JP2000013324A - Optical receiver using optical preamplifier and optical reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To absorb usual level fluctuations and momentary level fluctuations of an input optical signal while preventing production of light surge with respect to the optical receiver that receives a transmitted optical signal via an optical fiber. SOLUTION: The receiver is provided with an optical fiber amplifier 12 that amplifies an input optical signal, with a photo diode 16 that converts an output light of the optical fiber amplifier 12 into an electric signal, a variable amplification factor electric amplifier 22 that amplifies the electric signal outputted from the photo diode 16, a 1st level detection circuit 20 that generates a 1st control signal S1 based on an output signal from the variable amplification factor electric amplifier 22 and with a 1st level conversion circuit 24 that generates a 2nd control signal S2 based on the control signal S1. The optical fiber amplifier 12 and the variable amplification factor electric amplifier 22 execute feedback control based on the signal S1 or S2 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiving apparatus and an optical receiving method using an optical preamplifier, and more particularly to an optical preamplifier suitable as an apparatus and method for receiving an optical signal transmitted via an optical fiber. The present invention relates to an optical receiving device and an optical receiving method.

[0002]

2. Description of the Related Art Conventionally, in the field of optical fiber transmission,
2. Description of the Related Art An optical receiving device using an optical fiber amplifier for amplifying an optical signal as a preamplifier is known. FIG. 4 shows a system configuration diagram of a conventional optical receiver. The optical receiver shown in FIG. 4 includes an optical fiber amplifier 12 that receives an input optical signal supplied from an optical fiber 10. The optical fiber amplifier 12 is an optical amplifier whose amplification factor can be changed. A photodiode 16 is connected to the optical fiber amplifier 12 via an optical fiber 14.

The photodiode 16 is a device that converts an optical signal supplied from the optical fiber amplifier 12 into an electric signal having an intensity corresponding to the intensity of the optical signal.
An electric amplifier 18 is connected to the photodiode 16. The electric amplifier 18 is a circuit that generates an output signal by amplifying an electric signal generated by the photodiode 16 at a predetermined amplification factor.

[0004] The conventional optical receiver includes a first level detection circuit 20 for detecting the amplitude intensity of the output signal generated by the electric amplifier 18. The first level detection circuit 20 generates a control signal based on the strength of the output signal. The control signal generated by the first level detection circuit 20 is supplied to the optical fiber amplifier 12. The optical fiber amplifier 12 controls the amplification factor for the input optical signal based on the control signal so that the intensity of the output signal becomes a constant value.

[0005] As described above, in the conventional optical receiver,
The optical fiber amplifier 12 has a function of automatically controlling the gain so that the intensity of the output signal is constant, that is, AG
It has a C (Automatic Gain Control) function. For this reason, according to the conventional optical receiving device, it is possible to generate an output signal having a stable intensity irrespective of the fluctuation of the intensity of the input optical signal.

[0006]

The input optical signal supplied to the optical receiving apparatus has a normal level fluctuation for changing the intensity relatively slowly and in a relatively wide range, and
Instantaneous level fluctuations that cause the intensity to fluctuate instantaneously and within a relatively small range may occur. Of these level fluctuations, normal level fluctuations can be properly absorbed in the above-mentioned conventional optical receiver without significantly increasing the feedback response speed of the optical fiber amplifier 12.

On the other hand, when the intensity of an input optical signal is instantaneously decreased due to an instantaneous level fluctuation, in order to absorb the level decrease and maintain a stable output intensity,
It is necessary to provide the optical fiber amplifier 12 with a high response speed. However, the optical fiber amplifier 12
Has such a characteristic that the higher the response speed is, the more likely it is that an optical surge is generated in response to the rising of the intensity of the input optical signal, and that the more likely it is to fall into an oscillation state.

