An ultra-wideband noise-like pulse generation and power amplification system and method

Abstract

The application discloses an ultra-wideband noise-like pulse generation and power amplification system and method, which sequentially comprises a noise-like pulse oscillator, an inter-stage optical isolator and a single-stage optical fiber power amplifier; the noise-like pulse oscillator generates a 1.4-micron-band noise-like pulse seed by using a first gain optical fiber in a nonlinear amplification ring mirror; the single-stage optical fiber power amplifier uses a second gain optical fiber to perform gain amplification and nonlinear spectral broadening on the noise-like pulse seed; and the first gain optical fiber and the second gain optical fiber are both low-germanium-bismuth-doped germanosilicate optical fibers. The application can continuously realize noise-like pulse generation, power promotion and spectral broadening, reduce the influence of optical feedback in a later stage on oscillation in an earlier stage, does not need to additionally set a spectral broadening unit, and enables the amplified output to maintain a double-time-scale intensity autocorrelation structure and repetition characteristics, and takes into account ultra-wideband spectrum formation and noise-like pulse state maintenance.

Description

Technical Field

[0001] This invention relates to the field of ultrafast fiber laser technology, and in particular to an ultrawideband noise pulse generation and power amplification system and method. Background Technology

[0002] Noise-like pulses (NLPs) are a special pulse type in ultrafast fiber lasers. Macroscopically, they are pulse envelopes output at a fixed repetition frequency, containing numerous ultrashort sub-pulses with pulse widths ranging from femtoseconds to picoseconds and random amplitude and phase variations. Compared to conventional solitons and dissipative solitons, the intensity autocorrelation curves of noise-like pulses typically exhibit a dual-timescale structure with narrow coherent peaks superimposed on a wide time base. Because the multiple ultrashort sub-pulses within a noise-like pulse can continuously evolve under the influence of gain, dispersion, and nonlinearity, noise-like pulses possess high pulse energy and a broad spectrum, making them valuable for applications in supercontinuum generation, broadband spectroscopy, imaging, and nonlinear frequency conversion.

[0003] Existing noise-like pulse (MLP) technologies mainly fall into two categories. One approach directly generates broadband MLPs by increasing nonlinear phase accumulation in a mode-locked oscillator. The other approach uses the MLP as a seed input to an fiber amplifier, increasing average power and single-pulse energy while maintaining or further broadening the output spectrum through gain, dispersion, and nonlinear effects within the amplifier. Current technologies have already achieved ultra-wideband MLP generation, MLP power amplification, or a combination of both in the approximately 1.0 μm, 1.55 μm, and 2.0 μm bands, demonstrating that the output power and spectral range of MLPs can be further expanded through the coordination of the oscillator and subsequent amplifier.

[0004] However, the 1.4-micron band lies between the main gain bands of commonly used ytterbium-doped and erbium-doped silica fibers. There are relatively few gain fibers and matching fiber devices available for generating and amplifying noise-like pulses in this band. Factors such as insufficient gain, ground-state reabsorption, device insertion loss, and dispersion and nonlinear accumulation in long active fibers interact, making it difficult to simultaneously achieve stable generation, power enhancement, and broadband spectrum formation of 1.4-micron noise-like pulses. Especially in the subsequent power amplification process, while increasing the length of the active fiber helps improve pump absorption and gain, it also increases signal reabsorption, transmission loss, and dispersion and nonlinear accumulation; increasing the pump power may cause gain saturation and pulse state changes.

[0005] Existing 1.4-micron mode-locked fiber laser technology can generate noise-like pulses using bismuth-doped germanium silicate fiber and a nonlinear amplifying ring mirror. However, related solutions mainly focus on the oscillator output and have not yet formed an independent, same-band power amplification link that matches the oscillator for this type of noise pulse. Therefore, there is still a lack of an integrated solution for how to continue spectral broadening while increasing the output power of the noise-like pulse output by the oscillator after it enters the subsequent amplification stage.

[0006] Furthermore, the formation of ultrawideband spectra for noise-like pulses typically requires sufficient nonlinear phase accumulation, while power amplification necessitates coordination of gain, dispersion, and nonlinear propagation. Insufficient nonlinearity results in limited spectral broadening after amplification; excessive nonlinearity and dispersion accumulation can lead to significant changes in the temporal and phase correlations between random sub-pulses within the pulse, affecting the original dual-timescale structure and repetitive characteristics of the noise-like pulse. Therefore, simply increasing output power or merely obtaining a wide spectrum cannot completely solve the technical problems in the generation and power amplification of 1.4-micron noise-like pulses. Summary of the Invention

[0007] Therefore, the technical problem to be solved by the present invention is to overcome the difficulty in the prior art of simultaneously achieving stable generation of noise-like pulses, effective power enhancement and ultra-wideband spectrum formation in the 1.4 micrometer band, and maintaining the dual time-scale intensity autocorrelation structure and repetitive characteristics of noise-like pulses during power amplification and spectral broadening.

[0008] To address the aforementioned technical problems, this invention provides an ultra-wideband noise pulse generation and power amplification system, comprising: A noise-like pulse oscillator, an interstage optical isolator, and a single-stage fiber power amplifier are arranged sequentially along the signal transmission direction; The noise-like pulse oscillator includes a first pump source, a first gain fiber, a nonlinear amplifying ring mirror, and an output coupler. The first pump source provides pump light to the first gain fiber, which is disposed in the nonlinear amplifying ring mirror. The nonlinear amplifying ring mirror forms intensity-correlated transmission based on nonlinear propagation in the first gain fiber, generating noise-like pulse seeds in the 1.4-micron band. The output coupler outputs a portion of the noise-like pulse seeds to the single-stage fiber power amplifier via the interstage optical isolator. The single-stage fiber power amplifier includes a second pump source, a second gain fiber, and an output optical isolator. The second pump source provides pump light to the second gain fiber. The noise-like pulse seed output by the interstage optical isolator is input into the second gain fiber. The second gain fiber amplifies the noise-like pulse seed and performs spectral broadening on the noise-like pulse seed based on its nonlinear propagation in the second gain fiber to obtain an ultra-wideband noise-like pulse with a center wavelength in the 1.4-micron band. The output optical isolator outputs the ultra-wideband noise-like pulse. Both the first gain fiber and the second gain fiber are low-germanium bismuth-doped germanium silicate fibers.

[0009] In one embodiment of the present invention, the nonlinear amplifying ring mirror includes a first wavelength division multiplexer, a first gain fiber, a polarization controller, and a fiber coupler. The first wavelength division multiplexer, the first gain fiber, and the polarization controller are connected to form a nonlinear loop, and the nonlinear loop is connected to the fiber coupler. The noise-like pulse oscillator further includes a polarization-independent optical isolator, and the fiber coupler, the polarization-independent optical isolator, and the output coupler are connected to form a main cavity; The fiber coupler divides the light field entering the nonlinear loop into a first light field and a second light field that propagate in opposite directions and have different intensities. The first light field and the second light field generate different nonlinear phase shifts under the action of self-phase modulation and cross-phase modulation, and couple and interfere at the fiber coupler to form the intensity-related transmission.

