An air-core fiber optic amplification system and method for communication using discarded submarine optical cables.

Abstract

This invention belongs to the field of optical fiber communication, specifically relating to an air-core fiber optical amplification system and method for communication using submarine waste optical cables. The system consists of a tunable laser, a multiplexer, a variable optical attenuator, and a first wavelength division multiplexer (WDM), connected sequentially. A pump laser is connected to the signal input of an erbium-doped fiber amplifier, and the output of the erbium-doped fiber amplifier is connected to the pump end of the first WDM. The fiber collimator, after being focused, is placed at the front end of an air cell. Two optical lenses are fixed at both ends of the air cell. An air-core fiber is placed inside the air cell, positioned to ensure that the signal light can enter the fiber. Another fiber collimator is placed at the rear end of the air cell. The signal light output from the air cell is input to a single port of a second WDM. The pump end of the second WDM is connected to a photodetector, and the signal output of the second WDM is connected to the waste optical cable channel. The output of the waste optical cable channel is sequentially connected to an isolator, a demultiplexer, and an optical power meter.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication, specifically relating to an air-core fiber optical amplification system and method for communication using discarded submarine optical cables. Background Technology

[0002] Submarine optical cables, serving as the main arteries ensuring interconnectivity between major global networks, handle 90% of international communication traffic. However, cables with extended service life may experience reduced communication efficiency and decreased system capacity, resulting in resource waste. Submarine optical cable communication devices are crucial for ensuring fiber optic communication transmission. Traditional devices primarily rely on total internal reflection, where light can only travel within the fiber core. They require dedicated integrated circuits with multiple-input multiple-output (MIMO) technology for signal transmission, resulting in a large number of fibers, low transmission capacity, and high device complexity. With the application of wavelength division multiplexing (WDM) and air-core fiber amplification technologies, the transmission capacity of submarine optical cables has increased by an order of magnitude. WDM is considered a key technology for future upgrades and expansions of fiber optic communication capacity. By fully utilizing the low-loss bands of optical fibers, it increases transmission capacity and has significant applications in submarine optical cable communication. For early submarine cables with a limited number of cores, it allows for the transmission of multiple signals without major modifications to the original system, further increasing the transmission capacity of the fiber optic communication system. Air-core fiber uses air as its core and has advantages such as low delay, high capacity, low dispersion, and low nonlinearity. Its light-guiding window can be extended to the mid-infrared range, far exceeding the light-guiding range of traditional solid-core fiber. At the same time, its gain coefficient is more than three times that of standard single-mode fiber. Summary of the Invention

[0003] To improve the communication efficiency of abandoned submarine optical cables, this invention proposes an air-core fiber optic amplification system for communication using abandoned submarine optical cables.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] An air-core fiber optic amplification system for communication using submarine waste optical cables is disclosed. The system includes a tunable laser, a multiplexer, a variable optical attenuator, an erbium-doped fiber amplifier, a pump laser, a first wavelength division multiplexer, an air cell, a fiber collimator, an optical lens, an air-core fiber, a second wavelength division multiplexer, a photodetector, a waste optical cable channel, an isolator, a demultiplexer, and an optical power meter. The tunable laser, multiplexer, variable optical attenuator, and first wavelength division multiplexer are sequentially connected. The pump laser is connected to the signal input of the erbium-doped fiber amplifier, and the input of the erbium-doped fiber amplifier is connected to the pump end of the first wavelength division multiplexer.

[0006] After adjusting the focus of the fiber collimator, it is placed at the front end of the air cell. Two optical lenses are fixed at both ends of the air cell. A gas-core fiber is placed in the air cell, and the placement position should ensure that the signal light can enter the gas-core fiber. Another fiber collimator is placed at the rear end of the air cell. The signal light output from the air cell is input to a single port of the second wavelength division multiplexer. The output end of the second wavelength division multiplexer is connected to a photodetector. The signal output end of the second wavelength division multiplexer is connected to the waste optical cable channel. The output end of the waste optical cable channel is connected in sequence to an isolator, a demultiplexer, and an optical power meter.

[0007] In a further optimization of this technical solution, the air-core optical fiber includes a quartz glass tube and six suspended silica capillaries disposed therein, wherein the six suspended silica capillaries are arranged in a hexagonal pattern and the distance between each capillary is equal.

[0008] In a further optimization of this technical solution, the capillary diameter is 33μm, the optical fiber cladding diameter is 250μm, and the air-core optical fiber length is 30m.

