Optical amplifier and optical communication system

Abstract

To provide an optical amplifier with a small operation current.SOLUTION: An optical amplifier G comprises: one or a plurality of rare earth element-added optical fibers EF, each of which includes one or a plurality of cores Ce; excitation light sources L, the number of which exceeds one per one core Ce of the rare earth element-added optical fibers EF, for emitting excitation light for exciting rare earth elements added to the rare earth element-added optical fibers EF according to operation current; and a synthesis unit PB for synthesizing excitation light Lp emitted from the respective excitation light sources L, the number of which exceeds one per one core Ce. The total number of the cores Ce is two or more. The excitation light Lp emitted from the excitation light sources L, the number of which exceeds one per one core Ce, is synthesized and introduced into each of the core Ce.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to optical amplifiers and optical communication systems. [Background technology]

[0002] Non-Patent Document 1 discloses an optical communication system including an optical submarine cable and an optical amplifier to which power is supplied through a power feed line from a power feeder installed in a landing station. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] NEC Technical Report, 2009, Vol.62, No4, p.20-23, 32-35, 44-47 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the optical amplifier described in Non-Patent Document 1 requires a large operating current, and the resistance loss of the optical communication system increases in proportion to the operating current of the optical amplifier. Therefore, an optical amplifier with a small operating current is required.

[0005] Therefore, an object of the present disclosure is to provide an optical amplifier with a small operating current. [Means for solving the problem]

[0006] The optical amplifier G of the present disclosure comprises one or more rare-earth-doped optical fibers EF each including one or more cores Ce, and a combination unit PB that emits pumping light to excite the rare-earth elements doped in the rare-earth-doped optical fiber EF in response to an operating current, and combines the pumping light Lp emitted by more than one pumping light source L per core Ce of the rare-earth-doped optical fiber EF, wherein there are two or more cores Ce in total, and the pumping light Lp emitted by more than one pumping light source L per core Ce is combined and introduced into each core Ce. Effect of the Invention

[0007] According to the present disclosure, an optical amplifier with a small operating current can be provided. [Brief description of the drawings]

[0008] [Figure 1] 1 is an equivalent circuit diagram illustrating a power supply configuration of an optical communication system according to an embodiment. [Diagram 2] FIG. 1 is a diagram illustrating a configuration of an optical amplifier according to a first embodiment. [Diagram 3] 1 is a cross-sectional view illustrating a configuration of an erbium-doped optical fiber. [Figure 4] 2 is an equivalent circuit diagram of a semiconductor laser drive circuit of the optical amplifier according to the first embodiment. [Diagram 5] FIG. 2 is a diagram showing a first example of the relationship between the operating current of an optical amplifier and the power consumption and supply voltage of an optical communication system. [Figure 6] FIG. 11 is a diagram illustrating a second example of the relationship between the operating current of an optical amplifier and the power consumption and supply voltage of an optical communication system. [Figure 7] 11 is a diagram illustrating a configuration of an optical amplifier according to a modified example. [Figure 8] FIG. 11 is a diagram illustrating the configuration of an optical amplifier according to a second embodiment. [Figure 9] FIG. 11 is an equivalent circuit diagram of a semiconductor laser drive circuit of an optical amplifier according to a third embodiment. [Figure 10]13 is a diagram illustrating a semiconductor laser in an optical amplifier according to a fourth embodiment. FIG. [Figure 11] FIG. 13 is an equivalent circuit diagram of a semiconductor laser drive circuit in an optical amplifier according to a fifth embodiment. [Figure 12] FIG. 13 is a diagram illustrating the configuration of an optical amplifier according to a sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Description of the embodiment of the present invention] First, the embodiments of the present disclosure will be described. An optical amplifier according to one aspect of the present disclosure includes one or more rare-earth-doped optical fibers each including one or more cores, a number of pumping light sources exceeding one per core of the rare-earth-doped optical fiber that emit pumping light for exciting the rare-earth elements doped in the rare-earth-doped optical fiber in response to a drive current, and a combining unit that combines the pumping light emitted by each of the number of pumping light sources exceeding one per core, where there are two or more cores in total, and the pumping light emitted by the number of pumping light sources exceeding one per core is combined and introduced into each core.

[0010] If the number of pump light sources per core is K (the number being greater than one), then in the above optical amplifier, the light emitted from each of the K pump light sources is combined and introduced into one core to pump that core. With this configuration, the drive current of the pump light source required to obtain the optical power to pump the core can be reduced to approximately 1 / K, making it possible to provide an optical amplifier with a small operating current.

[0011] An optical amplifier refers to an amplifier that directly amplifies an optical signal in the optical state without converting it into an electrical signal. The one or more rare-earth-doped optical fibers each containing one or more cores include a single rare-earth-doped optical fiber containing one core, a single rare-earth-doped optical fiber containing multiple cores, multiple rare-earth-doped optical fibers each containing one core, and multiple rare-earth-doped optical fibers each containing multiple cores. The rare-earth-doped optical fiber containing multiple cores includes a coupled multi-core optical fiber, a few-mode optical fiber, and an uncoupled multi-core optical fiber. In the following description, the term "multi-core optical fiber" refers to at least one of a coupled multi-core optical fiber, a few-mode optical fiber, and an uncoupled multi-core optical fiber.

[0012] The number exceeding one per core means an integer or a decimal. For example, if the optical amplifier has four pump light sources per two cores, the number exceeding one per core is 2. If the optical amplifier has three pump light sources per two cores, the number exceeding one per core is 1.5.

[0013] The operating current of an optical amplifier is a current for operating the optical amplifier to obtain a desired amplification factor. The drive current for driving the pumping light source is at least a part of the operating current of the optical amplifier. As the drive current becomes smaller, the operating current of the optical amplifier becomes smaller.

[0014] In the above optical amplifier, more than one pump light source per core may be driven by a drive current supplied from a plurality of drive circuits connected in series. For example, when drive current is supplied to K pump light sources, if K drive circuits are connected in parallel, it is necessary to supply approximately equal drive current I to each of the K drive circuits, so that a total drive current of K×I is required, and the operating current of the optical amplifier increases. By connecting K drive circuits in series, it is possible to drive all of the K drive circuits with drive current I, and the drive current can be reduced to approximately 1 / K compared to when the K drive circuits are connected in parallel.

[0015] In the optical amplifier, the combiner may combine pump light emitted by more than one pump light source per core by at least one of a polarization combining method, an optical injection locking method, a composite resonator method, and a Master Oscillator Power Amplifier (MOPA) method. The optical amplifier can combine pump light emitted by more than one pump light source per core by each method or a combination of each method.

[0016] The polarization synthesis method is a method of synthesizing multiple differently polarized waves using a polarizing element such as a polarizing beam splitter (PBS). Polarization refers to electromagnetic waves such as light or radio waves whose electric and magnetic fields oscillate in regular directions. The optical injection locking method is a method of synthesizing multiple different lights using the optical injection locking phenomenon. The optical injection locking phenomenon is a phenomenon in which the oscillation wavelength of a semiconductor laser is pulled to the wavelength of the incident light when light with a wavelength close to the oscillation wavelength of the semiconductor laser is incident from the outside on the semiconductor laser that is oscillating by itself.

[0017] The composite resonator method is a method of combining multiple different lights using a composite resonator. A composite resonator is a resonator in which multiple resonators are connected along a specific direction. The master oscillator output amplifier method is a method of combining multiple different lights using a master oscillator output amplifier. The master oscillator output amplifier independently controls the first master oscillator (or seed light) and the high-output second oscillator, and extracts high-output light from the second oscillator side, which is the combination of the lights emitted by the first oscillator and the second oscillator.

[0018] In the optical amplifier, the pumping light sources more than one per core may at least partially include a semiconductor laser group including a plurality of semiconductor lasers connected in series, and the plurality of semiconductor lasers included in the semiconductor laser group may be driven by a common drive current. The above "at least partially including a semiconductor laser group" includes both cases where the pumping light sources more than one per core are composed of a plurality of the semiconductor laser groups and cases where the pumping light sources are composed of the semiconductor laser groups as a part of the semiconductor laser groups.

