JPH06310792A - Optical amplifier - Google Patents

Abstract

PURPOSE:To protect a pumping light source against deterioration by selecting one of slow start means or output control means which decreases the driving power thereby suppressing the overcurrent flowing into the pumping light source. CONSTITUTION:An output signal split by an optical splitter 4 passes through a photodetector 6 and enters into an automatic output control circuit 7 which outputs a control signal S1. An input signal split by an optical splitter 2 passes through a photodetector 8 and enters into an input interruption detecting circuit 9 which delivers a reset signal CT to a slow start circuit 10. The slow start circuit 10 produces a control signal S2. A selection circuit 11 receives the control signals S1, S2 and selects one of them which decreases the driving current for a driving circuit 12. The driving circuit 12 feeds a pumping light source 13 with driving current thus exciting an Er added optical fiber 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplifier used for optical communication, and more particularly to an optical amplifier having a pumping light source.

[0002]

2. Description of the Related Art Recently, in the field of optical communication systems, research on optical amplifiers that directly amplify optical information such as wavelength and phase has become more important.

As a type of optical amplifier, an optical fiber doped with a rare earth element has been attracting attention because optical amplification can be easily realized. In particular, an erbium (Er) doped optical fiber is an optical amplification wavelength suitable for an optical communication system. It has attracted attention because it has a range and can realize a simple and high-performance amplifier.

FIG. 5 is a schematic block diagram of a conventional optical amplifier using an erbium-doped optical fiber.

In FIG. 1, an optical signal input from an input connector 1 passes through an optical branching device 2, is amplified by an Er-doped optical fiber 3 which is excited by pumping light, and is output from an output connector 5 via an optical branching device 4. It is sent to the transmission line.

In such an optical amplifier, an output control system for maintaining the power of output light at a predetermined value and an abnormal operation such as oscillation of the optical amplifier when an optical signal is disconnected are input. An excitation light blocking control system is provided.

In the output control system, the output optical signal split by the optical splitter 4 is monitored by the photodetector 101, and the drive circuit of the pumping light source 104 is controlled by the automatic output control circuit 102 so that the monitored value becomes constant. 103
Is controlled.

In the pumping light cutoff control system, the optical branching device 2 is used.
The input optical signal branched by the optical detector 105 is detected by the photodetector 105, and the input disconnection detection circuit 1 is detected based on the detected signal.
When 06 detects an input disconnection, it sends an input disconnection detection signal to the automatic output control circuit 102. As a result, the automatic output control circuit 102 shuts off the output of the pumping light source 104 via the drive circuit 103 and prevents abnormal operation such as oscillation.

[0009]

However, in the above conventional optical amplifier, the pumping light source 104 is rapidly activated when the power of the optical amplifier is turned on or when the optical signal changes from the no-input state to the input state. In order to increase the power of the output light to a predetermined value, the excitation light source 10
Excessive drive current flows through 4 and pump source 1
This results in faster deterioration of 04.

As a measure for preventing such a situation, it is possible to provide a large time constant in the output control system. However, since the output control system is operating even in a steady state, increasing this time constant will cause a steady operation. However, there is a problem that the response speed becomes slow.

[0011]

An optical amplifier according to the present invention has an optical amplification means for amplifying an input optical signal by the excitation light output from the excitation light source, and the excitation light source is based on the output of the optical amplification means. Output control means for stabilizing the output of the optical amplifying means by controlling the drive current of, and slow start means for controlling the pumping light source so as to moderate the rising speed of the driving current at the time of starting the pumping light source. Selecting means for selecting one of the control output from the slow start means and the control output from the output control means, whichever has a smaller drive current of the excitation light source,
Is provided.

The slow start means controls the pumping light source so as to moderate the starting speed of the pumping light source when the input optical signal changes from the input-off state to the input-present state or when the power is turned on. . The slow start method is
For example, it has a time constant circuit composed of a resistor and a capacitor in order to mitigate the rise of the drive current of the excitation light source.