[0009] In a further optimization of this technical solution, there are six tunable lasers, with center wavelengths of 1545.9nm, 1547.5nm, 1549.4nm, 1550.2nm, 1553.6nm, and 1555.9nm, respectively.

[0010] The technical solution is further optimized so that the center peak value of the pump laser is 980nm and the maximum pump power emitted is about 30W.

[0011] In a further optimization of this technical solution, the gas filled in the gas chamber is CO2, the gas inlet is located at the bottom of the gas chamber, the filling time is 120s, and the gas chamber pressure control device is connected above the gas chamber to pressurize the gas and inject it into the gas core optical fiber.

[0012] This technical solution is further optimized so that the system is set at room temperature with a temperature variation range of ±1℃.

[0013] A method for amplifying air-core optical fiber for communication using discarded submarine optical cables, characterized by comprising the following steps:

[0014] Step 1: The tunable lasers are connected to the multiplexer to generate a flat comb source. The total signal power is evenly distributed across the six spectral channels generated by the six tunable lasers. The signal light emitted by the tunable lasers enters the variable optical attenuator through the multiplexer.

[0015] Step 2: The signal light enters the variable optical attenuator, and the real-time control of the signal light is achieved by attenuating the transmitted optical power. The signal light then enters the first wavelength division multiplexer.

[0016] Step 3: The pump light emitted by the pump laser passes through the erbium-doped fiber amplifier, which excites the erbium ions in the erbium-doped fiber, releasing a large amount of energy and amplifying the pump light. The amplified pump light can better excite the CO2 in the gas-core fiber. The amplified pump light enters the first wavelength division multiplexer.

[0017] Step 4: The first wavelength division multiplexer combines the signal light and pump light into a single beam, which is then coupled into the gas-core fiber in the gas cell through an optical collimator and an optical lens. This increases the pressure in the gas cell, causing CO2 molecules to absorb the pump light and generate a photoacoustic effect. The capillary structure of the gas-core fiber acts as an acoustic resonant cavity, amplifying the sound waves generated within the gas-core fiber. When the frequency difference between the pump light and the signal light satisfies the Brillouin frequency shift of CO2, the pump light can amplify the power of the signal light.

[0018] Step 5: The amplified signal light passes through the second wavelength division multiplexer, and the obtained Brillouin gain is measured using a photodetector;

[0019] Step Six: The amplified signal light enters the channel of the waste optical cable to realize the transmission of the signal light. The reflected light is isolated by the isolator and transmitted to the demultiplexer. The demultiplexer demultiplexes the transmitted signal light, and finally the output optical power is detected by 6 optical power meters.

[0020] In a further optimization of this technical solution, the air-core optical fiber includes a quartz glass tube and six suspended silica capillaries disposed inside the quartz glass tube. The six suspended silica capillaries are arranged in a hexagonal pattern, and the distance between each capillary is equal.

[0021] In a further optimization of this technical solution, the capillary diameter is 33μm, the optical fiber cladding diameter is 250μm, and the air-core optical fiber length is 30m.

[0022] The above technical solution has the following advantages, unlike existing technologies:

[0023] This invention provides a gas-core fiber optical amplification system for communication using discarded submarine optical cables. Employing a gas cell based on gas-core fiber, it achieves long-distance light-gas interaction while providing strong coupling between the optical mode and the temperature and acoustic fields within the fiber. By using gas-core fiber under high pressure, leveraging its high molecular density and low acoustic attenuation, combined with tight optical confinement, it is possible to achieve a gain more than three times higher than that observed in solid silica-core fiber. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of an air-core fiber optic amplification system for communication using discarded submarine optical cables.

[0025] Figure 2 This is a schematic diagram of the end face of an air-core optical fiber. Detailed Implementation

[0026] To explain in detail the technical content, structural features, objectives, and effects of the technical solution, the following description is provided in conjunction with specific embodiments and accompanying drawings.

[0027] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0028] See Figure 1 The diagram shows a schematic of an air-core fiber optical amplification system for communication using discarded submarine optical cables. The system includes a tunable laser 1, a multiplexer (MUX) 2, a variable optical attenuator (VOA) 3, an erbium-doped fiber amplifier (EDFA) 4, a pump laser 5, a first wavelength division multiplexer 6, a fiber collimator 7, an optical lens 8, an air-core fiber 9, a second wavelength division multiplexer 16, a photodetector 10, a discarded optical cable channel 11, an isolator 12, a demultiplexer (DEMUX) 13, and an optical power meter 14.