For this reason, according to the above-mentioned conventional optical receiving apparatus, a function of maintaining the output intensity stably when the intensity of the input optical signal decreases momentarily and a function of maintaining the output intensity when the intensity of the input optical signal sharply rises. It has been difficult to realize both the function of preventing the occurrence of light surge.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and can appropriately absorb a normal level fluctuation of an input optical signal, and can appropriately prevent a momentary decrease in the intensity of the input optical signal. It is a first object of the present invention to provide an optical receiving device which can absorb light into the optical signal and does not generate a surge when the intensity of the input optical signal rises.

Further, the present invention can appropriately absorb the ordinary level fluctuation of the input optical signal, can appropriately absorb the instantaneous decrease in the intensity of the input optical signal, and can properly absorb the input optical signal. It is a second object of the present invention to provide an optical receiving method that does not generate a surge when the intensity rises.

[0011]

According to a first aspect of the present invention, there is provided an optical receiving apparatus using an optical preamplifier, wherein the optical receiving apparatus transmits an optical signal. A gain variable optical preamplifier for amplifying according to a control signal; signal conversion means for converting an optical signal output from the variable gain optical preamplifier into an electric signal having an intensity corresponding to the intensity of the optical signal; An amplification variable electric amplifier that generates an output signal by amplifying the electric signal generated by the means according to a second control signal;
First feedback means for feedback-controlling the first control signal so that the intensity of the output signal has a predetermined value; and feedback control of the second control signal so that the intensity of the output signal has a predetermined value. And second feedback means for performing the above.

According to a second aspect of the present invention, in the optical receiving apparatus using the optical preamplifier, the first feedback unit includes:
A first level detection circuit that generates the first control signal based on the intensity of the output signal, wherein the second feedback unit controls the first control signal generated by the first level detection circuit. A level conversion circuit for generating the second control signal based on the signal.

An optical receiving apparatus using an optical preamplifier according to a third aspect of the present invention, wherein the variable amplification factor electric amplifier amplifies an electric signal generated by the signal conversion means in accordance with the second control signal. And a fixed amplifier that generates the output signal by amplifying a signal generated by the variable amplifier at a predetermined amplification factor, wherein the first feedback unit is configured to output the second signal based on the intensity of the output signal. A first level detection circuit for generating one control signal, and wherein the second feedback means generates the second control signal based on the intensity of the signal generated by the variable amplifier. Is provided.

An optical receiver using an optical preamplifier according to a fourth aspect of the present invention is an optical receiver for transmitting an optical signal, wherein the amplifier amplifies an optical signal input to the optical receiver according to a first control signal. A variable-gain optical preamplifier, an amplification-variable-signal converting unit that converts an optical signal output from the amplification-variable-optical preamplifier into an electric signal, and controls an amplification factor during the conversion in accordance with a third control signal; An electric amplifier for amplifying an electric signal generated by the amplification factor variable signal converting means to generate an output signal; and a first for feedback-controlling the first control signal so that the intensity of the output signal becomes a predetermined value. Feedback means, and third feedback means for performing feedback control on the third control signal so that the intensity of the output signal becomes a predetermined value. Is shall.

According to a fifth aspect of the present invention, in the optical receiving apparatus using the optical preamplifier, the first feedback means includes:
A first level detection circuit that generates the first control signal based on the intensity of the output signal, wherein the third feedback means controls the first control signal generated by the first level detection circuit. A second level conversion circuit for generating the third control signal based on the signal.

According to a sixth aspect of the present invention, in the optical receiving apparatus using the optical preamplifier, the first feedback means includes:
A first level detection circuit that generates the first control signal based on the intensity of the output signal; and the third feedback unit controls the intensity of the electric signal generated by the variable amplification factor signal conversion unit. And a third level detection circuit that generates the third control signal based on the third control signal.

