JP7221901B2 - optical amplifier - Google Patents

Description

The present invention relates to an optical amplifying device.

Optical amplifiers using erbium-doped optical fibers (EDF) are used in optical communication systems. Signal light propagating through the EDF is amplified by pump light propagating through the EDF. US Pat. No. 6,200,000 discloses a multi-core optical fiber (MCF)-EDF. MCF is an optical fiber having multiple cores, and MCF-EDF is an optical fiber in which each of the multiple cores is an EDF. For optical amplification by MCF-EDF, cladding pumping is used in addition to core pumping. Core pumping is a method in which pump light is directly incident on each core. On the other hand, cladding pumping is a method of making pump light incident on the cladding of the MCF-EDF. In cladding pumping, signal light propagating through each core is amplified by pump light propagating from the cladding to each core.

On the other hand, in Patent Document 2, signal light transmitted and received by an optical communication device connected to one end of an optical communication system are not accommodated in different MCFs, but are accommodated in different cores of the same MCF. configuration is disclosed. In other words, Patent Document 2 selects two cores from a plurality of cores included in an MCF to form a core pair, and pairs one core pair of the same MCF with two opposing optical communication devices (one set of optical communication devices). A configuration used for transmitting and receiving signal light in a device) is disclosed.

Japanese Patent No. 5950426 JP 2013-106135 A

Consider applying the configuration disclosed in Patent Document 2, in which one core pair of the same MCF is used for transmitting and receiving signal light in two opposing optical communication devices, to an optical amplifying device having an MCF-EDF. FIG. 1 shows such an optical amplification device. The optical amplifier shown in FIG. 1 amplifies signal light traveling from MCF#m to MCF#n and signal light traveling from MCF#n to MCF#m. MCF#m is one optical fiber accommodated in the first optical cable, and MCF#n is one optical fiber accommodated in the second optical cable. Each core of MCF#m is connected to each core of a single-core optical fiber (SCF) by a converter (not shown). In FIG. 1, only SCF11 and SCF12 are shown. However, there may be as many SCFs as there are cores in MCF#m. Similarly, each core of MCF#n is connected to each core of SCF by a conversion unit (not shown). In FIG. 1, only SCF71 and SCF72 are shown. However, there may be as many SCFs as there are cores in MCF#n. These converters are so-called Fan-in/out.

Signal light #1 input from one core of MCF#m to SCF 11 is amplified by the optical amplifier and output to one core of MCF#n via SCF 71 . Similarly, signal light #2 input from one core of MCF#n to SCF 72 is amplified by the optical amplifier and output to one core of MCF#m via SCF 12 . Signal light #1 propagating through SCF11 and SCF71 and signal light #2 propagating through SCF72 and SCF12 are signal light transmitted and received by a pair of opposing optical communication devices.

The SCFs 11, 12, 71 and 72 are provided with optical isolators 21, 22, 23 and 24, respectively. The optical isolators 21 to 24 allow light to pass in the directions indicated by the arrows in the drawing, but block light propagation in the direction opposite to the arrows. The optical isolators 21 to 24 are provided to prevent pump light and ASE (amplified spontaneous emission) light generated by the optical amplifier from propagating in the core in the direction opposite to the signal light.

Reference numeral 6 in FIG. 1 is MCF-EDF. The converter 31 is a so-called Fan-in/out. That is, the conversion unit 31 is an optical member that connects each core of a plurality of SCFs including SCF11 and SCF12 and each core of MCF9. The number of cores and core arrangement of MCF9 are the same as those of MCF-EDF6. The light source 4 generates pump light and outputs it to the multiplexer 5 . The multiplexer 5 connects each core of the MCF 9 and the corresponding core of the MCF-EDF 6 and outputs the pump light from the light source 4 to the clad of the MCF-EDF 6 . Therefore, signal light propagating through each core of MCF-EDF 6 is amplified by cladding pumping.

The converter 32 is a so-called Fan-in/out. That is, the conversion unit 32 is an optical member that connects each core of the MCF-EDF 6 and each core of a plurality of SCFs including the SCF 71 and SCF 72 .

In the configuration of FIG. 1, the signal light #1 is forward-pumped and the signal light #2 is backward-pumped. Forward pumping is a pumping method in which signal light and pump light propagate in the same direction, and backward pumping is a pumping method in which signal light and pump light propagate in opposite directions. Forward pumping and backward pumping have different amplification characteristics. More specifically, ASE light, which becomes noise, is less in forward pumping than in backward pumping. Therefore, in the configuration of FIG. 1, the signal quality differs depending on the direction of the signal light.

The present invention provides a technique for suppressing differences in signal quality depending on the direction of signal light.

According to one aspect of the present invention, the first signal light from the first optical fiber is amplified and output to the second optical fiber, the second signal light from the second optical fiber is amplified, and the first optical fiber a light source for generating pump light; and a multi-core optical fiber having a plurality of cores for amplifying signal light propagating through the plurality of cores by means of the pump light. The first signal light and the second signal light are incident on the core of the multi-core optical fiber from the same end of the multi-core optical fiber.

According to the present invention, it is possible to suppress the difference in signal quality depending on the direction of signal light.

Explanatory diagram of the task. 1 is a configuration diagram of an optical amplifying device according to an embodiment; FIG. 1 is a configuration diagram of an optical amplifying device according to an embodiment; FIG.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more of the features described in the embodiments may be combined arbitrarily. Also, the same or similar configurations are denoted by the same reference numerals, and redundant explanations are omitted.