[0029] Tunable laser 1 is connected to multiplexer 2 to generate a flat comb source. The total signal power is uniformly distributed across the six spectral channels generated by the six tunable lasers. The center wavelengths of the six tunable lasers are 1545.9 nm, 1547.5 nm, 1549.4 nm, 1550.2 nm, 1553.6 nm, and 1555.9 nm, respectively. Multiplexer 2 is connected to variable optical attenuator 3 to achieve real-time control of the signal light by attenuating the transmitted optical power. The other end of variable optical attenuator 3 is connected to the signal input of wavelength division multiplexer 6, which in turn connects pump laser 5 to the signal input of erbium-doped fiber amplifier 4. The output of erbium-doped fiber amplifier 4 is connected to the pump end of the first wavelength division multiplexer 6.

[0030] After adjusting the focus of the fiber collimator 7, place it at the front end of the air cell. Two optical lenses 8 are fixed at both ends of the air cell. Place the air core fiber 9 in the air cell. The placement position should ensure that the signal light can enter the air core fiber 9. Place another fiber collimator 7 at the rear end of the air cell.

[0031] The signal light output from the gas chamber is input to a single port of the second wavelength division multiplexer 16. The pump end of the second wavelength division multiplexer 16 is connected to a photodetector 10 to measure the obtained Brillouin gain. The signal output end of the second wavelength division multiplexer 16 is connected to the waste optical cable channel 11. The output end of the waste optical cable channel 11 is connected in sequence to an isolator 12 and a demultiplexer 13. Finally, the output optical power is detected by an optical power meter 14.

[0032] See Figure 2 The diagram shown is a schematic representation of the end face of the air-core fiber. The air-core fiber 9 includes a large quartz glass tube and six suspended silica capillaries. The six suspended silica capillaries are arranged in a hexagonal pattern, with equal distances between each capillary. The capillary diameter is 33 μm, the fiber cladding diameter is 250 μm, and the length of the air-core fiber is 30 m.

[0033] In this invention, the property that CO2 is not optically damaged under high intensity is fully utilized, which can show a potentially wider transparent window from vacuum ultraviolet to mid-infrared regions. At the same time, by utilizing the photoacoustic interaction within the optical fiber, the air-core optical fiber 9 exhibits ultra-high nonlinear gain, which is of great significance for improving the communication efficiency of submarine waste optical cables.

[0034] This embodiment utilizes the multi-ring microstructure of the gas-core fiber 9 as an acoustic resonant cavity. When the frequency difference between the pump light and the signal light satisfies the Brillouin frequency shift of the gas within the gas-core fiber 9, the pump light can amplify the power of the signal light. The pump laser has a central peak at 980 nm and emits a maximum pump power of approximately 30 W. Brillouin scattering within the gas-core fiber 9 is caused by the interaction between optical modes and guided acoustic modes. Among these, the acoustic modes in the suspended silica capillary structure have a higher acoustic quality factor, which can better amplify the acoustic waves generated within the gas-core fiber.

[0035] The gas chamber based on gas-core fiber enables long-distance light-gas interaction while providing strong coupling between optical modes and the temperature and acoustic fields within the fiber. The gas inside the chamber is CO2, with an inlet at the bottom. The inflation time is approximately 120 seconds. A pressure control device is connected above the chamber to pressurize the gas before injecting it into the gas-core fiber 9. The fiber collimators 7 and optical lenses 8 at both ends of the chamber ensure that spatial light can couple into the gas-core fiber 9.

[0036] In this embodiment, the gas Brillouin gain in the gas-core fiber 9 is proportional to the square of the gas pressure. When the gas pressure in the gas-core fiber 9 is increased, its Brillouin gain will be greatly enhanced.

[0037] In this embodiment, all experiments were conducted at an ambient temperature of 24±1℃. At a working vacuum wavelength of 1550nm, the gain coefficient of the gas-core fiber filled with 9bar CO2 was 0.112m. -1 W -1 When the pressure reaches 25 bar, the measured Brillouin gain coefficient is 0.51 m. -1 W -1At this point, the Brillouin gain coefficient has exceeded that of standard single-mode fiber; when the pressure reaches 35 bar, the measured Brillouin gain coefficient is 1.07 m. -1 W -1 When the pressure reaches 40 bar, the measured Brillouin gain coefficient is 1.53m. -1 W -1 .