An optical receiving method using an optical preamplifier according to a seventh aspect of the present invention is an optical receiving method for transmitting an optical signal, the method comprising: amplifying an input optical signal according to a first control signal; A signal converting step of converting the optical signal amplified in the optical signal amplifying step into an electric signal having an intensity corresponding to the intensity of the optical signal; and converting the electric signal generated in the signal converting step into a second control signal. An electric signal amplification step of generating an output signal by amplifying according to the following: a first feedback step of performing feedback control of the first control signal so that the intensity of the output signal becomes a predetermined value; and an intensity of the output signal. And a second feedback step of performing feedback control of the second control signal so that the value of the second control signal becomes a predetermined value. That.

[0018] In the optical receiving method using the optical preamplifier according to claim 8 of the present invention, the electric signal amplifying step converts the electric signal generated by the signal converting step into the second electric signal.
A variable amplification step of amplifying according to the control signal of the above, and a fixed amplification step of generating the output signal by amplifying the signal generated by the variable amplification step at a predetermined amplification factor, wherein the first feedback step , A first level detection step of generating the first control signal based on the strength of the output signal, and
The second feedback step is based on the strength of the signal generated by the variable amplification step.
And a second level detecting step of generating the control signal of (1).

An optical receiving method using an optical preamplifier according to a ninth aspect of the present invention is an optical receiving method for transmitting an optical signal, the method comprising: amplifying an input optical signal according to a first control signal; An amplification variable signal converting step of converting the amplified optical signal amplified in the optical signal amplification step into an electric signal and controlling an amplification factor at the time of conversion in accordance with a third control signal; and the amplification factor variable signal converting step. An electric signal amplifying step of amplifying the electric signal generated in the step of generating an output signal, and a first feedback step of performing feedback control of the first control signal so that the intensity of the output signal becomes a predetermined value. And a third feedback step of performing feedback control on the third control signal so that the intensity of the output signal becomes a predetermined value. Is shall.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. Elements common to the drawings are denoted by the same reference numerals, and redundant description will be omitted.

Embodiment 1 FIG. 1 shows a system configuration diagram of the optical receiver according to the first embodiment of the present invention. As shown in FIG. 1, the optical receiving device of the present embodiment is a first-stage amplifier that receives an input optical signal supplied from an optical fiber 10,
That is, the optical fiber amplifier 12
It has. The optical fiber amplifier 12 is an optical amplifier whose amplification factor can be changed, and amplifies an input optical signal according to a first control signal S1 described later. A photodiode 16 is connected to the optical fiber amplifier 12 via an optical fiber 14.

The photodiode 16 is a device that converts an optical signal supplied from the optical fiber amplifier 12 into an electric signal having an intensity corresponding to the intensity of the optical signal.
The photodiode 16 includes a variable amplification factor electric amplifier 22.
Is connected. The variable amplification factor electric amplifier 22 is a main part of the optical receiver of the present embodiment,
6 is amplified according to a second control signal S2 described later. The optical receiving device of the present embodiment includes:
An electric signal generated by the variable gain electric amplifier 22 is output as an output signal.

The optical receiving apparatus according to the present embodiment includes a first level detecting circuit 20 for detecting a voltage amplitude (hereinafter, referred to as an intensity) of an output signal output from a variable amplification factor electric amplifier 22.
It has. The first level detection circuit 20 generates a first control signal S1 based on the intensity of the output signal. First
The first control signal S1 generated by the level detection circuit 20 is supplied to the optical fiber amplifier 12 and the first level conversion circuit 24.

The optical fiber amplifier 12 receives the control signal S
Based on 1, the amplification factor for the input optical signal is controlled so that the intensity of the output signal becomes a constant value. In the optical receiving device of the present embodiment, an AGC (Automatic Gain Control) function related to amplification of an optical signal is realized by the optical fiber amplifier 12 performing the above-described feedback control.

The first level conversion circuit 24 performs a predetermined level conversion on the first control signal S1 to generate a second control signal S2. The second control signal S2 is supplied to the variable amplification factor electric amplifier 22. The variable gain electric amplifier 22 controls the gain of the electric signal based on the control signal S2 such that the intensity of the output signal becomes a constant value. In the optical receiver according to the present embodiment, the AGC function relating to the amplification of the electric signal is realized by the variable amplification factor electric amplifier 22 performing the above-described feedback control.