[0010] In one embodiment of the present invention, the fiber optic coupler is a 2×2 fiber optic coupler, and the splitting ratio of the 2×2 fiber optic coupler is 20:80; The splitting ratio of the output coupler is 70:30. 30% of the output of the output coupler is connected to the interstage optical isolator, and 70% of the output of the output coupler is connected to the fiber optic coupler.

[0011] In one embodiment of the present invention, the first pump source is a polarization-maintaining laser diode with a center wavelength of 1310 nm, and the first wavelength division multiplexer is a 1310 / 1450 nm wavelength division multiplexer.

[0012] In one embodiment of the present invention, the single-stage fiber power amplifier further includes a second wavelength division multiplexer, the output of the interstage optical isolator and the output of the second pump source are respectively connected to the second wavelength division multiplexer, and the output of the second wavelength division multiplexer is connected to the second gain fiber.

[0013] In one embodiment of the present invention, the second pump source is a polarization-maintaining laser diode with a center wavelength of 1310 nm, the second wavelength division multiplexer is a 1310 / 1450 nm wavelength division multiplexer, and the length of the second gain fiber is 150 meters. The second wavelength division multiplexer, the second gain fiber, and the output optical isolator are connected sequentially along the transmission direction of the noise-like pulse seed.

[0014] In one embodiment of the present invention, the second gain fiber amplifies the gain of the noise-like pulse seed using broadband gain, and broadens the spectrum of the noise-like pulse seed by the combined effect of the self-phase modulation generated by the propagation of the noise-like pulse seed in the second gain fiber and the fiber dispersion of the second gain fiber.

[0015] In one embodiment of the present invention, the first gain fiber and the second gain fiber are independent of each other and use the same material composition and bismuth doping system. Both the first gain fiber and the second gain fiber have gain characteristics in the 1.4 to 1.5 micrometer band.

[0016] In one embodiment of the present invention, the intensity autocorrelation curve of the noise-like pulse seed exhibits a dual-timescale structure with narrow coherent spikes superimposed on a wide time base. The intensity autocorrelation curve of the ultra-wideband noise pulse exhibits a dual-timescale structure with narrow coherent peaks superimposed on a wide time base, and the repetition frequency of the ultra-wideband noise pulse is the same as the repetition frequency of the noise pulse seed.

[0017] Based on the same inventive concept, this invention also provides a method for generating and amplifying ultra-wideband noise pulses, including: A noise-like pulse seed located in the 1.4-micron band is generated using a nonlinear amplifying ring mirror containing a first gain fiber. The noise-like pulse seed is subjected to interstage optical isolation, and the noise-like pulse seed after interstage optical isolation is input into the second gain fiber. The noise-like pulse seed is amplified by the second gain fiber, and its spectrum is broadened based on the nonlinear propagation of the noise-like pulse seed in the second gain fiber to obtain an ultra-wideband noise-like pulse with a center wavelength in the 1.4 micrometer band. Both the first gain fiber and the second gain fiber are low-germanium bismuth-doped germanium silicate fibers.

[0018] The technical solution of the present invention has the following advantages compared with the prior art: This invention constructs a continuous transmission link between noise-like pulse oscillation and single-stage fiber power amplification in the 1.4-micron band. Low-germanium bismuth-doped germanium silicate fiber with the same material composition and bismuth doping system is used in both the oscillation and amplification stages, enabling the generation, power enhancement, and spectral broadening of the noise-like pulse to be achieved on a matching gain fiber platform. A 1.4-micron noise-like pulse seed is generated using a nonlinear amplifying ring mirror and input to the single-stage fiber power amplifier after inter-stage optical isolation, which helps reduce the influence of reflected light from subsequent stages on the oscillation state of preceding stages.

[0019] This invention simultaneously amplifies the gain of the noise-like pulse seed and broadens the nonlinear spectrum, eliminating the need for a dedicated spectral broadening unit and simplifying the system structure. The amplified output retains the dual-timescale intensity autocorrelation structure and repetitive characteristics of the noise-like pulse, thus achieving a balance between power enhancement, ultra-wideband spectrum formation, and noise-like pulse state preservation. Attached Figure Description

[0020] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0021] Figure 1 This is a schematic diagram of an ultra-wideband noise pulse generation and power amplification system according to an embodiment of the present invention; Figure 2 This is the optical spectrum of a noise-like pulse seed in an embodiment of the present invention; Figure 3 This is a pulse sequence diagram of a noise pulse seed in an embodiment of the present invention; Figure 4 This is a radio frequency spectrum diagram of a noise pulse seed in an embodiment of the present invention; Figure 5 This is an example of the intensity autocorrelation curve of a noise-like pulse seed in an embodiment of the present invention. Figure 6 This is the optical spectrum of an ultra-wideband noise pulse amplified by a single-stage fiber power amplifier in an embodiment of the present invention. Figure 7 This is a pulse sequence diagram of ultra-wideband noise pulses amplified by a single-stage fiber power amplifier in an embodiment of the present invention; Figure 8 This is the radio frequency spectrum diagram of the ultra-wideband noise pulse amplified by a single-stage fiber power amplifier in an embodiment of the present invention; Figure 9 This is an autocorrelation curve of the intensity of an ultra-wideband noise pulse amplified by a single-stage fiber power amplifier in an embodiment of the present invention. Figure 10 This is a graph showing the relationship between the output average power and single pulse energy as a function of the pump power of the second pump source in an embodiment of the present invention. Figure 11 This is a schematic flowchart of an ultra-wideband noise pulse generation and power amplification method according to an embodiment of the present invention.

[0022] Explanation of reference numerals in the accompanying drawings: 1. Noise-like pulse oscillator; 2. Interstage optical isolator; 3. Single-stage fiber power amplifier; 11. First pump source; 12. First wavelength division multiplexer; 13. First gain fiber; 14. Polarization controller; 15. Fiber coupler; 16. Polarization-independent optical isolator; 17. Output coupler; 18. Nonlinear amplifying ring mirror; 19. Nonlinear loop; 20. Main cavity; 21. Single-mode fiber; 31. Second pump source; 32. Second wavelength division multiplexer; 33. Second gain fiber; 34. Output optical isolator. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0024] Example 1: like Figure 1 As shown, the present invention provides an ultra-wideband noise pulse generation and power amplification system, comprising: A noise-like pulse oscillator 1, an interstage optical isolator 2, and a single-stage fiber power amplifier 3 are arranged sequentially along the signal transmission direction; The noise-like pulse oscillator 1 includes a first pump source 11, a first gain fiber 13, a nonlinear amplifying ring mirror 18, and an output coupler 17. The first pump source 11 provides pump light to the first gain fiber 13, which is disposed in the nonlinear amplifying ring mirror 18. The nonlinear amplifying ring mirror 18 forms intensity-correlated transmission based on the nonlinear propagation in the first gain fiber 13, generating noise-like pulse seeds in the 1.4-micron band. The output coupler 17 outputs a portion of the noise-like pulse seeds to the single-stage fiber power amplifier 3 via the interstage optical isolator 2. The single-stage fiber power amplifier 3 includes a second pump source 31, a second gain fiber 33, and an output optical isolator 34. The second pump source 31 provides pump light to the second gain fiber 33. The noise-like pulse seed output by the interstage optical isolator 2 is input to the second gain fiber 33. The second gain fiber 33 amplifies the gain of the noise-like pulse seed and performs spectral broadening on the noise-like pulse seed based on its nonlinear propagation in the second gain fiber 33, resulting in an ultra-wideband noise-like pulse with a center wavelength in the 1.4-micron band. The output optical isolator 34 outputs the ultra-wideband noise-like pulse. The first gain fiber 13 and the second gain fiber 33 are both low germanium bismuth doped germanium silicate fibers.

