JPH10173269A - Automatic optical power control circuit and control signal generator - Google Patents

Abstract

(57) Abstract: A control signal for an automatic optical power control without causing a light emitting element to emit excessive light, with respect to an automatic optical power control circuit used in an electric-optical conversion device for an optical subscriber system. Provided is an automatic optical power control circuit that can ensure the accuracy of the optical power. SOLUTION: When transmission data is being output, a comparison section for detecting the fact, a reference voltage generation section for generating a reference voltage from a reference signal output from the comparison section, and a monitor light of a laser diode. A monitor voltage generator that generates a monitor voltage from the electrical converted monitor signal, a difference voltage generator that calculates a difference between the reference voltage and the monitor voltage, and a control that supplies an output of the difference voltage generator to a laser diode driver. An automatic optical power control circuit comprising a control signal generation unit for generating a signal, a delay unit is provided at at least one position between a terminal for supplying data to the comparison unit and an output terminal of the reference voltage generation unit, The delay time of the unit is configured to be equal to the sum of the delay time of the laser diode driving unit and the emission delay of the laser diode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic optical power control circuit and a control signal generator used in an electro-optical converter for an optical subscriber system. The present invention relates to an automatic optical power control circuit and a control signal generation unit that can ensure the accuracy of a control signal for automatic optical power control.

[0002] For a long time since the beginning of development, optical communication has been used only on the main transmission line, mainly because of the cost of optical fibers and the cost of light emitting elements. However, recently, the cost of optical fibers and light-emitting elements has decreased, so that optical communication devices can be applied to subscriber lines.
Further, demand for multimedia transmission through a subscriber line is also increasing, and the development and introduction of a so-called PON (Passive Optical Network) system are becoming active.

In the optical subscriber system, there is a strong demand for low power consumption in addition to the demand for low cost.
It is desirable to use a semiconductor circuit using a field-effect transistor of the (mentary Metal Oxide Semiconductor) type. In this case, means for avoiding performance degradation due to leakage current of the MOS element becomes important.

In addition, circuits using MOS transistors are generally susceptible to stray capacitance due to the high impedance level of the circuit, and have a longer delay time than circuits using bipolar transistors. is important.

[0005]

2. Description of the Related Art FIG. 8 shows a configuration of an electro-optical conversion circuit to which a conventional automatic optical power control circuit is applied.

In FIG. 8, 1 is a data receiving section for receiving data and a clock to generate an inverted signal and a non-inverted signal for driving a laser diode, and 2 is receiving an output of the data receiving section and receiving a control signal described later. A laser diode drive circuit (shown as an LD drive circuit in the figure) that drives a laser diode under the control of a control signal for automatic optical power control generated by a generation unit. Make up the part. Reference numeral 3 denotes a laser diode that converts an electric signal into an optical signal, supplies output light to an optical transmission line, and outputs monitor light. Reference numeral 4 denotes a photo diode for converting the monitor light output from the laser diode into an electric signal again. Reference numeral 5 denotes a comparator for comparing an inverted signal and a non-inverted signal output from the data receiver. A reference voltage generator for generating a reference voltage for automatic optical power control from a reference signal which is an output signal of
The monitor signal, which is the output current of the diode, is converted to a voltage,
A monitor voltage generator for generating a monitor voltage for automatic optical power control, 9 is a difference voltage generator for generating a difference between the output voltage of the reference voltage generator and the monitor voltage generator, and 10 is a difference voltage generator for the difference voltage generator. A control signal generation unit that generates a control signal for automatic optical power control according to the output, and constitutes an automatic optical power control unit (shown as an APC unit in FIG. 8) by 5 to 10.

The configuration shown in FIG. 8 is based on the difference voltage between the reference voltage generated from the inverted and non-inverted signals output from the data receiver and the monitor voltage generated from the monitor signal output from the photodiode. This is to control the drive current of the diode, control the output light of the laser diode to a constant level, and output the output light to the optical transmission line.

FIG. 10 shows the configuration of a conventional control signal generator, which is shown together with a reference voltage generator, a monitor voltage generator, and a difference voltage generator. In FIG. 10, 7 is a reference voltage generator, 8 is a monitor voltage generator, and 9 is a difference voltage generator, which is a circuit external to the control signal generator. Reference numeral 101 denotes a field-effect transistor that causes a current to flow according to the output of the differential voltage generation unit and charges a capacitor described below to generate a control signal. Reference numerals 102-1 and 102-2 denote a capacitor described below that is mounted outside the LSI. Therefore, a field-effect transistor that forms a diode for protecting a circuit inside the LSI from surges is provided by the field-effect transistor 1.
A capacitor that charges a current of 01 to generate a control voltage,
109 is an inverter, 110 is a field-effect transistor that conducts when the transmission signal is on, 111 is a resistor that discharges an excessive control signal voltage when the transmission signal is on, 112 is from when power is turned on until shutdown is released. A field-effect transistor for turning off during the automatic optical power control operation to eliminate the dead zone of the automatic optical power control operation; 113, a field-effect transistor for generating a threshold voltage for eliminating the dead zone of the automatic optical power control operation; Current sources 101 and 10
2 and 108 to 114 constitute a control signal generator.

