JPS5911216B2 - light level monitoring circuit - Google Patents
light level monitoring circuitInfo
- Publication number
- JPS5911216B2 JPS5911216B2 JP55136228A JP13622880A JPS5911216B2 JP S5911216 B2 JPS5911216 B2 JP S5911216B2 JP 55136228 A JP55136228 A JP 55136228A JP 13622880 A JP13622880 A JP 13622880A JP S5911216 B2 JPS5911216 B2 JP S5911216B2
- Authority
- JP
- Japan
- Prior art keywords
- level
- optical
- monitoring circuit
- level monitoring
- apd
- 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
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/66—Non-coherent receivers, e.g. using direct detection
- H04B10/69—Electrical arrangements in the receiver
- H04B10/691—Arrangements for optimizing the photodetector in the receiver
- H04B10/6911—Photodiode bias control, e.g. for compensating temperature variations
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Optical Communication System (AREA)
- Testing Of Optical Devices Or Fibers (AREA)
Description
【発明の詳細な説明】
本発明はアバランシエフオトダイオードのバイアス電圧
によつて自動利得調整を行う光ファイバ通信システムの
光−電気変換器において光入力パワーの監視を行う光レ
ベル監視回路に関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical level monitoring circuit that monitors optical input power in an optical-to-electrical converter of an optical fiber communication system that performs automatic gain adjustment using the bias voltage of an avalanche photodiode. be.
従来の、アバランシエフオトダィオード（以下ＡＰＤと
称す）のバイアス電圧によつて自動利得調整を行う光−
電気変換器においては、ＡＰＤの増倍係数を変化させて
電気出力レベルを一定にするという回路の特性上、電気
出力レベルから光入力レベルを検出することは不可能で
あつた。A conventional optical device whose gain is automatically adjusted using the bias voltage of an avalanche photodiode (hereinafter referred to as APD).
In electrical converters, it has been impossible to detect the optical input level from the electrical output level due to the characteristics of the circuit, which keeps the electrical output level constant by changing the multiplication coefficient of the APD.
すなわち光信号にパイロット信号を重畳し、このパイロ
ット信号のレベルを検知してＡＰＤのバイアスを変える
様にした場合、このパイロット信号レベルが小さくなつ
た時光信号も小さくなつているのかパイロット信号だけ
が小さくなつたのか、の正則を行う必要がある。し力化
従来ではパイロット信号レベルに応じて１０常にＡＰＤ
バイアスを変えて、電気出力レベルを一定にしているの
でＡＰＤの電気出力レベルから光入力レベルを検出でき
なかつた。In other words, if a pilot signal is superimposed on an optical signal and the level of this pilot signal is detected to change the bias of the APD, when this pilot signal level decreases, does the optical signal also decrease? Only the pilot signal decreases. It is necessary to follow the rules of summer. Conventionally, the APD is always 10 depending on the pilot signal level.
Since the electrical output level was kept constant by changing the bias, it was not possible to detect the optical input level from the electrical output level of the APD.
本発明はそうした従来の欠点を解決するために電気出力
レベルが或る範囲からはずれたときに、ＡＰＤバイアス
１５電圧を固定として光入力レベルを検出できるように
したものである。以下実施例に基づいて本発明を説明す
る。In order to solve such conventional drawbacks, the present invention makes it possible to detect the optical input level by fixing the APD bias 15 voltage when the electrical output level deviates from a certain range. The present invention will be explained below based on Examples.
図は本発明の実施例のブロック図である。The figure is a block diagram of an embodiment of the invention.