[0019] For example, when a driving circuit for driving an excitation light source includes a current source, the current source includes a resistor, so that the voltage drop increases as the number of driving circuits increases, and the operating current of the optical amplifier increases. In contrast, the optical amplifier described above can reduce the number of driving circuits in accordance with the number of semiconductor laser groups by driving multiple semiconductor lasers included in the semiconductor laser group with a common driving current. This makes it possible to suppress the voltage drop and reduce the operating current of the optical amplifier. Furthermore, the optical amplifier described above can reduce the area in which the driving circuits are arranged by reducing the number of driving circuits.

[0020] In the above optical amplifier, the rare-earth-element-doped optical fiber is preferably a multi-core optical fiber in which multiple cores are covered with a single cladding, because the optical amplifier includes a multi-core optical fiber, which increases the number of cores included in the optical amplifier, and as the number of cores increases, the effect of suppressing the operating current of the optical amplifier per core becomes greater.

[0021] When the rare-earth-doped optical fiber is a coupled multi-core optical fiber, the power coupling coefficient between adjacent cores among the multiple cores is preferably 10[ / m] or more. In an optical amplifier including a rare-earth-doped optical fiber having practical characteristics, the length of the rare-earth-doped optical fiber is approximately 10[m] or more. In this case, mode dependent gain (MDG) can be sufficiently suppressed by using a coupled multi-core optical fiber having a power coupling coefficient between adjacent cores of 10[ / m] or more. Due to the redundancy obtained by suppressing MDG, the above optical amplifier can reduce the gain difference between modes even when the optical power of the pump light introduced into each core is significantly deviated from the optimal state.

[0022] The power coupling coefficient is the ratio of the power of a component that couples to another guided mode when a certain guided mode propagates through a unit length, and is defined as the coefficient of the power coupling equation. [m] represents the unit of meters, and [ / m] represents the unit of the reciprocal of meters. In the following, the letters in [] represent the units.

[0023] The optical communication system of the present disclosure includes one or more optical fibers for transmitting optical signals, and the optical amplifier for amplifying the optical signals transmitted by the optical fibers. By including the optical amplifier, the optical communication system can reduce the operating current of the optical amplifier and the resistance loss of the optical communication system. In addition, the temperature rise of elements such as the pumping light source and the power transistor in the optical amplifier can be suppressed, thereby extending the life of each element.

[0024] [Details of the embodiment of the present disclosure] Specific examples of optical amplifiers according to embodiments of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is intended to include all modifications within the scope of the claims and meaning equivalent to the claims. In the description, the same reference numerals will be used for the same elements or elements having the same functions, and duplicate descriptions will be omitted as appropriate.

[0025] [Embodiment] (Configuration of optical communication system 100) An optical communication system 100 including an optical amplifier G according to an embodiment of the present disclosure will be described. The optical communication system 100 is, for example, an optical submarine cable system that performs long-distance optical communication between Japan and the United States, etc., using an optical submarine cable installed across the Pacific Ocean. The optical communication system 100 includes one or more optical fibers that transmit optical signals, and an optical amplifier G that amplifies the optical signals transmitted by the optical fibers.

[0026] One or more optical fibers are provided in an optical submarine cable. In the optical communication system 100, a plurality of repeaters are placed on the seabed in the transmission path of the optical fibers to compensate for the transmission loss of the optical signal transmitted through the optical fibers. An optical amplifier G is provided in each of the plurality of repeaters.

[0027] 1 is an equivalent circuit diagram illustrating a configuration of a power supply system that supplies power to each of a plurality of repeaters in an optical communication system 100. The optical communication system 100 includes a first power supply device 10, a second power supply device 20, and a power supply line PL 1 From the power supply line PL N+1 In addition, N is a natural number, and the power supply line PL 1 and power supply line PL N+1The subscripts (subscripts) in the above are added to distinguish each of the N+1 power feeders. In the following description, when the N+1 power feeders are not particularly distinguished from each other, the subscripts may be omitted and they may be collectively referred to as the power feeder PL. This also applies to the repeater T, optical amplifier G, semiconductor laser L, driver circuit D, erbium-doped optical fiber EF, etc., which are referred to using subscripts in the following description.

[0028] In optical communication systems, in order to improve the reliability of the power supply system, a power supply device capable of supplying the necessary power is installed at each of multiple landing stations. A landing station is a base where an optical submarine cable that has been installed on the seabed is pulled up to land.

[0029] In the optical communication system 100, the first power supply device 10 is provided in a first landing station (e.g., Japan) and supplies a constant DC current from a DC current source Ai to the repeater. The second power supply device 20 is provided in a second landing station (e.g., the United States) and supplies a constant DC current from a DC current source Ao to the repeater. The first power supply device 10 and the second power supply device 20 are each earthed underwater. The optical communication system 100 can perform power supply to both the first landing station and the second landing station, with the first landing station and the second landing station sharing the power supply.

[0030] Power line PL 1 From the power supply line PL N+1 The power supplied from each of the first power supply device 10 and the second power supply device 20 is fed to a repeater T 1 From Repeater T N+1 These are transmission lines that transmit electricity to each of them.

[0031] The voltage Vs is 1 From Repeater T N+1 It represents the voltage supplied to the entire system. Voltage VL 1 to voltage VL N+1 Repeater T 1 From Repeater T N+1 The voltages supplied to the resistors R 1 From the resistance R N+1 is the power supply line PL1 From the power supply line PL N+1 Each of these represents a corresponding electrical resistance.

[0032] In an optical submarine cable system such as the optical communication system 100, a resistor R 1 From the resistance R N+1 Resistance loss occurs due to resistance such as those mentioned above. Since resistance loss is proportional to the square of the current, it is preferable to reduce the current supplied. However, in an optical submarine cable system, there is a limit to the adjustment of the voltage-to-current ratio because the repeaters are fed with direct current, and it is necessary to pass the current required by the repeaters through the feeder. Therefore, the optical amplifiers included in the repeaters are required to have a small operating current in order to reduce the resistance loss in the optical submarine cable system.

[0033] [First embodiment] (Configuration of optical amplifier G) The configuration of the optical amplifier G will be described with reference to Figures 2 and 3. Figure 2 is a diagram illustrating the configuration of the optical amplifier G included in a repeater T of the optical communication system 100. Figure 3 is a cross-sectional view illustrating the configuration of an erbium-doped optical fiber EF provided in the optical amplifier G. The cross-sectional view of Figure 3 corresponds to a view of the erbium-doped optical fiber EF viewed from the light transmission direction side when the erbium-doped optical fiber EF is cut along a plane substantially perpendicular to the light transmission direction.

[0034] As shown in FIG. 2, the repeater T includes an optical amplifier G 1 and optical amplifier G 2 and optical amplifier G M The repeater T shown in FIG. 1 From Repeater T N+1 Each of the optical fibers has the same configuration as that shown in Fig. 2. M is a natural number representing the number of cores (hereinafter referred to as "signal cores") that transmit optical signals contained in an optical fiber that transmits optical signals in either the upstream direction from the first landing station to the second landing station or the downstream direction from the second landing station to the first landing station. In this embodiment, M is 8. However, this is not limited to this, and the value of M can be changed as appropriate.

[0035] The repeater T is connected to an upstream optical fiber Fu for transmitting an optical signal from the first landing station side to the second landing station side, and a downstream optical fiber Fd for transmitting an optical signal from the second landing station side to the first landing station side. The upstream optical fiber Fu is connected to a signal core Cs 1 , signal core Cs 3 and signal core Cs 2M-1 The downstream optical fiber Fd is a multi-core optical fiber in which eight signal cores Cs, including the odd-numbered signal cores Cs, are covered with a single clad. 2 , signal core Cs 4 and signal core Cs 2M It is a multi-core optical fiber in which eight signal cores Cs including (even-numbered signal cores Cs) are covered with a single clad. The upstream optical fiber Fu and the downstream optical fiber Fd transmit signal light Ls having a wavelength of, for example, approximately 1550 [nm] as an optical signal. However, the wavelength of the signal light Ls is not limited to approximately 1550 [nm] and can be changed as appropriate.

