Ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering

Abstract

The invention relates to the technical field of optical fiber lasers, and provides an ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering. Comprising a 1 [mu] m wave band seed source, an electro-optical modulator, a signal generator, an optical fiber amplifier, a solid core-hollow core compact coupling device, an optical fiber end cap, a hollow core optical fiber, a miniature gas cavity, a lens and a dichroic mirror, and the tuning range of the methane gas 1 [mu] m wave band tunable pumping source at least covers 1024-1126 nm. The laser can be converted into communication wave band laser covering the whole S + C + L + U wave band, and benefited from the Raman characteristic of methane molecules, the output laser under single wavelength pumping has a corresponding narrow-linewidth single spectral line, no accompanying ASE noise amplification and the like, and secondary filtering is not needed for selection; and meanwhile, the use of the hollow-core optical fiber ensures that the output laser is only a single mode, and high beam quality can be ensured without other operations.

Description

Technical Field

[0001] The invention mainly relates to the technical field of optical fiber lasers, in particular to an ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering. Background Art

[0002] With the popularization of the Internet and the acceleration of the digitalization process, new communication technologies and applications are constantly emerging. Traditional communication bands are gradually unable to meet the growing demand for data transmission, and widening the communication bands has become an inevitable choice. At present, the main communication wavelengths are concentrated in the C and L bands. Further expansion of the S and U bands will help to further improve spectrum utilization and address spectrum congestion. In addition, wider communication bands will also help support new technologies and new applications, improve communication security and anti-interference capabilities, and promote the development of the digital economy.

[0003] At present, the main methods for broadening the communication band include the following: fiber amplifier based on semiconductor seed source, doped fiber laser based on same-band pumping, and nonlinear effect based on stimulated Raman scattering. Although fiber amplifier based on tunable semiconductor seed source can achieve multi-wavelength laser output in a large range, it requires a large number of seed sources, semiconductor pump sources, amplifiers in different bands, and various customized wavelength division multiplexers, which makes the system structure complex and the manufacturing cost extremely high; at the same time, due to the different characteristics of amplifiers corresponding to different bands, there are also differences in the gain characteristics of optical fibers at different wavelengths in the same band, so it is difficult to unify the output communication band laser characteristics. Doped fiber lasers based on co-band pumping can achieve high quantum efficiency communication band laser output. At the same time, by changing the doping concentration and composition in the gain fiber, the output laser wavelength range can be further broadened. However, this method is currently mainly used in the S band, C band and L band, and the U band in the long-wave direction needs further exploration. At the same time, limited by the fiber characteristics such as annihilation of erbium particle concentration in erbium-doped fiber and the characteristics of semiconductor pump sources, it is difficult for the co-band pumping source to achieve high-power output, which limits its amplification capacity. The Raman laser based on the nonlinear effect of stimulated Raman scattering has a relatively flexible output band and strong power amplification capability, but it is difficult to achieve precise wavelength tuning due to the grating pair used. At the same time, due to the high probability of cascade Raman reaction, filtering and other means are required to achieve the output of a single spectrum line. In addition, limited by the Raman gain characteristics of the solid core fiber itself, the output laser line width is relatively wide, which is difficult to be directly used in optical fiber communication.

[0004] In summary, the existing technical solutions are difficult to simultaneously take into account the characteristics of simple system structure, wide output laser range and high wavelength tuning accuracy, and there are many inconveniences in practical applications. Summary of the invention

