Multi-channel feedback chaotic laser generating device based on Sagnac optical fiber ring

Abstract

The invention belongs to the technical field of chaotic lasers, and discloses a multi-channel feedback chaotic laser generating device based on a Sagnac optical fiber ring, which comprises a semiconductor laser, and the output end of the semiconductor laser is connected with the first input end of a first optical fiber coupler; the first output end of the first optical fiber coupler is connected with the optical reflector, and the second output port is connected with the input end of the second optical fiber coupler; two output ends of the second optical fiber coupler are respectively connected with first input ends of the third optical fiber coupler and the fifth optical fiber coupler; two output ends of the third optical fiber coupler and the fifth optical fiber coupler are respectively connected through optical fibers to form a Sagnac optical fiber ring; the second input ends of the third optical fiber coupler and the fifth optical fiber coupler are respectively connected with two input ends of a fourth optical fiber coupler; the first output end of the fourth optical fiber coupler is connected with the second input end of the first optical fiber coupler. According to the invention, low-delay and wide-linewidth chaotic laser can be generated, the structure is simple, and integration and modularization are easy.

Description

Technical Field

[0001] The present invention relates to the technical field of chaotic semiconductor lasers, and in particular to a multi-path feedback chaotic laser generating device based on a Sagnac optical fiber ring. Background Art

[0002] As a non-steady-state output of a laser, chaotic lasers have characteristics such as wide spectral linewidth, noise-like properties, and low coherence. They currently demonstrate important application value in chaotic secure optical communications, random number generators, lidar, and distributed fiber-optic sensing technologies. The structures that generate chaotic lasers mainly include optical feedback structures, optical injection structures, and photoelectric feedback structures. Among them, the optical injection structure is highly flexible, and the performance of the chaotic laser can be controlled by adjusting the detuning of the master and slave lasers and the injected light intensity. However, the introduction of an external light source increases the complexity and cost of the system. The photoelectric feedback method requires converting the optical signal into an electrical signal for modulation. The chaotic laser generated by the photoelectric feedback method generally has advantages such as a relatively flat power spectrum and a high correlation dimension. However, due to the presence of electrical components such as capacitors and filters, the response rate is limited, and the bandwidth of the chaotic laser is relatively narrow. Among the above methods, the optical feedback method and the optical injection method are all-optical structures. Among them, the optical feedback method is most likely to generate chaotic lasers due to the rich modes in the external cavity (IEEE Journal of Selected Topics in Quantum Electronics, 2017, 23(6): 1801309).

[0003] Current feedback-based chaotic semiconductor lasers suffer from a single external cavity, resulting in implicit periodicity in the chaotic laser's intensity time series and a significant time delay characteristic (TDS). This limits the laser's practical engineering applications, for example, by threatening the confidentiality of chaotic lasers and affecting the randomness of high-speed random number generation. To address these issues, researchers have proposed various methods to reduce this time delay characteristic. For example, by adjusting the current to make the relaxation oscillation frequency close to the external cavity resonant frequency (Optics Letters, 2007, 32(20): 2960-2962), TDS hiding can be achieved. In addition, by optimizing the external cavity structure, such as based on fiber Bragg grating (IEEE Photonics Journal, 2012, 4(5): 1930-1935) and chirped fiber Bragg grating feedback structure (Optics Express, 2017, 25(10): 10911-10924), the relaxation oscillation frequency of the laser is adjusted to the edge of the main band of the grating reflection spectrum, thereby enhancing the dispersion effect and suppressing the chaotic signal TDS. Furthermore, researchers have proposed the random fiber Bragg grating feedback method (Optics Letters, 2017, 42(20): 4107-4110) and the scattering feedback method (Applied Optics, 2018, 57(22): 6314-6317), random feedback with low phase correlation in the optical fiber introduces a large number of uncorrelated external cavity modes to achieve TDS suppression. The above methods are all discrete chaotic semiconductor lasers, and the structure usually uses experimental devices such as erbium-doped fiber amplifiers, polarization controllers, and attenuators, which are large in size and low in integration. However, the chaotic semiconductor laser based on on-chip integration (Journal of Lightwave Technology, 2022, 40(17): 5952-5957) has complex processes and high costs, which is not conducive to the mass production of chaotic semiconductor lasers. In addition, the chaotic laser generated based on the optical feedback structure also has the problem of limited spectral linewidth. Summary of the Invention