The intensity of the input optical signal supplied to the optical receiver may fluctuate relatively slowly and in a relatively wide range. Hereinafter, this variation is referred to as “normal level variation”. In order to absorb a normal level fluctuation occurring in an input optical signal and obtain a stable output intensity, an AGC function capable of coping with a wide change is required. On the other hand, in order to absorb the above-mentioned normal level fluctuation, a very fast feedback response speed is not required for the AGC function.

In the optical receiver of the present embodiment, the characteristics of the optical fiber amplifier 12 include (1) an AGC function which has a relatively low feedback response speed and (2) can cope with a wide change. Is set to Therefore, in the present embodiment, the normal level fluctuation occurring in the input optical signal can be properly absorbed by the AGC function of the optical fiber amplifier 12.

The optical fiber amplifier 12 has such a characteristic that the higher the feedback response speed is given, the more easily the optical surge is generated when the input optical signal rises sharply. In the present embodiment, the optical fiber amplifier 12 is given a relatively low response speed as described above. For this reason, in the optical receiving circuit of this embodiment, the optical fiber amplifier 12
An AGC function that absorbs normal level fluctuation can be realized.

The intensity of the input optical signal supplied to the optical receiver may also vary instantaneously and in a relatively narrow range. Hereinafter, this variation is referred to as “instantaneous level variation”. In order to absorb the instantaneous level fluctuation occurring in the input optical signal and obtain a stable output intensity, an AGC function having a fast feedback response speed is required. On the other hand, in order to absorb the instantaneous level fluctuation described above,
A very wide control width is not required.

In the optical receiver of the present embodiment, the characteristics of the variable gain electric amplifier 22 are as follows: (1) an AGC function having a relatively high feedback response speed and (2) a relatively narrow control width. It is set to be realized.
The amplifier that amplifies the electric signal is less likely to generate a surge signal than the optical fiber amplifier 12 when a high feedback response speed is given. For this reason, according to the variable gain electric amplifier 22, the problem of surge does not occur.
An AGC function that appropriately absorbs instantaneous level fluctuations of an input optical signal can be realized.

As described above, according to the optical receiving circuit of the present embodiment, the AGC function of the optical fiber amplifier 12 absorbs the normal level fluctuation, and the AGC function of the variable gain electric amplifier 22
The C function can absorb the instantaneous level fluctuation and effectively prevent the occurrence of a surge in response to a sudden rise of the input optical signal. Therefore, according to the optical receiving circuit of the present embodiment, it is possible to always maintain a stable output intensity regardless of the level fluctuation of the input optical signal.

In the optical receiving circuit of the present invention, the first control signal is generated based on the output signal, and the second control signal is generated by level-converting the second control signal. And According to the above configuration, it is not necessary to newly provide a circuit for detecting the level of the output signal in order to generate the second control signal. In this regard, the optical receiving circuit of the present embodiment has an advantage that it can be realized with a simple configuration.

In the above embodiment, the optical fiber amplifier 12 corresponds to the "amplifier variable optical preamplifier" and the photodiode 16 corresponds to the "signal converting means". The first level detection circuit 20 corresponds to the "first feedback means" of the first aspect, and the first level conversion circuit 24 corresponds to the "second feedback means" of the first aspect. ing.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 2, the same components as those shown in FIG.
The same reference numerals are given and the description is omitted or simplified. FIG. 2 shows a system configuration diagram of the optical receiver according to the second embodiment of the present invention. The optical receiver according to the present embodiment includes a variable amplifier 2
6. Fixed amplifier 28 and second level detection circuit 3
It is characterized by having 0.

The variable amplifier 26 includes the photodiode 16
Is an amplifier having a variable gain that amplifies the electric signal generated according to the second control signal described later. The fixed amplifier 28 is a circuit that amplifies the signal amplified by the variable amplifier 26 at a predetermined gain to generate an output signal. Further, the second level detection circuit 30 includes the variable amplifier 2
6 is a circuit that generates a second control signal S2 based on the intensity of the signal generated by the control signal S6. The variable amplifier 26 controls the amplification factor for the electric signal based on the control signal S2 such that the intensity of the output signal becomes a constant value.

