JP3923060B2 - Optical amplifier - Google Patents

Description

  The present invention relates to a long-distance optical fiber communication system such as an optical submarine cable that traverses the ocean. In particular, a transmission system (optical transmission) using a rare earth (eg, erbium) -doped optical fiber that directly amplifies an optical signal. The present invention relates to an optical amplifier employed in a system, a reception system, a relay system, and the like.

  As a relay system of a long-distance optical fiber communication system including an optical submarine cable crossing the ocean, an optical direct amplification relay system is often used due to the progress of optical direct amplification technology. In this optical direct amplification repeater, an optical amplifier incorporating a rare earth element (lanthanoid, actinoid or erbium) or a semiconductor laser diode is usually used as an amplification medium.

  FIG. 11 is a configuration block diagram of a conventional optical amplifier. In the optical amplifier of FIG. 11, a normal silica-based optical fiber (hereinafter referred to as “optical fiber Fib”) is used as a transmission medium, and an optical fiber (hereinafter referred to as “EDF”) to which erbium (Er) is added as an amplification medium. Is used). In this optical amplifier, the input optical signal L1 as the main signal transmitted through the input side optical fiber Fib is amplified by the amplification action of the EDF and output as the output optical signal L2 through the output side optical fiber Fib. Has been.

  The excitation light source LD is a high-power semiconductor laser diode for exciting the EDF, and is, for example, an InGaAsP / InP laser diode with an oscillation wavelength of about 1475 nm or an InGaAs laser diode with an oscillation wavelength of 980 nm. This excitation light source LD is controlled by the control circuit Cn. The excitation light output from the excitation light source LD is transmitted by the optical fiber Fib on the excitation side.

An optical multiplexer WDM (Wavelength Division Multiplexer) is an optical component for combining pump light from the pump light source LD and input light on the main signal side, and is provided between the EDF and the optical fiber Fib on the output side. ing. Excitation light from an excitation light source LD having a wavelength different from that of the input signal L1 is introduced into the EDF via the optical multiplexer WDM.

  Erbium (Er) doped in the EDF is excited by the introduced excitation light, and amplifies the light having a wavelength of 1520 to 1570 nm. Therefore, the input optical signal L1 having a wavelength of 1558 nm is amplified in the EDF and then output as the output optical signal L2.

  By the way, if the excitation light source LD deteriorates or breaks down after being used for a long period of time, the necessary excitation light cannot be output. In view of this, when one pumping light source LD cannot be used due to deterioration or failure, or when the performance deteriorates, it is conceivable to make the pumping light source LD redundant so that the other pumping light source LD can be used instead.

FIG. 12 is a block diagram of the configuration when the pumping light source has a redundant configuration with an optical amplifier using an EDF. In this optical amplifier, two pumping light sources LD1 and LD2 are provided, and each is controlled by a control circuit Cn. The control circuit Cn includes a changeover switch, and when a changeover command is input from an input unit (not shown), the drive current supplied to one excitation light source is changed over to the other excitation light source by the changeover switch. The optical coupler Cp has a structure in which two optical fibers are aligned and fused and the output side end of one optical fiber is cut at the end of the welded portion. The two pumping light sources LD1 and LD2 introduce pumping light into optical fibers extending from the input side of the optical coupler Cp. An optical fiber Fib extending from the output side of the optical coupler Cp is connected to the optical multiplexer WDM. Therefore, the optical coupler Cp disperses the pumping light to the other optical fiber at the inner welded portion even if the pumping light is introduced from any optical fiber Fib extending from the input side. It can be transmitted over fiber. Therefore, the pumping light emitted from either one of the pumping light sources LD1 and LD2 is introduced into the EDF through the optical coupler WDM via the optical coupler Cp.

  By the way, due to the above-described structure of the optical coupler, even if the pumping light is introduced into any one of the optical fibers extending from the input side, the introduced pumping light is respectively transmitted to the two optical fibers at the internal fusion part. Since the light is evenly dispersed, the excitation light dispersed in the optical fiber whose output side is cut leaks to the outside at the cut portion, causing excessive loss. For example, when a 3db optical coupler is used, there is a problem that an excessive loss of excitation light of 3db or more occurs.

  In order to minimize the excess loss of light, it is conceivable to use a polarization coupler with the polarization plane matched, but the polarization coupler is very expensive and has an economic problem.

  Furthermore, in an optical amplifier using an EDF, when the pumping light source has a redundant configuration, when the pumping light source that emits pumping light is switched from one to the other, the output value of the pumping light introduced into the EDF is There was a problem of becoming zero temporarily.

  The first object of the present invention is to make it possible to efficiently introduce the pumping light into the EDF side by minimizing the excess loss of the pumping light even if the pumping light source is made redundant with an optical amplifier using EDF and an optical coupler is used. It is to provide an inexpensive optical amplifier.