[0036] The optical amplifier G amplifies the signal light Ls incident on the repeater T from the first landing station side through the upstream optical fiber Fu, and outputs the amplified signal light Ls to the second landing station side through the upstream optical fiber Fu. The optical amplifier G also amplifies the signal light Ls incident on the repeater T from the second landing station side through the downstream optical fiber Fd, and outputs the amplified signal light Ls to the first landing station side through the downstream optical fiber Fd.

[0037] In FIG. 2, the optical amplifier G includes an erbium-doped optical fiber EF, a semiconductor laser L, and a polarization element PB. 1 EF is an erbium-doped optical fiber 1 and Erbium-doped optical fiber EF 2 and the semiconductor laser L 1 From Semiconductor Laser L 4 Four semiconductor lasers L and a polarization element PB 1 From PB 2 The optical amplifier G2 EF is an erbium-doped optical fiber 3 and Erbium-doped optical fiber EF 4 and the semiconductor laser L 5 From Semiconductor Laser L 8 Four semiconductor lasers L and a polarization element PB 3 From PB 4 The optical amplifier G M EF is an erbium-doped optical fiber 2M-1 and Erbium-doped optical fiber EF 2M and the semiconductor laser L 4M-3 From Semiconductor Laser L 4M Four semiconductor lasers L and a polarization element PB 2M-1 From PB 2M and two polarizing elements PB.

[0038] The erbium-doped optical fiber EF is an example of one or more rare-earth-doped optical fibers, each of which includes one or more cores. The core (hereinafter referred to as the "pumping core") Ce in which the signal light is amplified in the rare-earth-doped optical fiber is an example of one or more cores included in the rare-earth-doped optical fiber.

[0039] As shown in Fig. 3, an erbium-doped optical fiber EF 2M-1 and erbium-doped optical fiber EF 2M are multi-core optical fibers in which eight pump cores Ce are covered with a single cladding CL. The erbium-doped optical fiber EF 1 Erbium-doped optical fiber EF 2M The erbium-doped optical fibers EF have the same configuration.

[0040] In this embodiment, the upstream optical fiber Fu and the downstream optical fiber Fd are also multi-core optical fibers in which eight signal cores Cs are covered with a single cladding CL. In this embodiment, a configuration in which the number of signal cores Cs is equal to the number of pumping cores Ce is illustrated as an example, but the numbers of the two are not necessarily equal.

[0041] Erbium-doped optical fiber EF 2M-1 is the excited core Ce 1 From Ce 2M-1 The eight excitation cores Ce are arranged in odd-numbered order, and the odd-numbered signal cores Cs 1 From signal core Cs 2M-1 The signal light Ls transmitted through each of them is amplified. Erbium-doped optical fiber EF 2M is the excited core Ce 2 From Ce 2M The even-numbered signal cores Cs 2 From signal core Cs 2M The signal light Ls transmitted through each of the erbium-doped optical fibers EF is amplified. When a coupled multi-core optical fiber is used as the erbium-doped optical fiber EF, it is preferable that the power coupling coefficient between adjacent pumping cores Ce among the multiple pumping cores Ce is 10 [ / m] or more.

[0042] 2, a semiconductor laser L is an example of a pumping light source that emits pumping light Lp that excites erbium doped in an erbium-doped optical fiber EF in response to a drive current. The semiconductor laser L emits, for example, pumping light Lp having a wavelength of approximately 1480 [nm] or approximately 980 [nm] that can excite erbium. However, the pumping light source is not limited to the semiconductor laser L, and may be another light source as long as it can emit pumping light having a wavelength that can excite erbium.

[0043] In this embodiment, the optical amplifier G is provided with two semiconductor lasers L for each pump core Ce of the erbium-doped optical fiber EF. Specifically, in order to amplify the signal light Ls transmitted through each of the total of 16 signal cores Cs included in the upstream optical fiber Fu and the downstream optical fiber Fd, the optical amplifier G is provided with 16 pump cores Ce of the erbium-doped optical fiber EF. The optical amplifier G is also provided with a total of 32 semiconductor lasers L, two for each pump core Ce of the erbium-doped optical fiber EF.

[0044] Semiconductor Laser L 1 and semiconductor laser L 2 is the excited core Ce1 The erbium doped in the semiconductor laser L is pumped. 3 and semiconductor laser L 4 is the excited core Ce 2 The erbium doped in the semiconductor laser L is pumped. 5 and semiconductor laser L 6 is the excited core Ce 3 The erbium doped in the semiconductor laser L is pumped. 7 and semiconductor laser L 8 is the excited core Ce 4 The erbium doped in the semiconductor laser L is pumped. 4M-3 and semiconductor laser L 4M-2 is the excited core Ce 2M-1 The erbium doped in the semiconductor laser L is pumped. 4M-1 and semiconductor laser L 4M is the excited core Ce 2M This excites the erbium doped in the laser.

[0045] Optical Amplifier G 1 In the semiconductor laser L 1 and semiconductor laser L 2 The pump light Lp emitted by the polarizing element PB 1 The light is incident on the polarizing element PB 1 Two semiconductor lasers L per pump core Ce 1 and semiconductor laser L 2 This is an example of a combining unit that combines the pump light Lp emitted by each of the polarization elements PB. 1 The method of combining the pump light Lp by the polarization combining method corresponds to the polarization combining method.

[0046] Polarizing element PB 1 is a polarizing beam splitter that includes an optical surface that transmits the P-polarized component and reflects the S-polarized component. 1 For example, a semiconductor laser L 1 The excitation light Lp, which is a linearly polarized P-polarized light emitted by the semiconductor laser L 2 The polarizing element PB combines the two by reflecting the linearly polarized S-polarized excitation light Lp emitted by the polarizing element PB.1 By using polarization, the semiconductor laser L 1 and semiconductor laser L 2 The pumping light Lp emitted by each of the semiconductor lasers L can be efficiently combined. The pumping light Lp emitted by the semiconductor laser L is not limited to linearly polarized light and may be elliptically polarized light or the like. However, from the viewpoint of suppressing optical loss, linearly polarized light is preferable.

[0047] Similarly, the semiconductor laser L 3 and semiconductor laser L 4 The pump light Lp emitted by the polarizing element PB 2 The light is incident on the polarization element PB 2 It is synthesized by:

[0048] Polarizing element PB 1 The pump light Lp, which is synthesized by the polarization element PB 2 The pump light Lp is fed to the 3DB coupler B. 1 3DB coupler B 1 is a passive optical element that combines two incoming beams and then splits them into two beams with a split ratio of approximately 1:1. 1 One of the pumping lights Lp split by the pump junction P 1 After being guided toward the pump junction P 1 is incident on

[0049] Pump junction P 1 is, for example, a wavelength division multiplexing (WDM) coupler. 1 One of the pumping lights Lp split by the pump junction P 1 The signal core Cs 1 The signal light Ls is then combined with the signal light Ls transmitted through the erbium-doped optical fiber EF 1 Excitation core Ce 1 is incident on

[0050] In other words, the semiconductor laser L 1 and semiconductor laser L2 The pump light Lp emitted by the two semiconductor lasers L is polarized by the polarization element PB 1 After being combined into the pump junction P 1 Excitation of the core Ce via 1 is introduced to

[0051] Erbium-doped optical fiber EF 1 The excited core Ce is excited by the incident pump light Lp. 1 The erbium doped in the fiber is excited to form a population inversion. 1 The erbium-doped optical fiber EF 1 The signal light Ls transmitted through the signal core Cs is amplified by stimulated emission. The amplified signal light Ls is then directed to the second landing station. 1 The signal is then transmitted again through the