[0005] In view of the technical problems existing in the prior art, the present invention proposes an ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering, which obtains a communication laser with full coverage of the S+C+L+U bands, and realizes an ultra-wideband optical fiber communication light source with compact structure, precise tuning, pure spectrum and stable power.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides an ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering, including a 1 μm band tunable seed source, an electro-optic modulator, an optical fiber amplifier module, a solid-hollow compact coupling device, an optical fiber end cap, a hollow-core optical fiber, a micro gas cavity, a lens, and a dichroic mirror; The 1μm band tunable seed source is a tunable narrow linewidth laser, which is used to output seed light of the required wavelength in the 1μm band; An electro-optic modulator, used for modulating the seed light outputted by the 1 μm-band tunable seed source into a pulsed laser as pump light; Fiber amplifier module, used for power amplification of pulsed laser; Solid-hollow compact coupling device, connected between the output end of the fiber amplifier module and the hollow-core fiber, used for close-range and efficient coupling between the solid-core fiber at the output end of the fiber amplifier module and the hollow-core fiber input end; The hollow core fiber is an anti-resonant hollow core fiber, which is filled with a gain gas to provide a place for the pump light to interact with the gain gas molecules to generate an ultra-wideband tunable communication band laser; the gain gas is methane; A micro gas cavity is connected to the output end of the hollow core optical fiber, used to fix and seal the hollow core optical fiber, and output ultra-wideband tunable communication band laser to the dichroic mirror at the same time; The dichroic mirror is used to separate the pump light from the ultra-wideband tunable communication band laser and output the ultra-wideband tunable communication band laser.

[0007] Furthermore, the optical fiber amplifier module contains multiple amplification units and an amplification switching unit, each amplification unit is used to realize pulse laser power amplification of different sub-bands within the 1μm band, and the amplification switching unit is used to realize switching of each amplification unit, switching the amplification unit of the sub-band corresponding to the seed light wavelength to realize power amplification of the seed light.

[0008] Furthermore, the optical fiber amplifier module contains three amplification units, which are respectively used to achieve pulse laser power amplification of 1024nm-1060nm, 1060nm-1090nm and 1090-1126nm.

[0009] Furthermore, the output pigtail of the optical fiber amplifier module is fixed to the input end of the solid-hollow-core compact coupling device. By adjusting the end face position of the output pigtail of the optical fiber amplifier module, the pump light is collimated through the lens group in the solid-hollow-core compact coupling device; the input end of the hollow-core optical fiber is fused with the optical fiber end cap at the output end of the solid-hollow-core compact coupling device.

[0010] Furthermore, the 1 μm band tunable seed source is a narrow linewidth laser tunable within 1024 nm-1126 nm, and the tuning accuracy is 0.01 nm.

[0011] Furthermore, the operating wavelength of the electro-optic modulator covers 1μm-1.5μm, and the output extinction ratio is greater than 30 dB. The electro-optic modulator is connected to a signal generator, which is used to generate the electrical signal required for modulation of the electro-optic modulator and load the electrical signal on the electro-optic modulator. The output pulse width of the signal generator is in the nanosecond level, and the repetition frequency can be freely adjusted.

[0012] Furthermore, the end face of the optical fiber end cap is plated with a metal film, and the transmittance in the 1 μm band is greater than 99.9%, and the transmittance in the 1.4 μm-1.7 μm band is less than 0.1%.

[0013] Furthermore, the micro gas cavity has an air inlet / exhaust port, which is connected to a corresponding exhaust device / inflating device through a pipeline, and can evacuate the inside of the hollow-core optical fiber into a vacuum state and fill it with methane gas at a certain pressure.

[0014] Furthermore, the lens is coated with an anti-reflection film, and the transmittance in the 1 μm and 1.4 μm-1.7 μm bands is greater than 99.9%.

[0015] Furthermore, the dichroic mirror has a transmittance greater than 99.9% within the range of 1024 nm to 1126 nm and a reflectivity greater than 99.9% within the range of 1460 nm to 1675 nm.