  The second object of the present invention is to provide a pumping light source that emits pumping light from one to another while maintaining the output of pumping light introduced into the EDF at a predetermined value when the optical amplifier has a redundant configuration. It is an object to provide an optical amplifier that can be controlled to be switched to a certain one.

In order to achieve the first object, an optical amplifier according to the present invention amplifies an optical signal incident from its incident end according to pumping light, and then emits the rare earth-doped optical fiber emitted from its outgoing end, and emits the pumping light. first and second pump light source that, the configured so that the excitation light emitted from the pumping light source for multiplexing a first optical coupler which outputs equally at least two excitation light, the first a first pumping light introducing means for introducing one into Thus transmitted the excitation light of the two optical fibers constituting an optical coupler from the incident end of the rare earth doped optical fiber, said first optical a second optical coupler for outputting the input at least two excitation light the excitation light transmitted by the other of the two optical fibers constituting a coupler of the pumping light output from the second optical coupler depending on one of the out The transmitted the excitation light is characterized in that a second excitation light introducing means for introducing from the output end of said rare earth-doped optical fiber.

The optical amplifier of the present invention includes an optical / electrical signal converting means for converting the other of the pumping light output from the second optical coupler into an electric signal, and the electric signal converted by the optical / electrical signal converting means. Control means for controlling the first and second excitation light sources so that the signal becomes a predetermined value may be provided.

Furthermore, the optical amplifier of the present invention includes the rare earth-doped optical fiber, the optical coupler, and the first and second excitation light introducing units mounted on a first substrate, and the first substrate on the first substrate. An excitation light source is mounted, the second excitation light source is mounted on a third substrate, and the first substrate and the second substrate are configured to be detachable. The first substrate and the third substrate You may comprise so that attachment or detachment is possible.

  In order to achieve the second object, the control means of the optical amplifier according to the present invention adjusts the electrical signal to a predetermined value and supplies a driving current to the first and second pumping light sources. When switching the circuit and the excitation light source to which the drive current is to be supplied from one to the other, the drive current supplied to the one excitation light source is gradually reduced within a predetermined time from the switching time, and the other excitation light source is And a time constant circuit for controlling the driving current to be gradually increased within the predetermined time from the switching time (corresponding to claim 1).

  Further, the control means of the optical amplifier of the present invention adjusts the electrical signal to a predetermined value and supplies a driving current to the first and second pumping light sources, and from the power circuit, the power circuit A first state in which the drive currents supplied to the first and second excitation light sources are respectively the same amount of predetermined values, and a drive current supplied to the first excitation light source is double the predetermined value. And a second state in which the drive current supplied to the second excitation light source is 0, and a drive current supplied to the first excitation light source is 0 and supplied to the second excitation light source. You may comprise so that a switching circuit which switches a drive current to the 3rd state which doubles the said predetermined value may be provided (corresponding to claim 2).

  The optical amplifier of the present invention can efficiently introduce the pumping light into the EDF side by minimizing the excess loss of the pumping light even if the pumping light source is made redundant with an optical amplifier using EDF and an optical coupler is used.

Embodiments of an optical amplifier according to the present invention will be described below with reference to the drawings.
<Embodiment 1> FIG. 1 is a block diagram showing the configuration of an optical amplifier according to a first embodiment of the present invention.

  In FIG. 1, an optical amplifier 10 is a device for directly amplifying a main signal and relaying it in a long-distance optical fiber communication system, and is constructed on a single substrate. The optical amplifier 10 has three sub-boards each having an optical amplifying unit 20 and an excitation light source unit 13 or 14 mounted on the upper surface thereof.

  The optical amplifier 10 includes an optical connector C1 connected to an external device for introducing the main signal to be amplified, and an optical connector connected to the external device for transmitting the amplified main signal. C2 is provided. The optical connector C1 is connected to an optical connector C3 for sending the main signal to be amplified to the optical amplifying unit 20 via a quartz optical fiber (hereinafter referred to as "optical fiber") F. On the other hand, the optical connector C2 is connected via an optical fiber F to an optical connector C4 for receiving the amplified main signal from the optical amplifying unit 20. Further, in the optical amplifier 10, an optical connector C5 for receiving pumping light from the pumping light source unit 13, an optical connector C7 for receiving pumping light from the pumping light source unit 14, and pumping light are introduced into the optical amplifying unit 20, respectively. Optical connectors C6 and C8 are provided. The optical connectors C5 and C6 and the optical connectors C7 and C8 are connected by the optical fiber F, respectively.

On the optical amplifying unit 20, between the optical connector C3 and the optical connector C4 (main signal side transmission line), a forward optical multiplexer 21 and an erbium-doped optical fiber (hereinafter referred to as “EDF”) in order of the main signal traveling direction. 22), a rear optical multiplexer 23, and a monitoring optical coupler 24 are connected via an optical fiber F, respectively. One of the two optical fibers F extending from the output side of the optical coupler 25 is connected to the front optical multiplexer 21 and the rear optical multiplexer 23, respectively. The two optical fibers F extending from the input side of the optical coupler 25 are connected to the optical connector C6 or the optical connector C8, respectively.