In the optical receiver according to the present embodiment, similarly to the first embodiment, the optical fiber amplifier 12
By performing a predetermined feedback control according to the control signal S1, the AGC function for the optical signal is realized. Further, in the optical receiver of the present embodiment,
The AGC function relating to the amplification of the electric signal is realized by the variable amplifier 26 performing the above-described feedback control.

In this embodiment, the optical fiber amplifier 1
The characteristics of (2) are set so as to realize (1) an AGC function having a relatively low feedback response speed and (2) capable of coping with a wide change, similarly to the first embodiment. ing. In this embodiment, the variable amplifier 2
6, the AGC function having (1) a relatively high feedback response speed and (2) a relatively narrow control width is the same as the characteristic of the variable gain electric amplifier 22 in the first embodiment. It is set to be realized.

The variable amplifier 26 is an amplifier for amplifying an electric signal. Therefore, the variable amplifier 26 does not cause a surge problem even if it has a high feedback response speed. Therefore, according to the optical receiving apparatus of the present embodiment, as in the apparatus of the first embodiment, normal level fluctuations and instantaneous level fluctuations are effectively absorbed without causing a surge problem, and stable output intensity is obtained. Can be realized.

By the way, in the optical receiving apparatus of the present embodiment, the first control signal S1 for realizing the AGC function of the optical fiber amplifier 12 and the second control signal for realizing the AGC function of the variable amplifier 26 S2 is generated by different feedback loops. More specifically, the first control signal S1 is based on the strength of the signal output from the fixed amplifier 28, while the second control signal S1 is
2 is generated based on the intensity of the signal output from the variable amplifier 26.

By generating the first control signal S1 and the second control signal S2 by independent feedback loops as described above, the two control signals S1, S2
Can be generated independently of each other. In this case, the response speed and control width of the feedback control based on the two control signals S1 and S2, or the rate of change of the control gain can be set independently of each other. Therefore, according to the optical receiving device of the present embodiment, a high degree of freedom can be ensured regarding the characteristics of the device, and a desired AGC function can be easily realized.

In the above embodiment, the variable amplifier 26 and the fixed amplifier 28 correspond to the "amplifier variable electric amplifier" of the first embodiment, and the second level detection circuit 30 corresponds to the "amplifier of the first embodiment". Second feedback means "
Each is equivalent.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to FIG. In FIG. 3, the same components as those shown in FIG. 1 or FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted or simplified. FIG. 3 shows a system configuration diagram of the optical receiver according to the third embodiment of the present invention. The optical receiver according to the present embodiment is characterized in that it includes an avalanche photodiode (APD) 32.

The APD 32 outputs an optical signal supplied from the optical fiber amplifier 12 to a third control signal S3 to be described later.
Is a device that converts the optical signal into an electric signal while amplifying according to the following equation. The electric signal generated by the APD 32 is supplied to the fixed amplifier 28. The fixed amplifier 28
An output signal is generated by amplifying the electric signal at a predetermined amplification factor.

The light receiving circuit of the present embodiment includes a second level conversion circuit 34. The second level conversion circuit is
This is a circuit that generates a third control signal S3 by performing a predetermined level conversion on the first control signal S1 generated by the first level detection circuit 20. Third control signal S
3 is supplied to the APD 32. The APD 32 performs feedback control according to the control signal S3 so that the output signal has a constant value.

In the optical receiver according to the present embodiment, as in the case of the first or second embodiment, the optical fiber amplifier 1
2 executes a predetermined feedback control according to the first control signal S1, whereby an AGC function for the optical signal is realized. Further, in the optical receiving device of the present embodiment, the AGC function regarding the amplification of the electric signal is realized by the APD 32 performing the above-described feedback control.