[0016] Compared with the prior art, the technical effects of the present invention are: 1. The tuning range of the 1μm band tunable pump source of the present invention covers at least 1024μm-1126 nm. Based on the stimulated Raman scattering effect of methane gas, it can be converted into a communication band laser covering the entire S+C+L+U band. Thanks to the Raman characteristics of methane molecules, the output laser under a single wavelength pump has a corresponding narrow line width single spectrum line, without accompanying ASE noise amplification, etc., and does not need to be selected through secondary filtering; at the same time, the use of hollow-core optical fiber ensures that the output laser is only single-mode, and high beam quality can be guaranteed without other operations. In the prior art, in order to obtain laser output with the same bandwidth, multiple groups of amplifiers or multiple pairs of grating pairs are required to be used in combination, and the amplifier capacity of some bands such as the U band is limited. It is difficult for the system to achieve indiscriminate amplification from the S to the U band. At the same time, in order to achieve high spectral purity and high beam quality, it is necessary to use customized devices for multiple filtering and complex winding of doped optical fibers, which has high manufacturing costs and complex process flows.

[0017] 2. Each amplifier unit in the fiber amplifier module of the present invention is an ytterbium-doped fiber pulse amplifier. Based on the advantages of the simple energy level structure of ytterbium ions and the wide absorption and emission spectrum, it is relatively easy to obtain high-power output with a wide tuning range, high tuning accuracy, and flexible timing characteristics, thereby directly improving the output laser power in the communication band. In the existing technical solutions, the high-power potential of the pump source is limited, and it is difficult to directly generate high-power output. It is necessary to connect multiple relay amplifiers of different bands to amplify the signal light power, which is costly and complex in structure, and does not have the advantages of the present invention.

[0018] 3. The present invention uses a solid-hollow compact coupling device to efficiently couple the pump source pigtail with the hollow-core optical fiber input end after the fiber end cap is fused, effectively reducing the spatial distance and improving the coupling stability and compactness of the system. In other prior art solutions that do not use such methods for fixed coupling, the pump light and the hollow-core optical fiber are mostly injected through spatial coupling exposed to the environment. The longer coupling distance makes its coupling efficiency more susceptible to external physical or mechanical factors, and also directly leads to system redundancy, which is not conducive to the miniaturization and integration of communication light sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0020] Figure 1A schematic diagram of the structure of an ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering provided by an embodiment; Figure 2 A schematic diagram of the three-dimensional structure of a methane molecule provided in an embodiment; Figure 3 This is an output spectrum diagram of a 1 μm band tunable seed source in one embodiment; Figure 4 This is a spectrum diagram of the output of a tunable pulse pump source in one embodiment; Figure 5 This is an output spectrum diagram of an ultra-wideband tunable optical fiber communication light source under the pumping of a 1035nm wavelength pulse pump light in one embodiment; Figure 6 is a diagram showing the stability of the output power of the 1482.7 nm Raman laser output in one embodiment; Figure 7 FIG. 4 is a graph showing the evolution of the Raman laser output power at different methane gas pressures as a function of the pump power in an embodiment.

[0021] Numbers in the figure: 1 is a tunable seed source in the 1 μm band; 2 is an electro-optic modulator; 3 is a signal generator; 4 is a fiber amplifier module; 5 is a first amplifying unit; 6 is a second amplifying unit; 7 is a third amplifying unit; 8 is a solid-hollow compact coupling device; 9 is a first lens; 10 is a second lens; 11 is a fiber end cap; 12 is a hollow-core fiber; 13 is a micro gas cavity; 14 is a third lens; 15 is a dichroic mirror. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The present invention is based on the principle of gas stimulated Raman scattering and utilizes readily available 1 μm tunable pump light to directly realize a compact communication band laser light source that fully covers the S+C+L+U bands.

[0024] S-band (1460nm-1530nm): The fiber loss in this band is lower than that in the O-band and is commonly used in passive optical network (PON) systems.

[0025] C band (1530nm-1565nm): This is a conventional band. Optical fiber exhibits the lowest loss in the C band and is commonly used in metropolitan, long-distance and submarine optical transmission systems.

[0026] L-band (1565nm-1625nm): This is the long wavelength band, the second lowest loss wavelength band, often used to expand the capacity of terrestrial DWDM optical networks and the total capacity of submarine cables.

[0027] U-band (1625nm-1675nm): This is an ultra-long wavelength band that further expands the transmission capacity of optical networks.

