Optical amplifier and optical communication system
The optical amplifier configuration with branching pump light and Raman amplification addresses the non-uniform amplification gain issue in rare-earth-doped fibers, achieving improved wavelength uniformity and amplification efficiency in optical communication systems.
Patent Information
- Application Number
- JP2023189487
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-11-06
- Publication Date
- 2025-05-19
AI Technical Summary
The amplification gain of rare-earth-doped fibers, such as bismuth-doped fibers, is not uniform across the wavelength range to be amplified, leading to non-uniformity in optical signal amplification.
An optical amplifier configuration that includes a light source generating pump light, branching means to split the pump light into at least two pump lights, a rare earth doped fiber for amplifying signal light with one pump light, and a wavelength division multiplexing coupler to output the second pump light to the optical fiber, thereby reducing wavelength-dependent amplification gain non-uniformity through Raman amplification.
The proposed solution effectively reduces the non-uniformity of amplification gain across different wavelengths, enhancing the uniformity and efficiency of optical signal amplification in optical communication systems.
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Figure 2025077361000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to an optical amplifier used in an optical communication system.
Background Art
[0002] In order to increase the communication capacity of an optical communication system, in addition to the S band (1460 nm to 1530 nm), C band (1530 nm to 1565 nm), and L band (1565 nm to 1625 nm), the use of the O band (1260 nm to 1360 nm) and E band (1360 nm to 1460 nm) has been studied. Non-Patent Document 1 discloses the use of a bismuth-doped fiber (BDF) for amplifying an optical signal in the O band. The BDF can also be used for amplifying an optical signal in the E band.
Prior Art Documents
Non-Patent Documents
[0003]
Non-Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] The amplification gain of a rare-earth-doped fiber such as BDF is not uniform over the wavelength range to be amplified.
[0005] The present disclosure provides a technique for reducing the non-uniformity of the amplification gain depending on the wavelength.
Means for Solving the Problems
[0006] According to one aspect of the present disclosure, an optical amplifier connected to an optical fiber for transmitting signal light includes a light source that generates pump light, branching means for branching the pump light into at least two pump lights, a rare earth doped fiber that amplifies the signal light with a first pump light among the at least two pump lights, and a wavelength division multiplexing coupler that outputs a second pump light among the at least two pump lights to the optical fiber. is provided.
Advantages of the Invention
[0007] According to the present disclosure, non-uniformity of the amplification gain depending on the wavelength can be reduced.
Brief Description of the Drawings
[0008]
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Embodiments for Carrying Out the Invention
[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of the features described in the embodiments are essential for the invention. Two or more of the plurality of features described in the embodiments may be arbitrarily combined. Also, the same or similar configurations are given the same reference numerals, and duplicate descriptions are omitted.
[0010] <First Embodiment> FIG. 1 is a configuration diagram of an optical communication system according to the present embodiment. The optical transmitter 200 outputs one or more signal lights in the O band, or one or more signal lights in the O band and one or more signal lights in the E band to the optical fiber 401. The optical amplifier 100 is connected to the optical fiber 401 and the optical fiber 402. The optical amplifier 100 optically amplifies the signal light from the optical fiber 401 and outputs it to the optical fiber 402. The optical receiver 300 demodulates the signal light from the optical fiber 402. In FIG. 1, the number of optical amplifiers 100 in the optical communication system is one, but the optical communication system may have two or more optical amplifiers 100.
[0011] FIG. 2 shows a configuration example of the optical amplifier 100. The signal light from the input-side optical fiber 401 passes through the wavelength division multiplexing (WDM) coupler 10, isolator 12, BDF 16, WDM coupler 11, and isolator 13 in this order and is output to the output-side optical fiber 402. The light source 14 generates pump light. The wavelength of the pump light generated by the light source 14 will be described later. The coupler 15 branches the pump light into at least two, outputs one of the at least two pump lights to the WDM pla 10, and outputs one of the at least two pump lights to the WDM coupler 11.
[0012] In the present embodiment, the pump light is propagated in the direction opposite to the signal light. That is, the pump light input to the WDM coupler 10 is output to the input-side optical fiber 401. The signal light is amplified (Raman amplification) by the Raman effect in the optical fiber 401. Also, the pump light input to the WDM coupler 11 is output to the BDF 16 and is used for amplification in the BDF 16. Note that the isolators 12 and 13 are provided to block the light propagating in the direction opposite to the signal light.