In this embodiment, the optical fiber amplifier 1
The characteristic of No. 2 is the same as in the case of Embodiment 1 or 2.
(1) has a relatively low feedback response speed, and
(2) It is set so that the AGC function that can cope with a wide change is realized. In the present embodiment, A
The characteristics of the PD 32 are, as with the characteristics of the variable amplification electric amplifier 22 in the first embodiment or the characteristics of the variable amplifier 26 in the second embodiment, (1) having a relatively high feedback response speed, and (2) It is set so that the AGC function having a relatively narrow control width is realized.

The APD 32 has such a characteristic that even when a high feedback response speed is given, a surge does not easily occur when the input optical signal rises. Therefore, even if the APD 32 is given a high feedback response speed as described above, the problem of surge does not occur. Therefore, according to the optical receiver of the present embodiment, similar to the device of the first or second embodiment, normal level fluctuations and instantaneous level fluctuations are effectively absorbed without causing a surge problem, and stable. AGC function for maintaining the output intensity can be realized.

By the way, in the above embodiment, A
The third control signal S3 for controlling the amplification factor of the PD 32 is generated by performing level conversion on the first control signal S1, but the present invention is not limited to this. That is, similarly to the second control signal S2 in the second embodiment, the third control signal may be generated in a feedback loop independent of the first control signal.

In the above embodiment, the optical fiber amplifier 12 corresponds to the "variable gain preamplifier" according to the fourth aspect, and the APD 32 corresponds to the "variable gain signal converting means" according to the fourth aspect. 5. The fixed amplifier 28 according to claim 4,
The "level amplifier" according to claim 4, wherein the first level detection circuit 20 includes the "first feedback means" according to claim 4,
Further, the second level conversion circuit 34 corresponds to the "third feedback means" of the fourth aspect.

In the above embodiment, the APD
By providing a level detection circuit that generates a third control signal based on the intensity of the signal output from the second signal generator, the “third level detection circuit” according to claim 6 is realized.

[0051]

Since the present invention is configured as described above, it has the following effects. Claim 1
According to the described invention, the output intensity is stabilized by the gain control function (AGC function) of the variable gain optical preamplifier and the gain control function (AGC function) of the variable gain electrical amplifier. The variable gain electric amplifier can operate at a high response speed without generating a surge with respect to the rising of the input intensity. Therefore, according to the optical receiver of the present invention, the instantaneous decrease in the input intensity can be appropriately absorbed without increasing the response speed of the variable gain preamplifier so much. Therefore, according to the optical receiver of the present invention, it is possible to appropriately absorb the normal level fluctuation and the instantaneous level fluctuation of the input optical signal while preventing the occurrence of the surge.

According to the second aspect of the present invention, the level of the first control signal for realizing the AGC function of the variable gain optical preamplifier is converted, so that the A of the variable gain electrical amplifier is changed.
The second control signal for realizing the GC function can be easily generated. Therefore, according to the present invention, it is possible to realize an optical receiving circuit that realizes a desired function with a simple configuration.

According to the third aspect of the invention, independent feedback loops can be formed for each of the variable gain optical preamplifier and the variable gain electrical amplifier. Therefore, according to the present invention, it is possible to independently and independently set the feedback response speed, the control width, and the like for each of the variable gain optical preamplifier and the variable gain electrical amplifier. Therefore, according to the optical receiver of the present invention, a desired AGC function can be easily realized.

According to the fourth aspect of the invention, the output intensity is stabilized by the AGC function of the variable gain optical preamplifier and the AGC function of the variable gain signal conversion means. The variable amplification factor signal conversion means can operate at a high response speed without generating a surge with respect to the rise of the input intensity. Therefore, according to the optical receiver of the present invention,
The instantaneous decrease in input intensity can be properly absorbed without significantly increasing the response speed of the variable gain preamplifier. Therefore, according to the optical receiver of the present invention, it is possible to appropriately absorb the normal level fluctuation and the instantaneous level fluctuation of the input optical signal while preventing the occurrence of the surge.