  The EDF 22 directly amplifies a main signal as an optical signal when erbium (Er) added to the inside is excited by excitation light. Therefore, the input main signal L1 is introduced from the optical connector C1 to the optical amplifier 10, amplified by the EDF 22, and then output from the optical connector C2 (see L2).

  The front optical multiplexer 21 and the rear optical multiplexer 23 are on both sides before and after the EDF 22 that amplifies the main signal, respectively, and combines the excitation light supplied from the output side of the optical coupler 25 with the main signal to the EDF 22. It has been introduced. Note that the wavelength of the excitation light is different from the wavelength of the main signal.

  The optical coupler 25 is a 3 db one-to-one one-wave synthesis coupler, and has a structure in which two optical fibers F are welded to each other at an intermediate portion thereof. When pumping light is input from one of the optical fibers F extending from the input side, the optical coupler 25 uniformly distributes the pumping light to both the optical fibers F at the inner welded portion, and both optical multiplexers 21. , 23 are output equally. The configuration from the output side of the optical coupler 25 to the front optical multiplexer 21 corresponds to the first pumping light introducing means, and the configuration from the output side of the optical coupler 25 to the rear optical multiplexer 23 is the second pumping light introduction. It corresponds to the means.

  The monitoring optical coupler 24 is an optical component that branches input light for monitoring at a level that does not affect the main signal. For example, the monitoring optical coupler 24 is an optical component that branches the main signal 10 to 1, and sends the main signal amplified by the EDF 22 to the optical connector C4 and the photodiode 26 at a ratio of 10 to 1 ( Equivalent to optical signal branching means).

The photodiode 26 is an optical fiber F with respect to the monitoring optical coupler 24.
Is connected to the control circuit 27 via a signal line, and the output light branched by the monitoring optical coupler 24 is converted into an electric signal and output to the control circuit 27. (Equivalent to optical / electrical signal conversion means).

  An excitation light source 11 connected to the optical connector C5 via an optical fiber F is provided on the sub-substrate on the excitation light source unit 13 side. An excitation light source 12 connected to the optical connector C7 via the optical fiber F is provided on the sub-substrate on the excitation light source unit 14 side.

  The excitation light sources 11 and 12 are excitation laser diodes (Pump-Laser Diodes) that oscillate excitation light for exciting the EDF 22 of the optical amplification unit 20. A drive current is supplied to the excitation light sources 11 and 12 by the control circuit 27 of the optical amplification unit 20.

  Since the pumping light sources 11 and 12 have a redundant configuration, they have the same characteristics. When one of the pumps is faulty, the other is used instead. Exchanged. When the pumping light source 11 is exchanged, the optical fiber F is disconnected at the optical connector C5, and the pumping light source unit 13 is removed from the optical amplifier 10 together with the sub-board so that it can be exchanged. When the pumping light source 12 is exchanged, the optical fiber F is cut at the connector C7, and the pumping light source unit 14 is removed from the optical amplifier 10 together with the sub-board so that it can be exchanged.

  FIG. 2 is a block diagram showing the configuration of the control circuit 27. The control circuit 27 includes a control unit 27 a connected to the excitation light source 11 and a control unit 27 b connected to the excitation light source 12. The control unit 27 a and the control unit 27 b are both connected to the photodiode 26.

The control unit 27a includes a power supply circuit Am and a time constant circuit Ta. When a switching trigger signal that rises from OFF to ON is input, the time constant circuit Ta of the control unit 27a gradually increases the output voltage to a steady value after a predetermined time determined by the time constant. When a switching trigger signal that falls from on to off is input, the output voltage is gradually lowered to zero after a predetermined time determined by the time constant.

  The power supply circuit Am of the control unit 27a includes two operational amplifiers Op1 (Operational Amplifier), Op2, resistors R0 to R4, a capacitor Co, and a transistor Tr. The resistor R0 converts the current output from the photodiode 26 into a voltage signal and inputs the voltage signal to the non-inverting input terminal of the operational amplifier Op1. The output voltage from the time constant circuit Ta is also input to the non-inverting input terminal of the operational amplifier Op1. The operational amplifier Op1 raises or lowers the output voltage according to the difference between the voltages input to both input terminals. The output voltage of the operational amplifier Op1 is input to the non-inverting input terminal of the operational amplifier Op2, and is amplified at a predetermined gain by the amplifier circuit comprising the operational amplifier Op2, transistor Tr, resistors R3 and R4. Therefore, the power supply circuit Am supplies a drive current to the excitation light source 11 so that the output current of the photodiode 26 has a magnitude corresponding to the voltage value from the time constant circuit Ta. As a result, when the voltage value from the time constant circuit Ta is 0, the power supply circuit Am does not supply a drive current to the excitation light source 11.