[0025] This invention uses a noise-like pulse oscillator 1 as the pre-stage pulse generation unit. Intensity-correlated transmission is achieved using a first gain fiber 13 housed in a nonlinear amplifying ring mirror 18 to obtain a noise-like pulse seed in the 1.4-micron band. This seed is then input to a single-stage fiber power amplifier 3 after inter-stage optical isolation. The subsequent stage amplifies the noise-like pulse seed through a second gain fiber 33, and simultaneously performs spectral broadening using its nonlinear propagation within the second gain fiber 33, thereby obtaining an ultra-wideband noise-like pulse with a center wavelength in the 1.4-micron band. Because the pre-stage oscillation and subsequent amplification stages both utilize low-germanium-bismuth-doped germanium-silicate fibers, pulse generation, power amplification, and spectral broadening can be continuously completed within the same gain medium system. Furthermore, the inter-stage optical isolation separates the oscillation and amplification processes, reducing interference from subsequent stage optical feedback to the pre-stage oscillation and enabling the single-stage amplification link to simultaneously enhance output power and achieve wide-spectrum formation.

[0026] The following is combined with Figure 1 A preferred embodiment is further described below. This embodiment employs an all-fiber structure, using low-germanium-bismuth-doped germanium-silicate fiber as the gain medium for both the pre-stage noise-like pulse oscillation and the post-stage power amplification. A 1.4-micron band noise-like pulse seed is formed through a nonlinear amplifying ring mirror, and a single-stage fiber power amplification structure is used to amplify the gain and nonlinearly broaden the noise-like pulse seed. The specific device parameters, fiber lengths, and splitting ratios described below correspond to the specific configuration of this embodiment and are used to illustrate the implementation process of the invention, not to limit other possible embodiments. The low-germanium-bismuth-doped germanium-silicate fiber is an active fiber with germanium-silicate glass as the matrix and bismuth-related active centers introduced. By controlling the germanium content and bismuth doping system, the fiber achieves corresponding optical gain characteristics around 1.4 microns. The silicon-related bismuth active centers in this type of fiber can provide gain in the 1.4-micron band and can be used for the generation and amplification of laser signals in this band. Based on this gain characteristic, this embodiment uses low germanium-bismuth doped germanium silicate fiber as the gain medium for the first gain fiber 13 and the second gain fiber 33, and uses 1310 nanometer pump light to pump the corresponding gain fibers.

[0027] The noise-like pulse oscillator 1 adopts an all-fiber mode-locked structure based on a nonlinear amplifying ring mirror 18. The noise-like pulse oscillator 1 includes a first pump source 11, a first wavelength division multiplexer 12, a first gain fiber 13, a polarization controller 14, an fiber coupler 15, a polarization-independent optical isolator 16, and an output coupler 17. The first pump source 11 is connected to the first wavelength division multiplexer 12. The first wavelength division multiplexer 12, the first gain fiber 13, and the polarization controller 14 are connected to form a nonlinear loop 19. The nonlinear loop 19 is connected to the fiber coupler 15. The fiber coupler 15, the polarization-independent optical isolator 16, and the output coupler 17 are connected to form a main cavity 20. The pump light generated by the first pump source 11 is coupled into the first gain fiber 13 through the first wavelength division multiplexer 12, so that the first gain fiber 13 provides gain for the 1.4-micron band optical signal under the pumping action; the first gain fiber 13 is also set in the nonlinear loop 19 of the nonlinear amplification ring mirror 18, and participates in the nonlinear propagation and nonlinear phase shift accumulation in the nonlinear amplification ring mirror 18.

[0028] Preferably, the first pump source 11 is a polarization-maintaining laser diode with a center wavelength of 1310 nm. The 1310 nm pump wavelength is selected based on the absorption characteristics of the low-germanium-bismuth-doped germanium silicate fiber. The low-germanium-bismuth-doped germanium silicate fiber has good absorption characteristics for the 1310 nm pump light, so that the pump light output from the first pump source 11 can be effectively absorbed by the first gain fiber 13, and provide corresponding gain for the formation of 1.4 μm band noise-like pulses.

[0029] In the experimental configuration of this embodiment, the pump power of the first pump source 11 is set to a maximum of 151.7 milliwatts to observe the upper limit of the output power of the noise-like pulse seed under noise-like pulse mode-locked state. The first wavelength division multiplexer 12 adopts a 1310 / 1450 nm wavelength division multiplexer, wherein the 1310 nm wavelength corresponds to the pump wavelength of the first pump source 11, and the 1450 nm wavelength corresponds to the gain spectrum of the low germanium bismuth doped germanium silicate fiber, so that the 1310 nm pump light and the 1.4 μm band optical signal can be wavelength divided multiplexed by the first wavelength division multiplexer 12 and coupled to the first gain fiber 13.

[0030] The first gain fiber 13 is a low-germanium bismuth-doped germanium silicate fiber with a length of approximately 38 meters. Under the cavity structure and pumping conditions corresponding to this embodiment, experiments have verified that when the length of the first gain fiber 13 is shorter than approximately 38 meters, a noise-like pulse mode-locked output cannot be formed. Therefore, the length of the first gain fiber 13 is set to approximately 38 meters to meet the gain and nonlinear phase shift accumulation conditions required for the formation of the noise-like pulse.

[0031] The nonlinear amplifying ring mirror 18 is used to form intensity-dependent nonlinear transmission characteristics in the noise-like pulse oscillator 1. Preferably, the fiber coupler 15 is a 2×2 fiber coupler with a splitting ratio of 20:80. Using an asymmetric splitting ratio of 20:80 allows for a more significant intensity difference between the two counter-propagating light fields entering the nonlinear loop 19, thus providing conditions for the nonlinear amplifying ring mirror 18 to form strong intensity-dependent nonlinear transmission characteristics.

[0032] Specifically, the optical field entering the nonlinear amplifying ring mirror 18 is split into a first optical field and a second optical field by the fiber coupler 15, propagating in opposite directions along the nonlinear loop 19. Due to the asymmetric splitting effect of the fiber coupler 15, the first and second optical fields have different intensities. As the first and second optical fields propagate in the nonlinear loop 19, they accumulate nonlinear phase shifts under self-phase modulation and cross-phase modulation, respectively, and form a nonlinear phase shift difference due to the difference in light intensity. After propagating along the nonlinear loop 19, the first and second optical fields re-arrive at the fiber coupler 15 and undergo coupling interference at the fiber coupler 15, causing the transmission state at the fiber coupler 15 to change with the incident light intensity, forming intensity-dependent transmission. This intensity-dependent transmission constitutes an artificial saturable absorption type nonlinear transmission mechanism, enabling the nonlinear amplifying ring mirror 18 to achieve passive mode-locking.