In the control signal generator of FIG. 10, in order to shorten the charging time of the capacitor 108, the capacitor 108
Of the field effect transistor 10
1 may be increased. However, the capacitor 10
If the capacitance of the capacitor 8 is small, the operation of holding the control signal in the reception time zone is hindered, so that the capacitance of the capacitor cannot be easily reduced.

Therefore, it is necessary to increase the current of the field effect transistor 101. For this purpose, it is necessary to increase the size of the field effect transistor 101 itself. As a result, there is a problem that the leak current of the field effect transistor 101 increases. Occurs.

When the leak current of the field effect transistor 101 increases, the capacitor 108 is charged by the leak current in the reception time zone, and the output light level is increased at the head of the burst signal in the next transmission time zone. As a result, there is a possibility that the pulse mask standard cannot be satisfied at the beginning of the next burst signal.

FIG. 11 is a diagram for solving the above problem.
This is a configuration of a conventional control signal generation unit that takes measures against leakage current. In FIG. 11, 7 is a reference voltage generator, 8 is a monitor voltage generator, and 9 is a difference voltage generator, which is a circuit external to the control signal generator. Reference numeral 101 denotes a field-effect transistor that causes a current to flow according to the output of the difference voltage generation unit and charges a capacitor described later to generate a control signal.
Reference numeral 02-2 denotes a field-effect transistor that forms a diode for protecting a circuit inside the LSI from a surge because a capacitor described later is mounted outside the LSI.
Is a capacitor for charging the current of the field effect transistor 101 to generate a control voltage; 109 is an inverter;
0 is a field-effect transistor that conducts when the transmission signal is on, 111 is a resistor that discharges excessive control signal voltage when the transmission signal is on, 112 is on from the time power is turned on until shutdown is released. A field effect transistor for eliminating the dead zone of the automatic optical power control operation; 113, a field effect transistor for generating a threshold voltage for eliminating the dead zone of the automatic optical power control;
114 is a current source for supplying a current to the field effect transistor 113, 117 is a resistor for shunting a leak current, 118
Is a diode which becomes forward with respect to the current of the field effect transistor 101 and becomes reverse with respect to the discharge of the electric charge of the capacitor 108. The control signal generation unit is formed by 101 and 102, 108 to 114, 117 and 118. Configure.

In the configuration of FIG. 11, the capacitor 108 is sufficiently charged during the reception time period.
The leak current of the field effect transistor is shunted to the resistor 117, and the capacitor 108 is not charged by the leak current. On the other hand, the diode 118 is in the opposite direction to the discharge of the charge of the capacitor 108, so that the charge of the capacitor 108 is not discharged during the reception time zone. Therefore, the configuration of FIG. 11 is a circuit that can compensate for the disadvantage of the configuration of FIG.

[0014]

In the configuration shown in FIG.
Since the reference signal is generated only by digitally comparing the inverted and non-inverted signals output from the data receiving unit, the delay time of the reference signal from the inverted and non-inverted signals can be ignored.
On the other hand, the delay time of the monitor signal from the inverted or non-inverted signal is the sum of the delay time of the laser diode driving unit and the light emission delay time of the laser diode, and cannot be ignored.

Therefore, there is a delay time difference between the reference signal and the monitor signal. Therefore, there is a difference between the timing at which the reference signal generator outputs the reference voltage and the timing at which the monitor voltage generator outputs the monitor voltage.

This is shown in FIG. 9 showing a problem of the conventional automatic optical power control circuit. As shown in FIG. 9, the reference signal has no delay with respect to the input signal of the laser diode driving circuit. On the other hand, the monitor signal is delayed from the input signal of the laser diode drive circuit by the delay of the laser diode drive circuit and the emission delay of the laser diode.

Since the control signal is generated based on the difference voltage between the reference voltage and the monitor voltage, the control voltage generation unit determines that the output light of the laser diode is at a predetermined level during a time period when the monitor voltage is behind the reference voltage. The drive current of the laser diode is controlled such that it is determined to be lower than the value and the control voltage is increased to increase the level of the output light of the laser diode.

In this state, when a signal corresponding to the output of the data receiving circuit is supplied to the laser diode, the output light level of the laser diode becomes higher than a predetermined value. For this reason, the output light of the laser diode may not be within the pulse mask standard that defines its waveform. In the worst case, the output light level of the laser diode becomes too high, which may lead to deterioration or destruction of the laser diode itself.