  Further, when a switching trigger signal that rises from OFF to ON is input to the time constant circuit Ta, the power supply circuit Am generates a drive current to the excitation light source 11 in direct proportion to the output voltage of the time constant circuit Ta gradually increasing. And increase to a predetermined value necessary for excitation after a predetermined time. Furthermore, the switching trigger signal that falls from on to off is input to the time constant circuit Ta, and the power supply circuit Am decreases the drive current to the excitation light source 11 in direct proportion to the output voltage of the time constant circuit Ta gradually decreasing. And 0 after a predetermined time.

  The control unit 27b includes a power supply circuit Am and a time constant circuit Tb, and controls a current supplied to the excitation light source 12. In addition, in the structure of the electric power supply of the control part 27b, since the thing of the same code | symbol as the control part 27a is the same structure, description is abbreviate | omitted. However, the time constant circuit Ta of the control unit 27a and the time constant circuit Tb of the control unit 27b perform contradictory operations. Therefore, when the time constant circuit Ta of the control unit 27a causes the voltage to fall, the time constant circuit Tb of the control unit 27b raises the voltage.

  Next, a description will be given of a circuit operation for keeping the total of the current values output to the respective excitation light sources 11 and 12 by the control units 27a and 27b when switching the excitation light source that emits the excitation light at a predetermined value.

  FIG. 3 is a time chart for explaining the circuit operation for switching the excitation light source that emits the excitation light from the excitation light source 11 to the excitation light source 12. Here, based on FIG.2 and FIG.3, it demonstrates taking the case of switching from the excitation light source 11 to the excitation light source 12 as an example.

At the point of time P0, the pumping light is input from the pumping light source 11 to the optical amplifying unit 20, and the output light of the main signal branched by the monitoring optical coupler 24 is converted into an electrical signal by the photodiode 26, and this electrical signal Is input to the control circuit 27. Therefore, based on the electrical signal from the photodiode 26, the control unit 27a supplies a constant current to the excitation light source 11 (see FIG. 3B). On the other hand, the control unit 27b does not supply current to the excitation light source 12 (see FIG. 3C).

When a signal for switching the excitation light source from the excitation light source 11 to the excitation light source 12 (a switching trigger signal that falls from on to off) is input at time P1 (see FIG. 3A), the time constant circuit of the control unit 27a Ta gradually decreases the voltage, and the time constant circuit Tb of the control unit 27b gradually increases the voltage.

  Then, the control unit 27a gradually decreases the drive current supplied to the excitation light source 11 from the time point P1 to the time point P2, and turns off at the time point P2 (see FIG. 3B). On the other hand, the control unit 27b gradually increases the current supplied to the excitation light source 12 from the time point P1 to the time point P2, and sets the steady value at the time point P2 (see FIG. 3C). As a result, the output level of the excitation light introduced into the EDF 22 is always a predetermined value from the time point P1 to the time point P2 (see FIG. 3D). The control circuit 27 is supplied with power from a power circuit (not shown).

  Thus, when switching the excitation light source, the control circuit 27 controls the increase / decrease in the excitation output of the excitation light sources 11 and 12 so that the output level of the excitation light introduced into the EDF 22 is always a predetermined value. At this time, the pumping light from the pumping light sources 11 and 12 is introduced into the EDF 22 via the two optical fibers F extending from the output side of the optical coupler 25 and the optical multiplexers 21 and 23. After the time point P2, if the output level of the excitation light introduced into the EDF 22 by only the excitation light from the excitation light source 12 reaches a predetermined value, the excitation light source unit 13 including the excitation light source 11 can be replaced with a new one. . Since the excitation light source unit 13 of the first embodiment has a simple configuration in which only the excitation light source 11 is placed on the substrate, other parts are not wasted even if the substrate is replaced, which is economical.

  In the conventional configuration in which the pumping light is introduced into the EDF only through one optical fiber F extending from the output side of the 3 db one-to-one optical coupler, the pumping light is transmitted from the cut surface of the other optical fiber F of the optical coupler. Although it was only leaked and caused an excessive loss, in the configuration of the present embodiment, two optical fibers F are extended from the output side of the optical coupler 25, and the pumping light is introduced into the EDF 22 through these optical fibers F. Therefore, almost all the energy of the pumping light that has entered the optical coupler 25 is introduced into the EDF 22, and the excess loss of the pumping light can be minimized.

Further, based on information from the monitoring optical coupler 24 installed on the output side of the main signal, the control circuit 27 performs auto power control on the drive current to each of the pumping light sources 11 and 12 and also uses the pumping light source 11. , 12 to balance the drive current. Therefore, the output level of the pumping light introduced from the redundant pumping light sources 11 and 12 to the EDF 22 can be controlled to be constant.
<Embodiment 2> FIG. 4 is a block diagram showing the configuration of a control circuit according to Embodiment 2 of the present invention. The control circuit 27 according to the second embodiment includes a control unit 27 c connected to the excitation light source 11 and a control unit 27 d connected to the excitation light source 12. The control unit 27c and the control unit 27d are both connected to the photodiode 26. In addition, in the structure of the control parts 27c and 27d, since the thing of the same code | symbol as the control part 27a or the control part 27b of FIG. 2 is the same structure, description is abbreviate | omitted.