図中１はＡＰＤ、２は固定利得の前段増巾器、３はメイ
ンアンプ、４は自動利得調整回路、５は光レベル監視回
路、６はパイロット信号を除去するためのローパスフィ
ルタ、ＴはＡＰＤのバイアス用トランジスタである。動
作を説明すると、ＡＰＤＩからの電気出力は前段増幅器
２、メインアンプ３２５により増幅され、ローパスフィ
ルタ６により、パイロット信号成分が除去されて出力端
子ＯＵＴに出力される。一方メインアンプ３の出力は分
岐され、自動利得調整回路４に入力する。自動利得調整
回路４ではバンドパスフィルタ４１によりパイ３０ロッ
ド信号を抽出し、アンプ４２により増幅し、整流器４３
により整流した後比較器４４、４５に入力する。比較器
４４、４５ではそれぞれ基準電圧と比較し、パイロット
信号レベルが所定値以上の時はトランジスタ４６に接続
したリレー４？が３５動作していて、接点ｒｌが閉じて
いる。従つて、パイロット信号レベルに応じてトランジ
スタＴの導通度が変化し、ＡＰＤのバイアス電−ツハー
圧を制御することが可能である。In the figure, 1 is an APD, 2 is a fixed gain preamplifier, 3 is a main amplifier, 4 is an automatic gain adjustment circuit, 5 is an optical level monitoring circuit, 6 is a low-pass filter for removing the pilot signal, and T is an APD. This is a bias transistor. To explain the operation, the electrical output from the APDI is amplified by the pre-stage amplifier 2 and the main amplifier 325, the pilot signal component is removed by the low-pass filter 6, and the result is output to the output terminal OUT. On the other hand, the output of the main amplifier 3 is branched and input to an automatic gain adjustment circuit 4. In the automatic gain adjustment circuit 4, a bandpass filter 41 extracts a pi-30 rod signal, the amplifier 42 amplifies the signal, and the rectifier 43 extracts the pi-30 rod signal.
After rectifying the signal, the signal is input to comparators 44 and 45. Comparators 44 and 45 compare each with the reference voltage, and when the pilot signal level is above a predetermined value, relay 4? connected to transistor 46 is activated. 35 is operating and contact rl is closed. Therefore, the degree of conductivity of the transistor T changes depending on the pilot signal level, making it possible to control the bias current voltage of the APD.
ここでパイロツト信号レベルが所定値より低下すると、
比較器４５の出力が反転し、トランジスタ４６がオフと
なるので、リレー４７が復旧し、接点ｒｌ力放する。If the pilot signal level drops below the predetermined value,
Since the output of the comparator 45 is inverted and the transistor 46 is turned off, the relay 47 is restored and the contact rl is released.
これにより比較器４４の出力は固定される様になり、▲
ＰＤｌのバイアス電圧も固定される。As a result, the output of the comparator 44 becomes fixed, and ▲
The bias voltage of PDl is also fixed.
この状態においてはＡＰＤｌの電気出力は光信号のレベ
ルに応じて変化するため、プリアンプ２の出力に含まれ
る直流分（光信号のレベルに比例する）を監視回路５に
より監視すると、光信号のレベルを知ることができる。
以上の様に本発明によれば、パイロツト信号レベル低下
時、ＡＰＤのバイアスを固定しているので光信号のレベ
ルを監視することが可能となる。In this state, the electrical output of the APDl changes according to the level of the optical signal, so when the DC component (proportional to the level of the optical signal) included in the output of the preamplifier 2 is monitored by the monitoring circuit 5, the level of the optical signal is can be known.
As described above, according to the present invention, since the bias of the APD is fixed when the pilot signal level drops, it is possible to monitor the level of the optical signal.
図は本発明の実施例を示し、図中１はＡＰＤｌ２は前置
増幅器、３はメインアンプ、４は自動利得調整回路であ
る。The figure shows an embodiment of the present invention, in which 1 is an APDl2 a preamplifier, 3 is a main amplifier, and 4 is an automatic gain adjustment circuit.
Claims (1)
御することにより自動利得調整を行う光ファイバ通信シ
ステムの光−電気変換器において、変換された電気レベ
ルが或る範囲からはずれたとき該バイアス電圧を固定と
し、その時の変換された電気出力レベルから光入力レベ
ルを検出することを特徴とする光レベル監視回路。1. In an optical-to-electrical converter for an optical fiber communication system that performs automatic gain adjustment by controlling the bias voltage of an avalanche photodiode, the bias voltage is fixed when the converted electrical level deviates from a certain range, An optical level monitoring circuit that detects an optical input level from the converted electrical output level at that time.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP55136228A JPS5911216B2 (en) | 1980-09-30 | 1980-09-30 | light level monitoring circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP55136228A JPS5911216B2 (en) | 1980-09-30 | 1980-09-30 | light level monitoring circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5761349A JPS5761349A (en) | 1982-04-13 |
| JPS5911216B2 true JPS5911216B2 (en) | 1984-03-14 |
Family
ID=15170277
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP55136228A Expired JPS5911216B2 (en) | 1980-09-30 | 1980-09-30 | light level monitoring circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5911216B2 (en) |
-
1980
- 1980-09-30 JP JP55136228A patent/JPS5911216B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5761349A (en) | 1982-04-13 |
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