In FIG. 9, the leading edge of the monitor signal is higher because the monitor signal is proportional to the output light level. Also, the reason why the control signal has a constant value before the input signal of the laser diode drive circuit rises is that the function of holding the control signal from the previous burst signal to the next burst signal in the control signal generating unit is provided. It depends.

Next, in optical burst transmission, power is not supplied to the main signal portion of the electro-optical conversion circuit of FIG. 8 while a burst signal is not transmitted, and power is supplied to the automatic optical power control circuit. However, at this time, the output potential of the data receiving unit has the same value on the inverted output side and the non-inverted output side. Therefore, during this period, the output of the comparison unit is undefined and may be fixed at “H”. In this case, the control voltage generator determines that the output light level of the laser diode is low, and controls the control signal to increase the output light level of the laser diode.

In this state, when a signal corresponding to the output of the data receiving circuit is supplied to the laser diode, the output light level of the laser diode becomes higher than a predetermined value. For this reason, the output light of the laser diode may not be within the pulse mask standard that defines its waveform.

The control signal generator having the configuration shown in FIG.
Although it is possible to make up for the drawbacks of the control signal generation section having the configuration described above, the diode 1 introduced to realize its function can be used.
18 requires a voltage of about 0.7V to operate.

When the power supply voltage supplied to the control signal generator having the configuration shown in FIG. 11 is relatively high (for example, about 5 V),
There is no significant problem if diode 118 occupies a voltage of 0.7 volts.

However, when the power supply voltage becomes about 3 V, the diode 118 occupies a voltage of 0.7 volts.
It is difficult to secure the source-drain voltage of 1 and it is difficult to stably realize the control signal generation function itself.

[0025]

The first means of the present invention is as follows.
In the automatic optical power control circuit of FIG. 8, this is a technique of providing a delay unit between a comparison unit and a reference voltage generation unit.

In the first means of the present invention, if the delay time of the delay unit is set equal to the delay time obtained by adding the delay time of the laser diode driving unit and the light emission delay time of the laser diode, The phase of the reference signal, which is an input, and the phase of the monitor voltage, which is an input of the monitor voltage generator, can be matched. Therefore, the rise of the reference voltage output by the reference voltage generator and the monitor voltage output by the monitor voltage generator are Since the rising timings coincide, the control signal generation unit does not determine that the output is insufficient when the laser diode is outputting the output light at the predetermined level. Therefore, the output level does not increase at the head of the burst signal and the pulse mask cannot be satisfied.

According to a second means of the present invention, in the first means, a switch is provided between the output terminal of the comparison section and the ground, the switch being turned off during transmission and turned on during reception. According to the second means of the present invention, even when the output of the comparing section becomes unstable and "H" is output at the time of reception, the voltage is grounded. And the pulse mask cannot be satisfied at the beginning of the burst signal.

A third means of the present invention is a control signal generating section shown in FIG. 10, in which a bipolar transistor is connected between a field effect transistor serving as a current source of a charging current and a capacitor charging the current of the field effect transistor. A collector and an emitter are connected, and a second field-effect transistor whose gate is connected to a field-effect transistor that is a current source is provided, and a resistor is connected to a current supply-side terminal of the second field-effect transistor. The other terminal of the resistor is connected to a constant voltage point to which a terminal of the capacitor electrode that is not connected to the bipolar transistor is connected, and the base of the bipolar transistor is connected to a second resistor through a second resistor. This is a circuit technique for connecting a connection point between two field effect transistors and a first resistor.

According to the third aspect of the present invention, when the field-effect transistor serving as a current source of the charging current is off, the second field-effect transistor is also turned off. Since no effect occurs, the bipolar
The transistor is also turned off.

Therefore, even if the field effect transistor serving as the current source of the charging current tries to supply a leakage current, the bipolar transistor is turned off, and the leakage current of the bipolar transistor itself is reduced by the leakage of the field effect transistor. Since the current is sufficiently smaller than the current, the leak current of the field-effect transistor serving as the current source of the charging current does not charge the capacitor, and the problem that the control signal has an error due to the leak current is solved.

According to a fourth aspect of the present invention, in the third aspect of the present invention, a connection point between the field effect transistor serving as a current source of the charging current and the bipolar transistor is turned on at the time of reception to set a constant voltage point. This is a technology to provide a switch that connects to

According to the fourth means of the present invention, the leakage current of the second field-effect transistor in the third means of the present invention is so large that the off-resistance of the bipolar transistor is small. Even so, the problem that the control signal has an error due to the leak current is completely eliminated because the leak current of the field effect transistor serving as the current source of the charging current does not charge the capacitor.

A fifth means of the present invention is a control signal generating section shown in FIG. 9, wherein a connection point between a field-effect transistor serving as a current source of the charging current and the capacitor is turned on at the time of reception to reach a constant voltage point. This is a technique for providing a switch to be connected.

