JP3518559B2 - Light reception signal detection circuit and light reception signal processing device - Google Patents

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Field of Industrial Application Conventional Technology (FIG. 5) Problem to be Solved by the Invention (FIGS. 6 and 7) Means for Solving the Problem (FIGS. 1, 2 and 4) Working Example (1) Overall Configuration (FIG. 1) (2) Amplifier circuit with light-reception detection function of the first embodiment (FIGS. 2 and 3) (3) Amplifier circuit with light-reception detection function of the second embodiment (FIG. 4)

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a received light signal detection circuit and a received signal processing device, and is suitable for application to, for example, those used in the field of optical communication.

[0003]

2. Description of the Related Art Today, a received light signal received by a photodiode is amplified by a preamplifier circuit and sent to an amplifier circuit with a received light detecting function. An amplifier circuit having a circuit configuration shown in FIG. 5 is generally used as the light receiving detection function amplifying circuit. The light receiving detection function circuit is a preamplification circuit (not shown).
The amplifying stage has a function of further amplifying and outputting the received light signal that has been current-voltage converted and amplified by, and a function of detecting the presence or absence of input of the received light signal.

As shown in FIG. 5, in the light receiving and detecting function amplifying circuit 1, the optical signal voltage V _in which is current-voltage converted and amplified by the preamplifying circuit (not shown) is used as the main amplifier circuit 2A.
After being further amplified by, the output buffer circuit 5 further amplifies and outputs as an amplifier output V _OUT . Further, in the amplifier circuit 1 with the light receiving and detecting function, after being amplified by the main amplifier circuit 2A, it is inputted to the fixed gain amplifier circuit 3A, further amplified by the fixed gain amplifier circuit 3A, and inputted through the peak hold circuit 4A. The signal voltage V _in and the set voltage input from the alarm level setting input terminal V _ref , amplified by the main amplifier circuit 2B, further amplified by the fixed gain amplifier circuit 3B, and input via the peak hold circuit 4B. The hysteresis comparator circuit 5 compares and outputs the alarm signal S1 when the optical signal voltage V _in exceeds the voltage (threshold value) set at the alarm level setting input terminal V _ref .

[0005]

Generally, in the circuit 1 with the light receiving and detecting function, the main amplifier circuits 2A and 2B are provided.
In order to minimize the error due to the variation between the fixed gain amplifier circuits 3A and 3B, the main amplifier circuit 2B and the fixed gain amplifier circuit 3B on the alarm level setting side, and the main amplifier circuit 2A and the fixed gain amplifier circuit 3A on the optical signal input side. An amplifier with the same configuration as is used. The relationship between the alarm setting level and the amplifier gain of the amplifier circuit 1 with the light receiving and detecting function having such a configuration is as follows.
If the maximum amplitudes of 4 and 4B are V _M , it is expressed as shown in FIG.

Namely the input voltage V _a of the by the optical signal voltage V _IN to the hysteresis comparator circuit 6, the gain of the main amplifier circuit 2A and 2B G1, when the gain of the fixed gain amplifier circuit 3A and 3B and G2, V _a = G
1 · G2 · V _IN , and the input voltage V _a increases with a gradient G1 · G2 until it reaches the maximum amplitude V _M of the peak hold circuits 4A and 4B. Further, the input voltage V _b to the hysteresis comparator circuit 6 by the alarm level setting input terminal V _ref is V _b = G1 · G like the input voltage V _a.
2 · V _ref .

From the above, the maximum voltage that can be set by the alarm at the alarm level setting input terminal V _ref is up to the point V _lin until the slopes G1 and G2 of the maximum amplitude V _M change linearly. Set voltage V
It can be seen that _lin is related to amplifier gains G1 and G2. That is, when the gradients G1 and G2 are small, the maximum alarm level setting voltage V _lin is large and the gradient G1 is large.
・ When G2 is large, the maximum alarm level setting voltage V
It turns out that _lin becomes smaller.

Next, FIG. 7 shows the relationship between the alarm setting level and the noise resistance. Normally, the comparator circuit of the amplifier circuit 1 with a light receiving detection function is provided with a hysteresis of a predetermined standard value in order to make it strong against chattering (noise) near the threshold value. FIG. 8 shows the relationship between the alarm setting level and the hysteresis voltage width (ΔV) when the hysteresis width is 3 [db]. As shown in FIG. 8, when the alarm setting level is low, the hysteresis voltage width ΔV is small, and when the alarm setting level is high,
It can be seen that the hysteresis voltage width ΔV is large.