[0033] A polarization controller 14 is disposed in the nonlinear loop 19 to adjust the polarization state of the optical field within the nonlinear loop 19. Adjusting the polarization controller 14 can change the propagation state of the first and second optical fields in the nonlinear loop 19, and adjust the interference state formed by the two counter-propagating optical fields at the fiber coupler 15, thereby adjusting the nonlinear transmission characteristics and mode-locked operation state of the nonlinear amplifying ring mirror 18. When the first pump source 11 provides the corresponding pump power and adjusts the polarization controller 14 to an appropriate state, the noise-like pulse oscillator 1 can enter the noise-like pulse mode-locked operation state and obtain a noise-like pulse seed with a center wavelength located in the 1.4-micron band.

[0034] In the main cavity 20, a polarization-independent optical isolator 16 is disposed between the fiber coupler 15 and the output coupler 17 to define the propagation direction of the optical signal within the main cavity 20, allowing the optical signal to circulate in the main cavity 20 along a predetermined direction and suppressing the influence of back reflection and unexpected feedback on the mode-locking operation. A polarization-independent optical isolator 16 is preferably used to reduce the selective effect of the optical isolator on the polarization state of the optical field within the cavity, and to reduce the additional polarization-dependent transmission characteristics that may be introduced when the polarization-selective device, polarization controller 14, and fiber birefringence work together. Through this configuration, the influence of other polarization-dependent mechanisms on the mode-locking process can be reduced, allowing the mode-locking state of the noise-like pulse oscillator 1 to be mainly established by the intensity-dependent transmission mechanism formed by the nonlinear amplifying ring mirror 18, thereby facilitating the verification and characterization of the mode-locking effect of the nonlinear amplifying ring mirror 18.

[0035] Output coupler 17 is positioned at the output of the main cavity 20. Preferably, the splitting ratio of output coupler 17 is 70:30, where 30% of the optical power is coupled out through output coupler 17, and 70% of the optical power remains within the main cavity 20 for continued propagation. Using this splitting ratio, a significant amount of optical power within the cavity can be retained to maintain the cyclic oscillation of the main cavity 20, while simultaneously providing the output with a noise-like pulse seed that meets the input optical power requirements for subsequent power amplification and experimental testing. The 30% output of output coupler 17 is connected to interstage optical isolator 2, coupling out a portion of the optical power in the main cavity 20 to form a noise-like pulse seed for subsequent power amplification; the 70% output of output coupler 17 is connected to the main cavity 20 where fiber optic coupler 15 is located, allowing the remaining optical power to return to the main cavity 20 for continued propagation. The above-mentioned output coupling method enables the noise-like pulse oscillator 1 to extract a mode-locked optical signal with corresponding output power from the output coupler 17 while maintaining the cyclic oscillation of the main cavity 20. This signal is used as the input seed of the single-stage fiber power amplifier 3 and is then used for experimental characterization of the output characteristics.

[0036] The noise-like pulse oscillator 1 employs an all-fiber fusion splicing structure. The first wavelength division multiplexer 12, the first gain fiber 13, the polarization controller 14, the fiber coupler 15, the polarization-independent optical isolator 16, and the output coupler 17 within the noise-like pulse oscillator 1 are interconnected via single-mode fiber 21. Preferably, the total cavity length of the noise-like pulse oscillator 1 is approximately 52.18 meters, of which the length of the first gain fiber 13 is approximately 38 meters, and the total length of the remaining single-mode fibers 21 is approximately 14.18 meters. The second-order dispersion coefficient of the single-mode fiber 21 in the 1450 nm wavelength band is approximately -0.01 ps. 2 / m, corresponding to a total net intracavity dispersion of approximately -0.522 ps for the noise-type pulse oscillator 1. 2 .

[0037] The total cavity length of the noise-like pulse oscillator 1 determines the propagation time of one complete cycle of the optical pulse within the main cavity 20, and corresponds to the fundamental frequency repetition frequency of the noise-like pulse oscillator 1. Under the aforementioned total cavity length of approximately 52.18 meters, the subsequent actual measurement yielded a fundamental frequency repetition frequency of approximately 3.916 MHz, which matches the actual cavity length of the noise-like pulse oscillator 1.

[0038] The noise-like pulse seed output via output coupler 17 enters interstage optical isolator 2 and is transmitted to single-stage fiber power amplifier 3. Interstage optical isolator 2 is positioned between noise-like pulse oscillator 1 and single-stage fiber power amplifier 3 to prevent reflected light generated on one side of single-stage fiber power amplifier 3 from propagating back towards noise-like pulse oscillator 1, thereby reducing the disturbance of subsequent optical feedback to the mode-locked state of nonlinear amplifying ring mirror 18. Interstage optical isolator 2 isolates the preceding oscillation process from the subsequent amplification process in the reverse light propagation direction, allowing the noise-like pulse seed to propagate along the direction from noise-like pulse oscillator 1 to single-stage fiber power amplifier 3.

[0039] The first pump source 11 in the noise-like pulse oscillator 1 and the second pump source 31 in the single-stage fiber power amplifier 3 are independently configured and their pump power can be adjusted separately. The first pump source 11 corresponds to the first gain fiber 13 and is used to adjust the pump state of the noise-like pulse oscillator 1 and the formation state of the noise-like pulse seed; the second pump source 31 corresponds to the second gain fiber 33 and is used to adjust the pump state of the single-stage fiber power amplifier 3 and the subsequent power amplification state. By adjusting the first pump source 11 and the second pump source 31 respectively, the subsequent amplification conditions can be changed while maintaining the working state of the preceding seed, or the formation state of the preceding noise-like pulse seed can be adjusted independently when needed.

[0040] The single-stage fiber power amplifier 3 includes a second pump source 31, a second wavelength division multiplexer 32, a second gain fiber 33, and an output optical isolator 34. The output of the interstage optical isolator 2 is connected to the signal input side of the second wavelength division multiplexer 32. The output of the second pump source 31 is connected to the pump input side of the second wavelength division multiplexer 32. The output of the second wavelength division multiplexer 32 is connected to the second gain fiber 33. The output of the second gain fiber 33 is connected to the output optical isolator 34, such that the second wavelength division multiplexer 32, the second gain fiber 33, and the output optical isolator 34 are arranged sequentially along the transmission direction of the noise-like pulse seed. The noise-like pulse seed output from the interstage optical isolator 2 and the pump light output from the second pump source 31 are coupled through the second wavelength division multiplexer 32 and then enter the second gain fiber 33.