[0052] On the other hand, 3DB coupler B 1 The other of the pumping light Lp branched by the pump junction P 2 The signal is incident on the signal core Cs 2 After being combined with the signal light Ls transmitted through the erbium-doped optical fiber EF 2 Excitation core Ce 2 is incident on

[0053] Erbium-doped optical fiber EF 2 The excited core Ce is excited by the incident pump light Lp. 2 The erbium doped in the fiber is excited to form a population inversion. 2 The erbium-doped optical fiber EF 2 The signal light Ls transmitted through the signal core Cs is amplified by stimulated emission. The amplified signal light Ls is then fed to the signal core Cs 2 The signal is then transmitted again through the

[0054] Optical Amplifier G 1 is the signal core Cs included in the upstream optical fiber Fu.1 The signal light Ls transmitted through the downstream optical fiber Fd and the signal core Cs 2 The signal light Ls transmitted through the optical amplifier G is amplified in pairs to provide redundancy to the repeater T. 1 is the semiconductor laser L 1 From Semiconductor Laser L 4 Even if some of the optical fibers are unable to emit pumping light Lp due to a malfunction or the like, the effect can be dispersed and it is possible to prevent some of the optical signals transmitted through the upstream optical fiber Fu and the downstream optical fiber Fd from being amplified.

[0055] Similarly, the optical amplifier G 2 is the semiconductor laser L 5 From Semiconductor Laser L 8 The excitation light Lp emitted by each semiconductor laser L is used to form a signal core Cs 3 and signal core Cs 4 The optical amplifier G amplifies the signal light Ls transmitted through the M is the semiconductor laser L 4M-3 From Semiconductor Laser L 4M The excitation light Lp emitted by each semiconductor laser L is used to form a signal core Cs 2M-1 and signal core Cs 2M The amplifier amplifies the signal light Ls transmitted through the amplifier.

[0056] Optical Amplifier G 2 Optical amplifier G M The configuration and function of the optical amplifier G is the same as that of the optical amplifier G except that the signal core Cs to be optically amplified is different. 1 is the same as:

[0057] (Example of the configuration of the driving circuit D of the semiconductor laser L) FIG. 4 is an equivalent circuit diagram illustrating the configuration of a driving circuit D for driving a semiconductor laser L included in an optical amplifier G. The optical amplifier G includes a semiconductor laser L 1 From Semiconductor Laser L 4M In order to drive 32 semiconductor lasers L (M=8), a driving circuit D 1 From drive circuit D 4MThe driver circuit D is equipped with 32 driver circuits D. 1 From drive circuit D 4M are connected in series. 1 From drive circuit D 4M The semiconductor laser L is driven in response to a drive current I, which is at least a part of the operating current S supplied from the first power supply device 10. 1 From Semiconductor Laser L 4M Each of the semiconductor lasers L is driven to emit light. The voltage VL represents the voltage supplied to the repeater T.

[0058] In FIG. 4, the driving circuit D 1 is the constant voltage circuit Cv 1 and the constant current circuit Ci 1 The constant voltage circuit Cv 1 is the Zener diode Z 1 and a driving circuit D 1 The reference voltage V r The constant voltage control is performed so that the voltage is approximately constant.

[0059] Constant current circuit Ci 1 is the current source A1 1 and current source A2 1 and a driving circuit D 1 The current source A1 is controlled to be constant so that the current flowing through the 1 is the semiconductor laser L 1 The semiconductor laser L 1 The drive current I 1 The current source A1 supplies a current so that the current is approximately constant. 2 is the semiconductor laser L 1 are connected in parallel to the drive circuit D 1 Semiconductor laser L 1 Current I flowing through s1 The current is supplied so that the driving current I 1 , current I s1 and constant voltage circuit Cv 1 The reference current I r is the driving circuit D 1 Then, they flow through the drive circuit D 2 The reference current Ir and the drive current I 1 and current I s1 The sum of these is approximately equal to the operating current S.

[0060] Drive circuit D 2 From drive circuit D 4M The configuration and functions of the driving circuit D are the same as those of the driving circuit D except that the semiconductor laser L to be driven is different. 1 is the same as:

[0061] (Effect of optical amplifier G) As described above, the optical amplifier G according to this embodiment includes one erbium-doped optical fiber EF (rare earth element-doped optical fiber) including eight pumping cores Ce (cores), and two semiconductor lasers L (pumping light sources) for each pumping core Ce of the erbium-doped optical fiber EF, which emit pumping light Lp for pumping the erbium (rare earth element) doped in the erbium-doped optical fiber EF in response to a driving current. The optical amplifier G also includes a polarization element PB (combining unit) for combining the pumping light Lp emitted by each of the two semiconductor lasers L for each pumping core Ce. There are a total of eight pumping cores Ce, and the pumping light Lp emitted by the two semiconductor lasers L for each of the eight pumping cores Ce is combined and introduced.

[0062] The optical amplifier G drives two semiconductor lasers L together with a drive current I, and pumps one pumping core Ce with pumping light Lp obtained by combining pumping light Lp from each of the two semiconductor lasers L. Therefore, the optical amplifier G can reduce the drive current I to approximately half that required when one pumping core is pumped with pumping light from one semiconductor laser. By reducing the drive current I, an optical amplifier with a small operating current can be provided.

[0063] Here, Fig. 5 and Fig. 6 are diagrams for explaining the results of a simulation showing the relationship between the operating current of the optical amplifier, the power consumption of the optical communication system, and the voltage supplied to the optical communication system. Fig. 5 shows the case where there are four pump cores Ce, and Fig. 6 shows the case where there are eight pump cores Ce.

[0064] The horizontal axis of Figures 5 and 6 indicates the operating current [A] of the optical amplifier, and the vertical axis indicates the power consumption [kW] and the supply voltage [kV]. The dashed line graphs in Figures 5 and 6 indicate the supply voltage, and the solid line graphs indicate the power consumption.

[0065] 5, power consumption Gp1X indicates the power consumption of the optical amplifier GX according to the comparative example, and supply voltage Gv1X indicates the supply voltage of the optical amplifier GX according to the comparative example. The comparative example is the result of a simulation based on the numerical conditions described in Non-Patent Document 1. Power consumption Gp1 indicates the power consumption of the optical amplifier G according to this embodiment, and supply voltage Gv1 indicates the supply voltage of the optical amplifier G according to this embodiment.

[0066] 6, power consumption Gp2X indicates the power consumption of the optical amplifier GX according to the comparative example, and supply voltage Gv2X indicates the supply voltage of the optical amplifier GX according to the comparative example. Power consumption Gp2 indicates the power consumption of the optical amplifier G according to the present embodiment, and supply voltage Gv2 indicates the supply voltage of the optical amplifier G according to the present embodiment.

[0067] The operating current of the optical amplifier GX is about 1.1 [A], while the operating current of the optical amplifier G is about half that, or about 0.5 [A]. In the example of Fig. 5, as the operating current decreases, the power consumption Gp1 decreases to about 6 [kW] compared to the power consumption Gp1X of about 12 [kW]. Also, the supply voltage Gv1 decreases to about 9 [kV] compared to the supply voltage Gv1X of about 11 [kV].

[0068] In the example of Figure 6, the power consumption Gp2 was reduced to about 9 [kW] while the power consumption Gp2X was about 15 [kW]. Also, the supply voltage Gv1 was about 15 [kV] while the supply voltage Gv2X was about 14 [kV], which increased by about 1 [kV].

[0069] From these results, it was found that by including the optical amplifier G according to this embodiment, the resistance loss of the optical communication system is reduced, and the power consumption of the optical communication system can be reduced to about half that of the comparative example. It was also found that the supply voltage is reduced or, if it increases, the increase is small compared to the comparative example.

