JPS583337A - Temperature compensating system - Google Patents

Abstract

PURPOSE:To perform photoelectric conversion with the best condition, by keeping the center value of a multiple factor of a photodetector to an optimum multiple regardless of temperature change, through the provision of a means changing the gain of an amplifier of a reception circuit depending on ambient temperatures. CONSTITUTION:An optical input signal is converted into an electric signal with an avalanche photodiode ADP1 and amplified at an amplifier 2 and a peak value is detected at a peak value detection circuit 3. An optical AGC circuit 4 and an electric AGC circuit 5 are controlled with an output of the circuit 3 to control the multiplication factor of the ADP1 and the gain of the amplifier 2. The amplifier 2 of a reception circuit thus constituted is provided with thermisters 12 and 13 resistance value of which is changed with the change in ambient temperature, a signal is applied to a base of a transistor TR11, and when the ambient temperature is changed, the output terminal voltage of the emitter of the TR11 is changed according to the resistance change in the thermisters 12 and 13, the gain of the amplifier 2 is controlled, the change in the optimum multiplication factor of the ADP1 is compensated and the photo-electric conversion is made with the best condition.

Description

[Detailed Description of the Invention] Akihiro Kinoe discovered that it is difficult to maintain the best O state at 8/N regardless of changes in ambient temperature by using hVh in the receiving sub-path that performs multiplication/electrical conversion using full AGCl. This is related to the 14111 compensation method that can be used.

In repeaters of optical communication systems, avalanche
A receiving circuit is used that uses an optical diode (AFJ) as a light receiving element to perform optical/electrical conversion of received light and further amplify it to generate a received signal consisting of an electrical signal. As is well known (the multiplication effect of the APDKFI signal is p′,
Therefore, in such receiving circuits, full AGC is often used, which uses optical A (JCj) for APRK and electric AGG for the amplification system. P4V showing an example
This is a diagram. In the figure, 1 is an AID, 2 is a width of 11, s is an optical AGC path, and 5 is an electric AGO path.

The 1st #AIC receives the optical signal input from the APD 1, converts it into electricity and converts the converted electrical signal, and the generated large electrical signal is amplified by the amplifier 1 and outputted. Occur. The amplification@20a&power is detected by the peak detection circuit 5 by the amount of the beam II[t4Ilk.

According to the output of the peak detection circuit 5, the AID I C) bias voltage is changed through the optical AGC-step 4, and the APD 10 density increase rate Mf is controlled accordingly, and at the same time, the electric AGO is controlled by the output of the peak detection circuit JsO. Full AGC is performed by controlling the gain of amplifier 2 via link 5, so that the signal amplitude at the output of amplifier II2 remains constant regardless of changes in the optical input level. The gain value of the amplifier 2 is maximum 0- at the normal pre-input level.
It is controlled to a constant value, and in response to fluctuations in the optical input level, the AID 10 multiplication factor M is changed mainly through the optical JLGC circuit 4, so that the MGC function is performed. A due to increase in optical input level and AID j O multiplication factor change
When the GC limit is exceeded, the gain of the amplifier 2 is changed via the electric AGC circuit 4vt to keep the output signal amplitude constant.

What is the optical input level and modulus in the receiving circuit of Figure H1a and Figure 1? The relationship between the multiplication factor MfIP of D and the amplifier gain G is -
゛It shows an example. As seen in the figure, when the optical input level is small, the wire gain G is a constant value close to zero, and as the optical input level increases, the multiplication factor M decreases. When the optical input level is high 11i, the multiplication factor M is a constant value of 1, and as the optical input level further increases, the gain G takes a negative value and decreases. As a result of performing AGC as shown in Figure B, in the receiving circuit shown in Figure #11, the output signal amplitude in the amplifier circuit 2 is kept constant regardless of changes in the optical input level.

On the other hand, it is known that APDFI noise (dark current) is generated and its value changes depending on the multiplication factor M.

That is, the APD has a unique maximum multiplication factor (optimal multiplication factor Mope). For example, in a germanium PDK with a long wavelength (about 1.5 tones), M ν8 expansion 10~
It is 20. Therefore, in the receiving circuit shown in the first wJK, the central value of the multiplication factor M of APDl in the AGC operation is generally set to be equal to the optimum multiplication factor M·t# in the standard operating state.

However, it also changes depending on the optimum multiplication factor M·ptas temperature 1 of APD. For example, the above-mentioned long steel germanicum AF
In J), if @pt is set as the optimum multiplication factor at room temperature, as the temperature rises, the optimum multiplication factor M・pt I
d decreases, and if the temperature decreases, it will conversely increase. Conventionally, the center value line of the multiplication factor M of AID in the receiving circuit, the circumference lll1
Therefore, the ambient temperature changes from the standard state and the AID multiplication factor M
There is a drawback that the center value of light is different from the optimum multiplication factor M.it.

The present invention is based on an attempt to eliminate such drawbacks of the prior art, and it is possible to maintain the center value of the multiplication factor M of the AID as a light receiving element even if the fishing line and ambient temperature JII change. Keeping the optimum multiplication factor KepgK at temperature II
5. Therefore, it is an object of the present invention to provide a system that can always keep a receiving circuit in the best condition at that temperature.