The selecting means selects a control subject such that the slow start means controls the excitation light source when the excitation light source is activated, and the output control means controls the excitation light source after the activation. To do.

[0014]

When the input optical signal changes from the input-off state to the input-present state or when the pumping light source is activated as when the power is turned on, the drive current of the pumping light source is gradually controlled by the control from the slow start means. When the output light rises to a substantially steady state, the output light source is controlled by the output control means to stabilize the output light signal.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an optical amplifier according to the present invention.

In FIG. 1, the optical signal input from the input connector 1 passes through the optical branching device 2, is amplified by the Er-doped optical fiber 3 excited by the pumping light, and is output from the output connector 5 via the optical branching device 4. It is sent to the transmission line.

The optical signal split by the optical splitter 4 is
Used by the output control system to maintain the power of the output optical signal sent to the transmission line at a predetermined value. The output control system includes a photodetector 4, an automatic output control circuit 7, a drive circuit 12,
And an excitation light source 13.

In the output control system, the output optical signal split by the optical splitter 4 is input to the photodetector 6, and the photodetector 6 outputs the output detection signal corresponding to the power of the output light by the automatic output control circuit 7 Output to. Based on the output detection signal, the automatic output control circuit 7 outputs the control signal S1 so as to maintain the power of the output optical signal sent to the transmission line at a predetermined value.

On the other hand, the input optical signal split by the optical splitter 2 is input to the photodetector 8, and the photodetector 8 outputs the input detection signal corresponding to the power of the input light to the input break detection circuit 9. . Based on the input detection signal, the input disconnection detection circuit 9 detects an input presence state and an input disconnection state indicating the presence or absence of an input optical signal, and sends an input state detection signal (reset signal) CT to the slow start circuit 10. .

The slow start circuit 10 outputs a control signal S2 according to the reset signal CT. This control signal S
2 includes the following control signals. One is the drive current to the excitation light source 13 when the power is turned on or when the optical signal from the input connector 1 changes from no input to the input present state (when the reset signal CT is released (OFF)). Is a control signal for alleviating the rising speed of the other, and the other one is to block the excitation light when the input signal changes from the input existence to the input disconnection, that is, when the reset signal CT rises (when it becomes ON). Is a control signal for performing. Slow start circuit 1
The configuration of 0 will be described later.

The selection circuit 11 inputs the control signal S1 from the automatic output control circuit 7 and the control signal S2 from the slow start circuit 10 and selects a signal having a smaller drive current to the excitation light source 13. Drive circuit 12 as control signal S
Send to. The configuration of the selection circuit 11 will also be described later.

The drive circuit 12 supplies a drive current to the pumping light source 13 in accordance with the control signal S, and the Er-doped optical fiber 3 is pumped by the pumping light from the pumping light source 13 to supplement the input optical signal. The excitation light source 13 is, for example, a semiconductor laser.

Next, the operation of this embodiment will be described with reference to FIG.

FIG. 2 shows the slow start circuit 1 of this embodiment.
7 is an operation explanatory diagram showing changes over time in the control signal output S1 of 0, the control signal output S2 of the automatic output control circuit 7, and the control signal output S of the selection circuit 11. FIG.

The output start point in the figure is the time when the power is turned on or the time when the input optical signal changes from the no input state to the input present state, that is, the reset signal CT from the input break detection circuit 9 is released (OFF). It is the time when it was done.

As shown in the figure, at the output start point, since the output optical signal of the optical amplifier is zero, the control signal S1 from the automatic output control circuit 7 has the maximum value for raising the output optical signal. (Dotted line in the figure).

On the other hand, when the reset signal CT is released, the slow start circuit 10 outputs the control signal S2 which gradually increases according to the set time constant (broken line in the figure).