[0070] (Modification) An optical amplifier Ga according to a modified example will be described. Note that the same elements or elements having the same functions as those in the first embodiment will be denoted by the same reference numerals, and duplicated explanations will be omitted as appropriate. This also applies to other embodiments described below.

[0071] In this modification, the optical amplifier Ga includes three semiconductor lasers L for each two pump cores Ce of an erbium-doped optical fiber EF.

[0072] FIG. 7 is a diagram illustrating the configuration of an optical amplifier Ga included in a repeater Ta. In FIG. 1 EF is an erbium-doped optical fiber 1 and Erbium-doped optical fiber EF 2 and the semiconductor laser L 1 From Semiconductor Laser L 3 The three semiconductor lasers L and the polarization element PB 1 From PB 3 The optical amplifier Ga 2 EF is an erbium-doped optical fiber 3 and Erbium-doped optical fiber EF 4 and the semiconductor laser L 4 From Semiconductor Laser L 6 The three semiconductor lasers L and the polarization element PB 4 From PB 6 The optical amplifier Ga M EF is an erbium-doped optical fiber 2M-1 and Erbium-doped optical fiber EF 2M and the semiconductor laser L 3M-2 From Semiconductor Laser L 3M The three semiconductor lasers L and the polarization element PB3M-2 From PB 3M and three polarization elements PB.

[0073] In order to amplify the signal light Ls transmitted through each of the total of 16 signal cores Cs included in the upstream optical fiber Fu and the downstream optical fiber Fd, the optical amplifier Ga has 16 pump cores Ce of an erbium-doped optical fiber EF. The optical amplifier Ga also has a total of 24 semiconductor lasers L, three for every two pump cores Ce of the erbium-doped optical fiber EF.

[0074] Optical amplifier Ga 1 In the semiconductor laser L 1 The excitation light Lp emitted by the polarization element PB 1 The laser diode L 2 The excitation light Lp emitted by the polarization element PB 2 The laser diode L 3 The excitation light Lp emitted by the polarization element PB 3 is incident on

[0075] Semiconductor Laser L 2 The excitation light Lp by the polarization element PB 2 The part that is polarized and separated by the semiconductor laser L 1 The pump light Lp by the 3DB coupler B is combined with 1 Similarly, the laser diode L 2 The excitation light Lp by the polarization element PB 2 The part that is polarized and separated by the semiconductor laser L 3 The pump light Lp by the 3DB coupler B is combined with 1 is incident on

[0076] Semiconductor Laser L 2 The excitation light Lp emitted by the polarizing element PB 2 It is preferable that the polarization splitting is performed with approximately equal optical power, and it is particularly preferable that the difference in optical power between the respective polarizations is 1 dB or less.

[0077] 3DB Coupler B1 After combining the two incident pump lights Lp, the coupler splits them into two with a split ratio of approximately 1:1. 1 One of the pumping lights Lp split by the pump junction P 1 The signal is incident on the signal core Cs 1 The signal light Ls is then coupled with the signal light Ls transmitted through the erbium-doped optical fiber EF 1 Excitation core Ce 1 The erbium-doped optical fiber EF 1 The erbium-doped optical fiber EF forms a population inversion by erbium excited by pump light Lp. 1 The signal light Ls passing through is amplified.

[0078] On the other hand, 3DB coupler B 1 The other of the pumping light Lp branched by the pump junction P 2 The signal is incident on the signal core Cs 2 The signal light Ls is then coupled with the signal light Ls transmitted through the erbium-doped optical fiber EF 2 Excitation core Ce 2 The erbium-doped optical fiber EF 2 The erbium doped optical fiber EF forms a population inversion by erbium excited by pump light Lp. 2 The signal light Ls passing through is amplified.

[0079] Similarly, the optical amplifier Ga 2 is the semiconductor laser L 4 From Semiconductor Laser L 6 The excitation light Lp emitted by each semiconductor laser L is used to form a signal core Cs 3 and signal core Cs 4 The optical amplifier Ga amplifies the signal light Ls transmitted through the M is the semiconductor laser L 3M-2 From Semiconductor Laser L 3M The excitation light Lp emitted by each semiconductor laser L is used to form a signal core Cs 2M-1 and signal core Cs 2M The amplifier amplifies the signal light Ls transmitted through the amplifier.

[0080] Optical amplifier Ga 2 Optical amplifier Ga M The configuration and function are the same as those of the optical amplifier Ga 1 is the same as:

[0081] The driving circuits for driving the semiconductor lasers L included in the optical amplifier Ga are the same as the driving circuit D shown in FIG.

[0082] In this way, the optical amplifier Ga drives the three semiconductor lasers L together with the drive current I, and pumps the two pumping cores Ce with the pumping light Lp that is a combination of the pumping light Lp from each of the three semiconductor lasers L. This allows the optical amplifier Ga to reduce the drive current I to approximately 2 / 3 compared to when the pumping cores are pumped with the pumping light from one semiconductor laser. By reducing the drive current I, an optical amplifier with a small operating current can be provided.

[0083] In the first embodiment, the configuration in which the pumping light Lp from four semiconductor lasers L is combined and introduced per two pumping cores Ce is exemplified, and in the modified example, the configuration in which the pumping light Lp from three semiconductor lasers L is combined and introduced per two pumping cores Ce is exemplified, but the present invention is not limited to this. As long as there are two or more pumping cores in total, and the pumping light emitted by more than one semiconductor laser L per core Ce is combined and introduced for each pumping core, there is no particular limit to the number of pumping cores Ce and the semiconductor lasers L.

[0084] [Second embodiment] An optical amplifier Gb according to the second embodiment will be described below. In this embodiment, the optical amplifier Gb combines pumping lights Lp emitted from more than one semiconductor laser L per pumping core Ce by optical injection locking.

[0085] FIG. 8 is a diagram illustrating the configuration of an optical amplifier Gb included in a repeater Tb. In FIG. 1EF is an erbium-doped optical fiber 1 and Erbium-doped optical fiber EF 2 and the semiconductor laser L 1 From Semiconductor Laser L 4 The semiconductor laser L is provided with four semiconductor lasers L. 1 From Semiconductor Laser L 4 Among them, semiconductor laser L 1 and semiconductor laser L 2 are connected in series, and the semiconductor laser L 3 and semiconductor laser L 4 are connected in series.

[0086] Optical Amplifier Gb 2 EF is an erbium-doped optical fiber 3 and Erbium-doped optical fiber EF 4 and the semiconductor laser L 5 From Semiconductor Laser L 8 The semiconductor laser L is provided with four semiconductor lasers L. 5 From Semiconductor Laser L 8 Among them, semiconductor laser L 5 and semiconductor laser L 6 are connected in series, and the semiconductor laser L 7 and semiconductor laser L 8 are connected in series.

[0087] Optical Amplifier Gb M EF is an erbium-doped optical fiber 2M-1 and Erbium-doped optical fiber EF 2M and the semiconductor laser L 4M-3 From Semiconductor Laser L 4M The semiconductor laser L is provided with four semiconductor lasers L. 4M-3 From Semiconductor Laser L 4M Among them, semiconductor laser L 4M-3 and semiconductor laser L 4M-2 are connected in series, and the semiconductor laser L 4M and semiconductor laser L 4M-1 are connected in series.

[0088] In order to amplify the signal light Ls transmitted through each of the total of 16 signal cores Cs included in the upstream optical fiber Fu and the downstream optical fiber Fd, the optical amplifier Gb has 16 pump cores Ce of an erbium-doped optical fiber EF. The optical amplifier Gb also has a total of 32 semiconductor lasers L, two for each pump core Ce of the erbium-doped optical fiber EF.