According to the temperature compensation method of the present invention, when the optimum multiplication factor Mgt of the pn changes due to a change in the ambient temperature, the output signal amplitude can be kept constant and the AID can be increased by changing the gain of the amplifier. Control is performed so that the central value of the magnification is always the optimum multiplication factor M@pgk at that temperature.

Hereinafter, the present invention will be explained in detail with reference to Examples.

An embodiment of the temperature compensation method of the present invention is shown in Fig. This shows the case where compensation is provided.

IIs diagram KThlnte, 11 is transition, *#, 12.
11ij and 14.15 are resistors. Thermistor 12.13dMean used as a light receiving element? Depending on the characteristics of D, only one of i may be used. For example, in the case of the long wave germanium AID described above, the thermistor 12 is not used and that part is shorted, and the thermistor 13 is
Use only.

#Ii diagram K"sP%/-&, the signal is the transistor 11
input to the page and output from the collector. When the ambient temperature changes, the internal resistance of the t-i switch 2,15 changes, and therefore the gain between the input and output in the circuit of the Hs diagram changes, and the output level applied to the collector changes. The gain change in the circuit of 12.1 in the first circuit is such that the gain change in the circuit of 12. By selecting ** in No. 15 and other component constants, even if the value of the APR optimum multiplication factor y/p# changes due to a change in temperature, the APD
The 1st 1111 receiving circuit KTh is connected to the GC excitation so that the center value of the multiplication at K is always the optimum multiplication factor y·ν at the temperature 1, and the amplitude of the output signal of the amplifier is kept constant. can be made to work.

FIG. 4 shows another embodiment of the temperature compensation system of the present invention. In FIG. Figure i shows a case where gain control is performed.

In the 411th, the old control voltage input terminal, 22°23
, 24.25 replaces the thermistor with a nine-enlarged diode, 26Ii
Tondista, 27 is Paliorossa, 28.29. S
o.

51, 52 is a Hiro resistor, 55 is a Hiro signal input terminal, and 54 is a signal output terminal. Thermistor 22.25.24.25
Depending on the characteristics of the AID used as a photodetector, -
For example, in the case of the long wavelength germanium diode mentioned above, the sensor (star 22) is used.
Either use only the sensor 24 and short-circuit the other parts, or use only the sensor 24 and short-circuit the other parts. Moreover, it can also be used in combination with the company star 22.24t.

&t+P In FIG. Thermistor 22. Resistance 29. A large voltage divided by 1 and divided by a voltage divider consisting of Sernstar 2S is applied to the transistor 260, thereby changing the internal resistance of the transistor 26, and thus from the power supply Y#- to the resistor 52. Paliorotsu t
27. Thermistor 25. Resistance 51. Transistor 26.
The value of the current flowing to ground KfIL via the 50° thermistor 24 changes. The resistance value of the variosser 27 changes significantly depending on the current flowing through it. Therefore, the loss applied to the signal input from the terminal SS and output to the terminal 34 changes, and the AGC operation as explained in connection with jlIm is performed. At this time, thermistor 22.25°24,
25 The resistance value changes depending on the expanded ambient temperature, so l
The gain (loss) in a 14 wA circuit varies with temperature. The gain change in the circuit of Figure 4 with respect to the change in ambient temperature is based on the change in temperature (x I 22$ 25- By selecting the characteristics of 24 and 25 and other component constants, it is possible to cause the 11th Il receiving circuit to perform AGC operation using the required temperature compensation method.

As explained above, according to the temperature compensation method of the present invention, JIc, even if the ambient temperature changes, the central value of the multiplication factor M of the AID, which is the light receiving element, is adjusted to 1f! The iac@ production can be performed while maintaining the optimum multiplication factor M·pt multiplied by K.

Therefore, according to the method of the present invention, the receiving path can always be operated in its best condition, so that
This is extremely effective in improving line quality.

[Brief explanation of the drawing]

[111 is a block diagram showing an example of the configuration of the optical reception circuit, 1E
211 is a diagram showing an example of the relationship between the optical input level, the multiplication factor M, and the gain G, and sg and $1411 are circuit layers each showing the configuration of an embodiment of the temperature compensation system of the present invention. 1... Avalanche photo diode (API)
)%2...Amplifier, 5...Peak detection circuit, 4...
・Light AGO@ro, 5...Electric AGOa road, 11...
Transistor%12゜15...1-1 star, 14
; 15-resistance, 21... control input terminal, 22.25
．． 24.25 river thermistor or diode% 26°
...transistor, 27...vario mouth yt. 2B, 29.3G, 31.52...Resistance, 55.
...Signal output terminal, 54...Signal output terminal Patent applicant Fujitsu Ltd. Yagaki Patent attorney Gobe Tamamushi (5 others)

Claims (1)

[Claims] In an optical receiver circuit that uses an avalanche photodiode as a light-receiving element and uses both an optical AGc to control the multiplication factor of the light-receiving element and an electric AGc to control the gain of the amplifier, the output signal amplitude is kept constant. A means is provided to change the gain of the intensifier according to the ambient temperature, so that the center value of the multiplication factor in the light receiving element is maintained at the optimum multiplication factor at that temperature for the scissors light receiving element, regardless of ambient temperature fluctuations. Temperature compensation method that does 1**.