[0028] Figure 1 A schematic structural diagram of an ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering provided in one embodiment, including a 1μm band tunable seed source 1, an electro-optic modulator 2, an optical fiber amplifier module 4, a solid-core-hollow-core compact coupling device 8, an optical fiber end cap 11, a hollow-core optical fiber 12, a micro gas cavity 13, a lens, and a dichroic mirror 15.

[0029] The 1 μm band tunable seed source 1 is a tunable narrow linewidth laser, which is used to output seed light of the required wavelength in the 1 μm band; The electro-optic modulator 2 is used to modulate the seed light output by the tunable seed source in the 1 μm band into a pulsed laser as a pump light. The electro-optic modulator 2 is connected to a signal generator 3, and the signal generator 3 is used to generate the electrical signal required for the modulation of the electro-optic modulator 2 and load the electrical signal onto the electro-optic modulator 2. The repetition frequency range of the modulated pulse of the present invention is in the kHz-MHz order, and the pulse width is in the ns order. In practical applications, the repetition frequency and pulse width of the modulated pulse need to be determined based on the final actual communication needs and specific applications. The general repetition frequency is in the kHz-MHz order. The present invention is limited by principle. The gas gain is large under ns-level pulses, so the output is above ns.

[0030] Optical fiber amplifier module 4, used for amplifying the power of pulsed laser; A solid-hollow compact coupling device 8 is connected between the output end of the optical fiber amplifier module and the hollow-core optical fiber 12, and is used for close-range and efficient coupling between the solid-core optical fiber at the output end of the optical fiber amplifier module and the input end of the hollow-core optical fiber; The hollow core fiber 12 is an antiresonant hollow core fiber, which is filled with gain gas to provide a place for the pump light to interact with the gain gas molecules to generate ultra-wideband tunable communication band laser; the gain gas is methane, without other accompanying noise; methane gas has a large Raman scattering cross section and a large Raman gain, and under the action of a single-wavelength pump light, only a single vibration stimulated Raman scattering effect occurs, which can achieve the corresponding single-wavelength communication band laser output without other accompanying noise.

[0031] The micro gas cavity 13 is connected to the output end of the hollow core optical fiber, and is used to fix and seal the hollow core optical fiber, and output ultra-wideband tunable communication band laser to the third lens 14; The third lens 14 outside the micro gas cavity 13 collimates the laser output from the hollow core optical fiber to make it parallel light, and transmits it to the dichroic mirror 15; The dichroic mirror 15 is used to separate the pump light from the ultra-wideband tunable communication band laser and output the ultra-wideband tunable communication band laser.

[0032] The wavelength stability requirement of communication laser is very high, because a slight change in wavelength will cause distortion and attenuation of optical signals during transmission. At the same time, the narrower the line width of the communication laser, the smaller the dispersion effect of the optical signal during transmission, thereby improving the transmission distance and quality of the signal. In a preferred embodiment, the 1μm band tunable seed source 1 is a tunable narrow linewidth laser with high wavelength stability, a tuning accuracy of 0.01 nm, and a tuning range covering 1024nm-1126nm.

[0033] The electro-optic modulator 2 has an operating wavelength covering 1 μm-1.5 μm, and an output extinction ratio greater than 30 dB.

[0034] The output pulse width of the signal generator 3 is in nanosecond order, and the repetition frequency can be freely adjusted.

[0035] The fiber amplifier module contains multiple amplification units and amplification switching units, each of which is used to realize pulse laser power amplification of different sub-bands in the 1μm band, and the amplification switching unit is used to realize the switching of each amplification unit, and the amplification unit of the sub-band corresponding to the seed light wavelength is switched to realize the power amplification of the seed light. The implementation method of the amplification switching unit is not limited, such as combining manual wavelength input with automatic digital circuit control to realize automatic switching between different amplification units. In a preferred embodiment, the fiber amplifier module contains three amplification units, the first amplification unit 5, the second amplification unit 6 and the third amplification unit 7, which are respectively used to realize pulse laser power amplification of 1024nm-1060nm, 1060nm-1090nm and 1090nm-1126nm. Each amplifier unit in the fiber amplifier module is an ytterbium-doped fiber pulse amplifier. Based on the advantages of simple ytterbium ion energy level structure and wide absorption and emission spectrum bandwidth, it is relatively easier to obtain high-power stable output with a wide tuning range, high tuning accuracy and flexible timing characteristics.

