A coherent collapse laser light source and fiber-optic gyroscope

Abstract

The present application relates to a kind of coherent collapse laser light source and fiber-optic gyroscope, belong to fiber-optic gyroscope technical field, solve the problems of complex structure, higher cost, complex process and application limit in prior art.The coherent collapse laser light source of the present application, using self-injection light induced laser enters coherent collapse state, laser spectrum is widened to several tens of GHz, without high bandwidth photoelectric modulator and complex multistage amplification circuit, the widening effect is good, and the application cost is low;The light source structure adopts all-optical loop feedback structure, and the devices used are common optical devices easy to obtain, simple structure, convenient to realize, no additional process difficulty;The light source adopts full polarization-maintaining optical path structure, and the output is linearly polarized light, greatly reduces the additional loss caused by polarization mismatch when light source and gyro Y waveguide coupling, adapts to various fiber-optic gyroscopes;The fiber-optic gyroscope driven by the coherent collapse laser light source disclosed in the present application has low cost, good performance, and is easy to miniaturize and civilianize.

Description

Technical Field

[0001] This invention relates to the field of fiber optic gyroscope technology, specifically to a coherent collapse laser source and a fiber optic gyroscope. Background Technology

[0002] Spectral-stretched laser-driven fiber optic gyroscopes represent an important development direction for fiber optic gyroscopes. Compared to traditional fiber optic gyroscopes using ASE light sources, spectral-stretched laser-driven fiber optic gyroscopes exhibit significant advantages, such as high scaling factor stability, low relative intensity noise, low cost, and low system complexity.

[0003] The key technology for laser-driven fiber optic gyroscopes with broadened spectral width is to broaden the laser linewidth. Theoretical models predict that to achieve navigation-grade noise (0.001deg / √h) and drift (0.01deg / h) for this type of fiber optic gyroscope, the laser linewidth needs to be broadened to 40GHz. However, the linewidth of ordinary lasers is in the MHz range, which obviously cannot meet the application requirements of fiber optic gyroscopes with this precision. Currently, there are two common laser linewidth stretching techniques. One is achieved through external optoelectronic modulation. Existing technology is based on pseudo-random bit-sequence (PRBS) phase modulation, which can stretch the laser linewidth to 11.3 GHz using a pseudo-random signal with a bit rate of 11.3 GHz. Since the laser stretching width achieved by this method is proportional to the bandwidth of the injected pseudo-random signal, but the generation of high-bandwidth pseudo-random signals is very difficult, further increasing the stretching width requires high costs. The other method is to use Gaussian white noise to modulate the laser phase to stretch the laser linewidth. Using a 3 dB bandwidth 11 GHz Gaussian white noise source, the laser linewidth can be stretched to 27 GHz. This method also requires the use of a high-bandwidth optoelectronic modulator and complex multi-stage amplification circuits, which increases the application cost. The second type of method is based on laser coherent collapse. Existing technologies use laser coherent collapse as the light source and construct an internal reflector in the fiber by depositing a TiO2 coating on the fiber end face. This allows some light to be reflected back into the multimode laser, inducing the multimode laser to enter the coherent collapse state. However, this method requires coating processing of the fiber, which is technically challenging and has high application costs. It is not suitable for miniaturized and civilian fiber optic gyroscopes.

[0004] In summary, current methods for laser spectral broadening are all quite complex. Existing external modulation broadening requires complex modulation circuits and expensive high-bandwidth electro-optic modulators, resulting in complex structures and high costs. Existing laser coherence collapse-based schemes require special processing of optical fibers, which is complex and limits their application in gyroscopes. Fiber optic gyroscopes based on existing laser spectral broadening light sources are costly and difficult to miniaturize and commercialize. Summary of the Invention

[0005] In view of the above problems, the present invention provides a coherence-collapsed laser (CCL) light source and a fiber optic gyroscope, which solves the problems of existing technologies that require complex modulation circuits and expensive high-bandwidth electro-optic modulators for external modulation broadening, resulting in complex structures and high costs; laser coherence collapse-based schemes require special processing of optical fibers, which is complex and limits their application in gyroscopes; and fiber optic gyroscopes based on existing laser spectral broadening light sources are costly and difficult to miniaturize and commercialize.