[0041] Preferably, the second pump source 31 employs a polarization-maintaining laser diode with a center wavelength of 1310 nm and a maximum pump power of approximately 178 milliwatts; the second wavelength division multiplexer 32 employs a 1310 / 1450 nm wavelength division multiplexer; and the second gain fiber 33 employs a low-germanium bismuth-doped germanium silicate fiber with a length of approximately 150 meters. The 1310 nm pump light generated by the second pump source 31 is coupled into the second gain fiber 33 via the second wavelength division multiplexer 32, providing the corresponding pumping conditions for the second gain fiber 33. Simultaneously, the noise-like pulse seed output from the interstage optical isolator 2 is input into the second gain fiber 33 via the second wavelength division multiplexer 32, and amplified and propagated within the second gain fiber 33. The length of the second gain fiber 33 is set to 150 meters. Since the gain coefficient of the low-germanium bismuth-doped germanium silicate fiber is relatively low, using a longer second gain fiber 33 increases the interaction length between the pump light and the noise-like pulse seed in the gain medium, allowing the noise-like pulse seed to obtain sufficient power gain. Meanwhile, the longer second gain fiber 33 can extend the nonlinear propagation distance of the noise-like pulse seed, so that self-phase modulation and fiber dispersion continue to act on the noise-like pulse seed during propagation. This is beneficial to improve the output power while promoting further broadening of the output spectrum, so that the second gain fiber 33 can take into account both gain amplification and nonlinear spectrum broadening within the same fiber segment.

[0042] An output optical isolator 34 is located at the output end of the second gain fiber 33. The optical signal propagated through the second gain fiber 33 is output through the output optical isolator 34. The output optical isolator 34 is used to suppress external feedback light and output end-face reflected light from returning to the second gain fiber 33, and to suppress parasitic oscillations that may be caused by reverse feedback, thereby reducing the impact of external feedback on the operating state of the single-stage fiber power amplifier 3. The inter-stage optical isolator 2 and the output optical isolator 34 are located on the input and output sides of the single-stage fiber power amplifier 3, respectively, isolating the propagation directions of light entering and leaving the single-stage fiber power amplifier 3.

[0043] The second gain fiber 33 serves not only as the gain medium in the single-stage fiber power amplifier 3, but also as the nonlinear propagation medium for noise-like pulse seeds. After the noise-like pulse seed enters the second gain fiber 33, it is amplified by the broadband gain provided by the second pump source 31, thereby increasing the average power and single-pulse energy of the noise-like pulse seed. As the noise-like pulse seed propagates along the second gain fiber 33, it also generates self-phase modulation. This self-phase modulation, along with fiber dispersion in the second gain fiber 33, affects the spectral evolution of the pulse, further broadening the output spectrum compared to the seed spectrum before entering the second gain fiber 33.

[0044] The second gain fiber 33 thus simultaneously performs broadband gain amplification and nonlinear spectral broadening functions within the same fiber segment. The single-stage fiber power amplifier 3 does not require a dedicated high-nonlinear fiber for broadening after the second gain fiber 33, nor does it require an external pulse compression unit. The power enhancement and spectral broadening of the noise-like pulse seed are both completed during the propagation of the second gain fiber 33, enabling the single-stage fiber power amplifier 3 to simultaneously amplify the power of the noise-like pulse seed and form a broadband spectrum within a single amplification stage.

[0045] The first gain fiber 13 and the second gain fiber 33 are located in the noise-like pulse oscillator 1 and the single-stage fiber power amplifier 3, respectively. They are two independent gain fiber segments and are not formed by the same continuous fiber spanning the noise-like pulse oscillator 1 and the single-stage fiber power amplifier 3. Both the first gain fiber 13 and the second gain fiber 33 are made of low germanium-bismuth doped germanium silicate fiber.

[0046] In this embodiment, the first gain fiber 13 and the second gain fiber 33 are respectively disposed in the noise-like pulse oscillator 1 and the single-stage fiber power amplifier 3. Both are independent low-germanium bismuth-doped germanium silicate fiber segments, employing the same material composition and bismuth doping system, and both possess gain characteristics in the 1.4 to 1.5 micrometer wavelength range. Specifically, the first gain fiber 13 provides gain for the noise-like pulse oscillation under the pumping action of the first pump source 11, and participates in the nonlinear phase shift accumulation of the two back-propagating optical fields in the nonlinear amplifying ring mirror 18. The second gain fiber 33 amplifies the gain of the noise-like pulse seed output from the pre-stage under the pumping action of the second pump source 31, and further broadens the output spectrum by utilizing the self-phase modulation generated by the propagation of the noise-like pulse seed in the second gain fiber 33 and the fiber dispersion effect. The first gain fiber 13 and the second gain fiber 33 are not the same continuous fiber, but are independent gain fiber segments disposed in the pre-stage oscillation section and the post-stage amplification section, respectively. Using two sections of gain fiber with the same material composition and the same bismuth doping system is beneficial to continuously realize the generation of noise-like pulses, power enhancement and spectral broadening under matching gain bands and fiber transmission conditions.

[0047] With the above configuration, the noise-like pulse oscillator 1 and the single-stage fiber power amplifier 3 can operate in a matching 1.4 to 1.5 micrometer gain medium system, enabling the generation of noise-like pulse seeds, subsequent power enhancement, and nonlinear spectral broadening to be completed in a continuous all-fiber transmission link. This also helps to improve the matching degree between the preceding and following stages in terms of gain band, pump conditions, transmission characteristics, and fiber device compatibility.

[0048] experiment: To further verify the seed pulse state generated by the noise-like pulse oscillator 1, the power amplification and spectral broadening effects of the single-stage fiber power amplifier 3, and the preservation of the noise-like pulse characteristics before and after amplification, experimental tests were conducted on the outputs of the noise-like pulse oscillator 1 and the single-stage fiber power amplifier 3. The tests included optical spectra, pulse sequences, radio frequency spectra, intensity autocorrelation curves, and the output power and single-pulse energy of the single-stage fiber power amplifier 3.

[0049] In this embodiment, a Fujikura 87C+ fiber optic fusion splicer is used to splice the single-mode fiber 21, the first gain fiber 13, and the corresponding connecting fibers of each fiber optic device within the resonant cavity. The loss at each fiber fusion splice point is less than 0.01 dB to reduce the additional transmission loss introduced by the fiber connection location. The gain fibers in the noise-like pulse oscillator 1 and the single-stage fiber power amplifier 3 are both single-mode low-germanium bismuth-doped germanium silicate fibers.

[0050] During the experimental testing, a Yokogawa AQ6370D near-infrared spectrometer was used to measure the optical spectrum of noise-like pulses, and the center wavelength and spectral bandwidth were obtained through the spectrometer's built-in measurement function. A LeCroy Wavemaster 820Zi-B oscilloscope with a bandwidth of 20 GHz was used to measure the pulse sequence, and the corresponding repetition frequency was determined by the time interval between adjacent pulses. A Rohde FSV40 spectrum analyzer with a bandwidth of 40 GHz was used to measure the radio frequency spectrum, and the radio frequency signal-to-noise ratio was taken as the difference between the signal strength and noise strength at the fundamental frequency. An APE pulseCheck 50NX autocorrelation meter was used to measure the intensity autocorrelation curve of the pulses, and the hyperbolic secant square (sech) was used. 2 The model is fitted. Angle-type physical contact fiber optic connectors are used at each measurement position corresponding to the noise pulse output. Compared to planar physical contact fiber optic connectors, this reduces Fresnel reflections at the connection position and lowers the corresponding connection loss.