In FIG. 7, V _ref 1, VH 1, VL 1
Is the comparator circuit 6 when the alarm setting level is low
Hysteresis voltage width of V _ref 1 as a threshold value of (VH1-
Represents the value of _{VL1), V ref 2, VH2} , VL2 represents the value of the comparator circuit 6 when the high alarm setting level. As can be understood from FIGS. 7 and 8, when the main amplifier circuits 2A and 2B are set to the same gain and the fixed gain amplifiers 3A and 3B are set to the same gain, the comparator is used when the alarm setting level is low. The hysteresis voltage width ΔV ₁ (VH1-VL1) for the input voltage of the circuit 6 is small, and the hysteresis voltage width ΔV ₂ (VH2-V) when the alarm setting level is high.
L2) is large. This means that when the main amplifier circuits 2A and 2B and the fixed gain amplifier circuits 3A and 3B are fixed and set to the same amplifier gain, respectively,
This suggests that when the alarm setting level is low, the hysteresis voltage width becomes small, so that it becomes weak against noise.

By the way, in the amplifier circuit 1 with the received light detecting function,
The gain G1 of the main amplifier circuits 2A and 2B is set in consideration of the frequency characteristic and the noise characteristic required for the signal reproduction amplifier output. The gain G2 of the fixed gain amplifier circuits 3A and 3B is the alarm level setting input terminal V
Maximum alarm level setting voltage V set by _ref
lin is fixedly set to a value that maximizes the hysteresis voltage width ΔV in the hysteresis comparator circuit 6.

However, since the gain G2 of the fixed gain amplifier circuits 3A and 3B is fixedly set at the maximum alarm level setting voltage V _lin as described above, it is not possible to set an alarm level higher than the maximum alarm level and the alarm setting is made. When the voltage is low, there is a problem that the hysteresis voltage width ΔV in the hysteresis comparator circuit 6 becomes low and it becomes weak against noise. Therefore, based on the maximum alarm level set voltage, the light receiving detection function amplifier circuit 1 in which the gain G2 is set to a value that maximizes the hysteresis width ΔV in the hysteresis comparator circuit 6 must be individually designed. There was a problem.

The present invention has been made in consideration of the above points, and a reception signal detection circuit capable of optimally setting the gain of an amplifier circuit according to an input alarm setting voltage and a light reception circuit having the reception signal detection circuit. It is intended to propose a signal processing device.

[0013]

In order to solve such a problem, according to the present invention (FIGS. 2 and 4), the voltage of the received light signal which is current-voltage converted and input is amplified and output as an amplified received light signal. 1 variable gain amplifier circuit (21A),
Maximum value of the voltage of the amplified received light signal and the first peak hold means for detecting a (V _a) output the maximum value of the voltage (V _{a) (4A),} amplifies a predetermined level alarm setting voltage input The second variable gain amplifier circuit (21
B) and the maximum value of the amplified alarm setting voltage (V _b ).
Maximum of the maximum value (V _b) and the second peak hold means for outputting (4B), the maximum value (V _a) with the amplified alarm setting voltage of the voltage of the amplified received light signal of the detection to the alarm set voltage A comparison means (6) for comparing the value (V _b ) and detecting the presence or absence of the input of the received light signal is provided, and the gains of the first and second variable gain amplifier circuits (21A, 21B) are set to the alarm setting voltage. Independently and simultaneously, variable control can be performed.

Further, in the present invention, from FIG. 1, FIG. 2 and FIG. 4, the light receiving signal (I _IN ) photoelectrically converted by the light receiving element (PD) is input, and the light receiving signal (I _IN ) is supplied as a current. Light receiving signal amplifier circuit (13A) that converts and outputs voltage
An amplifying means (13B) for amplifying and outputting the current-voltage converted light receiving signal (V _OUT ), and a light receiving signal (V _IN ).
Voltage amplifying the first variable gain amplifier circuit (21A), amplified received light signal to output as an amplified received light signal (V _IN)
First peak hold means (4A) for detecting the maximum value (V _a ) of the voltage of V and outputting the maximum value (V _a ) of the voltage
And a second variable gain amplifier circuit (21B) that amplifies and outputs an input alarm setting voltage of a predetermined level, and detects the maximum value (V _b ) of the amplified alarm setting voltage and outputs the alarm setting voltage. comparing the maximum value and the second peak hold means for outputting (V _{b) (4B),} the maximum value of the voltage of the amplified received light signal (V _a) with the amplified alarm setting voltage maximum of the (V _b) of Then, the light receiving signal detection circuit (20, 3) having a comparison means (6) for detecting the presence or absence of the input of the light receiving signal
0) and the first and second variable gain amplifier circuits (21
The gain of A, 21B) can be variably controlled independently of and simultaneously with the alarm setting voltage.