[0004] In order to solve the technical problems of the existing chaotic laser generating devices such as obvious time delay characteristics, limited spectral linewidth and low integration, the present invention proposes a multi-path feedback chaotic laser generating device based on Sagnac fiber ring to achieve modularization of chaotic laser with low delay and wide linewidth chaotic laser output.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a multi-path feedback chaotic laser generating device based on a Sagnac fiber ring, comprising: a semiconductor laser, a first fiber coupler, a second fiber coupler, a third fiber coupler, a fourth fiber coupler, a fifth fiber coupler and an optical reflector; The output end of the semiconductor laser is connected to the first input end of the first optical fiber coupler; the first output end of the first optical fiber coupler is connected to the light reflector, and the second output port is connected to the input end of the second optical fiber coupler; the first output end of the second optical fiber coupler is connected to the first input end of the third optical fiber coupler, and the second output end is connected to the first input end of the fifth optical fiber coupler; the two output ends of the third optical fiber coupler are connected through optical fibers to form a first Sagnac optical fiber ring, and the two output ends of the fifth optical fiber coupler are connected through optical fibers to form a second Sagnac optical fiber ring; the second input end of the third optical fiber coupler and the second input end of the fifth optical fiber coupler are respectively connected to the two input ends of the fourth optical fiber coupler; the first output end of the fourth optical fiber coupler is connected to the second input end of the first optical fiber coupler; and the second output end of the fourth optical fiber coupler is used to output chaotic laser.

[0006] The third optical fiber coupler and the fifth optical fiber coupler have different splitting ratios.

[0007] The optical reflector is used to reflect the laser back to the semiconductor laser to form a feedback optical path; the first optical fiber coupler is a × optical fiber coupler, and the port splitting ratio of the first optical fiber coupler connected to the optical reflector and the fourth optical fiber coupler is 10% to 30%.

[0008] The second optical fiber coupler is a 1×2 optical fiber coupler with a splitting ratio of 50:50.

[0009] The third optical fiber coupler and the fifth optical fiber coupler are 2×2 optical fiber couplers.

[0010] The splitting ratio of the third optical fiber coupler is 90:10, and the splitting ratio of the fifth optical fiber coupler is 50:50.

[0011] The fourth optical fiber coupler is a 2×2 optical fiber coupler.

[0012] The splitting ratio of the second output port of the fourth optical fiber coupler is 10% to 50%.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention proposes a multi-path feedback chaotic laser generator based on a Sagnac fiber ring. By utilizing the interference principle of two asymmetric Sagnac fiber rings, the same beam of light is split into two beams. After the two beams circulate in opposite directions within the same loop, an interference effect occurs, which can greatly increase the complexity of the chaotic laser. 2. The present invention has a simple structure, comprising only semiconductor lasers, couplers, reflectors and other structures. A multi-path feedback loop can be realized through the simple structure. The multi-path feedback not only increases the complexity of the chaotic laser output by the laser, but also causes interference between different feedback lights when light is transmitted in loops with different optical paths, thereby widening the line width.

[0014] 3. Experiments have confirmed that the chaotic laser generating device of the present invention can produce a spectrum with a -3 dB greater than 14 GHz, a -20 dB greater than 65 GHz, and a TDS lower than 0.048, which is much better than the existing technology.

[0015] In summary, the present invention can not only generate chaotic lasers with low delay and wide linewidth, but also has small size, simple structure, low cost, and is conducive to modularization and mass production, and has great promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic structural diagram of a multi-path feedback chaotic laser generating device based on a Sagnac fiber ring provided in an embodiment of the present invention is shown.

[0017] Figure 2 Schematic diagram of Sagnac's fiber ring interferometry used in an embodiment of the present invention; Figure 3 The characteristic diagram of the chaotic laser output from the second output end of the fourth fiber coupler, where (a) is the spectrum diagram, and (b) is the autocorrelation curve diagram obtained by calculating the autocorrelation characteristics of the time series. The spectrum has a -3 dB linewidth greater than 14 GHz, a -20 dB linewidth greater than 65 GHz, and the TDS value (time delay characteristic value) of the autocorrelation curve is less than 0.048. In the figure: 1 - semiconductor laser, 2 - first fiber coupler, 3 - second fiber coupler, 4 - third fiber coupler, 5 - fourth fiber coupler, 6 - fifth fiber coupler, 7 - optical reflector. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0019] like Figure 1 As shown, an embodiment of the present invention provides a multi-path feedback chaotic laser generating device based on a Sagnac fiber ring, comprising: a semiconductor laser 1, a first fiber coupler 2, a second fiber coupler 3, a third fiber coupler 4, a fourth fiber coupler 5, a fifth fiber coupler 6 and a light reflector 7; The output end of the semiconductor laser 1 is connected to the first input end of the first fiber coupler 2; the first output end of the first fiber coupler 2 is connected to the light reflector 7, which is used to reflect the laser back to the semiconductor laser 1 along the original path; the second output port is connected to the input end of the second fiber coupler 3; the first output end of the second fiber coupler 3 is connected to the first input end of the third fiber coupler 4, and the second output end is connected to the first input end of the fifth fiber coupler 6; the two output ends of the third fiber coupler 4 are connected through optical fibers to form a first Sagnac fiber ring, and the two output ends of the fifth fiber coupler 6 are connected through optical fibers to form a second Sagnac fiber ring; the second input end of the third fiber coupler 4 and the second input end of the fifth fiber coupler 6 are respectively connected to the two input ends of the fourth fiber coupler 5; the first output end of the fourth fiber coupler 5 is connected to the second input end of the first fiber coupler 2; and the second output end of the fourth fiber coupler 5 is used to output chaotic laser.