[0089] Optical amplifier Ga 1 In this case, the self-oscillating semiconductor laser L 2 In contrast, the semiconductor laser L 1 When the excitation light Lp emitted by the semiconductor laser L is incident on the laser, the wavelength of the incident excitation light Lp is 2 The optical injection locking phenomenon occurs, in which the oscillation wavelength of the semiconductor laser L 1 Excitation light Lp and semiconductor laser L 2 The combined pump light Lp is fed to the 3DB coupler B 1 is incident on

[0090] Similarly, the self-oscillating semiconductor laser L 3 In contrast, the semiconductor laser L 4 When the excitation light Lp emitted by the semiconductor laser L is incident on the laser, the wavelength of the incident excitation light Lp is 3 The optical injection locking phenomenon occurs, in which the oscillation wavelength of the semiconductor laser L 4 Excitation light Lp and semiconductor laser L 3 The combined pump light Lp is fed to the 3DB coupler B 1 is incident on

[0091] 3DB Coupler B 1 After combining the two incident pumping lights Lp, the pumping light Lp is split into two so that the splitting ratio is approximately 1:1. One of the split pumping lights Lp is fed to the pump splitter P 1 Erbium-doped fiber EF 1 Excitation core Ce 1 By exciting the erbium into the signal core Cs 1The other of the branched pumping lights Lp is amplified by the pump combiner P 2 Erbium-doped fiber EF 2 Excitation core Ce 2 By exciting the erbium into the signal core Cs 2 The amplifier amplifies the signal light Ls transmitted through the amplifier.

[0092] Similarly, the optical amplifier Gb 2 is the semiconductor laser L 5 From Semiconductor Laser L 8 The excitation light Lp emitted by each semiconductor laser L is used to form a signal core Cs 3 and signal core Cs 4 The optical amplifier Gb amplifies the signal light Ls transmitted through the M is the semiconductor laser L 4M-3 From Semiconductor Laser L 4M The excitation light Lp emitted by each semiconductor laser L is used to form a signal core Cs 2M-1 and signal core Cs 2M The amplifier amplifies the signal light Ls transmitted through the amplifier.

[0093] Optical Amplifier Gb 2 Optical Amplifiers from Gb M The configuration and function are the same as those of the optical amplifier Gb 1 is the same as:

[0094] The driving circuit for driving the semiconductor laser L included in the optical amplifier Gb is similar to the driving circuit D shown in FIG.

[0095] As described above, the optical amplifier Gb combines the pumping light Lp emitted by more than one semiconductor laser L per pumping core Ce by optical injection locking. This reduces the drive current I, making it possible to provide an optical amplifier with a small operating current.

[0096] [Third embodiment] The optical amplifier Gc according to the third embodiment will be described. In this embodiment, the semiconductor lasers Lc, which are more than one per pump core Ce, are configured by a semiconductor laser group LG including a plurality of semiconductor lasers Lc connected in series. The semiconductor lasers Lc included in the semiconductor laser group LG are driven by a common drive current. The semiconductor laser group LG is a collective term for a plurality of semiconductor laser groups.

[0097] 9 is an equivalent circuit diagram illustrating the configuration of a driving circuit Dc for driving a semiconductor laser Lc included in an optical amplifier Gc. 1 Semiconductor laser Lc 4M The 32 semiconductor lasers Lc (M=8) are grouped into a semiconductor laser group LG 1 Semiconductor laser group LG 2M The laser diode LG is composed of 16 semiconductor laser groups.

[0098] The optical amplifier Gc is a semiconductor laser group LG 1 Semiconductor laser group LG 2M In order to drive the 16 semiconductor laser groups LG, a driving circuit Dc 1 From the drive circuit Dc 2M The driver circuit Dc has 16 drivers Dc. 1 From the drive circuit Dc 2M are connected in series. 1 From the drive circuit Dc 2M The semiconductor laser Lc 1 Semiconductor laser Lc 4M Each of the semiconductor lasers Lc is driven to emit light.

[0099] Each of the 16 semiconductor laser groups LG includes two semiconductor lasers Lc connected in series. 1 are the semiconductor lasers Lc connected in series. 1 and semiconductor laser Lc 2 Includes semiconductor laser Lc 1 and semiconductor laser Lc2 is the common drive current I 1 The semiconductor laser group LG 2 are the semiconductor lasers Lc connected in series. 3 and semiconductor laser Lc 4 Includes semiconductor laser Lc 3 and semiconductor laser Lc 4 is the common drive current I 2 The semiconductor laser group LG 2M are the semiconductor lasers Lc connected in series. 4M-1 and semiconductor laser Lc 4M Includes semiconductor laser Lc 4M-1 and semiconductor laser Lc 4M is the common drive current I 2M is driven by

[0100] The configuration and functions of the drive circuit Dc other than the configuration of the semiconductor laser Lc are the same as those of the drive circuit D described in the first embodiment.

[0101] The optical amplifier Gc drives the two semiconductor lasers Lc with a common drive current I, and thus, compared to the optical amplifier G of the first embodiment, the number of drive circuits Dc for driving the two semiconductor lasers Lc per pump core Ce can be reduced, and the number of current sources A1 can be reduced. This enables the optical amplifier Gc to suppress voltage drops and reduce the operating current of the optical amplifier Gc. Furthermore, by reducing the number of drive circuits Dc, the optical amplifier Gc can reduce the layout area of ​​the drive circuits Dc. Other effects are the same as those of the first embodiment.

[0102] The number of semiconductor lasers Lc constituting the semiconductor laser group LG is not limited to two, but may be three or more. The driving circuit Dc can also be applied to each of the optical amplifier Ga and the optical amplifier Gb. When the driving circuit Dc is applied to the optical amplifier Ga, for example, one driving circuit Dc is provided with three semiconductor lasers Lc.

[0103] [Fourth embodiment] An optical amplifier Gd according to a fourth embodiment will be described below. In this embodiment, the optical amplifier Gd combines pump light Lp emitted from more than one semiconductor laser Ld per pump core Ce by a compound resonator method.

[0104] FIG. 10 shows a semiconductor laser Ld among the multiple semiconductor lasers Ld included in the optical amplifier Gd. 1 and semiconductor laser Ld 2 FIG.

[0105] As shown in FIG. 10, the semiconductor laser Ld 1 and semiconductor laser Ld 2 are connected in series along the resonating direction 50 to form a composite resonator. 1 and semiconductor laser Ld 2 The semiconductor laser Ld is provided with an upper electrode 51, a lower electrode 52, and a current blocking layer 53 on the upper electrode 51 side. 1 and semiconductor laser Ld 2 is a semiconductor laser Ld 1 and semiconductor laser Ld 2 The semiconductor laser Ld is provided with an anti-reflection film 54 on each of its opposing end faces. 1 and semiconductor laser Ld 2 In each case, the semiconductor laser Ld 1 and semiconductor laser Ld 2 A reflecting surface is provided on the opposite end surface of the upper electrode 51. The upper electrode 51 is connected to a current source A1 via a wiring 55. 1 is connected to.

[0106] Drive current I 1 is the current source A1 1 The semiconductor laser Ld 1 The drive current I 1 is a semiconductor laser Ld 1 After flowing through the wiring 56, the semiconductor laser Ld 2 That is, the semiconductor laser Ld 1 and semiconductor laser Ld 2The common drive current I 1 is supplied.

[0107] Semiconductor laser Ld 1 and semiconductor laser Ld 2 is a driving current I 1 The light emitted by the flow of the ferroelectric liquid is reciprocated in the active layer 57 along the resonance direction 50, and laser light is oscillated by stimulated emission. 1 and semiconductor laser Ld 2 The laser light emitted by each of the laser diodes is combined and output as excitation light Lp in the output direction 58.

[0108] The current blocking layer 53 is provided, for example, to confine light within the active layer 57. The anti-reflection film 54 is provided, for example, to prevent the semiconductor laser Ld 1 and semiconductor laser Ld 2 The barrier 44 is provided to prevent reflection at the boundary surface with the laser beam and to increase the oscillation efficiency of the laser beam.