[0015]

The first and second variable gain amplifying circuits (21A, 2)
The gain of 1B) is variably controlled simultaneously according to the alarm setting voltage. As a result, the optimum gain can be set for each alarm setting voltage, so that the noise resistance can be improved over a wide range of alarm setting levels, and the alarm setting level can be set freely.

Further, by using the light receiving signal detecting circuit (20, 30) having such a configuration in the light receiving signal processing device (13), the optimum alarm gain setting is set according to the characteristics of the preamplifier circuit (13A) used. Therefore, it is possible to more accurately determine whether or not the light reception signal is input.
As a result, the reliability of signal processing by the light receiving signal processing device (13) can be further improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

(1) Overall Configuration FIG. 1 shows the overall configuration of an optical communication system using an optical fiber as a whole. This optical communication system 10 realizes information transmission by transmitting an optical signal output from an optical transmitter 11 to an optical receiver 13 via an optical fiber 12.

The optical communication system 10 is constituted by each unit described below. First, the optical transmitter 11 includes a laser diode (LD, Laser Diode) that outputs an optical signal and an LD drive circuit 11A that drives the laser diode. Here, the LD drive circuit 11A drives the LD according to the information, and L
The light amount of the light emission output of D is controlled.

On the other hand, the optical receiver 13 has a photodiode P.
It is an input stage for amplifying the signal current I _IN photoelectrically converted by D and supplying it to a signal processing circuit (not shown) arranged in the subsequent stage. This is because the signal current I _IN is a very small current of several μA or less, and the signal processing circuit cannot be driven even if the signal current I _IN is directly input to the signal processing circuit. The optical receiver 13 mainly comprises a two-stage amplifier circuit including a preamplifier circuit 13A and a photodetector amplifier circuit 13B which are connected via a coupling capacitor C.

First, the preamplifier circuit 13A is an amplifier stage which functions to perform current-voltage conversion and amplification of the signal current I _IN . The signal current I _IN is several [mV] depending on the preamplifier circuit 13A.
The signal is amplified to a signal V _OUT having a certain amplitude and output from the output terminal. In addition, the amplifier circuit 13B with the light receiving detection function is
_This is an amplification stage that functions to further amplify _OUT and to detect the presence or absence of optical signal input. That is, the amplifier circuit 13B with a light receiving detection function outputs the signal V _OUT to the signal V having an amplitude of about 0.8 [V].
It is designed to be amplified to _OUT1 and output from the output end. Further, the amplifier circuit 13B with a light receiving detection function detects the presence or absence of the input of the optical signal based on the signal level of the signal V _OUT , and outputs the alarm signal S1 whose logical level rises to the logical "H" when the optical signal is input, for example. Has been done.

(2) Amplification Circuit with Photodetection Function of First Embodiment FIG. 2 shows a schematic structure of the amplification circuit 20 with photodetection function, in which parts corresponding to those in FIG. In the case of the first embodiment, variable gain amplifier circuits 21A and 21B are used instead of the fixed gain amplifiers 3A and 3B as the gain amplifier circuit that constitutes the amplifier circuit 20 with the light reception detection function, and the external terminal V _cont is provided. The gain G2 of the variable gain amplifier circuits 21A and 21B can be controlled.

As shown in FIG. 2, the variable gain amplifier circuits 21A and 21B are connected to each other, and a line extending from an external terminal V _cont provided outside the amplification circuit 20 with the light receiving and detecting function is connected to this connection line. Has been done. Further, the gain G2 of the variable gain amplifier circuits 21A and 21B
_Can be adjusted by the external terminal V _cont according to the magnitude of the alarm setting level set at the alarm level setting input terminal V _ref .