[0020] like Figure 2 The figure shows a schematic diagram of the principle of the Sagnac fiber ring in this embodiment. The first Sagnac fiber ring includes a third fiber coupler 4. The two output ends of the third fiber coupler 4 are connected by an optical fiber. The input light ω is input from one input end of the third fiber coupler 4. According to the splitting ratio of the fiber coupler, the input light ω is divided into two light beams ω1 and ω2. The two light beams interfere at a certain position during the rotation along the fiber ring. The interfered light beams ω1' and ω2' continue to propagate along the fiber ring. Since the light in the fiber coupler is bidirectional, the interfered light beams will return to the two output ends and then be output from the two input ends. The light beams output from the third fiber coupler 4 are ω1 and ω2, respectively. f The principle of the second Sagnac fiber ring is the same.

[0021] Specifically, in this embodiment, the semiconductor laser 1 outputs continuous light which enters the first fiber coupler 2 and divides the light into two paths. One path of light is incident on the optical reflector 7, which reflects the laser light along the original path back to the semiconductor laser 1 to form a first feedback optical path. The other path is divided into two paths by the second fiber coupler 3, and the two paths of light enter the third fiber coupler 4 and the fifth fiber coupler 6 respectively; the two output ends of the third fiber coupler 4 and the fifth fiber coupler 6 are connected by optical fibers to form a Sagnac fiber ring, and the two output ends divide the light into different proportions, and the light interferes in the Sagnac fiber ring; the laser light output from the first input end of the third fiber coupler 4 after interference in the first Sagnac fiber ring passes through the second fiber coupler 3 and the first fiber coupler 2 in sequence and then returns to the semiconductor laser 1 to form a second feedback optical path, and the laser light output from the first input end of the fifth fiber coupler 6 after interference in the second Sagnac fiber ring passes through the second fiber coupler 3 and the first fiber coupler 2 in sequence and then returns to the semiconductor laser 1 to form a second feedback optical path. The laser light, which passes through the first fiber coupler 2 and the second Sagnac fiber ring, returns to the semiconductor laser 1, forming a third feedback optical path. The laser light, which is output from the second input end of the third fiber coupler 4 after passing through the first Sagnac fiber ring and from the second input end of the fifth fiber coupler 6 after passing through the second Sagnac fiber ring, returns to the second input end of the first fiber coupler 2 after passing through the first output end of the fourth fiber coupler 5, forming a fourth feedback optical path. Since this signal enters the second fiber coupler 3 together with the signal output by the laser 1, a portion of the light will eventually return to the laser 1 after passing through the Sagnac fiber ring formed by the third fiber coupler 4 and the fifth fiber coupler 6, thus forming a fourth feedback optical path. Therefore, the device of the present invention has at least four different optical feedback paths, which can achieve low-latency characteristics and high spectral linewidth chaotic performance output based on the generation of chaotic laser light.

[0022] Specifically, in this embodiment, based on the interference principle of the Sagnac fiber optic ring, in the second feedback optical path, the third fiber optic coupler 4 divides the light into two beams. After the two beams of light circulate in opposite directions in the first Sagnac fiber optic ring for one circle, an interference effect occurs, thereby increasing the complexity of the chaotic laser. Similarly, an interference effect will also occur in the corresponding second Sagnac fiber optic ring in the third feedback optical path. Since the splitting ratio of the fifth fiber optic coupler 6 is different from that of the third fiber optic coupler 4, there is a difference between the second feedback optical path and the third feedback optical path, which can further increase the complexity of the chaotic laser.

[0023] Specifically, in this embodiment, the optical fiber couplers are connected via optical fiber jumpers.

[0024] Specifically, in this embodiment, the first fiber coupler 2 is a 2×2 fiber coupler, and the splitting ratio between the first output end connected to the optical reflector 7 and the second input end connected to the fourth fiber coupler 5 is 10% to 30%.

[0025] Specifically, in this embodiment, the second optical fiber coupler 3 is a 1×2 optical fiber coupler with a splitting ratio of 50:50.