[0109] The driving circuit in the optical amplifier Gd can be the driving circuit Dc in FIG. 9. In this case, the semiconductor laser Ld in FIG. 1 is the semiconductor laser Lc in FIG. 1 The semiconductor laser Ld in FIG. 2 is the semiconductor laser Lc in FIG. 2 Corresponds to.

[0110] Among the multiple semiconductor lasers Ld included in the optical amplifier Gd, the semiconductor laser Ld 1 and semiconductor laser Ld 2 The structure and functions of the semiconductor laser Ld are the same as those of the semiconductor laser Ld 1 and semiconductor laser Ld 2 is the same as:

[0111] As described above, the optical amplifier Gd combines the pumping light Lp emitted by more than one semiconductor laser Ld per pumping core Ce using a compound resonator method, thereby reducing the drive current I and providing an optical amplifier with a small operating current.

[0112] Moreover, the optical amplifier Gd drives the two semiconductor lasers Ld with a common drive current I, thereby reducing the number of drive circuits Dc that supply drive current to the two semiconductor lasers Ld per pump core Ce, and reducing the number of current sources A1, compared to the optical amplifier G of the first embodiment. This enables the optical amplifier Gd to suppress voltage drops and reduce the operating current of the optical amplifier Gd. Furthermore, by reducing the number of drive circuits, the optical amplifier Gd can reduce the layout area of ​​the drive circuits. Other effects are the same as those of the first embodiment.

[0113] In this embodiment, the synthesis of the pump light Lp by the composite resonator method has been illustrated, but a master oscillator output amplifier method may also be applied. In the case of the master oscillator output amplifier method, in FIG. 1 corresponds to the first oscillator, and the semiconductor laser Ld 2 corresponds to the second oscillator. The first oscillator is, for example, a highly stable oscillator for generating a high-quality beam. The second oscillator is, for example, a high-output oscillator. The semiconductor laser Ld 1 The pump light Lp and the semiconductor laser Ld 2 The high-power pumping light Lp, which is a combination of the pumping light Lp by the semiconductor laser Ld 2 is taken out from the side.

[0114] [Fifth embodiment] The optical amplifier Ge according to the fifth embodiment will be described. In this embodiment, the semiconductor lasers Le, which are more than one per pump core Ce, are configured to include a semiconductor laser group LG including a plurality of semiconductor lasers Le connected in series. The plurality of semiconductor lasers Le included in the semiconductor laser group LG are driven by a common drive current.

[0115] The optical amplifier Ge can have the same configuration as the optical amplifier Ga included in the repeater Ta shown in FIG.

[0116] FIG. 11 is an equivalent circuit diagram illustrating the configuration of a driving circuit De that drives a semiconductor laser Le included in an optical amplifier Ge. 1 From the drive circuit De 2M are connected in series. 1 From the drive circuit De 2M The semiconductor laser Le is driven in response to a drive current I, which is at least a part of the operating current S supplied from the first power supply device 10. 1 Semiconductor laser Le 4M Each of the semiconductor lasers Lc is driven to emit light.

[0117] Drive circuit De 1 From the drive circuit De 2M Among them, the odd-numbered driving circuits De are provided with one semiconductor laser Le, and the even-numbered driving circuits De are provided with a semiconductor laser group LG including two semiconductor lasers Le connected in series.

[0118] Specifically, the drive circuit De 1 There is one semiconductor laser Le 1 A driving circuit De 2 The laser diode Le is connected in series. 2 and semiconductor laser Le 3 Semiconductor laser group LG including 2 The semiconductor laser Le 2 and semiconductor laser Le 3 is the common drive current I 2 The driving circuit De 2M The laser diode Le is connected in series. 3M-1 and semiconductor laser Le 3M Semiconductor laser group LG including 2M The semiconductor laser Le 3M-1 and semiconductor laser Le 3M is the common drive current I 2 is driven by

[0119] The configuration and functions of the driving circuit De other than the configuration of the semiconductor laser Le are the same as those of the driving circuit D described in the first embodiment.

[0120] As described above, the optical amplifier Ge drives the three semiconductor lasers Le together with the drive current I, and pumps the two pumping cores Ce with the pumping light Lp that is a combination of the pumping light Lp from each of the three semiconductor lasers Le. This allows the optical amplifier Ge to reduce the drive current I to approximately 2 / 3 compared to when the pumping cores are pumped with the pumping light from one semiconductor laser. By reducing the drive current I, an optical amplifier with a small operating current can be provided.

[0121] Moreover, the optical amplifier Ge drives two of the three semiconductor lasers Le with a common drive current I, thereby reducing the number of drive circuits De that supply drive currents to the three semiconductor lasers Le per two pump cores Ce, and reducing the number of current sources A1, compared to the optical amplifier G of the first embodiment. This enables the optical amplifier Ge to suppress voltage drops and reduce the operating current of the optical amplifier Ge. Furthermore, the optical amplifier Ge reduces the number of drive circuits De, thereby reducing the layout area of ​​the drive circuits De. Other effects are the same as those of the first embodiment.

[0122] [Sixth embodiment] An optical amplifier Gf according to the sixth embodiment will be described. In this embodiment, the semiconductor lasers Lf, which are more than one per pump core Ce, are configured to include a semiconductor laser group LG including a plurality of semiconductor lasers Lf connected in series. The plurality of semiconductor lasers Lf included in the semiconductor laser group LG are driven by a common drive current. In addition, three semiconductor lasers Lf are provided for two pump cores Ce of the erbium-doped optical fiber EF, and the pump light Lp emitted by each of the three semiconductor lasers Lf is combined by an optical injection locking method.

[0123] FIG. 12 is a diagram illustrating the configuration of an optical amplifier Gf included in a repeater Tf.

[0124] In FIG. 12, the optical amplifier Gf 1 EF is an erbium-doped optical fiber 1 and Erbium-doped optical fiber EF 2 and the semiconductor laser Lf 1 Semiconductor laser Lf 3 The semiconductor laser Lf is provided with three semiconductor lasers Lf. 1 Semiconductor laser Lf 3 are connected in series.

[0125] Optical amplifier Gf 2 EF is an erbium-doped optical fiber 3 and Erbium-doped optical fiber EF 4 and the semiconductor laser Lf 4 Semiconductor laser Lf 6 The semiconductor laser Lf is provided with three semiconductor lasers Lf. 4 Semiconductor laser Lf 6 are connected in series.

[0126] Optical amplifier Gf M EF is an erbium-doped optical fiber 2M-1 and Erbium-doped optical fiber EF 2M and the semiconductor laser Lf 3M-2 Semiconductor laser Lf 3M The semiconductor laser Lf is provided with three semiconductor lasers Lf. 3M-2 Semiconductor laser Lf 3M are connected in series.

[0127] The optical amplifier Gf includes 16 pump cores Ce of the erbium-doped optical fiber EF. The optical amplifier Gf also includes a total of 24 semiconductor lasers Lf, three for every two pump cores Ce of the erbium-doped optical fiber EF.

[0128] Optical amplifier Gf 1 In the case of 1 In contrast, the semiconductor laser Lf2 When the excitation light Lp emitted by the semiconductor laser Lf is incident 1 The optical injection locking phenomenon occurs in which the oscillation wavelength of the semiconductor laser Lf is pulled into the wavelength of the incident pump light Lp. 2 Excitation light Lp and semiconductor laser Lf 1 The combined pump light Lp is fed to the 3DB coupler B 1 is incident on

[0129] Similarly, the self-oscillating semiconductor laser Lf 3 In contrast, the semiconductor laser Lf 2 When the excitation light Lp emitted by the semiconductor laser Lf 3 The optical injection locking phenomenon occurs, in which the oscillation wavelength of the semiconductor laser Lf is pulled into the wavelength of the incident pump light Lp. 2 Excitation light Lp and semiconductor laser Lf 3 The combined pump light Lp is fed to the 3DB coupler B 1 is incident on

[0130] Semiconductor laser Lf 2 Semiconductor laser Lf 1 and semiconductor laser Lf 3 It is preferable that the optical power incident on each of the optical fibers is approximately equal, and it is particularly preferable that the difference in optical power between the two is 1 dB or less.