According to the fifth aspect of the present invention, the first control signal for realizing the AGC function of the variable gain optical preamplifier is level-converted to realize the third AGC function of the variable gain signal conversion means. Can be easily generated. Therefore, according to the present invention, it is possible to realize an optical receiving circuit that realizes a desired function with a simple configuration.

According to the sixth aspect of the present invention, independent feedback loops can be formed for each of the variable gain optical preamplifier and the variable gain signal conversion means. Therefore, according to the present invention, it is possible to independently and independently set the feedback response speed and the control width for each of the variable gain optical preamplifier and the variable gain signal conversion means. Therefore, according to the optical receiver of the present invention, a desired AGC function can be easily realized.

According to the present invention, the AGC function realized by amplifying the input optical signal according to the first control signal and the AGC function realized by amplifying the electric signal according to the second control signal are realized. The output intensity is stabilized by the AGC function. The amplification processing of the electric signal can be performed at a high response speed without unduly generating a surge. Therefore, according to the optical receiving method of the present invention,
The instantaneous decrease in input intensity can be properly absorbed without giving a high response speed to the amplification processing of the optical signal. Therefore, according to the optical receiver of the present invention, it is possible to appropriately absorb the normal level fluctuation and the instantaneous level fluctuation of the input optical signal while preventing the occurrence of the surge.

According to the eighth aspect of the invention, each of the amplification processing of the optical signal and the amplification processing of the electric signal can be executed by an independent feedback system.
Therefore, according to the present invention, it is possible to independently and independently set the feedback response speed, the control width, and the like for the optical signal amplification process and the electric signal amplification process. Therefore, according to the optical receiver of the present invention, a desired AGC function can be easily realized.

According to the ninth aspect of the invention, the optical signal obtained by amplifying the input optical signal according to the first control signal is converted into an electric signal while being amplified according to the third control signal. Output intensity is stabilized. The process of converting an optical signal into an electrical signal while amplifying the optical signal can be executed at a high response speed without generating a surge with respect to a rise in input intensity. For this reason, according to the optical receiving method of the present invention, it is possible to appropriately absorb the instantaneous decrease in the input intensity without significantly increasing the response speed in the amplification processing of the optical signal. Therefore, according to the optical receiving method of the present invention, it is possible to appropriately absorb the normal level fluctuation and the instantaneous level fluctuation of the input optical signal while preventing the occurrence of the surge.

[Brief description of the drawings]

FIG. 1 shows a system configuration diagram of an optical receiving circuit according to a first embodiment of the present invention.

FIG. 2 shows a system configuration diagram of an optical receiving circuit according to a second embodiment of the present invention.

FIG. 3 shows a system configuration diagram of an optical receiving circuit according to a third embodiment of the present invention.

FIG. 4 shows a system configuration diagram of a conventional optical receiving circuit.

[Explanation of symbols]

Reference Signs List 12 optical fiber amplifier, 16 photodiode, 20 first level detection circuit, 22 variable gain electric amplifier, 24 first level conversion circuit,
26 variable amplifier, 28 fixed amplifier, 3
0 second level detection circuit, 32 avalanche photodiode (ADP), 34 second level conversion circuit.

Claims (9)