That is, the variable gain amplifier circuit 21 is provided by the external terminal V _cont when the alarm setting level is low.
Increase the gain G2 of A and 21B to increase the comparator circuit 6
When it is desired to increase the noise margin in the above and set the alarm setting voltage to a high voltage, the gain G2 is lowered and the maximum alarm setting level is set to a high level. For example, as shown in FIG. 3, the optical signal voltage V _in is V _lin2
Then, the gain G of the variable gain amplifier circuits 21A and 21B
When 2 is G2 (2), when the alarm setting level is lowered and compared by the comparator circuit 6, the hysteresis width ΔV becomes small and becomes weak against noise as described above. Therefore, the variable gain amplifier circuits 21A and 21B Gain G
By increasing the amplification degree of 2 from G2 (2) to G2 (1), it is possible to increase the hysteresis width ΔV and make it resistant to noise.

Therefore, the user can use the external terminal V _cont to _adjust the variable gain amplifier circuits 21A and 21B.
The gain G2 can be set to a value that maximizes the amplitude of the hysteresis comparator circuit 7 according to the alarm setting level set at the alarm level setting input terminal V _ref .

Further, as shown in FIG. 3, when the voltage value of the optical signal voltage V _in which is current-voltage converted and input to the main amplifier circuit 2A is, for example, V _lin1 , V _lin2 , V _lin3 , the user Depending on the magnitude of the optical signal voltage V _in , the variable gain amplifier circuit 2 can be connected by the external terminal V _cont.
Since the gain G2 of 1A and 21B can be set to the gain G2 (1), the gain G2 (2), and the gain G2 (3) where the amplitude in the hysteresis comparator circuit 6 becomes the maximum, the alarm of the maximum alarm level or more is generated. You can set the level.

According to the above configuration, the variable gain amplifier circuits 21A and 21B are used as the gain amplifier circuit,
Due to the external terminal V _cont connected to the variable gain amplifier circuits 21A and 21B, the hysteresis width ΔV in the hysteresis comparator circuit 6 becomes maximum according to the alarm setting level set at the alarm level setting input terminal V _ref. Variable gain amplifiers 21A and 21A
Since the gain G2 of B can be set, the optimum amplifier gain G2 can be set for each alarm setting level. Therefore, noise resistance can be improved in a wide range of alarm setting levels, and the alarm resistance can be improved. The setting level can be set freely.

(3) Amplification Circuit with Photodetection Function of Second Embodiment A schematic structure of the amplification circuit 30 with photodetection function is shown in FIG. 4 with the same symbols as those in FIG. In the case of the second embodiment, instead of connecting the external terminal V _cont from the outside to the connection line of the variable gain amplifier circuits 21A and 21B, the gain control circuit 31 is provided and the variable gain amplifier circuit 2 is provided.
The gain G2 of 1A and 21B can be automatically and optimally adjusted according to the alarm setting voltage.

One end of the gain control circuit 31 is connected between the alarm level setting input terminal V _ref and the main amplifier 2B, and the other end is connected to a connection line connecting the variable gain amplifier circuits 21A and 21B. Accordingly, when the alarm setting level is set at the alarm level setting input terminal V _ref , the gain control circuit 31 automatically changes the variable gain amplifier circuits 21A and 21B according to the alarm setting level.
The gain G2 is controlled.

That is, the gain control circuit 31

[Equation 1] Based on the above, the gain G2 of the variable gain amplifier circuits 21A and 21B is adjusted according to the alarm setting level. Here, k ₁ is a constant. In this way, the gain control circuit 31 sets the values of the variable gain amplifiers 21A and 21B so that the hysteresis width ΔV in the hysteresis comparator circuit 6 becomes maximum in accordance with the alarm setting level set at the alarm level setting input terminal V _ref . Set the gain G2.

According to the above configuration, the gain G2 of the variable gain amplifier circuits 21A and 21B is automatically set to a value that maximizes the hysteresis voltage width ΔV in the hysteresis comparator circuit 6 according to the alarm setting level. By providing the gain control circuit 31 to be set between the alarm level setting input terminal V _ref and the connection line connecting the variable gain amplifier circuits 22A and 22B, the optimum amplifier gain G3 is automatically set for each alarm setting level. Since the noise resistance can be improved in a wide range of alarm setting levels, the user's labor can be greatly saved.