[0036] The length of the solid-hollow-core compact coupling device 8 is not more than 10 cm, and the input and output ends of the solid-hollow-core compact coupling device 8 are finely adjustable in three dimensions. The output pigtail of the optical fiber amplifier module is fixed to the input end of the solid-hollow-core compact coupling device. By adjusting the end face position of the output pigtail of the optical fiber amplifier module, the collimation of the pump light is achieved through the lens group composed of the first lens 9 and the second lens 10 in the solid-hollow-core compact coupling device; the input end of the hollow-core optical fiber is fused with the optical fiber end cap at the output end of the solid-hollow-core compact coupling device, and the efficient coupling of the pump light is achieved through the three-dimensional adjustment device at the output end of the solid-hollow-core compact coupling device and the focusing lens (the first lens 9 and the second lens 10) in the solid-hollow-core compact coupling device.

[0037] The end face of the optical fiber end cap is plated with a metal film, and the transmittance in the 1 μm band is greater than 99.9%, and the transmittance in the 1.4 μm-1.7 μm band is less than 0.1%.

[0038] The hollow core optical fiber 12 is an anti-resonant hollow core optical fiber and has extremely low transmission loss at 1 μm and 1.4 μm-1.7 μm.

[0039] The micro gas cavity 13 has a small volume and can fix the hollow-core optical fiber and seal it. At the same time, the micro gas cavity 13 has an air inlet / exhaust port, which is connected to the corresponding exhaust device / inflation device through a pipeline, and can draw the inside of the hollow-core optical fiber into a vacuum state and fill it with methane gas at a certain pressure.

[0040] The third lens 14 is coated with an anti-reflection film, and the transmittance in the 1 μm and 1.4 μm-1.7 μm bands is greater than 99.9%.

[0041] The dichroic mirror 15 has a transmittance greater than 99.9% within the range of 1024 nm to 1126 nm and a reflectance greater than 99.9% within the range of 1460 nm to 1675 nm.

[0042] Furthermore, the purity of the methane gas is greater than 99.99%, and vibration stimulated Raman scattering can occur under the action of 1 μm pump light to achieve communication band laser output.

[0043] The implementation method of the tunable pulse pump source with wide range tunability of the present invention is: based on a 1 μm tunable continuous light seed source, the 1 μm band tunable seed source output laser is directly modulated into a pulse signal through an electro-optical modulator, and then based on an optical fiber amplifier module containing multiple power amplification units, a high peak power 1 μm pulse laser is obtained for subsequent pumping. When single-wavelength pumping is used, since the stimulated Raman scattering output laser wavelength of methane gas is constant, the output laser wavelength is stable and changes closely with the change of the pump source tuning wavelength.

[0044] The output pigtail (solid core fiber) of the fiber amplifier module is connected to the hollow core fiber of the fused fiber end cap through a solid core-hollow core compact coupling device to achieve stable injection of pump light.

[0045] In this way, the present invention realizes communication band laser output and an ultra-wideband precisely tunable optical fiber communication light source through the interaction between a widely tunable tunable pulse pump source and methane gas molecules in a hollow-core optical fiber.

[0046] Compared with the traditional solid-core fiber laser, the gain medium used in the present invention is gas, which has a faster movement rate and relatively higher thermal conductivity. When high-power pump light is injected, the movement of gas molecules themselves will intensify, and the heat dissipation will be enhanced by gas flow, and heat accumulation is not easy to occur, thereby ensuring the stability of the gain, thereby achieving the stability of the output laser power. In the traditional solid-core fiber method, high power can easily cause the conversion of the fundamental mode to the higher-order mode in the optical fiber. The present invention is based on the emerging anti-resonant hollow-core optical fiber, and utilizes the characteristics of such optical fibers that the high-order mode has high loss and easy leakage (in principle, only single-mode is transmitted, the loss corresponding to the high-order mode is extremely high, and even if it is generated, it will leak from the cladding to the outside of the optical fiber during the transmission process). In principle, the generation of high-order modes is directly avoided, and the mode purity is guaranteed.