[0026] Specifically, in this embodiment, the third fiber coupler 4 and the fifth fiber coupler 6 are 2×2 fiber couplers, wherein the splitting ratio of the third fiber coupler 4 is 90:10, and the splitting ratio of the fifth fiber coupler 6 is 50:50.

[0027] Specifically, in this embodiment, the fourth optical fiber coupler 5 is a 2×2 optical fiber coupler.

[0028] Specifically, in this embodiment, the splitting ratio of the second output port of the fourth optical fiber coupler 5 is 10% to 50%.

[0029] like Figure 3 As shown, a multi-path feedback chaotic laser generating device based on a Sagnac fiber ring proposed in an embodiment of the present invention can achieve a chaotic laser output with a spectrum -3 dB linewidth greater than 14 GHz, a -20 dB linewidth greater than 65 GHz, and a TDS lower than 0.048 in the autocorrelation curve diagram obtained by calculating the autocorrelation characteristics of the timing under certain current and temperature conditions (the current is 3.5 times the threshold current and the temperature is 24.7°C).

[0030] In summary, the present invention provides a multi-path feedback chaotic semiconductor laser based on a Sagnac fiber ring. Through a multi-path different optical feedback structure composed of two different Sagnac fiber rings and a reflector, a chaotic laser output with a spectrum -3 dB linewidth greater than 14 GHz, a -20 dB linewidth greater than 65 GHz, and an autocorrelation curve TDS less than 0.048 obtained by calculating the autocorrelation characteristics of the timing is achieved. The chaotic laser is suitable for fields such as chaotic fiber sensing and chaotic secure communication.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-path feedback chaotic laser generating device based on a Sagnac fiber ring, characterized in that: include: Semiconductor laser (1), a first optical fiber coupler (2), a second optical fiber coupler (3), a third optical fiber coupler (4), a fourth optical fiber coupler (5), a fifth optical fiber coupler (6), and an optical reflector (7); The output end of the semiconductor laser (1) is connected to the first input end of the first optical fiber coupler (2); the first output end of the first optical fiber coupler (2) is connected to the light reflector (7), and the second output end is connected to the input end of the second optical fiber coupler (3); the first output end of the second optical fiber coupler (3) is connected to the first input end of the third optical fiber coupler (4), and the second output end is connected to the first input end of the fifth optical fiber coupler (6); the two output ends of the third optical fiber coupler (4) are connected through optical fibers to form a first Sagnac optical fiber ring, and the two output ends of the fifth optical fiber coupler (6) are connected through optical fibers to form a second Sagnac optical fiber ring; the second input end of the third optical fiber coupler (4) and the second input end of the fifth optical fiber coupler (6) are respectively connected to the two input ends of the fourth optical fiber coupler (5); the first output end of the fourth optical fiber coupler (5) is connected to the second input end of the first optical fiber coupler (2); and the second output end of the fourth optical fiber coupler (5) is used to output chaotic laser.

2. The multi-path feedback chaotic laser generating device based on a Sagnac fiber ring according to claim 1, characterized in that: The third optical fiber coupler (4) and the fifth optical fiber coupler (6) have different splitting ratios.

3. The multi-path feedback chaotic laser generating device based on Sagnac fiber ring according to claim 1, characterized in that: The optical reflector (7) is used to reflect laser light back to the semiconductor laser (1) to form a feedback optical path; the first optical fiber coupler (2) is a 2×2 optical fiber coupler, and the splitting ratio of the port connected to the optical reflector (7) and the fourth optical fiber coupler (5) is 10% to 30%.

4. The multi-path feedback chaotic laser generating device based on a Sagnac fiber ring according to claim 1, characterized in that: The second optical fiber coupler (3) is a 1×2 optical fiber coupler with a splitting ratio of 50:

50.

5. The multi-path feedback chaotic laser generating device based on Sagnac fiber ring according to claim 1, characterized in that: The third optical fiber coupler (4) and the fifth optical fiber coupler (6) are 2×2 optical fiber couplers.

6. The multi-path feedback chaotic laser generating device based on a Sagnac fiber ring according to claim 5, characterized in that: The splitting ratio of the third optical fiber coupler (4) is 90:10, and the splitting ratio of the fifth optical fiber coupler (6) is 50:

50.

7. The multi-path feedback chaotic laser generating device based on a Sagnac fiber ring according to claim 1, characterized in that: The fourth optical fiber coupler (5) is a 2×2 optical fiber coupler.

8. The multi-path feedback chaotic laser generating device based on a Sagnac fiber ring according to claim 7, characterized in that: The splitting ratio of the second output port of the fourth optical fiber coupler (5) is 10% to 50%.

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