In the above embodiments, the case where the hysteresis comparator circuit 6 is used as the comparator circuit has been described, but the present invention is not limited to this, and other comparator circuits may be used.

[0033]

As described above, according to the present invention, the gains of the first and second variable gain amplifier circuits can be variably controlled at the same time in accordance with the alarm setting levels, so that each alarm setting level can be controlled. Since the optimum gain can be set for the above, noise resistance can be improved over a wide range of alarm setting levels, and the alarm setting level can be set freely.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of an optical communication system.

FIG. 2 is a block diagram showing a schematic configuration of an amplifier circuit with a light reception detecting function according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram for explaining a relationship between a maximum alarm setting level and an amplifier gain in the amplifier circuit with a light receiving detection function according to the first embodiment of the present invention.

FIG. 4 is a block diagram showing a schematic configuration of an amplifier circuit with a light reception detecting function according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a schematic configuration of a conventional amplifier circuit with a light receiving detection function.

FIG. 6 is a schematic diagram for explaining a relationship between a maximum alarm setting level and an amplifier gain in a conventional light-receiving / detecting-strength amplifier circuit.

FIG. 7 is a schematic diagram for explaining a relationship between an alarm set level and noise resistance.

FIG. 8 is a schematic diagram for explaining a relationship between an alarm set level and a hysteresis voltage.

[Explanation of symbols]

1, 13B, 20, 30 ... Amplification circuit with received light detection function,
2A, 2B ... Main amplifier circuit, 3A, 3B ... Fixed gain amplifier circuit, 4A, 4B ... Peak hold circuit, 5 ... Output buffer circuit, 6 ... Hysteresis comparator circuit, 10 ... Optical communication system, 11 ...... Optical transmitter, 12 ...... Optical fiber, 13A ...... Preamplifier circuit,
21A, 21B ... Variable gain amplifier circuit, 31 ... Gain control circuit.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Junko Uchiyama 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation (56) References JP-A-5-211429 (JP, A) JP-A 5-283943 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14/00-14/08 G02B 6/42 H03G 3/00

Claims (5)

(57) [Claims] 1. A first variable gain amplifier circuit which amplifies a voltage of a received light signal which is current-voltage converted and is input, and outputs the amplified received light signal, and a maximum value of the voltage of the amplified received light signal is detected to detect the voltage. The first peak hold means for outputting the maximum value of the voltage, the second variable gain amplifier circuit for amplifying and outputting the input alarm setting voltage of a predetermined level, and the maximum value of the amplified alarm setting voltage The second peak hold means for detecting and outputting the maximum value of the alarm setting voltage is compared with the maximum value of the voltage of the amplified light receiving signal and the maximum value of the amplified alarm setting voltage of the light receiving signal. Comparing means for detecting the presence / absence of input, and the gains of the first and second variable gain amplifier circuits are
A photodetection signal detection circuit that can be variably controlled independently and simultaneously with the ramp setting voltage . 2. The light receiving signal detecting circuit according to claim 1, wherein the gains of the first and second variable gain amplifying circuits can be variably controlled based on the alarm setting voltage. 3. The received light signal detection circuit according to claim 1, wherein the first and second variable gain amplifier circuits have substantially the same gain. 4. The received light signal detection circuit according to claim 1, wherein said comparison means is a hysteresis circuit. 5. A light receiving signal amplifier circuit for inputting a light receiving signal photoelectrically converted by a light receiving element, converting the light receiving signal into a current voltage and outputting the amplified light receiving signal, and amplifying and outputting the current light voltage converted light receiving signal. Amplification means, a first variable gain amplifier circuit for amplifying the voltage of the received light signal and outputting it as an amplified received light signal, and a first variable gain amplifier circuit for detecting the maximum value of the voltage of the amplified received light signal and outputting the maximum value of the voltage. 1
Peak holding means, a second variable gain amplifier circuit that amplifies and outputs an input alarm setting voltage of a predetermined level, and detects the maximum value of the amplified alarm setting voltage to detect the maximum of the alarm setting voltage. Second peak-holding means for outputting a value, and comparing means for comparing the maximum value of the amplified light-receiving signal voltage with the maximum value of the amplified alarm setting voltage to detect whether or not the light-receiving signal is input. A received light signal detection circuit having a gain of the first and second variable gain amplifier circuits.
A light-receiving signal processing device, which is capable of variably controlling independently and simultaneously with a ramp setting voltage .