[Claims] 1. An optical receiver for transmitting an optical signal, comprising: a variable gain optical preamplifier for amplifying an optical signal input to the optical receiver according to a first control signal; Optical signal
Signal conversion means for converting into an electric signal having an intensity corresponding to the intensity of the optical signal; and amplification factor variable for generating an output signal by amplifying the electric signal generated by the signal conversion means according to a second control signal. An electric amplifier; first feedback means for performing feedback control on the first control signal so that the intensity of the output signal becomes a predetermined value; and second control so that the intensity of the output signal becomes a predetermined value. An optical receiving apparatus using an optical preamplifier, comprising: second feedback means for performing feedback control of a signal. 2. The first feedback unit includes a first level detection circuit that generates the first control signal based on the intensity of the output signal, and the second feedback unit includes a first level detection circuit. 2. An optical receiver using an optical preamplifier according to claim 1, further comprising a first level conversion circuit for generating said second control signal based on said first control signal generated by said level detection circuit. apparatus. 3. The variable amplification factor electric amplifier amplifies an electric signal generated by the signal conversion means in accordance with the second control signal, and a predetermined amplification factor for a signal generated by the variable amplifier. And a fixed amplifier that generates the output signal by amplifying the output signal. The first feedback unit includes a first level detection circuit that generates the first control signal based on the intensity of the output signal. And the second feedback means includes a second level detection circuit that generates the second control signal based on the intensity of a signal generated by the variable amplifier. An optical receiving device using the optical preamplifier. 4. An optical receiver for transmitting an optical signal, comprising: a variable gain optical preamplifier for amplifying an optical signal input to the optical receiver according to a first control signal; Means for converting an optical signal into an electrical signal, and controlling the amplification factor at the time of conversion in accordance with a third control signal; and amplifying the electrical signal generated by the variable gain signal conversion means. An electric amplifier that generates an output signal by using the first control signal, and a first feedback unit that performs feedback control on the first control signal so that the intensity of the output signal becomes a predetermined value. And a third feedback unit for performing feedback control of the third control signal. An optical receiving apparatus using an optical preamplifier. 5. The first feedback unit includes a first level detection circuit that generates the first control signal based on the intensity of the output signal, and the third feedback unit includes the first feedback unit. 5. An optical receiver using an optical preamplifier according to claim 4, further comprising a second level conversion circuit for generating said third control signal based on said first control signal generated by said level detection circuit. apparatus. 6. The first feedback unit includes a first level detection circuit that generates the first control signal based on the intensity of the output signal, and the third feedback unit includes: Based on the strength of the electric signal generated by the variable amplification factor signal converting means, the third
5. An optical receiving apparatus using an optical preamplifier according to claim 4, further comprising a third level detection circuit for generating said control signal. 7. An optical receiving method for transmitting an optical signal, comprising: an optical signal amplifying step of amplifying an input optical signal in accordance with a first control signal; and an optical signal amplified in the optical signal amplifying step. A signal conversion step of converting an electric signal having an intensity corresponding to the signal intensity, and an electric signal amplification step of generating an output signal by amplifying the electric signal generated in the signal conversion step according to a second control signal. A first feedback step of performing feedback control on the first control signal so that the intensity of the output signal becomes a predetermined value; and feeding back the second control signal so that the intensity of the output signal becomes a predetermined value. A second feedback step of controlling. An optical receiving method using an optical preamplifier, comprising: 8. The electric signal amplification step includes: a variable amplification step of amplifying an electric signal generated by the signal conversion step according to the second control signal; and a predetermined amplification of the signal generated by the variable amplification step. A fixed amplification step of generating the output signal by amplifying the output signal by a factor, wherein the first feedback step is a first level detection step of generating the first control signal based on the intensity of the output signal. And wherein the second feedback step is based on the strength of the signal generated by the variable amplification step.
8. The optical receiving method using an optical preamplifier according to claim 7, further comprising a second level detecting step of generating the control signal of (a). 9. An optical receiving method for transmitting an optical signal, comprising: an optical signal amplifying step of amplifying an input optical signal according to a first control signal; and an electrical signal amplifying the amplified optical signal amplified in the optical signal amplifying step. And an amplification factor variable signal conversion step of controlling the amplification factor at the time of conversion according to a third control signal; and amplifying the electric signal generated in the amplification factor variable signal conversion step to generate an output signal. An electric signal amplifying step; a first feedback step of performing feedback control on the first control signal so that the intensity of the output signal becomes a predetermined value; and a third feedback step so that the intensity of the output signal becomes a predetermined value. And a third feedback step of performing feedback control on the control signal of (a).