[0038] In this embodiment, using air-core fiber 9 can achieve a gain of more than 3 times higher than that of solid silica core fiber. This large amplification is due to the combination of high molecular density and low acoustic attenuation under high pressure.

[0039] The front-end pump power is further amplified by an erbium-doped fiber amplifier (EDFA), and the amplified pump light can better excite CO2 in the gas-core fiber.

[0040] To avoid unnecessary reflections and suppress amplifier spontaneous emission noise (ASE noise), an isolator is connected at the output port.

[0041] In this embodiment, the signal light passes through multiplexer 2 and then enters variable optical attenuator 3. After adjusting the optical power, it enters first wavelength division multiplexer 6. At the output port of first wavelength division multiplexer 6, it is coupled through optical lens 8 and fiber collimator 7 into air-core fiber 9 for amplification. At the same time, the pump light is first amplified by erbium-doped fiber amplifier 4. The amplified pump light passes through first wavelength division multiplexer 6, passes through optical lens 8 and fiber collimator 7, and is coupled into air-core fiber 9 for pumping. After passing through a certain length of air-core fiber 9, the amplified signal light enters waste optical cable channel 11, and finally passes through isolator 12 and demultiplexer 13 for output, which is detected by optical power meter 14.

[0042] A method for optical amplification of air-core optical fiber for communication using discarded submarine optical cables, comprising the following steps:

[0043] Step 1: The tunable lasers are connected to the multiplexer to generate a flat comb source. The total signal power is evenly distributed across the six spectral channels generated by the six tunable lasers. The signal light emitted by the tunable lasers enters the variable optical attenuator through the multiplexer.

[0044] Step 2: The signal light enters the variable optical attenuator, and the real-time control of the signal light is achieved by attenuating the transmitted optical power. The signal light then enters the first wavelength division multiplexer.

[0045] Step 3: The pump light emitted by the pump laser passes through the erbium-doped fiber amplifier, which excites the erbium ions in the erbium-doped fiber, releasing a large amount of energy and amplifying the pump light. The amplified pump light can better excite the CO2 in the gas-core fiber. The amplified pump light enters the first wavelength division multiplexer.

[0046] Step 4: The first wavelength division multiplexer combines the signal light and pump light into a single beam, which is then coupled into the gas-core fiber in the gas cell through an optical collimator and an optical lens. This increases the pressure in the gas cell, causing CO2 molecules to absorb the pump light and generate a photoacoustic effect. The capillary structure of the gas-core fiber acts as an acoustic resonant cavity, amplifying the sound waves generated within the gas-core fiber. When the frequency difference between the pump light and the signal light satisfies the Brillouin frequency shift of CO2, the pump light can amplify the power of the signal light.

[0047] Step 5: The amplified signal light passes through the second wavelength division multiplexer, and the obtained Brillouin gain is measured using a photodetector;

[0048] Step Six: The amplified signal light enters the channel of the waste optical cable to realize the transmission of the signal light. The reflected light is isolated by the isolator and transmitted to the demultiplexer. The demultiplexer demultiplexes the transmitted signal light, and finally the output optical power is detected by 6 optical power meters.

[0049] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Unless otherwise specified, an element defined by the phrase "comprising..." or "including..." does not exclude the presence of additional elements in the process, method, article, or terminal device that includes said element. Additionally, in this document, "greater than," "less than," "exceeding," etc., are understood to exclude the stated number; "above," "below," "within," etc., are understood to include the stated number.

[0050] Although the above embodiments have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the above descriptions are merely embodiments of the present invention and do not limit the scope of patent protection of the present invention. Any equivalent structural or procedural transformations made using the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A gas-core fiber optic amplification system for communication using discarded submarine optical cables, characterized in that, The system includes a tunable laser, a multiplexer, a variable optical attenuator, an erbium-doped fiber amplifier, a pump laser, a first wavelength division multiplexer, a gas cell, a fiber collimator, an optical lens, a gas-core fiber, a second wavelength division multiplexer, a photodetector, a waste optical cable channel, an isolator, a demultiplexer, and an optical power meter; the tunable laser, multiplexer, variable optical attenuator, and first wavelength division multiplexer are connected in sequence, and the tunable laser and multiplexer are connected to generate a flat comb source; Connect the pump laser to the signal output of the erbium-doped fiber amplifier, and connect the output of the erbium-doped fiber amplifier to the pump end of the first wavelength division multiplexer. After adjusting the focus of the fiber collimator, it is placed at the front end of the air cell. Two optical lenses are fixed at both ends of the air cell. The fiber collimator, optical lenses, and air cell are placed in front-to-back order. A gas-core fiber is placed in the air cell, and the placement position should ensure that the signal light can enter the gas-core fiber. Another fiber collimator is placed at the rear end of the air cell. The signal light output from the air cell is input to the input port of the second wavelength division multiplexer. The first output of the second wavelength division multiplexer is connected to a photodetector, and the second output of the second wavelength division multiplexer is connected to the waste optical cable channel. The output of the waste optical cable channel is connected in sequence to an isolator, a demultiplexer, and an optical power meter.