  The control unit 27 c includes a power supply circuit Am and a voltage switching unit Sa, and controls a current supplied to the excitation light source 11. The voltage switching unit Sa changes the voltage input to the non-inverting input terminal of the operational amplifier Op1 in three stages, thereby changing the current value output from the power supply circuit Am to 100% (max) of the steady value and the steady value. Switch to 3 levels of 50% (nor) and 0% (off).

  The control unit 27d includes a power supply circuit Am and a voltage switching unit Sb, and controls the current supplied to the excitation light source 12. The voltage switching unit Sb also changes the voltage input to the non-inverting input terminal of the operational amplifier Op1 in three stages, thereby changing the current value output from the power supply circuit Am to 100% (max) of the steady value and the steady value. Switching to three stages of 50% (nor) and 0% (off) (corresponding to switching means).

In the control circuit 27 according to the second embodiment, the switch SW that operates in response to an external command switches the voltage switching unit Sa and the voltage switching unit Sb to each other in three stages. Normally, the switch SW sets both the voltage switching unit Sa and the voltage switching unit Sb at a position (nor) where the current value output from the power supply circuit Am is 50% of the steady value. However, when the excitation light source 11 is replaced, the switch SW sets the voltage switching unit Sa to the “off” position and simultaneously sets the voltage switching unit Sb to the “max” position. Then, the voltage value input from the voltage switching unit Sa to the non-inverting input terminal of the operational amplifier Op1 becomes 0, and the power supply circuit Am of the control unit 27c does not supply driving power to the excitation light source 11. On the other hand, the voltage value input from the voltage switching unit Sb to the non-inverting input terminal of the operational amplifier Op1 becomes the “max” value, and the power supply circuit Am of the control unit 27d supplies the current supplied to the excitation light source 12 to 100% of the steady value. And When the excitation light source 12 is replaced, the switch SW sets the voltage switching unit Sa to the “max” position and simultaneously sets the voltage switching unit Sb to the “off” position. Then, the voltage value input from the voltage switching unit Sa to the non-inverting input terminal of the operational amplifier Op1 becomes the “max” value, and the power supply circuit Am of the control unit 27c supplies the current supplied to the excitation light source 11 to 100% of the steady value. And On the other hand, the voltage value input from the voltage switching unit Sb to the non-inverting input terminal of the operational amplifier Op1 is 0, and the power supply circuit Am of the control unit 27d does not supply driving power to the excitation light source 12.

  Next, a description will be given of a circuit operation for keeping the total of the current values respectively output to the respective excitation light sources 11 and 12 by the control units 27c and 27d when exchanging the excitation light source that emits the excitation light.

  FIG. 5 is a time chart for explaining the circuit operation for exchanging the excitation light source 11. At the point of time P 0, the pumping light obtained by adding 50% of the steady value from the pumping light source 11 and the pumping light source 12 is input to the optical amplification unit 20, and the main signal branched by the monitoring optical coupler 24 is input. Output light is converted into an electrical signal by the photodiode 26, and this electrical signal is input to the control circuit 27. Therefore, based on the electrical signal from the photodiode 26, the control unit 27c and the control unit 27d supply currents of 50% of the steady values to the respective excitation light sources 11 and 12 (FIG. 5B). ), FIG. 5 (c)). At this time, the switch SW of the control circuit 27 sets both the voltage switching unit Sa and the voltage switching unit Sb to the “nor” position.

  When a signal for switching the excitation light source from the excitation light source 11 to the excitation light source 12 (excitation light source 11 switching trigger signal) is input at the time of P1 (see FIG. 5A), the switch SW switches the voltage switching unit Sa to “ At the same time as setting to the “off” position, the voltage switching unit Sb is set to the “max” position (see the broken line portion in FIG. 4). Then, the voltage value input from the voltage switching unit Sa to the non-inverting input terminal of the operational amplifier Op1 becomes zero. Accordingly, the power supply circuit Am of the control unit 27c reduces the current value provided to the excitation light source 11 from 50% to 0% of the steady value, and does not supply drive power to the excitation light source 11 (see FIG. 5B). . On the other hand, the voltage value input from the voltage switching unit Sb to the non-inverting input terminal of the operational amplifier Op1 is a “max” value. Accordingly, the power supply circuit Am of the control unit 27d increases the current supplied to the excitation light source 12 from 50% to 100% of the steady value (see FIG. 5C). As a result, the excitation light introduced into the EDF 22 at the time of P1 is only the excitation light from the excitation light source 12 (see FIG. 5D).

  The control circuit 27 controls the excitation light source 12 to output 100% of the steady-state excitation light even when the excitation light of the excitation light source 11 is stopped. After the time point P1, if the output level of the excitation light to the optical amplifier 10 becomes a steady value with only the excitation light source 12, the sub-board including the excitation light source 11 can be replaced with a new one.