[0051] When testing the noise-like pulse seed, the pump power of the first pump source 11 was set to 151.7 milliwatts, and the polarization state within the nonlinear loop 19 was adjusted by the polarization controller 14 to make the noise-like pulse oscillator 1 operate in the corresponding mode-locked state. The optical spectrum, pulse sequence, radio frequency spectrum, and intensity autocorrelation curve of the noise-like pulse seed were measured respectively, yielding the following results: Figures 2 to 5 The test results are shown.

[0052] Among them, such as Figure 2As shown, a near-infrared spectrometer was used to measure the spectrum of the noise-like pulse seed output by the output coupler 17. The center wavelength of the noise-like pulse seed is approximately 1465 nm, and the 3 dB spectral bandwidth is approximately 9.18 nm, indicating that the noise-like pulse oscillator 1 can generate corresponding seed light output in the 1.4 μm band. The spectrum of this noise-like pulse seed is used as the input spectrum for subsequent gain amplification and spectral broadening by the single-stage fiber power amplifier 3, and can be compared with the amplified output spectrum.

[0053] like Figure 3 As shown, the noise-like pulse seed is converted into an electrical signal by photoelectric conversion, and time-domain measurements are performed using an oscilloscope. The time interval between adjacent pulses is measured to be approximately 0.255 microseconds, corresponding to a fundamental repetition frequency of approximately 3.916 MHz. The time interval between adjacent pulses remains essentially consistent. The total cavity length of the aforementioned noise-like pulse oscillator 1 is approximately 52.18 meters. The measured repetition frequency of 3.916 MHz matches the total length of the resonant cavity, indicating that the noise-like pulse seed is repeatedly output according to the corresponding intracavity round-trip cycle.

[0054] like Figure 4 As shown, the radio frequency signal-to-noise ratio (RF signal-to-noise ratio) of the noise-like pulse seed measured at the fundamental mode-locked frequency is approximately 64.95 dB. Within the 20 MHz and 1 GHz wideband scanning ranges, the RF signal intensity continuously decreases with increasing scanning frequency, and no obvious intensity modulation envelope is observed. Furthermore, no obvious non-integer multiple sidebands or low-frequency Q-switching modulation are observed at the current measurement resolution, indicating that the pulse sequence at this operating point has good periodic consistency. Slightly raised small side peaks exist on both sides of the RF fundamental frequency peak, and the RF spectrum exhibits a certain degree of noise floor elevation. This characteristic, along with subsequent intensity autocorrelation curves and optical spectra, can be used to determine the operating state of the noise-like pulse.

[0055] like Figure 5 As shown, within a 50 picosecond measurement time range, the intensity autocorrelation curve of the noise-like pulse seed exhibits a narrow coherent peak of approximately 284 femtoseconds. This narrow coherent peak is superimposed on a wide picosecond-scale time base, forming a distinct dual-timescale structure. This intensity autocorrelation trajectory differs from the autocorrelation trajectory formed by a single transform-limited pulse. For noise-like pulses, their macroscopic pulse envelope contains numerous ultrashort sub-pulses with randomly varying amplitudes and phases. The narrow coherent peak corresponds to the short-time correlation characteristics of the ultrashort sub-pulses within the random wave packet, while the wide time base corresponds to the longer-timescale correlation characteristics formed by the overall random pulse envelope.

[0056] The autocorrelation trajectory of a conventional coherent soliton typically exhibits a single, symmetrical pulse profile, while the intensity autocorrelation curve of a noise-like pulse usually shows a dual-timescale structure with narrow coherent peaks on the femtosecond scale superimposed on a wide time base on the picosecond scale. Therefore, Figure 5 The dual-timescale structure in the data can serve as an important basis for determining whether the current output belongs to a noise-like impulse state. Combined with... Figure 2 Relatively smooth optical spectrum Figure 4 Radio frequency spectrum with noise floor and Figure 5 The dual-timescale intensity autocorrelation structure in the model can determine that the noise-like pulse oscillator 1 outputs a noise-like pulse seed under the current pump power and polarization state, rather than a conventional coherent soliton with only superimposed noise.

[0057] After confirming that the noise-like pulse oscillator 1 is in the aforementioned seeded operating state, further testing is performed on the single-stage fiber power amplifier 3. During the testing process, the noise-like pulse oscillator 1 is kept in the same position as described above. Figure 2 In the operating state, the pump power of the first pump source 11 is maintained at 151.7 milliwatts, at which time the average output power of the noise-like pulse seed is approximately 13.59 milliwatts. By adjusting the pump power of the second pump source 31, the second gain fiber 33 amplifies the gain and broadens the nonlinear spectrum of the noise-like pulse seed. When the pump power of the second pump source 31 reaches approximately 178 milliwatts, the pulses output by the output optical isolator 34 are tested for optical spectrum, pulse sequence, radio frequency spectrum, and intensity autocorrelation, and the results are as follows. Figures 6 to 9 The results are shown.

[0058] like Figure 6 As shown, after amplification by the single-stage fiber power amplifier 3, the center wavelength of the output ultra-wideband noise-like pulse is approximately 1469 nm. The 3 dB spectral bandwidth of the noise-like pulse seed is approximately 9.18 nm, which increases to approximately 13.81 nm after propagation by the second gain fiber 33; the 10 dB spectral bandwidth of the noise-like pulse seed is approximately 14.38 nm, which increases to approximately 68.69 nm after amplification. Simultaneously, the short-wavelength end of the amplified actual output spectrum extends to approximately 1400 nm, the long-wavelength end exceeds 1650 nm, and the 20 dB spectral bandwidth is greater than 197.74 nm. These spectral data all correspond to the actual output spectrum obtained under the same amplification operating condition, indicating that the second gain fiber 33 can further broaden the output spectrum while increasing the power of the noise-like pulse seed.

[0059] The ultra-wideband spectrum here refers to the output spectrum actually measured under the single-type noise pulse operating condition. Combining the 3dB, 10dB, and 20dB spectral bandwidths with the actual measurable spectral coverage, the amplified ultra-wideband noise pulse can be characterized. This test result corresponds to the spectral evolution formed by the combined effects of broadband gain, self-phase modulation, and fiber dispersion in the aforementioned second-gain fiber 33.

[0060] like Figure 7As shown, the optical signal amplified by the single-stage fiber power amplifier 3 is converted into a photoelectric signal and then input to an oscilloscope for measurement. The fundamental frequency repetition frequency corresponding to the amplified pulse sequence is still approximately 3.916 MHz, which is consistent with... Figure 3 The fundamental repetition frequency of the middle-class noise pulse seed remains consistent. After power amplification and spectral broadening by the second gain fiber 33, the basic repetition period of the pulse sequence is not changed, indicating that the subsequent amplification process can maintain the repetition characteristics determined by the preceding middle-class noise pulse oscillator 1.