[0131] 3DB Coupler B 1 After combining the two incident pumping lights Lp, the pumping light Lp is split into two so that the splitting ratio is approximately 1:1. One of the split pumping lights Lp is fed to the pump splitter P 1 Erbium-doped fiber EF 1 Excitation core Ce 1 The other of the split pump light Lp enters the pump junction P 2 Erbium-doped fiber EF 2 Excitation core Ce 2 The optical amplifier Gf 1 By pumping erbium with pump light Lp, the signal core Cs1 and signal core Cs 2 The signal light Ls transmitted through each of the amplifiers is amplified.

[0132] Similarly, the optical amplifier Gf 2 is the semiconductor laser Lf 4 Semiconductor laser Lf 6 The pump light Lp emitted by each semiconductor laser Lf is used to generate the signal core Cs 3 and signal core Cs 4 The optical amplifier Gf amplifies the signal light Ls transmitted through the M is the semiconductor laser Lf 3M-3 Semiconductor laser Lf 3M The pump light Lp emitted by each semiconductor laser Lf is used to generate the signal core Cs 2M-1 and signal core Cs 2M The amplifier amplifies the signal light Ls transmitted through the amplifier.

[0133] Optical amplifier Gf 2 From the optical amplifier Gf M The configuration and function of the optical amplifier Gf is the same as that of the optical amplifier Gf except that the signal core Cs to be optically amplified is different. 1 is the same as:

[0134] The driving circuit for driving the semiconductor laser Lf included in the optical amplifier Gf can be the driving circuit De shown in FIG.

[0135] As described above, the optical amplifier Gf can provide an optical amplifier with a small operating current by combining the pumping light Lp emitted by each of the three semiconductor lasers Lf per two pumping cores Ce using the optical injection locking method, thereby reducing the driving current I. In addition, the optical amplifier Gf can suppress the voltage drop, reduce the operating current of the optical amplifier Ge, and reduce the layout area of ​​the driving circuit De.

[0136] Although the optical injection locking method is exemplified in this embodiment, a composite resonator method or a master oscillator output amplifier method may also be applied. The optical amplifier Gf may combine the polarization combining method, the optical injection locking method, the composite resonator method, or the master oscillator output amplifier method to combine the pump light Lp.

[0137] Although each embodiment and modified example have been described above, the embodiments disclosed herein are illustrative in all respects and should not be considered as being restrictive. The scope of the present invention is indicated by the claims, not by the above meaning, and is intended to include all modifications within the meaning and scope of the claims.

[0138] In the above-described embodiment, an optical submarine cable system is exemplified as an optical communication system, but the present invention is not limited to this. The embodiment can be applied to optical communication systems other than an optical submarine cable system.

[0139] The ordinal numbers, quantities, and other numbers used in the description of the embodiments are all given as examples to specifically explain the technology of the present invention, and the present invention is not limited to the exemplified numbers. [Explanation of symbols]

[0140] 100...Optical communication system, 10...First power supply device, 20...second power supply device, 50...resonance direction, 51...Top electrode, 52...Bottom electrode, 53...current blocking layer, 54...Anti-reflective film, 55,56…Wiring, 57...active layer, 58...Output direction, M: number of signal cores, Ai,Ao…DC current source, T, Ta, Tb, Tf... repeaters, PL...Power line, R...Resistance, V, Vs, VL: voltage, G, Ga, Gb, Gc, Gd, Ge, Gf...optical amplifiers, L, Lc, Ld, Le, Lf...semiconductor laser (excitation light source), PB: Polarizing element (combining section), B…3DB coupler, P…pump junction, EF: Erbium-doped optical fiber (rare earth element-doped optical fiber), Fu: upstream optical fiber, Fd: downstream optical fiber, Lp: excitation light, Ls...signal light, Cs: signal core, Ce…excited core (core), CL: Clad, Cv: constant voltage circuit, Ci...constant current circuit, I: drive current, Is...Current, Vr: Reference voltage, Ir: Reference current, A1,A2…Current source, Gv1, Gv1X, Gv2, Gv2X…supply voltage, Gp1,Gp1X, Gp2,Gp2X…Power consumption.

Claims

1. one or more rare earth doped optical fibers, each of which includes one or more cores; a plurality of pumping light sources each of which emits pumping light for exciting a rare earth element doped in the rare earth element doped optical fiber in response to a driving current, the number of which exceeds one for each of the cores of the rare earth element doped optical fiber; A combining unit that combines the pump light emitted by each of the pump light sources, the number of which is more than one per core, The cores are two or more in total, The pump light emitted by more than one pump light source per core is combined and introduced into each of the cores, An optical amplifier, wherein the pumping light sources, the number of which is more than one per core, are driven by driving currents supplied from a plurality of driving circuits connected in series.

2. One or more rare-earth-doped optical fibers, each of which includes one or more cores; a plurality of pumping light sources each of which emits pumping light for exciting a rare earth element doped in the rare earth element doped optical fiber in response to a driving current, the number of which exceeds one for each of the cores of the rare earth element doped optical fiber; A combining unit that combines the pump light emitted by each of the pump light sources, the number of which is more than one per core, The cores are two or more in total, The pump light emitted by more than one pump light source per core is combined and introduced into each of the cores, The combiner combines the pump light emitted from each of the pump light sources, the number of which is more than one per core, by at least one of a polarization combining method, an optical injection locking method, a composite resonator method, and a master oscillator output amplifier method; The polarization synthesis method is a method of synthesizing a plurality of different polarizations using a polarization element, The optical injection locking method is a method for combining a plurality of different lights by utilizing an optical injection locking phenomenon in which an oscillation wavelength of a semiconductor laser is pulled into the wavelength of the incident light by externally inputting light having a wavelength close to the oscillation wavelength of the semiconductor laser, The composite resonator method is a method of combining a plurality of different lights using a composite resonator in which a plurality of resonators are connected, The master oscillator output amplifier method is a method of combining a plurality of different lights using a master oscillator output amplifier, The master oscillator output amplifier is an optical amplifier that extracts light obtained by combining light emitted by a first oscillator and a second oscillator from the second oscillator side.

3. The combiner combines the pump light emitted from each of the pump light sources, the number of which is more than one per core, by at least one of a polarization combining method, an optical injection locking method, a composite resonator method, and a master oscillator output amplifier method; The polarization synthesis method is a method of synthesizing a plurality of different polarizations using a polarization element, The optical injection locking method is a method for combining a plurality of different lights by utilizing an optical injection locking phenomenon in which an oscillation wavelength of a semiconductor laser is pulled into the wavelength of the incident light by externally inputting light having a wavelength close to the oscillation wavelength of the semiconductor laser, The composite resonator method is a method of combining a plurality of different lights using a composite resonator in which a plurality of resonators are connected, The master oscillator output amplifier method is a method of combining a plurality of different lights using a master oscillator output amplifier, 2. The optical amplifier according to claim 1, wherein said master oscillator output amplifier extracts light obtained by combining light emitted by a first oscillator and a second oscillator from a side of said second oscillator.

4. the pumping light sources, the number of which is greater than one per core, at least in part include a semiconductor laser group including a plurality of semiconductor lasers connected in series; 4. The optical amplifier according to claim 1, wherein the plurality of semiconductor lasers included in the semiconductor laser group are driven by a common drive current.

5. 5. The optical amplifier according to claim 1, wherein the rare-earth-element-doped optical fiber is a multi-core optical fiber in which a plurality of the cores are covered with a single cladding.

6. 6. The optical amplifier according to claim 5, wherein a power coupling coefficient between adjacent cores among the plurality of cores is 10[ / m] or more.

7. one or more optical fibers for transmitting optical signals; 7. An optical communication system comprising: an optical amplifier according to claim 1 for amplifying the optical signal transmitted through the optical fiber.

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