JP2005277521A - Catv optical transmission apparatus - Google Patents

Catv optical transmission apparatus Download PDF

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JP2005277521A
JP2005277521A JP2004084327A JP2004084327A JP2005277521A JP 2005277521 A JP2005277521 A JP 2005277521A JP 2004084327 A JP2004084327 A JP 2004084327A JP 2004084327 A JP2004084327 A JP 2004084327A JP 2005277521 A JP2005277521 A JP 2005277521A
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catv
optical
laser diode
transmission apparatus
signal
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Hironori Uchida
弘徳 内田
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Maspro Denkoh Corp
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Maspro Denkoh Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a CATV optical transmission apparatus for maintaining stable image quality against variations in a laser diode at a low cost with a simple configuration. <P>SOLUTION: The CATV optical transmission apparatus for applying electro/optical conversion to a CATV signal transmitted from a head end and transmitting the converted signal through an optical fiber is characterized in to include at least: an automatic optical output control circuit; and a temperature compensation circuit with a temperature characteristic opposite to that of a modulation efficiency of a laser diode located just before an electro/optical conversion section provided with the laser diode subjected to direct luminance modulation by the CATV signal and a photo diode for controlling the automatic optical output control circuit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は，主にＣＡＴＶ信号を電気／光変換して，光ファイバーで伝送するＣＡＴＶ光伝送装置に関する。
The present invention mainly relates to a CATV optical transmission apparatus that performs electrical / optical conversion of a CATV signal and transmits the optical signal through an optical fiber.

従来のＣＡＴＶ光伝送装置は，ヘッドエンドから送出された信号が光送信部から光ファイバーを介して光受信部と接続されている。
ヘッドエンドから送出されたＣＡＴＶ信号は光送信部において可変減衰器で所定レベルに設定され，更に増幅器で所定レベルの増幅された後，自動光出力制御（ＡＰＣ）回路を介してレーザーダイオードを直接輝度変調することによって光出力として光ファーバーに送出されていた。
このレーザーダイオードはサーミスタやベルチェ素子等を内蔵させたレーザーダイオードモジュールとして構成されており，自動温度調節（ＡＴＣ）回路と接続されて，レーザーダイオードモジュール内の温度が一定となるように制御することで，周囲温度の変化によってレーザーダイオードの制御電流が変化し，この結果レーザーダイオードの変調効率が変動しＣＡＴＶ光伝送装置の出力レベルやＣ／Ｎが変化することの内容に構成していた。
（例えば，特許文献１参照）
In a conventional CATV optical transmission apparatus, a signal transmitted from a head end is connected to an optical receiver from an optical transmitter via an optical fiber.
The CATV signal transmitted from the head end is set to a predetermined level by a variable attenuator in the optical transmitter, and further amplified to a predetermined level by an amplifier, and then the brightness of the laser diode is directly controlled via an automatic light output control (APC) circuit. By modulating, it was sent to the optical fiber as an optical output.
This laser diode is configured as a laser diode module with a built-in thermistor, Beltier element, etc., and connected to an automatic temperature control (ATC) circuit to control the temperature inside the laser diode module to be constant. The control current of the laser diode is changed by the change of the ambient temperature, and as a result, the modulation efficiency of the laser diode is changed, and the output level and C / N of the CATV optical transmission device are changed.
(For example, see Patent Document 1)

特開平５−２５２５１８号公報JP-A-5-252518

しかし，従来の構成によれば，レーザーダイオードモジュールに冷却阻止であるベルチェ素子や温度検出素子であるサーミスタ等を内蔵させて温度補償を行う場合，回路が複雑になると共にレーザーダイオードモジュールのコストが高く，延いては製品のコストアップの要因となっていた。更に，ベルチェ冷却素子の温度制御電流から生ずるケース本体の発熱による特性劣化を防止するために，放熱器を取り付ける必要が生じることなどから製品のコストアップになっていた。
そこで本願においては，こうした問題点を解決するためになされたものであり，
その目的は，レーザーダイオードの変動に対して安定な画質を保持するＣＡＴＶ光伝送装置を提供することにある。
他の目的は，簡単な構成で且つ安価にレーザーダイオードの変動に対して安定な画質を保持するＣＡＴＶ光伝送装置を提供することにある。
他の目的は，周囲温度が変化しても出力のＣ／Ｎが安定的に得られるＣＡＴＶ光伝送装置を提供することにある。
However, according to the conventional configuration, when temperature compensation is performed with a laser diode module that incorporates a Belletier element that prevents cooling or a thermistor that is a temperature detection element, the circuit becomes complicated and the cost of the laser diode module increases. As a result, the cost of the product was increased. Furthermore, in order to prevent the deterioration of the characteristics due to the heat generation of the case main body caused by the temperature control current of the Beltier cooling element, it is necessary to attach a heatsink, thereby increasing the cost of the product.
Therefore, in this application, it was made to solve these problems.
An object of the present invention is to provide a CATV optical transmission apparatus that maintains stable image quality against fluctuations in a laser diode.
Another object of the present invention is to provide a CATV optical transmission apparatus having a simple configuration and capable of maintaining a stable image quality against fluctuations in a laser diode at a low cost.
Another object is to provide a CATV optical transmission apparatus that can stably obtain an output C / N even when the ambient temperature changes.