As described above, the pumping light obtained by adding 50% of the steady value from the pumping light source 11 and the pumping light source 12 is input to the optical amplifying unit 20, and either one of the pumping light sources is replaced with a new one. Since the output value of the other excitation light source can be switched from 50% to 100% of the steady value, the total output value of the excitation light does not become zero.
<Third Embodiment of the Invention> FIG. 6 is a block diagram showing the configuration of a third embodiment of the optical amplifier circuit according to the present invention.

  The difference between FIG. 1 and FIG. 6 is that the control circuit (control units 27a and 27b) 27 is provided on the sub-substrate side of the optical amplification unit 20 in FIG. 1, but the same configuration as each control unit 27a and 27b in FIG. The control circuits 27e and 27f having the above are provided on the sub-substrate side of the excitation light source units 13 and 14. In FIG. 6, those having the same reference numerals as those in FIG. 1 have the same functions, and thus detailed description thereof is omitted.

  An excitation light source 11 connected to the optical connector C5 via an optical fiber F is provided on the sub-substrate on the excitation light source unit 13 side. A control unit 27e that controls the excitation light source 11 is provided on the sub-substrate on the excitation light source unit 13 side. An excitation light source 12 connected to the optical connector C7 via the optical fiber F is provided on the sub-substrate on the excitation light source unit 14 side. A control unit 27 f that controls the excitation light source 12 is provided on the sub-substrate on the excitation light source unit 14 side. Accordingly, a drive current is supplied to the excitation light sources 11 and 12 by the control unit 27e and the control unit 27f.

  The photodiode 26 is connected to the monitoring optical coupler 24 via the optical fiber F, and is connected to the control unit 27e and the control unit 27f via a signal line. The branched output light is converted into an electrical signal and output to the control unit 27e and the control unit 27f.

  Since the pumping light sources 11 and 12 have a redundant configuration, they have the same characteristics. When one of the pumps fails, the other is used instead. Exchanged. When the pumping light source 11 is exchanged, the optical fiber F is disconnected at the optical connector C5, and the pumping light source unit 13 is removed from the optical amplifier 10 together with the sub-board so that it can be exchanged. When the pumping light source 12 is exchanged, the optical fiber F is disconnected at the connector C7, and the pumping light source unit 14 is removed from the optical amplifier 10 together with the sub-board so that it can be exchanged.

  According to the optical amplifier of FIG. 6, the sub-substrate side of the optical amplifying unit 20 is composed only of highly reliable optical components. Therefore, the optical amplification unit 20 is in a maintenance-free state for a long period of time, and maintenance of the optical amplification unit 20 becomes easy.

In the configuration of the optical amplifier shown in FIG. 6, the control circuit has a redundant configuration like the pumping light source, and as a whole, the reliability as the optical amplifier is remarkably increased.
<Fourth Preferred Embodiment> FIG. 7 is a block diagram showing the configuration of a fourth preferred embodiment of the optical amplifier according to the present invention.

  The difference between FIG. 7 and FIG. 1 is the connection position of the monitoring optical coupler 24. In FIG. 1, the monitoring optical coupler 24 is provided between the rear optical multiplexer 23 on the main signal side transmission line and the optical connector C4. However, in FIG. It is provided in the optical path between the output side and the rear optical multiplexer 23. In FIG. 7, the same reference numerals as those in FIG. 1 have the same functions, and detailed description thereof will be omitted.

  The monitoring optical coupler 24 b is connected to the output side of the optical coupler 25 via the optical fiber F, and is connected to the rear optical multiplexer 23 via the optical fiber F. The monitoring optical coupler 24b is an optical component that branches input light for monitoring. For example, the monitoring optical coupler 24b is an optical component that branches the input light 10 to 1, and sends the pumping light output from the optical coupler 25 to the rear optical multiplexer 23 and the photodiode 26 at a ratio of 10 to 1. is doing.

The photodiode 26 is connected to the monitoring optical coupler 24b via the optical fiber F, and is connected to the control circuit 27 via a signal line, and the output branched by the monitoring optical coupler 24b. Light is converted into an electrical signal and output to the control circuit 27.

  The control circuit 27 is a control unit described in the first or second embodiment, and performs control to maintain the output level of the output light of the excitation light sources 11 and 12 at a predetermined value. In the optical amplifier according to the fourth embodiment, one of the pumping lights from the optical coupler 25 is directly introduced into the EDF 22 from its incident end, and the other pumping light is introduced into the EDF 22 from its emitting end via the monitoring optical coupler 24b. In general, bi-directional excitation is performed.

In the optical amplifier of the fourth embodiment, a part of the optical amplifier is sent to the photodiode 26 via the monitoring optical coupler 24b, and the other excitation light enters the rear optical multiplexer 23 side, so that it enters from the incident end of the EDF 22. The excitation light that becomes larger than the excitation light incident from the exit end of the EDF 22. Therefore, the optical amplifier according to the fourth embodiment can be expected to be a low-noise optical amplifier because noise generated by interference between the main signal and the pumping light is minimized while being pumped from both directions.
<Fifth Embodiment of the Invention> FIG. 8 is a block diagram showing the configuration of an optical amplifier according to a fifth embodiment of the present invention.