[0047] like Figure 1As shown, the 1 μm tunable continuous light seed source used in the present invention is a narrow linewidth laser with finely adjustable output wavelength, and its output end is an optical fiber output, which is fused with the input fiber of the electro-optic modulator. The electrical signal generated by the signal generator is injected through the radio frequency signal interface of the electro-optic modulator to complete the pulse modulation of the continuous wave seed light. The electro-optic modulator output pigtail is fused with the input end of the optical fiber amplifier module. The optical fiber amplifier module contains three amplification units, which can respectively realize pulse laser power amplification of 1024nm-1060 nm, 1060nm-1090 nm and 1090nm-1126 nm. Through manual wavelength input and automatic digital circuit control, automatic switching between different amplification units is realized. The output pigtail of the optical fiber amplifier module is fixed to the input end of the solid-hollow compact coupling device. By adjusting the end face position of the output pigtail of the optical fiber amplifier module, the collimation of the pump light is realized through the lens group in the solid-hollow compact coupling device. The input end of the hollow-core fiber is fused with the fiber end cap and then inserted into the output end of the solid-hollow-core compact coupling device. The three-dimensional adjustment device at the output end of the solid-hollow-core compact coupling device and the focusing lens in the solid-hollow-core compact coupling device are used to achieve efficient coupling of the pump light. The micro gas cavity is small in size, and the hollow-core fiber can be placed firmly and well sealed. A special gas tube with a multi-stage valve can be connected to the micro gas cavity to extract the air in the hollow-core fiber and inject the Raman gain gas used. The hollow-core fiber is an anti-resonant hollow-core fiber. The incident pump light is confined in its micron-sized core and can interact strongly with gas molecules over a long distance. The hollow-core fiber has low transmission loss in both the 1 μm band and the S+C+L+U band, which can effectively reduce the pump light and the generated communication band laser loss. The methane used in the present invention is a high-purity gas with a purity greater than 99.99%. It is injected into the vacuum core of the hollow-core optical fiber through an inflating device. Based on the principle of vibration stimulated Raman scattering of gas molecules, the 1024nm-1126nm pump light is converted into a 1460nm-1675nm communication band available laser. The third lens outside the micro gas cavity collimates the hollow-core optical fiber output laser, making it parallel light and then transmitting it to the dichroic mirror. The dichroic mirror is placed at nearly 45° to the output laser. The communication band laser generated in the hollow-core optical fiber is mirror-emitted at a higher reflectivity on the surface of the dichroic mirror, and is output perpendicular to the original transmission direction. The residual 1 μm pump light is directly transmitted and output, so as to achieve the separation of the communication band laser and the residual pump light.

[0048] Figure 2 The diagram is a three-dimensional structure diagram of a methane molecule. Although a methane molecule is a polyatomic molecule with a relatively complex internal vibration and rotation process, it has a highly symmetrical molecular structure, such as Figure 2As shown in the figure, a regular tetrahedron structure with carbon atoms as the center and hydrogen atoms as the vertices is formed. Therefore, when the methane molecule rotates internally, the polarizability does not change in the rotation direction, so there is no rotational stimulated Raman scattering. When 1 μm pump light is incident, the methane molecule only undergoes a single vibrational stimulated Raman scattering, converting the pump wavelength into a single vibrational Raman wavelength, ensuring the purity of the output spectrum, which is beneficial to improving the overall efficiency of the laser light source.