上記課題を解決するために，請求項１の発明は，ヘッドエンドから送出されたＣＡＴＶ信号を電気／光変換して光ファイバーで伝送するＣＡＴＶ光伝送装置において，少なくとも，自動光出力制御回路と，前記ＣＡＴＶ信号によって直接輝度変調されるレーザーダイオードと，前記自動光出力制御回路の制御を行うフォトダイオードと，を備えた電気／光変換部の直前に，当該レーザーダイオードの変調効率の温度特性と反対の特性を有する温度補償回路を備えるように構成される。
In order to solve the above-mentioned problems, the invention of claim 1 is directed to a CATV optical transmission apparatus that performs electrical / optical conversion on a CATV signal transmitted from a head end and transmits the optical signal through an optical fiber, and includes at least an automatic optical output control circuit, Opposite to the temperature characteristic of the modulation efficiency of the laser diode immediately before the electrical / optical conversion unit comprising a laser diode that is directly luminance-modulated by a CATV signal and a photodiode that controls the automatic light output control circuit. A temperature compensation circuit having characteristics is provided.

請求項２の発明は，請求項１において前記電気／光変換部は，少なくとも前記ＣＡＴＶ信号によって直接輝度変調されるレーザーダイオードと，自動光出力制御を行うフォトダイオードと，が同一筐体に収納されたレーザーモジュールから構成される。
According to a second aspect of the present invention, in the first aspect, the electrical / optical conversion unit includes at least a laser diode whose luminance is directly modulated by the CATV signal and a photodiode that performs automatic light output control accommodated in the same casing. It consists of a laser module.

請求項３の発明は，請求項１又は請求項２に記載の前記温度補償回路は，ＣＡＴＶ信号が流れる信号線に温度検出素子を介設し，当該温度検出素子の前後に夫々抵抗素子を信号線と共通線との間に配列してなる。
According to a third aspect of the present invention, in the temperature compensation circuit according to the first or second aspect, a temperature detection element is provided on a signal line through which a CATV signal flows, and a resistance element is provided before and after the temperature detection element. It is arranged between the line and the common line.

請求項１の発明によれば，ヘッドエンドから送出されたＣＡＴＶ信号を電気／光変換して光ファイバーで伝送するＣＡＴＶ光伝送装置において，少なくとも，自動光出力制御回路と，前記ＣＡＴＶ信号によって直接輝度変調されるレーザーダイオードと，前記自動光出力制御回路の制御を行うフォトダイオードと，を備えた電気／光変換部の直前に，当該レーザーダイオードの変調効率の温度特性と反対の特性を有する温度補償回路を備えるように構成したので，簡単な構成で且つ安価にレーザーダイオードの周囲温度の変動に対して安定な画質を保持するＣＡＴＶ光伝送装置を提供することができる。
According to the first aspect of the present invention, in the CATV optical transmission apparatus for converting the CATV signal transmitted from the head end into an optical fiber by electrical / optical conversion, at least an automatic light output control circuit and direct luminance modulation by the CATV signal. Compensation circuit having a characteristic opposite to the temperature characteristic of the modulation efficiency of the laser diode immediately before the electrical / optical conversion unit comprising the laser diode to be controlled and the photodiode for controlling the automatic light output control circuit Therefore, it is possible to provide a CATV optical transmission apparatus that maintains a stable image quality with respect to fluctuations in the ambient temperature of the laser diode with a simple configuration and at a low cost.