According to the fifth means of the present invention, the leakage current of the field effect transistor serving as the current source of the charging current is shunted to the constant voltage point via the switch, so that the reception current causes the leakage current to be applied to the capacitor. The problem that the control signal has an error due to the leak current without being charged is solved. In addition, there is an advantage that the circuit configuration and the semiconductor process for forming the circuit are simple.

[0035]

FIG. 1 shows the configuration of an electro-optical conversion circuit to which an automatic optical power control circuit according to the present invention is applied.

In FIG. 1, reference numeral 1 denotes a data receiving unit which receives data and a clock and generates an inverted signal and a non-inverted signal for driving a laser diode; A laser diode drive circuit (shown as an LD drive circuit in the figure) that drives a laser diode under the control of a control signal for automatic optical power control generated by a generation unit. Configure the circuit.

A laser 3 converts an electric signal into an optical signal, supplies output light to an optical transmission line, and outputs monitor light.
It is a diode. Reference numeral 4 denotes a photo diode for converting the monitor light output from the laser diode into an electric signal again.

5 is a comparator for comparing the inverted signal and the non-inverted signal output from the data receiver, 6 is a delay for delaying the output of the comparator, and 7 is a reference signal which is the output of the comparator. A reference voltage generating unit for generating a reference voltage for automatic optical power control from a monitor voltage for converting a monitor signal, which is an output current of the photodiode, to generate a monitor voltage for automatic optical power control Generator,
Reference numeral 9 denotes a difference voltage generator for generating a difference between the output voltages of the reference voltage generator and the monitor voltage generator, and reference numeral 10 denotes a control for generating a control signal for automatic optical power control according to the output of the difference voltage generator. An automatic optical power control unit (shown as an APC unit in FIG. 1) is composed of 5 to 10 in the signal generation unit.

The configuration of FIG. 1 is characterized in that in the conventional automatic optical power control circuit, a delay unit is provided between the comparison unit and the reference voltage generation unit, and the delay time of the delay unit is set to the delay time of the laser diode drive circuit. And the sum of the emission delay times of the laser diodes.

FIG. 2 is a diagram showing the operation of the automatic optical power control circuit of the present invention. As shown in FIG. 2, a signal obtained by comparing an inverted signal and a non-inverted signal output from the data receiving unit, which is an input signal of the laser diode driving unit, is converted into a delay time of the laser diode driving circuit and a light emission delay of the laser diode. The reference signal is supplied to the reference voltage generator as a reference signal after being delayed by a time equal to the sum of the times.

On the other hand, when the output signal of the data receiving section is applied to the laser diode driving section, a monitor signal is output from the photodiode with a delay of the delay time of the laser diode driving section and the emission delay of the laser diode. You.

As a result, the phases of the reference signal and the monitor signal match, and the outputs of the reference voltage generator and the monitor voltage generator rise simultaneously. Therefore, unlike the conventional automatic optical power control circuit, the control voltage that raises the output light level of the laser diode to the laser diode driving section by raising the reference voltage earlier than the monitor voltage is not supplied, and the burst is not increased. The output light level of the laser diode becomes a predetermined value from the beginning of the signal. As a result, the pulse mask is satisfied even at the head of the burst signal.

Here, the configuration in which the delay unit is inserted between the comparison unit and the reference voltage generation unit has been described. However, even between the output of the data reception unit and the comparison unit, the delay unit is included in the reference voltage generation unit. You may. Further, in addition to inserting the delay unit at one location, a required delay time may be divided and inserted at a plurality of locations.

FIG. 3 shows the configuration of the delay unit shown in FIG. FIG.
, 61 is an inverter, 62 is a resistor, 63 is a P-CH type field effect transistor that short-circuits the source and drain, and forms a capacitance between the gate, 64 is short-circuited between the source and drain, and 64 An N-CH type field effect transistor which forms a capacitance between the transistors 65 and 65 is an inverter.

In the configuration shown in FIG. 3, the inverter operates as a buffer gate at the input terminal and the output terminal of the delay unit. Since an inverter is used on the input side, an inverter is also used on the output side so that the polarity of the signal does not change between the input and output of the delay unit. Therefore, if a non-inverting gate is used for one, a non-inverting gate may be used for the other.

Also, an N-CH type field effect transistor which short-circuits the source and drain to form a capacitance between the gate and a short-circuited source and drain to form a capacitance between the gate and the gate. The capacitance is configured by combining the P-CH type field effect transistors to cancel the change in the capacitance exhibited by both field effect transistors in the opposite direction due to the potential of the output signal of the inverter. This is to keep the capacity almost constant and to make the delay time constant.

Incidentally, in the configuration of FIG.
Although a resistor is inserted in series between the output terminal of the inverter 1 and the input terminal of the inverter 65, when a sufficient delay time can be obtained by the output resistance of the inverter 61 and the capacitance exhibited by the two field effect transistors, the resistance is reduced. Can be omitted.