[0013] Next, the wavelength of the pump light generated by the light source 14 will be described. To amplify an optical signal with a rare-earth-doped fiber, it is necessary to use pump light having a wavelength absorbed by the added rare-earth ions. Therefore, the wavelength of the pump light generated by the light source 14 is selected from the wavelengths absorbed by bismuth ions. Also, in Raman amplification, frequencies that are 12 THz to 15 THz higher than the pump light are amplified.
[0014] The solid line in FIG. 3 shows the amplification gain of the BDF 16. As shown in FIG. 3, the amplification gain decreases in the wavelength range of 1260 nm to 1300 nm on the short-wavelength side of the O band (1260 nm to 1360 nm). In the present embodiment, by Raman-amplifying at least a part of the second wavelength range within the first wavelength range in which the amplification gain of the BDF 16 decreases, the non-uniformity of the amplification gain of the optical amplifier due to wavelength is reduced. The wavelength of the pump light is determined so as to amplify a second wavelength range that at least partially overlaps with the wavelength range in which the amplification gain of the BDF 16 decreases.
[0015] In summary, the wavelength of the pump light generated by the light source 14 is a wavelength that can excite the BDF 16 and a wavelength that Raman-amplifies at least a part of the wavelength range of 1260 nm to 1300 nm. As an example, by using the wavelength of 1195 nm that can excite the BDF 16, the wavelength range of 1255 nm to 1270 nm can be Raman-amplified. Also, as another example, by using the wavelength of 1215 nm that can excite the BDF 16, the wavelength range of 1277 nm to 1293 nm can be Raman-amplified.
[0016] As described above, according to the present embodiment, the non-uniformity of the amplification gain due to wavelength can be reduced by optical amplification with the BDF 16 and Raman amplification with the optical fiber 401.
[0017] <Second Embodiment> Next, regarding the second embodiment, the differences from the first embodiment will be mainly described. In the first embodiment, both the pump light for Raman amplification and the pump light for amplification in the BDF16 were propagated in the direction opposite to the signal light. In other words, the pump light for Raman amplification was output to the input-side optical fiber 401, and the pump light for amplification in the BDF16 was input from an end different from the end of the BDF16 where the signal light was input. In this embodiment, both the pump light for Raman amplification and the pump light for amplification in the BDF16 are propagated in the same direction as the signal light.
[0018] Figure 4 shows a configuration example of the optical amplifier 100. The signal light of the optical fiber 401 passes through the isolator 12, WDM coupler 11, BDF16, isolator 13, and WDM coupler 10 in this order and is output to the optical fiber 402. The light source 14 generates pump light. The wavelength of the pump light is the same as that in the first embodiment. The coupler 15 branches the pump light into at least two, outputs one of the at least two pump lights to the WDM pla 10, and outputs one of the at least two pump lights to the WDM coupler 11.
[0019] The pump light input to the WDM coupler 10 is output to the output-side optical fiber 402. The signal light is amplified (Raman amplification) by the Raman effect in the optical fiber 402. Also, the pump light input to the WDM coupler 11 is output to the BDF16 and used for optical amplification in the BDF16. Thus, in this embodiment, the pump light for Raman amplification is output to the output-side optical fiber 402, and the pump light for amplification in the BDF16 is input to the same end as the end of the BDF16 where the signal light is input.
[0020] In this embodiment, the pump light for Raman amplification and the pump light for amplification in the BDF16 are both propagated in the same direction as the signal light. However, a configuration may be adopted in which the pump light for Raman amplification is propagated in the direction opposite to the signal light while the pump light for amplification in the BDF16 is propagated in the same direction as the signal light. In this case, the WDM coupler 10 in FIG. 4 is provided not between the isolator 13 and the optical fiber 402 but between the optical fiber 401 and the isolator 12. Similarly, a configuration may be adopted in which the pump light for Raman amplification is propagated in the same direction as the signal light while the pump light for amplification in the BDF16 is propagated in the direction opposite to the signal light. In this case, the WDM coupler 11 in FIG. 4 is provided not between the isolator 12 and the BDF16 but between the BDF16 and the isolator 13.
[0021] <Third Embodiment> Subsequently, the third embodiment will be described focusing on the differences from the first and second embodiments. In the first and second embodiments, only one BFD16 was used, but in this embodiment, two BDFs are used.