請求項２の発明によれば，前記電気／光変換部は，少なくとも前記ＣＡＴＶ信号によって直接輝度変調されるレーザーダイオードと，自動光出力制御を行うフォトダイオードと，が同一筐体に収納されたレーザーモジュールからなるよう構成したので，既存のレーザーモジュールを用いても，このモジュールの直前に温度補償回路を備えさせるだけで，レーザーダイオードの周囲温度の変動に対して安定な画質を保持するＣＡＴＶ光伝送装置を提供することができる。
According to a second aspect of the present invention, the electrical / optical converter includes a laser in which at least a laser diode whose luminance is directly modulated by the CATV signal and a photodiode that performs automatic light output control are housed in the same housing. Since it is composed of modules, even if an existing laser module is used, a CATV optical transmission that maintains stable image quality against fluctuations in the ambient temperature of the laser diode can be provided just by providing a temperature compensation circuit immediately before this module. An apparatus can be provided.

請求項３の発明によれば，請求項２又は請求項３の発明において，前記温度補償回路は，ＣＡＴＶ信号が流れる信号線に温度検出素子を介設し，当該温度検出素子の前後に夫々抵抗素子を信号線と共通線との間に配列してなるように構成したので，簡単な構成でレーザーダイオードの周囲温度の変動に対して安定な画質を保持するＣＡＴＶ光伝送装置を提供することができる。
According to a third aspect of the present invention, in the second or third aspect of the present invention, the temperature compensation circuit includes a temperature detecting element interposed in a signal line through which a CATV signal flows, and a resistance is provided before and after the temperature detecting element, respectively. Since the elements are arranged between the signal line and the common line, it is possible to provide a CATV optical transmission apparatus that maintains a stable image quality against fluctuations in the ambient temperature of the laser diode with a simple configuration. it can.

以下に，本発明を具体化した実施形態の例を，図面を基に詳細に説明する。図１は本発明に係るＣＡＴＶ光伝送装置のブロック図。図２は本発明に係る温度補償回路の実施例を示す。
Hereinafter, an example of an embodiment embodying the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a CATV optical transmission apparatus according to the present invention. FIG. 2 shows an embodiment of a temperature compensation circuit according to the present invention.

本願に示すＣＡＴＶ光伝送装置は，光送信部１０と光受信部２０とを光ファイバーケーブル１２を介して接続したＣＡＴＶシステムである。
ヘッドエンド装置１から送出された信号は，同軸ケーブルを介して光送信部１０に入力される。
光送信部１０では，入力されたＣＡＴＶ信号が可変減衰器２によって所定レベルに設定され，この信号は増幅器３で所定レベルまで増幅された後，温度補償回路４を通過して，レーザーダイオードモジュール５に備えられたレーザーダイオード駆動回路によってレーザーダイオード７を直接輝度変調するように構成されている。
レーザーダイオード７において生成された光信号は光ファイバー８，光コネクター９に接続されて光送信部１０から出力される。この光送信部１０によって出力された光信号は光ファイバーケーブル１２を介して光受信部２０に入力される。光受信部２０は光ファイバケーブル１２と接続された光コネクター１３，光信号を電気信号に変換するＯ／Ｅ変換部１４と，光信号からＣＡＴＶ信号に変換された信号を所定レベルまで増幅する増幅器１５と，当該増幅器１５からの出力を所定レベルに調整するための可変減衰器１６等から構成されている。
The CATV optical transmission apparatus shown in this application is a CATV system in which an optical transmitter 10 and an optical receiver 20 are connected via an optical fiber cable 12.
A signal transmitted from the head end device 1 is input to the optical transmitter 10 via a coaxial cable.
In the optical transmitter 10, the input CATV signal is set to a predetermined level by the variable attenuator 2, this signal is amplified to a predetermined level by the amplifier 3, passes through the temperature compensation circuit 4, and then the laser diode module 5 The laser diode 7 is configured to directly modulate the luminance of the laser diode 7 by the laser diode driving circuit provided in the above.
The optical signal generated in the laser diode 7 is connected to the optical fiber 8 and the optical connector 9 and output from the optical transmitter 10. The optical signal output by the optical transmitter 10 is input to the optical receiver 20 via the optical fiber cable 12. The optical receiver 20 includes an optical connector 13 connected to the optical fiber cable 12, an O / E converter 14 that converts an optical signal into an electrical signal, and an amplifier that amplifies the signal converted from the optical signal to the CATV signal to a predetermined level. 15 and a variable attenuator 16 for adjusting the output from the amplifier 15 to a predetermined level.