FIG. 4 shows an automatic optical power control circuit provided with a switch in the configuration of FIG. In FIG. 4, reference numeral 1 denotes a data receiving unit that receives data and a clock and generates an inverted signal and a non-inverted signal for driving a laser diode. A laser diode drive circuit (shown as an LD drive circuit in the figure) that drives a laser diode under the control of a control signal for automatic light power control to be generated.
And 2 constitute a main signal section.

A laser 3 converts an electric signal into an optical signal, supplies output light to an optical transmission line, and outputs monitor light.
It is a diode. Reference numeral 4 denotes a photo diode for converting the monitor light output from the laser diode into an electric signal again.

5 is a comparator for comparing the inverted signal and the non-inverted signal output from the data receiver, 6 is a delay for delaying the output of the comparator, and 7 is a reference signal which is the output of the comparator. A reference voltage generating unit for generating a reference voltage for automatic optical power control from a monitor voltage for converting a monitor signal, which is an output current of the photodiode, to generate a monitor voltage for automatic optical power control Generator,
Reference numeral 9 denotes a difference voltage generator for generating a difference between the output voltages of the reference voltage generator and the monitor voltage generator, and reference numeral 10 denotes a control for generating a control signal for automatic optical power control according to the output of the difference voltage generator. The signal generation unit 11 is turned off when the transmission / reception switching signal indicates the transmission state, and is turned on when the transmission / reception switching signal indicates the reception state. The automatic optical power control circuit includes 5 to 11.

The feature of FIG. 4 is that, in the configuration of FIG. 1, the transmission / reception switching signal is turned off when the transmission / reception switching signal indicates the transmission state between the signal line between the comparison unit and the delay unit and the ground point, and the transmission / reception switching signal is The point is that a switch that is turned on when indicating the reception state is provided.

In the receiving state, the potentials of the two output lines of the data receiving section in FIG. 1 are equal. Therefore, the output of the comparison unit is undefined, and "H" may be output. In the receiving state, since the monitor signal is "L", when the reference signal side is "H", the control signal generating unit controls the laser diode driving unit to increase the output of the laser diode. Is supplied, the output light level at the head of the burst signal becomes high in the next transmission state, and the pulse mask may not be satisfied.

Therefore, as shown in FIG. 4, the output of the comparison unit is forcibly grounded by a switch provided between the comparison unit and the delay unit in the reception state, so that the output of the comparison unit becomes unstable. However, this does not cause an error in the control signal, and the output light of the laser diode can be maintained at a predetermined level. Therefore, the output light can always satisfy the pulse mask.

Although there are many ways to configure this switch, since it can be easily configured by a field effect transistor, the semiconductor integrated circuit based on the field effect transistor also has compatibility.

Here, the example in which the switch is provided between the comparison unit and the delay unit has been described. However, the switch is provided between the data reception unit and the comparison unit and between the delay unit and the reference voltage generation unit. It may be in. It is of course conceivable to provide a plurality of switches, but there is no advantage in providing a plurality of switches, so providing a single switch may be sufficient.

FIG. 5 shows a first configuration of the control signal generator of the present invention, together with a reference voltage generator, a monitor voltage generator and a difference voltage generator. In FIG. 5, 7 is a reference voltage generator, 8 is a monitor voltage generator, 9 is a difference voltage generator,
This is a circuit external to the control signal generator. Reference numeral 101 denotes a first field-effect transistor that causes a current to flow according to the output of the difference voltage generation unit and charges a capacitor described later to generate a control signal, 102 denotes a surge protection circuit, and 103 denotes the first field-effect transistor. A second field-effect transistor having the same operation as that of the first embodiment; 104, a surge protection circuit; 105, a bipolar transistor; 106, a first resistor; 107, a second resistor; 109, an inverter; 110, a field-effect transistor that conducts when the transmission signal is on; 111, a resistor that discharges excessive control signal voltage when the transmission signal is on; 112, power-on To turn on during the time until the shutdown is released to eliminate the dead zone of the automatic optical power control operation. Field effect transistor, the field effect transistor for generating a threshold voltage to eliminate the dead zone of the automatic optical power control is 113, 114 field effect transistor 11
A control signal generation unit is configured by 101 to 114, which are current sources for supplying a current to the control signal 3.

The surge protection circuit 102 includes a field effect transistor 102-1 and a field effect transistor 102-2, as in FIG. 10, and the surge protection circuit 104 has the same configuration.

In the configuration shown in FIG. 5, since the first field-effect transistor and the second field-effect transistor have the same potential condition, the same current flows if the dimensions are the same. This current is I, the resistance of the first resistor is R ₁₀₆ , the resistance of the second resistor is R ₁₀₇ , the voltage between the base and the emitter of the bipolar transistor is V _BE , the terminal voltage of the capacitor (the control signal If the amplitude is set to V, if the circuit is designed so as to satisfy I × R ₁₀₆ > V _BE + V, the bipolar transistor is also turned on when the first and second field-effect transistors are turned on. The capacitor can be charged by the current of the field effect transistor.

