号伝送方法。5. The optical signal transmission method according to any one of claims 1 to 3, wherein the light source of the transmitting station (2) is responsive to the electric signal output from the light receiving section (8) of the transmitting station (2). An optical signal transmission method characterized in that the drive current of (3) is controlled to control the optical signal level sent from the transmitting station (2) to the optical multiplexer (4).
信号伝送方法において、送信局(2)の受光部(8)か
ら出力される電気信号に応じて送信局(2)の変調器
(1)の変調度を制御して、送信局(2)から光合波器
(4)に送り出される光信号レベルを制御するようにし
たことを特徴とする光信号伝送方法。6. The optical signal transmission method according to claim 1, wherein the modulation of the transmitting station (2) is performed according to an electric signal output from a light receiving section (8) of the transmitting station (2). An optical signal transmission method characterized in that the modulation level of the optical device (1) is controlled to control the optical signal level sent from the transmitting station (2) to the optical multiplexer (4).
信号伝送方法において、送信局(2)の受光部(8)が
受光器(11)と所望周波数の電気信号を取り出すフィ
ルタ(12)とから構成され、同フィルタ(12)から
出力される電気信号により送信局(2)から光合波器
(4)に送り出される光信号レベルを制御するようにし
たことを特徴とする光信号伝送方法。7. The optical signal transmission method according to any one of claims 1 to 6, wherein the light receiving section (8) of the transmitting station (2) and a filter (11) for extracting an electric signal of a desired frequency (11). 12), and an optical signal output from the transmitting station (2) to the optical multiplexer (4) is controlled by an electric signal output from the filter (12). Transmission method.
送信局(2)の受光部(8)のフィルタ(12)が、同
受光部(8)で電気変換された基準光信号の強度を取り
出すものであることを特徴とする光信号伝送方法。8. The optical signal transmission method according to claim 7,
The optical signal transmission method, wherein the filter (12) of the light receiving section (8) of the transmitting station (2) extracts the intensity of the reference optical signal electrically converted by the light receiving section (8).
送信局(2)の受光部(8)のフィルタ(12)が、同
受光部(8)で電気変換された自局より上流の送信局
(2)からの光信号のうち所望周波数の信号を取り出す
ものであることを特徴とする光信号伝送方法。9. The optical signal transmission method according to claim 7,
The filter (12) of the light receiving unit (8) of the transmitting station (2) outputs a signal of a desired frequency among the optical signals from the transmitting station (2) upstream of the own station which are electrically converted by the light receiving unit (8). An optical signal transmission method, characterized in that the optical signal is taken out.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP7041445A JPH08213956A (en) | 1995-02-07 | 1995-02-07 | Optical signal transmission method |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP7041445A JPH08213956A (en) | 1995-02-07 | 1995-02-07 | Optical signal transmission method |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH08213956A true JPH08213956A (en) | 1996-08-20 |
Family
ID=12608579
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP7041445A Pending JPH08213956A (en) | 1995-02-07 | 1995-02-07 | Optical signal transmission method |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH08213956A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2005020642A (en) * | 2003-06-30 | 2005-01-20 | Nec Engineering Ltd | Optical terminal device with level deviation suppression function |
-
1995
- 1995-02-07 JP JP7041445A patent/JPH08213956A/en active Pending
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2005020642A (en) * | 2003-06-30 | 2005-01-20 | Nec Engineering Ltd | Optical terminal device with level deviation suppression function |
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