[0061] like Figure 8 As shown, the RF signal-to-noise ratio measured at the amplified fundamental mode-locked frequency is approximately 59.74 dB. Within the 20 MHz and 1 GHz wideband scanning range, the RF signal strength continuously decreases with increasing scanning frequency; no obvious intensity modulation envelope was observed, and no obvious non-integer multiple sidebands or low-frequency Q-switching modulation were observed at the current measurement resolution. Combined with... Figure 7 The consistent pulse interval indicates that the single-stage fiber power amplifier 3 does not introduce obvious low-frequency Q-switching or aperiodic pulse modulation at this operating point, and the amplified pulse sequence still maintains the corresponding periodic consistency.

[0062] like Figure 9 As shown, within a 50 picosecond measurement time range, the amplified ultrawideband noise-like pulse still exhibits a dual-timescale intensity autocorrelation structure with narrow coherent spikes superimposed on a wide time substrate. Compared to before amplification, the full width at half maximum (FWHM) of the narrow coherent spikes increased from approximately 284 femtoseconds to approximately 553 femtoseconds, but the dual-timescale characteristic formed by the wide time substrate and the narrow coherent spikes still exists, indicating that the random wave packet structure corresponding to the noise-like pulse did not disappear after gain amplification and nonlinear propagation in the second gain fiber 33.

[0063] For noise-like pulses, the narrow coherence spike in the autocorrelation curve mainly reflects the correlation time of random ultrashort sub-pulses within the macroscopic wave packet. The narrow coherence spike broadens from approximately 284 femtoseconds to approximately 553 femtoseconds, indicating that after the noise-like pulse undergoes gain, nonlinear propagation, and dispersion in the second gain fiber 33, the group delay distribution, chirp, and phase correlation of the internal sub-pulses change accordingly. The amplified autocorrelation curve still maintains the basic shape of the narrow coherence spike superimposed on a wide time basis.

[0064] comprehensive Figures 6 to 9The test results show that the amplified output has a significantly wider actual output bandwidth than the seed spectrum, maintains the same repetition frequency of approximately 3.916 MHz as the seed in the time domain, and does not exhibit obvious non-integer multiple sidebands or low-frequency Q-switching modulation in the radio frequency spectrum. Simultaneously, it retains the dual-time-scale intensity autocorrelation structure characteristic of noise-like pulses. Therefore, after power amplification and spectral broadening of the noise-like pulse seed by the single-stage fiber power amplifier 3, the output still maintains the basic time-domain and repetitive characteristics corresponding to the noise-like pulse.

[0065] To further characterize the power amplification performance of the single-stage fiber power amplifier 3, the output average power and single-pulse energy were measured under different pump power conditions of the second pump source 31. The results are as follows: Figure 10 As shown, the average output power is obtained through a power meter. During the increase of the pump power from the second pump source 31, the average output power and single-pulse energy of the single-stage fiber power amplifier 3 change accordingly with the pump power.

[0066] When the pump power of the second pump source 31 reaches 178 milliwatts, the average output power of the single-stage fiber power amplifier 3 is approximately 103 milliwatts, and the single-pulse energy is approximately 26.30 nanojoules. Compared to the average power of the noise-like pulse seed of approximately 13.59 milliwatts, the amplified average power is increased by approximately 7.6 times, indicating that the second gain fiber 33 can achieve effective power amplification of the 1.4-micron noise-like pulse seed under the pumping conditions of this embodiment.

[0067] Further linear fitting was performed on the average output power data of the second pump source 31 within the range of 77.9 mW to 165.5 mW, yielding a slope efficiency of approximately 79% for the single-stage fiber power amplifier 3. This result indicates that within the aforementioned pump power range, the output signal power increases accordingly with the increase of the pump power of the second pump source 31, demonstrating that the second gain fiber 33 can convert the input pump energy into output power resembling a noise pulse. Combined with spectral test results, it can be seen that the second gain fiber 33 in this embodiment, while achieving power enhancement, can also further broaden the actual output spectrum by utilizing the nonlinear propagation of the noise pulse.

[0068] Based on the above experimental results, the noise-like pulse oscillator 1 can generate noise-like pulse seeds with a dual-timescale intensity autocorrelation structure consisting of narrow coherence spikes superimposed on a wide time substrate in the 1.4-micron band. After the noise-like pulse seed is input into the single-stage fiber power amplifier 3 via the interstage optical isolator 2, the second gain fiber 33 can significantly broaden the output spectrum while increasing the average output power and single-pulse energy. The amplified and spectrally broadened pulse still maintains the same repetition frequency and dual-timescale intensity autocorrelation structure as the noise-like pulse seed, experimentally verifying the feasibility of the above-mentioned all-fiber oscillation-amplification structure in the same system to achieve 1.4-micron noise-like pulse generation, power enhancement, spectral broadening, and pulse state maintenance.

[0069] Example 2: This embodiment provides a method for generating and amplifying ultra-wideband noise-like pulses. This method can be implemented using the ultra-wideband noise-like pulse generation and power amplification system described in Embodiment 1. The structural composition, connection relationships, and preferred parameters of the noise-like pulse oscillator, inter-stage optical isolator, and single-stage fiber power amplifier can all be referred to the corresponding descriptions in Embodiment 1, and will not be repeated here. Figure 11 As shown, the method described in this embodiment includes the following steps: A noise-like pulse seed located in the 1.4-micron band is generated using a nonlinear amplifying ring mirror containing a first gain fiber. Specifically, a first pump source provides pump light to the first gain fiber. The first gain fiber, positioned in the nonlinear amplifying ring mirror, provides gain to the 1.4-micron band optical signal under the pumping action and participates in the nonlinear phase shift accumulation of the two counter-propagating optical fields in the nonlinear amplifying ring mirror. The nonlinear amplifying ring mirror utilizes the nonlinear propagation in the first gain fiber to form intensity-correlated transmission at the fiber coupler, achieving passive mode-locking. This enables the noise-like pulse oscillator to generate the noise-like pulse seed in the main cavity, and a portion of the noise-like pulse seed is output through the output coupler.

[0070] The noise-like pulse seed is subjected to interstage optical isolation, and then the isolated noise-like pulse seed is input into the second gain fiber. Specifically, the noise-like pulse seed output from the output coupler is transmitted through an interstage optical isolator. The interstage optical isolator enables the noise-like pulse seed to be transmitted unidirectionally along the direction from the noise-like pulse oscillator to the single-stage fiber power amplifier, preventing reflected light generated on the single-stage fiber power amplifier side from propagating in the opposite direction to the noise-like pulse oscillator. After being isolated by the interstage optical isolator, the noise-like pulse seed is coupled with the pump light provided by the second pump source and then input into the second gain fiber.

[0071] The noise-like pulse seed is amplified using the second gain fiber, and its spectral broadening is performed based on the nonlinear propagation of the noise-like pulse seed within the second gain fiber, resulting in an ultra-wideband noise-like pulse with a center wavelength in the 1.4-micron band. Specifically, under the pumping action provided by the second pump source, the second gain fiber amplifies the noise-like pulse seed using broadband gain, increasing its average power and single-pulse energy. Simultaneously, the self-phase modulation generated by the noise-like pulse seed during propagation in the second gain fiber, combined with the fiber dispersion of the second gain fiber, further broadens the output spectrum while amplifying the gain. Thus, power amplification and spectral broadening are simultaneously completed within the same fiber segment of the second gain fiber, resulting in an ultra-wideband noise-like pulse with a center wavelength in the 1.4-micron band, which is then output via an output optical isolator.