ここで光送信部１０を構成する温度補償回路４について詳しく説明する。一般的にレーザーダイオードによる電気信号から光信号への変換を考えると，広い温度範囲にわたって安定した光出力を得るために，温度の変化に伴って電流を変化させるＡＰＣ（Ａｕｔｏｍａｔｉｃ Ｐｏｗｅｒ Ｃｏｎｔｒｏｌ 以下ＡＰＣと呼ぶ）回路１１を備えさせている。
ところがこのＡＰＣ回路１１による制御だけでは，レーザーダイオードの制御電流変化による特性の変化は避けられないため，周囲温度の変化に対してレーザーダイオードの制御電流変化を小さくするためにレーザーダイオードチップ温度を一定に制御するよう，ＡＴＣ（Ａｕｔｏｍａｔｉｃ Ｔｅｍｐｅｒａｔｕｒｅ Ｃｏｎｔｒｏｌ 以下ＡＴＣと呼ぶ）回路を備える方法がある。
しかし，ＡＴＣ回路には温度検出素子であるサーミスタや冷却素子であるベルチェ素子等を使う必要があり部品が高価になると共に回路が複雑になり，更に，ベルチェ冷却素子の温度制御電流から生ずるケース本体の発熱による特性劣化を防止するために，放熱器を取り付ける必要が生じることなどから製品のコストアップになっていた。
Here, the temperature compensation circuit 4 constituting the optical transmitter 10 will be described in detail. In general, considering the conversion from an electric signal to an optical signal by a laser diode, APC (Automatic Power Control, hereinafter referred to as APC) that changes the current with a change in temperature in order to obtain a stable optical output over a wide temperature range. ) A circuit 11 is provided.
However, since the change in characteristics due to the change in the control current of the laser diode is inevitable only by the control by the APC circuit 11, the laser diode chip temperature is kept constant in order to reduce the change in the control current of the laser diode with respect to the change in the ambient temperature. There is a method including an ATC (Automatic Temperature Control, hereinafter referred to as ATC) circuit so that the control is performed.
However, it is necessary to use a thermistor that is a temperature detection element or a Beltier element that is a cooling element for the ATC circuit, which increases the cost and complexity of the circuit. In order to prevent the deterioration of characteristics due to heat generation, it was necessary to install a heatsink.

そこで，本発明のＣＡＴＶ光伝送装置１０では，前記ＡＴＣ回路が無くとも光出力信号の出力レベルとＣ／Ｎが一定の値を得られるようにするものであり，ＣＡＴＶ信号をレーザーダイオードに入力する直前に，ＣＡＴＶ信号のレベルを制御する温度補償回路４を設けることで簡単な構成で且つ安価に実現させるものである。
即ち，ＣＡＴＶ光伝送装置１０の使用温度範囲におけるレーザーダイオード７の変調効率に対応する温度補償回路４を挿入するものであり，本願の実施例では，ＣＡＴＶ信号が流れる信号線に温度検出素子であるサーミスタ４ａ（本願では負の温度特性を有する）を介設し，当該サーミスタ４ａの前後に夫々抵抗素子４ｂ，４ｃを信号線と共通線との間に配列してなる温度補償回路が設けられている。
Therefore, in the CATV optical transmission apparatus 10 of the present invention, the output level of the optical output signal and the C / N can be obtained even without the ATC circuit, and the CATV signal is input to the laser diode. Immediately before, the temperature compensation circuit 4 for controlling the level of the CATV signal is provided to realize a simple configuration at low cost.
That is, the temperature compensation circuit 4 corresponding to the modulation efficiency of the laser diode 7 in the operating temperature range of the CATV optical transmission device 10 is inserted. In the embodiment of the present application, the temperature detection element is provided in the signal line through which the CATV signal flows. A thermistor 4a (having a negative temperature characteristic in the present application) is provided, and a temperature compensation circuit is provided in which resistance elements 4b and 4c are arranged between the signal line and the common line before and after the thermistor 4a, respectively. Yes.