[0049] The present invention uses an easily available 1 μm pump source and a single air-filled hollow core optical fiber to directly convert broadband tunable pump light (1 μm tunable pump light) into a communication-usable laser with a tuning range covering the S+C+L+U band, greatly simplifying the system structure and reducing production costs. By increasing the pump source power, the output power can be directly increased without the need for relay amplification, greatly simplifying the system structure and manufacturing costs.

[0050] The present invention is based on a solid-core-hollow-core compact coupling device, which realizes efficient and stable coupling of a pump source and a hollow-core optical fiber, improves the compactness of the system, reduces the size of the system, improves the overall stability, and is conducive to the long-term stable operation and promotion and application of the light source.

[0051] By adjusting the output wavelength of the 1 μm pump source, the large-scale precise tuning of the output communication band laser can be directly achieved without filtering and other operations. The output spectrum of the methane molecule is pure, and the communication band laser can be obtained more efficiently.

[0052] The present invention is based on the pumping of the Ytterbium-doped fiber amplifier with mature manufacturing technology, with a wide output wavelength range and high tuning accuracy. By increasing the pump power, it is expected to directly obtain higher-power communication band laser output, eliminating the common relay amplifier and saving production costs.

[0053] The gas used in the present invention is methane. If the gas is replaced with ethane or deuterium and the tuning range of the 1 μm pump source is adjusted accordingly, a similar effect can be obtained.

[0054] An embodiment, based on Figure 1 The structure shown provides an ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering, wherein the output spectrum of the 1 μm band tunable seed source is shown in Figure 3 shown. Figure 4 : is the output spectrum of the tunable pulse pump source, and its tuning range covers 1024nm-1135nm, the output power is up to 2W, and the corresponding peak power is up to 8kW. Further, the output spectrum of the ultra-wideband tunable optical fiber communication light source under the 1035nm wavelength pulse pump light pumping carried out in this embodiment is as follows: Figure 5As shown, in this embodiment, the working gas used in the hollow core optical fiber 12 is methane, and the Raman laser output by the hollow core optical fiber 12 is a 1482.7 nm Raman laser. Figure 5 It can be seen that when pumped by a single wavelength pulse laser in the 1 μm band, the output laser of the ultra-wideband tunable optical fiber communication light source presents a pure single spectrum, proving that methane gas is suitable for the present invention. Figure 6 , which is a graph showing the stability of the 1482.7 nm Raman laser output power of this embodiment. In a period of nearly 30 minutes, by sampling the power once a second, the average output laser power is about 0.272 W, and the standard deviation is only 0.00024, indicating that the output power of the present invention is extremely stable and suitable for communication.

[0055] In addition, the pressure of the methane gas introduced into the hollow core optical fiber 12 will also affect the output Raman laser power. By optimizing and adjusting the pressure of the methane gas introduced into the hollow core optical fiber 12, it is easy to obtain the highest Raman laser output power. Figure 7 , is a graph showing the evolution of the Raman laser output power under different methane gas pressures as a function of the pump power in an embodiment. In this embodiment, the 1064nm single-wavelength pulse laser output by the tunable pulse pump source is coupled into the hollow-core optical fiber 12 via a solid-hollow compact coupling device, wherein the hollow-core optical fiber used is 15m long, and the transmission loss at 1 μm and 1.5 μm is less than 0.03 dB / m. When methane gas at different pressures is introduced into the hollow-core optical fiber 12, the output power of the Raman laser (1540nm) is measured as a function of the coupled pump power. From Figure 7 It can be seen that the methane gas pressure is not as high as possible, nor is it as low as possible. The preferred range of methane gas pressure is between 1 bar and 2.5 bar, and the optimal value of methane gas pressure is 2.5 bar. When the methane gas pressure is 2.5 bar, with the increase of pump power, it is easy to obtain the highest Raman laser output power at this pressure. When the methane gas pressure is greater than 2.5 bar, with the increase of pump power, the effect of improving Raman laser output power is constantly decreasing.

[0056] Matters not covered by the present invention are known technologies.