[0072] The first gain fiber and the second gain fiber are both low-germanium bismuth-doped germanium silicate fibers. They are set up independently and use the same material composition and bismuth doping system, so that the noise-like pulse oscillation and amplification process can be realized on a matching gain fiber platform.

[0073] Using the above method, a 1.4-micron noise-like pulse seed is generated by the nonlinear propagation of the first gain fiber in the nonlinear amplification ring mirror. After interstage optical isolation, it is input into a single-stage fiber power amplifier with the second gain fiber as the gain and nonlinear propagation medium. This allows the power amplification and spectral broadening of the noise-like pulse seed to be completed synchronously within the same amplification stage, eliminating the need for a dedicated spectral broadening unit. Simultaneously, the interstage optical isolation separates the oscillation process from the amplification process in the reverse light propagation direction, which helps reduce the disturbance of the mode-locked state of the preceding stage by the optical feedback of the subsequent stage. The resulting ultra-wideband noise-like pulse maintains the same repetition frequency as the noise-like pulse seed, as well as a dual-timescale intensity autocorrelation structure with narrow coherent peaks superimposed on a wide time substrate. This achieves both increased output power and single-pulse energy while simultaneously ensuring ultra-wideband spectral formation and noise-like pulse state maintenance.

[0074] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0075] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0076] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0077] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0078] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A system for generating and amplifying ultra-wideband noise pulses, characterized in that, include: A noise-like pulse oscillator, an interstage optical isolator, and a single-stage fiber power amplifier are arranged sequentially along the signal transmission direction; The noise-like pulse oscillator includes a first pump source, a first gain fiber, a nonlinear amplifying ring mirror, and an output coupler. The first pump source provides pump light to the first gain fiber, which is disposed in the nonlinear amplifying ring mirror. The nonlinear amplifying ring mirror forms intensity-correlated transmission based on nonlinear propagation in the first gain fiber, generating noise-like pulse seeds in the 1.4-micron band. The output coupler outputs a portion of the noise-like pulse seeds to the single-stage fiber power amplifier via the interstage optical isolator. The single-stage fiber power amplifier includes a second pump source, a second gain fiber, and an output optical isolator. The second pump source provides pump light to the second gain fiber. The noise-like pulse seed output by the interstage optical isolator is input into the second gain fiber. The second gain fiber amplifies the noise-like pulse seed and performs spectral broadening on the noise-like pulse seed based on its nonlinear propagation in the second gain fiber to obtain an ultra-wideband noise-like pulse with a center wavelength in the 1.4-micron band. The output optical isolator outputs the ultra-wideband noise-like pulse. Both the first gain fiber and the second gain fiber are low-germanium bismuth-doped germanium silicate fibers.

2. The ultra-wideband noise pulse generation and power amplification system according to claim 1, characterized in that: The nonlinear amplifying ring mirror includes a first wavelength division multiplexer, a first gain fiber, a polarization controller, and a fiber coupler. The first wavelength division multiplexer, the first gain fiber, and the polarization controller are connected to form a nonlinear loop, and the nonlinear loop is connected to the fiber coupler. The noise-like pulse oscillator further includes a polarization-independent optical isolator, and the fiber coupler, the polarization-independent optical isolator, and the output coupler are connected to form a main cavity; The fiber coupler divides the light field entering the nonlinear loop into a first light field and a second light field that propagate in opposite directions and have different intensities. The first light field and the second light field generate different nonlinear phase shifts under the action of self-phase modulation and cross-phase modulation, and couple and interfere at the fiber coupler to form the intensity-related transmission.

3. The ultra-wideband noise pulse generation and power amplification system according to claim 2, characterized in that: The fiber optic coupler is a 2×2 fiber optic coupler, and the splitting ratio of the 2×2 fiber optic coupler is 20:

80. The splitting ratio of the output coupler is 70:

30. 30% of the output of the output coupler is connected to the interstage optical isolator, and 70% of the output of the output coupler is connected to the fiber optic coupler.

4. The ultra-wideband noise pulse generation and power amplification system according to claim 2, characterized in that: The first pump source is a polarization-maintaining laser diode with a center wavelength of 1310 nm, and the first wavelength division multiplexer is a 1310 / 1450 nm wavelength division multiplexer.

5. The ultra-wideband noise pulse generation and power amplification system according to claim 1, characterized in that: The single-stage fiber power amplifier further includes a second wavelength division multiplexer. The output of the interstage optical isolator and the output of the second pump source are respectively connected to the second wavelength division multiplexer, and the output of the second wavelength division multiplexer is connected to the second gain fiber.

6. The ultra-wideband noise pulse generation and power amplification system according to claim 5, characterized in that: The second pump source is a polarization-maintaining laser diode with a center wavelength of 1310 nm, the second wavelength division multiplexer is a 1310 / 1450 nm wavelength division multiplexer, and the length of the second gain fiber is 150 meters. The second wavelength division multiplexer, the second gain fiber, and the output optical isolator are connected sequentially along the transmission direction of the noise-like pulse seed.

7. The ultra-wideband noise pulse generation and power amplification system according to claim 1, characterized in that: The second gain fiber amplifies the noise-like pulse seed using broadband gain, and broadens the spectrum of the noise-like pulse seed by combining the self-phase modulation generated by the propagation of the noise-like pulse seed in the second gain fiber with the fiber dispersion of the second gain fiber.

8. The ultra-wideband noise pulse generation and power amplification system according to claim 1, characterized in that: The first gain fiber and the second gain fiber are independent of each other and use the same material composition and bismuth doping system. Both the first gain fiber and the second gain fiber have gain characteristics in the 1.4 to 1.5 micrometer band.

9. The ultra-wideband noise pulse generation and power amplification system according to claim 1, characterized in that: The intensity autocorrelation curve of the noise-like pulse seed exhibits a dual-timescale structure with narrow coherent spikes superimposed on a wide time base. The intensity autocorrelation curve of the ultra-wideband noise pulse exhibits a dual-timescale structure with narrow coherent peaks superimposed on a wide time base, and the repetition frequency of the ultra-wideband noise pulse is the same as the repetition frequency of the noise pulse seed.

10. A method for generating and amplifying ultra-wideband noise pulses, characterized in that, include: A noise-like pulse seed located in the 1.4-micron band is generated using a nonlinear amplifying ring mirror containing a first gain fiber. The noise-like pulse seed is subjected to interstage optical isolation, and the noise-like pulse seed after interstage optical isolation is input into the second gain fiber. The noise-like pulse seed is amplified by the second gain fiber, and its spectrum is broadened based on the nonlinear propagation of the noise-like pulse seed in the second gain fiber to obtain an ultra-wideband noise-like pulse with a center wavelength in the 1.4 micrometer band. Both the first gain fiber and the second gain fiber are low-germanium bismuth-doped germanium silicate fibers.

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