The selection circuit 11 compares the control signals S1 and S2, selects the smaller one and outputs it as the control signal S. That is, from the output start point to the time when the control signals S1 and S2 intersect, the gradually increasing control signal S2 from the slow start circuit 10 is selected, and after that time, the control signal from the automatic output control circuit 7 is selected. Select S1.
Therefore, the control signal S shown by the solid line in the figure is given from the selection circuit 11 to the drive circuit 12, and a drive current having a magnitude according to the control signal S is supplied to the excitation power supply 13.

By such an operation, it is possible to prevent an excessive drive current from flowing to the excitation power supply 13 at the start of output. Furthermore, during steady operation after the start of output, the output stabilization control is performed only by the automatic output control circuit 7, so the response speed of the optical amplifier does not decrease.

When the input disconnection detection circuit 9 detects the input disconnection in the steady operation state, the reset signal CT is turned on and the slow start circuit 10 immediately drops the control signal S2 to zero. Therefore, when the control signal S2 becomes lower than the control signal S1 of the automatic output control circuit 7, the selection circuit 11 selects the control signal S2 from the slow start circuit 10 to zero the control signal S to the drive circuit 12 without delay. To As a result, the excitation light source 13 can be turned off and an abnormal situation such as oscillation can be prevented.

Next, specific configurations of the slow start circuit 10 and the selection circuit 11 will be described.

FIG. 3 is a schematic circuit diagram showing an example of the slow start circuit 10 in this embodiment.

In the figure, the operational amplifier OP is used as a voltage follower. The inverting input terminal is connected to the output terminal, the non-inverting input terminal is connected to the power supply via the resistor R1, and further grounded via the capacitor C, the resistor R2, and the reset switch SWr. The control terminal of the reset switch SWr is connected to the output terminal of the input break detection circuit 9 and receives the reset signal CT.

The slow start circuit 10 controls the control signal S1 when the power is turned on or when there is a change from no input to an input state.
Is a circuit for gradually rising.

First, when the power is turned on, the reset switch SWr is open, and the current from the power flows into the capacitor C to gradually raise the potential of the non-inverting input terminal of the operational amplifier OP. Along with this, the control signal S2 which is the output of the operational amplifier OP also gradually rises. This time constant is determined by the capacitances of the resistors R1 and R2 and the capacitor C. By gradually increasing the control signal S2, the control signal S2 is selected as shown in FIG. 2, and a rapid increase in the drive current of the excitation power supply 13 can be suppressed.

When the input disconnection detection circuit 9 detects the input disconnection in the steady operation state and the reset signal CT is turned on, the reset switch SWr is closed and the capacitor C is discharged, and the non-inverting input terminal of the operational amplifier circuit OP is immediately released. Ground potential. As a result, the control signal S2, which is the output of the operational amplifier OP, also falls to the ground potential, and as described above, the drive current of the excitation power supply 13 can be immediately stopped to prevent abnormal operation such as oscillation.

When the reset switch SWr is in the closed state due to input interruption, an optical signal is input and changes to the input state, and the input interruption detection circuit 9 releases the reset signal CT,
A current flows from the power supply to the capacitor C, and the control signal S2 gradually rises similarly to when the power is turned on. As a result, it is possible to suppress a rapid increase in the drive current of the excitation power supply 13.

FIG. 4 is a schematic circuit diagram showing an example of the selection circuit 11 in this embodiment.

In the figure, operational amplifiers OP1 and OP
The control signal S2 from the slow start circuit 10 and the control signal S1 from the automatic output control circuit 7 are input to the non-inverting input terminal of No. 2, respectively.

The n terminals of the diodes D1 and D2 are connected to the output terminals of the operational amplifiers OP1 and OP2, respectively. The p terminals of the diodes D1 and D2 are connected to the inverting input terminals of the operational amplifiers, respectively, and are also connected to each other to serve as the output terminal of the selection circuit 11.

By providing the diodes D1 and D2 in this way, a minimum value circuit is formed, and the lower voltage signal of the control signals S1 and S2 input to the selection circuit 11 is sent to the drive circuit 12 as the control signal S. can do.