[0057] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0058] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering, characterized in that: Including 1μm band tunable seed source, electro-optic modulator, fiber amplifier module, solid-hollow compact coupling device, fiber end cap, hollow-core fiber, micro gas cavity, lens, dichroic mirror; The 1μm band tunable seed source is a tunable narrow linewidth laser, which is used to output seed light of the required wavelength in the 1μm band; An electro-optic modulator, used for modulating the seed light outputted by the 1 μm-band tunable seed source into a pulsed laser as pump light; Fiber amplifier module, used for power amplification of pulsed laser; Solid-hollow compact coupling device, connected between the output end of the fiber amplifier module and the hollow-core fiber, used for close-range and efficient coupling between the solid-core fiber at the output end of the fiber amplifier module and the hollow-core fiber input end; The hollow core fiber is an anti-resonant hollow core fiber, which is filled with a gain gas to provide a place for the pump light to interact with the gain gas molecules to generate an ultra-wideband tunable communication band laser; the gain gas is methane; A micro gas cavity is connected to the output end of the hollow core optical fiber, used to fix and seal the hollow core optical fiber, and output ultra-wideband tunable communication band laser to the dichroic mirror at the same time; The dichroic mirror is used to separate the pump light from the ultra-wideband tunable communication band laser and output the ultra-wideband tunable communication band laser.

2. The ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering according to claim 1, characterized in that: The optical fiber amplifier module contains multiple amplification units and an amplification switching unit. Each amplification unit is used to realize pulse laser power amplification of different sub-bands within the 1μm band. The amplification switching unit is used to realize the switching of each amplification unit, and the power amplification of the seed light is realized by switching the amplification unit of the sub-band corresponding to the wavelength of the seed light.

3. The ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering according to claim 2, characterized in that: The optical fiber amplifier module contains three amplification units, which are respectively used to achieve pulse laser power amplification of 1024nm-1060nm, 1060nm-1090nm and 1090nm-1126nm.

4. The ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering according to claim 1, 2 or 3, characterized in that: The output pigtail of the optical fiber amplifier module is fixed at the input end of the solid-hollow-core compact coupling device. By adjusting the end face position of the output pigtail of the optical fiber amplifier module, the pump light is collimated through the lens group in the solid-hollow-core compact coupling device; the hollow-core optical fiber input end is fused with the optical fiber end cap at the output end of the solid-hollow-core compact coupling device.

5. The ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering according to claim 4, characterized in that: The 1 μm band tunable seed source is a narrow line width laser tunable within 1024 nm-1126 nm, with a tuning accuracy of 0.01 nm.

6. The ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering according to claim 5, characterized in that: The electro-optic modulator has an operating wavelength of 1 μm-1.5 μm and an output extinction ratio greater than 30 dB. The electro-optic modulator is connected to a signal generator, which is used to generate the electrical signal required for modulation of the electro-optic modulator and load the electrical signal onto the electro-optic modulator. The output pulse width of the signal generator is in the nanosecond level, and the repetition frequency can be freely adjusted.

7. The ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering according to claim 5, characterized in that: The end face of the optical fiber end cap is plated with a metal film, and the transmittance in the 1 μm band is greater than 99.9%, and the transmittance in the 1.4 μm-1.7 μm band is less than 0.1%.

8. The ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering according to claim 1 or 2 or 3 or 5 or 6 or 7, characterized in that: The micro gas cavity has an air inlet / exhaust port, which is connected to a corresponding exhaust device / inflating device through a pipeline, and can extract the inside of the hollow-core optical fiber into a vacuum state and fill it with methane gas at a certain pressure.

9. The ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering according to claim 8, characterized in that: The lens is coated with an anti-reflection film, and the transmittance in the 1μm and 1.4μm-1.7μm bands is greater than 99.9%.

10. The ultra-wideband tunable optical fiber communication light source based on gas stimulated Raman scattering according to claim 8, characterized in that: The dichroic mirror has a transmittance greater than 99.9% within the range of 1024 nm to 1126 nm and a reflectivity greater than 99.9% within the range of 1460 μm to 1675 nm.

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