この回路によれば，周囲温度が高くなった場合,サーミスタ４ａの抵抗が減少することによりこの温度補償回路４の合成抵抗が小さくなり，また周囲温度が低くなった場合，サーミスタ４ａの抵抗が大きくなることによりこの温度補償回路４の合成抵抗が大きくなるように動作する。したがってレーザーダイオード７を直接輝度変調させるＣＡＴＶ信号レベルは，周囲温度が高くなると増加し，周囲温度が低くなると減少するのである。
一方，一般的にレーザーダイオード７は温度が変わると変調効率が変化し，温度が上昇すると変調効率が低下し，温度が低くなると変調効率が高くなる。
そこで上記温度補償回路４の温度特性を，レーザーダイオード７の温度特性に対して最適化することにより，周囲温度が上昇したときは温度補償回路４の通過損失が小さくなり，レーザーダイオード７に入力されるＣＡＴＶ信号のレベルが高くなることで，受信機２０の出力においてＣ／Ｎが低下するのを防ぎ，逆に，周囲温度が下がったときは温度補償回路４の通過損失が大きくなり，レーザー駆動回路に入力されるＣＡＴＶ信号のレベルを低くすることで受信機２０の出力においてＣ／Ｎが上昇するのを防ぐことにより，この結果受信機２０の出力のＣ／Ｎを一定にできるのである。
According to this circuit, when the ambient temperature is high, the resistance of the thermistor 4a is reduced, so that the combined resistance of the temperature compensation circuit 4 is small. When the ambient temperature is low, the resistance of the thermistor 4a is large. Thus, the combined resistance of the temperature compensation circuit 4 operates so as to increase. Therefore, the CATV signal level that directly modulates the luminance of the laser diode 7 increases as the ambient temperature increases, and decreases as the ambient temperature decreases.
On the other hand, in general, the modulation efficiency of the laser diode 7 changes as the temperature changes, the modulation efficiency decreases as the temperature increases, and the modulation efficiency increases as the temperature decreases.
Therefore, by optimizing the temperature characteristics of the temperature compensation circuit 4 with respect to the temperature characteristics of the laser diode 7, when the ambient temperature rises, the passage loss of the temperature compensation circuit 4 becomes small and is input to the laser diode 7. As the level of the CATV signal increases, the C / N is prevented from decreasing at the output of the receiver 20, and conversely, when the ambient temperature decreases, the passage loss of the temperature compensation circuit 4 increases and the laser drive By reducing the level of the CATV signal input to the circuit to prevent the C / N from increasing at the output of the receiver 20, the C / N of the output of the receiver 20 can be made constant as a result.

このように構成されたＣＡＴＶ伝送装置の送信部１０を用いたシステムについて説明する。
レーザーダイオード７において生成された光信号は光ファイバー８，光コネクター９に接続されて光送信部１０を形成している。この光送信部１０によって出力された光信号は光ファイバーケーブル１２を介して光受信部２０に入力される。光受信部２０は光ファイバケーブル１２と接続された光コネクター１３，光信号を電気信号に変換するＯ／Ｅ変換部１４と，バイアス・整合回路と，光信号からＣＡＴＶ信号に変換された信号を所定レベルまで増幅する増幅器１５と，当該増幅器１５からの出力を所定レベルに調整するための可変減衰器等１６から構成されている。
従って本発明のＣＡＴＶ光送信装置を用いれば，光受信部２０の出力１７におけるシステムの出力レベル及びＣ／Ｎを一定に保つことができるのである。

尚，本発明は上記実施の形態に限定されるものではなく，以下に例示するように，本発明の趣旨を逸脱しない範囲で各部の構成を適宜に変更して実施することも可能である。
A system using the transmission unit 10 of the CATV transmission apparatus configured as described above will be described.
An optical signal generated in the laser diode 7 is connected to an optical fiber 8 and an optical connector 9 to form an optical transmitter 10. The optical signal output by the optical transmitter 10 is input to the optical receiver 20 via the optical fiber cable 12. The optical receiver 20 includes an optical connector 13 connected to the optical fiber cable 12, an O / E converter 14 that converts an optical signal into an electrical signal, a bias / matching circuit, and a signal converted from an optical signal to a CATV signal. The amplifier 15 is configured to amplify to a predetermined level, and a variable attenuator 16 for adjusting an output from the amplifier 15 to a predetermined level.
Therefore, if the CATV optical transmitter of the present invention is used, the system output level and C / N at the output 17 of the optical receiver 20 can be kept constant.

The present invention is not limited to the above-described embodiment, and can be implemented by appropriately changing the configuration of each part without departing from the spirit of the present invention, as exemplified below.

本発明に係るＣＡＴＶ光伝送装置のブロック図。1 is a block diagram of a CATV optical transmission apparatus according to the present invention. 本願の温度補償回路の実施例を示す。An embodiment of the temperature compensation circuit of the present application will be described.