Further, since the on-voltage of the bipolar transistor is about 0 volt, even if the bipolar transistor is interposed between the first field-effect transistor and the capacitor, it hardly affects the voltage design. Therefore, the control voltage generator having the configuration shown in FIG. 5 can operate at a low voltage.

On the other hand, when the first and second field effect transistors are off, the voltage developed across the first resistor is about 0 volts and the bipolar transistor is off.

This prevents the capacitor from being charged by the leak current of the first field-effect transistor and the field-effect transistor constituting the surge protection circuit.

Therefore, no error occurs in the control signal due to the leakage current of the first field effect transistor and the field effect transistor of the surge protection circuit. still,
When the dimension of the second field-effect transistor is different from the dimension of the first field-effect transistor, the current of the second field-effect transistor has a value different from the current of the first field-effect transistor. However, in this case, if the resistance value of the first resistor is set so that I × R ₁₀₆ > V _BE + V is satisfied,
The same operation as described above can be realized.

FIG. 6 shows a second configuration of the control signal generator of the present invention, together with a reference voltage generator, a monitor voltage generator, and a difference voltage generator. In FIG. 6, 7 is a reference voltage generator, 8 is a monitor voltage generator, 9 is a difference voltage generator,
This is a circuit external to the control signal generator.

Reference numeral 101 denotes a first field-effect transistor which causes a current to flow according to the output of the difference voltage generation unit and charges a capacitor described later to generate a control signal, 102 denotes a surge protection circuit, and 103 denotes the first field-effect transistor. A second field-effect transistor that operates the same as the field-effect transistor; 104, a surge protection circuit; 105, a bipolar transistor;
06 is a first resistor, 107 is a second resistor, 108 is a capacitor for charging the current of the field-effect transistor 101 to generate a control voltage, 109 is an inverter, and 110 is a field-effect transistor that conducts when a transmission signal is on. Transistor, 1
Reference numeral 11 denotes a resistor for discharging an excessive control signal voltage when the transmission signal is turned on. Reference numeral 112 denotes an electric field for turning on the power supply from when the power is turned on until the shutdown is released to eliminate a dead zone of the automatic optical power control operation. Effect transistor,
Reference numeral 113 denotes a field-effect transistor that generates a threshold voltage for eliminating a dead zone of automatic optical power control.
Is a current source for supplying a current to the field effect transistor 113, 115 is an inverter, 116 is a field effect transistor which is turned off when the transmission / reception switching signal indicates transmission and turned on when reception indicates the reception. Make up the part.

The surge protection circuit 102 comprises a field effect transistor 102-1 and a field effect transistor 102-2, as in FIG. 10, and the surge protection circuit 104 has the same configuration.

The feature of the configuration of FIG.
5 and the transistor 116, when receiving, that is,
When the first field-effect transistor is off, the field-effect transistor is turned on, and a connection point between the first field-effect transistor, the surge protection circuit, and the capacitor is grounded.

As a result, even if the leakage current of the second field-effect transistor is large and a voltage that cannot be ignored is generated across the first resistor, and the bipolar transistor is slightly turned on, the second field-effect transistor is turned on. Since the leak current of one field effect transistor and the surge protection circuit is shunted to the ground, the capacitor is never charged by the leak current.

FIG. 7 shows a third configuration of the control signal generator according to the present invention, together with a reference voltage generator, a monitor voltage generator and a difference voltage generator. In FIG. 7, 7 is a reference voltage generator, 8 is a monitor voltage generator, 9 is a difference voltage generator,
This is a circuit external to the control signal generator.

Reference numeral 101 denotes a field effect transistor which supplies a current according to the output of the difference voltage generation unit and charges a capacitor described later to generate a control signal;
Reference numeral -2 denotes a field effect transistor which forms a diode for protecting a circuit inside the LSI from a surge because a capacitor described later is mounted outside the LSI, and 108 generates a control voltage by charging the current of the field effect transistor 101. A capacitor 109, an inverter 109, a field-effect transistor 110 that conducts when a transmission signal is on,
Reference numeral 111 denotes a resistor for discharging an excessive control signal voltage when the transmission signal is on. Reference numeral 112 denotes an electric field for turning on the power supply from when the power is turned on until the shutdown is released to eliminate a dead zone of the automatic optical power control operation. An effect transistor 113 is a field effect transistor that generates a threshold voltage for eliminating a dead zone of automatic optical power control.
14 is a current source for supplying a current to the field effect transistor 113, 115 is an inverter, 116 is a field effect transistor which is turned off when the transmission / reception switching signal indicates transmission, and turned on when reception indicates the reception, and 101 to 102 to 108 to 108 1
The control signal generator 16 is constituted by 16.