[0043]

As described in detail above, in the optical amplifier according to the present invention, the pumping light source is slow-started and started when the input optical signal changes from the input disconnection state to the input presence state or when the power is turned on. After that, the pump light source is controlled to be stabilized, so that an excessive current flow into the pump light source at the time of starting the pump light source is suppressed without reducing the response speed of the output stabilization control system during steady operation. Therefore, it is possible to prevent deterioration of the excitation light source or to extend the life of the excitation light source.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an optical amplifier according to the present invention.

FIG. 2 is an operation explanatory diagram showing changes over time in the control signal output S1 of the slow start circuit 10, the control signal output S2 of the automatic output control circuit 7, and the control signal output S of the selection circuit 11 of this embodiment.

FIG. 3 is a schematic circuit configuration diagram showing an example of a slow start circuit 10 in the present embodiment.

FIG. 4 is a schematic circuit configuration diagram showing an example of a selection circuit 11 in the present embodiment.

FIG. 5 is a block diagram showing an example of a conventional optical amplifier.

[Explanation of symbols]

 1 input connector 2 optical branching device 3 erbium-doped optical fiber 4 optical branching device 5 output connector 6 photodetector 7 automatic output control circuit 8 photodetector 9 input disconnection detection circuit 10 slow start circuit 11 selection circuit 12 drive circuit 13 excitation light source

Claims (8)

[Claims] 1. An optical amplifier having an optical amplification means for amplifying an input optical signal by pumping light output from a pumping light source, wherein the drive current of the pumping light source is controlled based on the output of the optical amplifying means. Output control means for stabilizing the output of the optical amplification means, slow start means for controlling the excitation light source so as to moderate the rising speed of the drive current at the time of starting the excitation light source, and control output from the slow start means And an selecting unit that selects one of the control outputs from the output control unit, whichever has a smaller drive current of the excitation light source, and an optical amplifier. 2. The slow start means includes an input state detection means for detecting an input disconnection state and an input presence state of the input optical signal, and when the input state detection means changes the input disconnection state to the input presence state. 2. The optical amplifier according to claim 1, further comprising: a time constant setting means for generating a control output that relaxes the rising speed of the drive current of the pumping light source when the power is turned on. 3. The slow start means generates a control output for shutting off the pumping light source when the input state detecting means detects a change from an input-present state to an input-off state. Item 2. The optical amplifier according to item 2. 4. The optical amplifier according to claim 1, wherein the optical amplifying means is an optical fiber doped with a rare earth element. 5. The optical amplifier according to claim 4, wherein the optical amplifying means is an optical fiber doped with erbium. 6. The optical amplifier according to claim 1, wherein the pumping light source is a semiconductor laser. 7. An optical amplifier having optical amplification means for amplifying an input optical signal by means of pumping light output from a pumping light source, wherein the optical amplification means is controlled by controlling the pumping light source based on the output of the optical amplification means. An output control means for stabilizing the output of the pump light source, when the input optical signal changes from an input disconnection state to an input existence state or when power is turned on, the pumping light source is controlled so as to moderate the starting speed of the pumping light source. Slow start means for controlling, and a selecting means for selecting a control subject so that the slow start means controls the excitation light source when the excitation light source is activated, and the output control means controls the excitation light source during the steady operation. An optical amplifier characterized by being provided with. 8. A pumping light source for supplying pumping light to a rare earth element-doped optical fiber for amplifying an input optical signal,
An excitation light source control circuit that controls a drive current of the excitation light source, wherein the excitation light source control circuit stabilizes the output of the optical amplification means based on the output of the optical amplification means. Means, a slow start means having a time constant setting circuit for relaxing the rising speed of the drive current of the excitation light source, a control output from the slow start means and a control output from the output control means, of the excitation light source. An optical amplifier comprising: a selection unit that selects a control output having a smaller drive current.