符号の説明Explanation of symbols

１…ヘッドエンド，２…自動利得調整回路，３…増幅器，４…温度補償回路，５…レーザーダイオードモジュール，６…フォトダイオード，７…レーザーダイオード，８…光ファイバ，９…光コネクタ，１０…光送信機，１１…光コネクタ，１２…光ファイバケーブル，１３…光コネクタ，１４…光／電気変換部，１５…増幅器，１６…可変減衰器，２０…光受信機
DESCRIPTION OF SYMBOLS 1 ... Head end, 2 ... Automatic gain adjustment circuit, 3 ... Amplifier, 4 ... Temperature compensation circuit, 5 ... Laser diode module, 6 ... Photo diode, 7 ... Laser diode, 8 ... Optical fiber, 9 ... Optical connector, 10 ... Optical transmitter, 11 ... optical connector, 12 ... optical fiber cable, 13 ... optical connector, 14 ... optical / electrical converter, 15 ... amplifier, 16 ... variable attenuator, 20 ... optical receiver

Claims (3)

ヘッドエンドから送出されたＣＡＴＶ信号を電気／光変換して光ファイバーで伝送するＣＡＴＶ光伝送装置において，
少なくとも，自動光出力制御回路と，
前記ＣＡＴＶ信号によって直接輝度変調されるレーザーダイオードと，
前記自動光出力制御回路の制御を行うフォトダイオードと，
を備えた電気／光変換部の直前に，前記レーザーダイオードの変調効率の温度特性と反対の特性を有する温度補償回路を備えたことを特徴としたＣＡＴＶ光伝送装置。
In a CATV optical transmission apparatus that performs electrical / optical conversion on a CATV signal transmitted from a head end and transmits the optical fiber through an optical fiber,
At least an automatic light output control circuit;
A laser diode that is directly luminance modulated by the CATV signal;
A photodiode for controlling the automatic light output control circuit;
A CATV optical transmission apparatus comprising a temperature compensation circuit having a characteristic opposite to the temperature characteristic of the modulation efficiency of the laser diode immediately before the electrical / optical conversion unit comprising
前記電気／光変換部は，少なくとも前記ＣＡＴＶ信号によって直接輝度変調されるレーザーダイオードと，自動光出力制御を行うフォトダイオードと，が同一筐体に収納されたレーザーモジュールからなることを特徴とした請求項１に記載のＣＡＴＶ光伝送装置。
The electrical / optical converter comprises a laser module in which at least a laser diode whose luminance is directly modulated by the CATV signal and a photodiode that performs automatic light output control are housed in the same housing. Item 9. The CATV optical transmission apparatus according to Item 1.
前記温度補償回路は，ＣＡＴＶ信号が流れる信号線に温度検出素子を介設し，当該温度検出素子の前後に夫々抵抗素子を信号線と共通線との間に配列してなることを特徴とした請求項１又は請求項２に記載のＣＡＴＶ光伝送装置。
The temperature compensation circuit is characterized in that a temperature detection element is provided on a signal line through which a CATV signal flows, and resistance elements are arranged between the signal line and the common line before and after the temperature detection element, respectively. The CATV optical transmission apparatus according to claim 1 or 2.
JP2004084327A 2004-03-23 2004-03-23 Catv optical transmission apparatus Pending JP2005277521A (en)

Priority Applications (1)

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Application Number Priority Date Filing Date Title
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Publications (1)

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Country Link
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0429227U (en) * 1990-06-29 1992-03-09
JPH05252518A (en) * 1992-03-05 1993-09-28 Matsushita Electric Ind Co Ltd Catv light transmitter
JPH09139646A (en) * 1995-11-15 1997-05-27 Tekudaiya Kk Temperature variable attenuator
JPH10229240A (en) * 1997-02-14 1998-08-25 Furukawa Electric Co Ltd:The Optical signal transmitter
JPH11330600A (en) * 1998-05-08 1999-11-30 Kokusai Electric Co Ltd Analog optical modulation method and its circuit

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0429227U (en) * 1990-06-29 1992-03-09
JPH05252518A (en) * 1992-03-05 1993-09-28 Matsushita Electric Ind Co Ltd Catv light transmitter
JPH09139646A (en) * 1995-11-15 1997-05-27 Tekudaiya Kk Temperature variable attenuator
JPH10229240A (en) * 1997-02-14 1998-08-25 Furukawa Electric Co Ltd:The Optical signal transmitter
JPH11330600A (en) * 1998-05-08 1999-11-30 Kokusai Electric Co Ltd Analog optical modulation method and its circuit

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