2. The air-core fiber optic amplification system for communication using discarded submarine optical cables as described in claim 1, characterized in that, The air-core optical fiber includes a quartz glass tube and six suspended silica capillaries disposed therein. The six suspended silica capillaries are arranged in a hexagonal pattern, and the distance between each capillary is equal.

3. The air-core fiber optic amplification system for communication using discarded submarine optical cables as described in claim 2, characterized in that, The capillary diameter is 33μm, the fiber cladding diameter is 250μm, and the air-core fiber length is 30m.

4. The air-core fiber optic amplification system for communication using discarded submarine optical cables as described in claim 1, characterized in that, There are six tunable lasers, with center wavelengths of 1545.9nm, 1547.5nm, 1549.4nm, 1550.2nm, 1553.6nm, and 1555.9nm, respectively.

5. The air-core fiber optic amplification system for communication using discarded submarine optical cables as described in claim 1, characterized in that, The pump laser has a central peak at 980nm and emits a maximum pump power of approximately 30W.

6. The air-core fiber optic amplification system for communication using discarded submarine optical cables as described in claim 1, characterized in that, The gas filled in the gas chamber is CO2, with an air inlet at the bottom and a filling time of 120 seconds. A gas chamber pressure control device is connected above the gas chamber, which pressurizes the gas and injects it into the gas-core optical fiber.

7. The air-core fiber optic amplification system for communication using discarded submarine optical cables as described in claim 1, characterized in that, The system is set to operate at room temperature with a temperature variation range of ±1℃.

8. A method for optical amplification of air-core optical fiber for communication using discarded submarine optical cables, characterized in that, It includes the following steps: Step 1: The tunable lasers are connected to the multiplexer to generate a flat comb source. The total signal power is evenly distributed across the six spectral channels generated by the six tunable lasers. The signal light emitted by the tunable lasers enters the variable optical attenuator through the multiplexer. Step 2: The signal light enters the variable optical attenuator, and the real-time control of the signal light is achieved by attenuating the transmitted optical power. The signal light then enters the first wavelength division multiplexer. Step 3: The pump light emitted by the pump laser passes through the erbium-doped fiber amplifier, which excites the erbium ions in the erbium-doped fiber, releasing a large amount of energy and amplifying the pump light. The amplified pump light can better excite the CO2 in the gas-core fiber. The amplified pump light enters the first wavelength division multiplexer. Step 4: The first wavelength division multiplexer combines the signal light and pump light into a single beam, which is then coupled into the gas-core fiber in the gas cell through an optical collimator and an optical lens. This increases the pressure in the gas cell, causing CO2 molecules to absorb the pump light and generate a photoacoustic effect. The capillary structure of the gas-core fiber acts as an acoustic resonant cavity, amplifying the sound waves generated within the gas-core fiber. When the frequency difference between the pump light and the signal light satisfies the Brillouin frequency shift of CO2, the pump light can amplify the power of the signal light. Step 5: The amplified signal light passes through the second wavelength division multiplexer, and the obtained Brillouin gain is measured using a photodetector; Step Six: The amplified signal light enters the channel of the waste optical cable to realize the transmission of the signal light. The reflected light is isolated by the isolator and transmitted to the demultiplexer. The demultiplexer demultiplexes the transmitted signal light, and finally the output optical power is detected by 6 optical power meters.

9. The method for air-core fiber optical amplification for communication using discarded submarine optical cables as described in claim 8, characterized in that, The air-core optical fiber includes a quartz glass tube and six suspended silica capillaries disposed inside the quartz glass tube. The six suspended silica capillaries are arranged in a hexagonal pattern, and the distance between each capillary is equal.

10. The method for air-core fiber optical amplification for communication using discarded submarine optical cables as described in claim 8, characterized in that, The capillary diameter is 33μm, the fiber cladding diameter is 250μm, and the air-core fiber length is 30m.

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