<First embodiment>
FIG. 2 is a configuration diagram of the optical amplifying device according to this embodiment. In the following description, differences from the configuration of FIG. 1 will be mainly described, and the same reference numerals will be given to the same components as in FIG. 1, and the description thereof will be basically omitted. The difference from FIG. 1 is that the SCF 72 is connected to the conversion section 31 instead of the conversion section 32 and the SCF 12 is connected to the conversion section 32 instead of the conversion section 31 . Therefore, the propagation direction of signal light in each core of MCF-EDF 6 is the same, and all signal light is forward pumped in MCF-EDF 6 .

<Second embodiment>
FIG. 3 is a configuration diagram of the optical amplifying device according to this embodiment. Components similar to those in FIG. 2 are denoted by the same reference numerals, and descriptions thereof are basically omitted. In FIG. 2, the optical isolators 21-24 were SCF isolators. In this embodiment, optical isolators 81 and 82 are provided instead of the optical isolators 21-24. Optical isolators 81 and 82 are MCF isolators. The number of cores and core arrangement of the optical isolators 81 and 82 are the same as those of the MCF-EDF6.

The optical isolator 81 is provided upstream of the MCF-EDF 6 in the propagation direction of signal light in the MCF-EDF 6 . Also, the optical isolator 82 is provided downstream of the MCF-EDF 6 in the propagation direction of the signal light in the MCF-EDF 6 . Specifically, the input side of the optical isolator 81 is connected to the MCF 9 and the output side of the optical isolator 81 is connected to the MCF 91 . Then, the MCF 91 is connected to the combining section 5 . Furthermore, the input side of the optical isolator 82 is connected to the MCF-EDF 6 , the output side of the optical isolator 82 is connected to the MCF 92 , and the MCF 92 is connected to the conversion section 32 . The number of cores and core arrangement of MCF 91 and 92 are the same as those of MCF-EDF6. Then, as in the second embodiment, the SCF 72 is connected to the converter 31 and the SCF 12 is connected to the converter 32 . Therefore, the propagation direction of signal light in each core of MCF-EDF 6 is the same, and all signal light is forward pumped in MCF-EDF 6 . Moreover, in this embodiment, the configuration of the optical amplifier can be simplified by using the MCF isolator instead of the SCF isolator. Also, although not shown in FIG. 3, when a gain equalizer is provided to adjust the gain in the optical amplifier of each core, an MCF type gain equalizer can be used. The configuration can be simplified. The MCF type gain equalizer can be provided, for example, between the optical isolator 82 and the conversion section 32 .

In addition, in 1st embodiment and 2nd embodiment, a 1st optical cable and a 2nd optical cable shall accommodate MCF. Therefore, each core of the MCF was connected to the SCFs 11 and 12 and the SCFs 71 and 72 in the converters (not shown) in FIGS. However, the present invention is applicable even if the first optical cable and the second optical cable accommodate SCFs. In this case, a conversion unit (not shown) is not required. In summary, the present invention can be applied to any optical communication system in which two signal lights transmitted and received by a pair of opposing optical communication devices are amplified by the same MCF-EDF. Furthermore, in each of the above embodiments, all signal light is forward pumped, but all signal light may be backward pumped. In the configuration of the first embodiment, when the MC-EDF 6 amplifies the signal light transmitted and received by a plurality of sets of optical communication devices, the signal light transmitted and received by all the sets of optical communication devices is forward-pumped or backward-pumped. does not need to be For example, the signal light transmitted/received by one set of optical communication devices is inputted from the converter 31 so as to be forward pumped, and the signal light transmitted/received by another set of optical communication devices is set to be backward pumped. A configuration in which the signal light is input from the conversion unit 32 may also be used. By inputting two signal lights transmitted and received by one set of optical communication devices from the same end of the MC-EDF 6, the difference in signal quality due to the direction of the signal lights can be suppressed.

The invention is not limited to the above embodiments, and various modifications and changes are possible within the scope of the invention.

4: light source, 6: MCF-EDF

Claims (5)

An optical amplifying device for amplifying a first signal light from a first optical fiber and outputting it to a second optical fiber, and amplifying a second signal light from the second optical fiber and outputting it to the first optical fiber. hand,
a light source for generating pump light;
a multi-core optical fiber having a plurality of cores and amplifying signal light propagating through the plurality of cores with the pump light;
with
An optical amplifying device, wherein the first signal light and the second signal light are incident on the core of the multi-core optical fiber from the same end of the multi-core optical fiber. 2. The optical amplifying device according to claim 1, wherein the pump light is incident on the clad of the multi-core optical fiber from the first end of the multi-core optical fiber. 3. The optical amplifying device according to claim 2, wherein the first signal light and the second signal light enter the core of the multi-core optical fiber from the first end of the multi-core optical fiber. 3. The method according to claim 2, wherein the first signal light and the second signal light enter the core of the multi-core optical fiber from a second end different from the first end of the multi-core optical fiber. An optical amplification device as described. 5. The apparatus according to any one of claims 1 to 4, further comprising a multi-core optical isolator for blocking propagation of light in a direction opposite to the propagation direction of said first signal light and said second signal light. Optical amplifier.

Images