  The difference between FIG. 8 and FIGS. 1 and 7 is the connection position of the monitoring optical coupler. In FIG. 1, the monitoring optical coupler 24 is provided between the rear optical multiplexer 23 on the main signal side transmission line and the optical connector C4. However, in FIG. It is provided in the optical path between the output side and the forward optical multiplexer 21. In FIG. 8, the same reference numerals as those in FIG. 1 have the same functions, and detailed description thereof will be omitted.

  The monitoring optical coupler 24 c is connected to the output side of the optical coupler 25 via the optical fiber F, and is connected to the front optical multiplexer 21 via the optical fiber F. The monitoring optical coupler 24c is an optical component that branches input light for monitoring. For example, the monitoring optical coupler 24c is an optical component that branches the input light into 10 to 1, and sends the excitation light output from the optical coupler 25 to the front optical multiplexer 21 and the photodiode 26 at a ratio of 10 to 1. is doing.

  The photodiode 26 is connected to the monitoring optical coupler 24c via the optical fiber F, and is connected to the control circuit 27 via a signal line, and the output branched by the monitoring optical coupler 24c. Light is converted into an electrical signal and output to the control circuit 27.

  The control circuit 27 is a control unit described in the first or second embodiment, and performs control to maintain the output level of the output light of the excitation light sources 11 and 12 at a predetermined value. In the optical amplifier according to the fifth embodiment, one of the excitation lights from the optical coupler 25 is directly introduced into the EDF 22 from its emission end, and the other excitation light is introduced into the EDF 22 from its incident end via the monitoring optical coupler 24b. In general, bi-directional excitation is performed.

Further, in the optical amplifier according to the fifth embodiment, a part of the optical amplifier is sent to the photodiode 26 via the monitoring optical coupler 24c, and the other excitation light enters the front optical multiplexer 21, so that it enters from the incident end of the EDF 22. The excitation light is smaller than the excitation light incident from the exit end of the EDF 22. Therefore, in the optical amplifier according to the fifth embodiment, the main signal and the pumping light interfere with each other, the amplification operation becomes large, and a high output optical amplifier can be expected.
<Sixth Embodiment of the Invention> FIG. 9 is a block diagram showing the configuration of an optical amplifier according to a sixth embodiment of the present invention.

The difference between FIG. 9 and FIGS. 1, 7, and 8 is the difference in the connection position of the monitoring optical coupler. In FIG. 9, the monitoring optical coupler is provided on the optical path between the optical connectors C6 and C8 connected to the excitation light sources 11 and 12 and the input side of the optical coupler 25, respectively. In FIG. 9, FIG.
Since those having the same reference numerals have the same functions, detailed description thereof will be omitted. The monitoring optical coupler 24d1 is connected to the connector C6 via the optical fiber F and connected to the input side of the optical coupler 25 via the optical fiber F. The monitoring optical coupler 24d1 is an optical component that branches input light for monitoring. For example, the monitoring optical coupler 24d1 is an optical component that branches the input light 10 to 1, and the excitation light output from the excitation light source 11 is supplied to the input side of the optical coupler 25 and the photodiode 26a at a ratio of 10 to 1. Sending out. The photodiode 26a is connected to the monitoring optical coupler 24d1 via the optical fiber F, and is connected to the control circuit 27 via a signal line, and the output branched by the monitoring optical coupler 24d1. Light is converted into an electrical signal and output to the control circuit 27.

  The monitoring optical coupler 24d2 is connected to the connector C8 via the optical fiber F and to the input side of the optical coupler 25 via the optical fiber F. The monitoring optical coupler 24d2 is an optical component that branches input light for monitoring. For example, the monitoring optical coupler 24d2 is an optical component that branches the input light 10 to 1, and the pumping light output from the pumping light source 12 is supplied to the input side of the optical coupler 25 and the photodiode 26b at a ratio of 10 to 1. Sending out. The photodiode 26b is connected to the monitoring optical coupler 24d2 via the optical fiber F, and is connected to the control circuit 27 via a signal line, and the output branched by the monitoring optical coupler 24d2. Light is converted into an electrical signal and output to the control circuit 27.

  The control circuit 27 is a control unit described in the first or second embodiment, and performs control to maintain the output level of the output light of the excitation light sources 11 and 12 at a predetermined value. Therefore, in the sixth embodiment, since the excitation light can be directly monitored, the failure of the excitation light sources 11 and 12 can be instantaneously determined. <Seventh Embodiment of the Invention> FIG. 10 is a block diagram showing the configuration of an optical amplifier according to a seventh embodiment of the present invention.