The feature of FIG. 7 is that, in the configuration of FIG. 10, the inverter 115 and the transistor 116 are provided, and the field effect transistor 116 is turned on during reception, that is, when the first field effect transistor is off. The connection point of the first field-effect transistor, the surge protection circuit, and the capacitor is grounded.

Therefore, even if the leakage current of the first field-effect transistor and the transistor constituting the surge protection circuit is large, the leakage current flows to the ground and does not flow to the capacitor. The control signal, which is the charging voltage of the capacitor, does not include an error due to a leak current.

Further, the configuration of FIG. 7 includes the second field-effect transistor and the second transistor in the configuration of FIG. 5 or FIG.
Since the resistor and the bipolar transistor are not required, there is an advantage that the circuit configuration of the control signal generation unit and the semiconductor process for realizing it are simplified.

In FIGS. 5 to 7, since the first field effect transistor and the second field effect transistor are of the P-CH type, the bipolar transistor is of the NPN type. The source of the second field-effect transistor is a positive power supply (highest potential), the electrode of the capacitor opposite to the first field-effect transistor, and the opposite side of the first resistor from the second field-effect transistor. Are grounded (lowest potential), and FIG.
Alternatively, the source of the N-CH type field effect transistor 116 in FIG. 7 is configured to be grounded, but when the first and second field effect transistors are N-CH type, The voltage relationship is reversed, the bipolar transistor is of the PNP type, and the field effect transistor corresponding to the field effect transistor 116 of FIG.
What is necessary is just to be CH type.

Therefore, the configuration of the control signal generation circuit of the present invention is not limited to those shown in FIGS. 5 to 7, but can be selected in design depending on the polarity of the field effect transistor used.

Here, the field effect transistor is connected to the connection point between the first field effect transistor and the bipolar transistor. This is an element that is open when data is transmitted and short-circuited when receiving data. Any switch may be used, that is, a switch that is open when transmitting data and short-circuited when receiving data may be provided.

[0076]

As described above, according to the present invention, the conventional problems relating to the automatic optical power control circuit and the control signal generation unit which is a part of the automatic optical power control circuit are completely solved.

That is, according to the first means of the present invention, the phase of the reference signal input to the reference voltage generator in the automatic optical power control circuit can be matched with the phase of the monitor voltage input to the monitor voltage generator. Therefore, since the rise of the reference voltage output from the reference voltage generator and the rise of the monitor voltage output by the monitor voltage generator coincide with each other, when the laser diode is outputting output light of a predetermined level, The control signal generation unit does not determine that the output is insufficient. Therefore, the pulse mask cannot be satisfied at the beginning of the burst signal.

Next, according to the second means of the present invention, even if the output of the comparing unit in the automatic optical power control circuit becomes unstable at the time of reception and "H" is output, the voltage is grounded. Therefore, the control signal generation unit does not judge that the output is insufficient at the time of reception, and the pulse mask cannot be satisfied at the head of the burst signal.

Further, according to the third means of the present invention, when the field effect transistor serving as a current source of the charging current in the control signal generating section is off, the second field effect transistor is also off, so that Since no voltage effect occurs on the first resistor, the bipolar transistor is also turned off.

Therefore, even if the field effect transistor serving as a current source of the charging current attempts to supply a leakage current, the bipolar transistor is turned off, and the leakage current of the bipolar transistor is reduced by the leakage current of the field effect transistor. Since it is sufficiently smaller, the leakage current of the field-effect transistor serving as the current source of the charging current does not charge the capacitor, and the problem that the control signal has an error due to the leakage current is solved.

According to the fourth means of the present invention, the leakage current of the second field effect transistor in the third means of the present invention is so large that the off-resistance of the bipolar transistor is small. Even so, the problem that the control signal has an error due to the leak current is completely eliminated because the leak current of the field effect transistor serving as the current source of the charging current does not charge the capacitor.

According to the fifth aspect of the present invention, the leakage current of the field effect transistor serving as the current source of the charging current in the control signal generation section is divided into the constant voltage point via the switch, so that the Thus, the capacitor is not charged, and the problem that the control signal has an error due to the leak current is solved. In addition, there is an advantage that the circuit configuration and the semiconductor process for forming the circuit are simple.

[Brief description of the drawings]

FIG. 1 is an electric-optical conversion circuit to which an automatic optical power control circuit according to the present invention is applied.

FIG. 2 shows the operation of the automatic optical power control circuit of the present invention.

FIG. 3 is a configuration of a delay unit in FIG. 1;

FIG. 4 is an electro-optical conversion circuit to which an automatic optical power control circuit provided with a switch in the configuration of FIG. 1 is applied;

FIG. 5 is a first configuration of a control signal generation unit according to the present invention.

FIG. 6 shows a second configuration of the control signal generator of the present invention.