[0022] FIG. 5 shows a configuration example of the optical amplifier 100. The signal light from the optical fiber 401 passes through the WDM coupler 10, isolator 12, BDF16, WDM coupler 11, isolator 13, WDM coupler 21, BDF26, and isolator 23 in this order and is output to the optical fiber 402. The light sources 14 and 24 generate pump light. The wavelength of the pump light is the same as that in the first embodiment. The coupler 15 branches the pump light from the light source 14 into at least two, outputs one of the at least two pump lights to the coupler 28, and outputs one of the at least two pump lights to the WDM coupler 11. The coupler 25 branches the pump light from the light source 24 into at least two, outputs one of the at least two pump lights to the coupler 28, and outputs one of the at least two pump lights to the WDM coupler 21. The coupler 28 combines the pump light from the coupler 15 and the pump light from the coupler 25 and outputs the combined pump light to the WDM coupler 10.
[0023] The pump light input to the WDM coupler 10 is output to the optical fiber 401 and used for Raman amplification in the optical fiber 401. Also, the pump light input to the WDM coupler 11 is output to the BDF 16 and used for amplification in the BDF 16. Further, the pump light input to the WDM coupler 21 is output to the BDF 26 and used for amplification in the BDF 26.
[0024] In this embodiment, the pump light is propagated in the BDF 16 in the direction opposite to the signal light. In the BDF 26, the pump light is propagated in the same direction as the signal light. However, the configuration may be such that the pump light is propagated in the same direction as the signal light in the BDF 16, or the pump light is propagated in the direction opposite to the signal light in the BDF 26. Further, the Raman amplification may be caused not in the optical fiber 401 but in the optical fiber 402.
[0025] Furthermore, the amplification may be performed using three or more BDFs. Further, the Raman amplification may be performed using both the optical fiber 401 and the optical fiber 402.
[0026] Note that the embodiment has been described by taking an optical amplifier using a BDF as a rare-earth doped fiber as an example. However, the content of the present disclosure can also be applied to an optical amplifier using a rare-earth doped fiber different from the BDF. In this case, the wavelength of the pump light is selected so as to be able to be used for exciting the rare-earth doped fiber and Raman amplify a predetermined second wavelength range within the first wavelength range amplified by the rare-earth doped fiber. The second wavelength range can be determined based on the amplification gain of the rare-earth doped fiber. For example, the second wavelength range can be determined so as to at least partially overlap with a wavelength range where the amplification gain is lower than a predetermined value by a predetermined value or more than the maximum value of the amplification gain of the first wavelength range.
[0027] With the above configuration, it is possible to reduce the non-uniformity of the amplification gain with respect to wavelength. Therefore, it becomes possible to contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, which is to "build resilient infrastructure, promote sustainable industrialization and foster innovation."
[0028] The invention is not limited to the above-described embodiments, and various modifications and changes are possible within the scope of the gist of the invention.
Explanation of Reference Numerals
[0029] 14: Light source, 15: Coupler, 16: Bismuth-doped fiber, 10: Wavelength division multiplexing coupler
Claims
1. An optical amplifier connected to an optical fiber that transmits signal light, a light source generating pump light; A splitter means for splitting the pump light into at least two pump lights; a rare-earth doped fiber for amplifying the signal light with a first pump light of the at least two pump lights; a coupler that outputs a second pump light of the at least two pump lights to the optical fiber; An optical amplifier comprising:
2. 2. The optical amplifier according to claim 1, wherein a propagation direction of said signal light and a propagation direction of said second pump light in said optical fiber are different.
3. 2. The optical amplifier according to claim 1, wherein a propagation direction of said signal light and a propagation direction of said second pump light in said optical fiber are the same.
4. 2. The optical amplifier according to claim 1, wherein the first pump light is input to an end of the rare-earth doped fiber different from an end to which the signal light is input.
5. 2. The optical amplifier according to claim 1, wherein the first pump light is input to the same end of the rare-earth doped fiber as the end to which the signal light is input.
6. 2. The optical amplifier according to claim 1, wherein the second pump light is used for Raman amplification of the signal light in the optical fiber.
7. 7. The optical amplifier according to claim 6, wherein the pump light has a wavelength that excites the rare-earth doped fiber and Raman amplifies a second wavelength range within a first wavelength range amplified by the rare-earth doped fiber.
8. 7. The optical amplifier of claim 6, wherein the rare-earth doped fiber is a bismuth doped fiber.
9. 9. The optical amplifier according to claim 8, wherein the wavelength of the pump light is 1195 nm or 1215 nm.
10. An optical communication system comprising an optical amplifier according to any one of claims 1 to 9.