  In FIG. 10, the monitoring optical coupler is configured to monitor the output level of the back beam of the excitation light emitted from the excitation light sources 11 and 12 using the photodiodes 11 a and 12 a built in the excitation light sources 11 and 12. In FIG. 10, the same reference numerals as those in FIG. 1 have the same functions, and detailed description thereof will be omitted.

  The sub-substrate of the excitation light source unit 13 is provided with an excitation light source 11, a photodiode 11 a built in the excitation light source 11, and a control circuit 15. The sub-substrate of the excitation light source unit 14 is provided with the excitation light source 12, a photodiode 12 a built in the excitation light source 12, and a control circuit 16.

  The photodiodes 11a and 12a convert the back beams of the excitation light from the excitation light sources 11 and 12 into electric signals and output them to the control circuits 15 and 16. The control circuits 15 and 16 are the control means described in the first or second embodiment, and perform control to maintain the output level of the output light of the excitation light sources 11 and 12 at a predetermined value.

  Therefore, in the seventh embodiment, since the excitation light can be directly monitored, the failure of the excitation light sources 11 and 12 can be instantaneously determined.

Configuration block diagram of Embodiment 1 of an optical amplifier of the present invention Configuration block diagram of control circuit Time chart of circuit operation to switch excitation light source to another excitation light source Configuration block diagram of control circuit of embodiment 2 Time chart of circuit operation for exchanging the excitation light source with another excitation light source Configuration block diagram of optical amplifier according to Embodiment 3 of the present invention Configuration block diagram of optical amplifier according to Embodiment 4 of the present invention Configuration block diagram of Embodiment 5 of optical amplifier of the present invention Configuration block diagram of Embodiment 6 of optical amplifier of the present invention Configuration Block Diagram of Embodiment 7 of Optical Amplifier of the Present Invention Configuration block diagram of a conventional optical amplifier Configuration block diagram when the pump light source of the conventional optical amplifier is made redundant

Explanation of symbols

10 Optical amplifiers 11 and 12 Excitation light source (excitation laser diode)
13, 14 Excitation light source unit 20 Optical amplification unit 21 Forward optical multiplexer 22 EDF
23 Rear optical multiplexer 24 Monitor optical coupler 25 Optical coupler 26 Photo diode 27 Control circuit C1 to C8 Optical connector

Claims (2)

A rare-earth-doped optical fiber that introduces excitation light, amplifies an optical signal incident from its incident end, and emits it from its output end;
First and second excitation light sources that emit the excitation light;
A first optical coupler configured to multiplex the excitation light emitted from each of the excitation light sources, and to uniformly output at least two excitation lights;
A first pumping light introducing means for introducing one of the excitation light output from the first optical coupler from the incident end of the rare earth doped optical fiber,
A second optical coupler that inputs the other of the pumping lights output from the first optical coupler and outputs at least two pumping lights;
Second pumping light introducing means for introducing one of the pumping lights output from the second optical coupler from the exit end of the rare earth-doped optical fiber ;
Optical / electrical signal converting means for converting the other of the excitation light output from the second optical coupler into an electrical signal;
Control means for controlling the first and second excitation light sources so that the electrical signal converted by the optical / electrical signal conversion means has a predetermined value;
The control means adjusts the electric signal to a predetermined value, and supplies either a power supply circuit that supplies a driving current to the first and second excitation light sources, or an excitation light source that should supply the driving current. When switching from one to the other, the drive current supplied to the one excitation light source is gradually reduced within a predetermined time from the switching time, and the drive current supplied to the other excitation light source is within the predetermined time from the switching time. And a time constant circuit that is controlled so as to increase gradually. A rare-earth-doped optical fiber that introduces excitation light, amplifies an optical signal incident from its incident end, and emits it from its output end;
First and second excitation light sources that emit the excitation light;
A first optical coupler configured to multiplex the excitation light emitted from each of the excitation light sources, and to uniformly output at least two excitation lights;
A first pumping light introducing means for introducing one of the excitation light output from the first optical coupler from the incident end of the rare earth doped optical fiber,
A second optical coupler that inputs the other of the pumping lights output from the first optical coupler and outputs at least two pumping lights;
Second pumping light introducing means for introducing one of the pumping lights output from the second optical coupler from the exit end of the rare earth-doped optical fiber ;
Optical / electrical signal converting means for converting the other of the excitation light output from the second optical coupler into an electrical signal;
Control means for controlling the first and second excitation light sources so that the electrical signal converted by the optical / electrical signal conversion means has a predetermined value;
The control means adjusts the electric signal to a predetermined value and supplies a driving current to the first and second excitation light sources, and the first and second excitations from the power supply circuit. A first state in which drive currents supplied to the light sources are set to the same amount of predetermined values, and a drive current supplied to the first excitation light source is doubled the predetermined values and the second excitation light source The second state in which the drive current supplied to 0 is set to 0, the drive current supplied to the first excitation light source is set to 0, and the drive current supplied to the second excitation light source is set to the predetermined value. An optical amplifier comprising a switching circuit for switching between a third state to be doubled.

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