FIG. 7 shows a third configuration of the control signal generator of the present invention.

FIG. 8 shows an electric-optical conversion circuit to which a conventional automatic optical power control circuit is applied.

FIG. 9 shows a problem of the conventional automatic optical power control circuit.

FIG. 10 shows a configuration of a conventional control signal generator.

FIG. 11 shows a conventional control signal generation unit that takes measures against leakage current.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 data receiving unit 2 laser diode driving unit (LD driving unit) 3 laser diode 4 photodiode 5 comparison unit 6 delay unit 7 reference voltage generation unit 8 monitor voltage generation unit 9 difference voltage generation unit 10 control signal generation unit 11 Switch 61 Inverter 62 Resistance 63 Field effect transistor 64 Field effect transistor 65 Inverter 101 First field effect transistor 102 Surge protection circuit 103 Second field effect transistor 104 Surge protection circuit 105 Bipolar transistor 106 First resistor 107 Second Resistance 108 Capacitor 109 Inverter 110 Field effect transistor 111 Resistance 112 Field effect transistor 113 Field effect transistor 114 Current source 115 Inverter 116 Field effect transistor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Miki 2-1-1 Kitaichijo Nishi, Chuo-ku, Sapporo City, Hokkaido Inside Fujitsu Hokkaido Digital Technology Co., Ltd. (72) Inventor Shuichi Yasuda Kitaichijo-Nishi, Chuo-ku, Sapporo, Hokkaido 2-1-1 Fujitsu Hokkaido Digital Technology Co., Ltd. (72) Inventor Kiyotoshi Noheji 2-1-1 Kita-Ichijo Nishi, Chuo-ku, Sapporo, Hokkaido Fujitsu Hokkaido Digital Technology Co., Ltd. (72) Inventor Norio Murakami Hokkaido Sapporo, Hokkaido Fujitsu Hokkaido Digital Technology Co., Ltd., 2-1-1 Kita-Ichijo-Nishi, Chuo-ku, Tokyo (72) Inventor Kazuyoshi Shimizu 4-1-1 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Akazawa Yukio 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Within Nippon Telegraph and Telephone Corporation (72) Inventor Noboru Ishihara 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan Within Telegraph and Telephone Corporation (72) Makoto Nakamura 3-192, Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (5)

[Claims] 1. A comparison section for detecting when transmission data is being output, a reference voltage generation section for generating a reference voltage from a reference signal output from the comparison section, and a monitor light of a laser diode. A monitor voltage generator for generating a monitor voltage from a monitor signal obtained by electrically converting the reference voltage, a difference voltage generator for obtaining a difference between the reference voltage and the monitor voltage, and supplying the difference voltage generator with an output of the difference voltage generator to a laser diode driving unit. An automatic optical power control circuit including a control signal generation unit for generating a control signal, wherein a delay unit is provided between a terminal for supplying data to the comparison unit and an output terminal of the reference voltage generation unit; An automatic optical power control circuit, wherein the time is made equal to the sum of the delay time of the laser diode drive unit and the light emission delay of the laser diode. 2. The automatic optical power control circuit according to claim 1, wherein a switch is provided between an output terminal of the comparison unit and an input terminal of the reference voltage generation unit, and the switch is opened when transmitting data. An automatic optical power control circuit, wherein the switch is short-circuited at the time of reception, and a signal line is grounded between an output terminal of the comparison unit and an input terminal of the reference voltage generation unit. 3. A first field-effect transistor that receives an output of the differential voltage generator according to claim 1, supplies current when transmitting data, charges a capacitor, and turns off when receiving data. A capacitor charged by the current of the field-effect transistor, wherein a gate is connected to the output of the difference voltage generation circuit to flow a current when transmitting data and to turn off when receiving data. A field-effect transistor, a first resistor for flowing a current of the second field-effect transistor, a second resistor connected to a connection point between the first field-effect transistor and the first resistor, A bipolar transistor having a base connected to the other terminal of the second resistor and having a collector and an emitter connected between the first field-effect transistor and the capacitor. The provided, during data transmission, the voltage developed across said first resistor to turn on the said bipolar transistor, the control signal generating unit when data reception is characterized by having a structure for turning off the bipolar transistor. 4. The control signal generator according to claim 3, wherein a switch is provided at a connection point between the first field-effect transistor and the bipolar transistor, the switch is opened when data is transmitted, and the switch is received when data is received. A control signal generation unit comprising a configuration for short-circuiting the control signal. 5. A first field-effect transistor that receives an output of the differential voltage generator according to claim 1, supplies current when transmitting data to charge a capacitor, and turns off when receiving data. A control signal generating unit including a capacitor charged by a current of the field effect transistor, a switch is provided at a connection point between the first field effect transistor and the capacitor, the switch is opened when data is transmitted, and the data is received when data is received. A control signal generation unit comprising a configuration for short-circuiting the switch.