[0006] This invention provides a coherent collapse laser source, comprising a semiconductor DFB (Distributed Feedback) laser 1, a driving and temperature control circuit 2, a first polarization-maintaining circulator 3, a polarization-maintaining fiber isolator 4, and a polarization-maintaining coupler 5; wherein, the first polarization-maintaining circulator 3 includes a first port 3a, a second port 3b, and a third port 3c; the polarization-maintaining coupler 5 includes a beam-combining end 5a, a first beam-splitting end 5b, and a second beam-splitting end 5c.

[0007] The semiconductor DFB laser 1 is driven by the driving and temperature control circuit 2. The output end of the semiconductor DFB laser 1 is connected to the second port 3b of the first polarization-maintaining circulator. The third port 3c of the first polarization-maintaining circulator is connected to the input end of the polarization-maintaining fiber isolator 4. The output end of the polarization-maintaining fiber isolator 4 is connected to the beam-combining end 5a of the polarization-maintaining coupler. The first beam-splitting end 5b of the polarization-maintaining coupler is the output of the polarization-maintaining broadband laser source based on coherent collapse. The second beam-splitting end 5c of the polarization-maintaining coupler is connected to the first port 3a of the first polarization-maintaining circulator.

[0008] Furthermore, the driving current output by the temperature control and driving circuit 2 is greater than the threshold current of the semiconductor DFB laser 1.

[0009] Furthermore, the splitting ratio of the first beam-splitting end 5b of the polarization-maintaining coupler is m%, and the splitting ratio of the second beam-splitting end 5c of the polarization-maintaining coupler is n%. The splitting ratio m:n of the polarization-maintaining coupler 5 is 90:10 to 98:2.

[0010] Furthermore, the laser output from the semiconductor DFB laser 1 passes sequentially through the second port 3b of the first polarization-maintaining circulator, the third port 3c of the first polarization-maintaining circulator, the polarization-maintaining fiber isolator 4, and the polarization-maintaining coupler 5. The polarization-maintaining coupler 5 splits the laser into two beams. When the second beam-splitting end 5c of the polarization-maintaining coupler is not connected to the first port 3a of the first polarization-maintaining circulator, the output of the first beam-splitting end 5b of the polarization-maintaining coupler is the initial laser of the semiconductor DFB laser 1. When the second beam-splitting end 5c of the polarization-maintaining coupler is connected to the first port 3a of the first polarization-maintaining circulator, the feedback light passes through the first port 3a of the first polarization-maintaining circulator and is injected into the semiconductor DFB laser 1 through the second port 3b of the first polarization-maintaining circulator, inducing the semiconductor DFB laser 1 to enter the coherent collapse state, thus completing the broadening of the intrinsic laser spectrum. At this time, the output of the first beam-splitting end 5b of the polarization-maintaining coupler is the coherent collapse laser.

[0011] Furthermore, the semiconductor DFB laser 1 has no built-in isolator, outputs linearly polarized light, and uses polarization-maintaining fiber for the output pigtail.

[0012] Furthermore, the splitting ratio m:n of the polarization maintaining coupler 5 is 93:7; the driving current output by the temperature control and driving circuit 2 is twice the threshold current of the semiconductor DFB laser 1.

[0013] Furthermore, the spectrum of the initial laser has an intrinsic linewidth of 100 kHz to 20 MHz; the spectrum of the coherent collapse laser has a linewidth of 10 GHz to 50 GHz.

[0014] The present invention also provides a fiber optic gyroscope, which is driven by the coherent collapse laser source provided by the present invention.

[0015] The present invention also provides a fiber optic gyroscope, which is an interferometric fiber optic gyroscope driven by a coherent collapse laser source provided by the present invention, including a semiconductor DFB laser 1, a temperature control and driving circuit 2, a first polarization-maintaining circulator 3, a polarization-maintaining fiber isolator 4, a polarization-maintaining fiber coupler 5, a second polarization-maintaining circulator 6, a Y waveguide 7, a fiber optic ring 8, and a photodetector 9.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects:

[0017] (1) The coherent collapse laser source disclosed in this invention uses self-injected light to induce the laser to enter the coherent collapse state, which broadens the laser spectrum to tens of GHz. It does not involve high-bandwidth optoelectronic modulators and complex multi-stage amplification circuits, providing a feasible technical approach for the development of broadband laser-driven fiber optic gyroscope sources. It has good broadening effect and low application cost.

[0018] (2) The coherent collapse laser source disclosed in this invention adopts a full optical path feedback structure, which does not require complex photoelectric modulation. All the devices used are common optical devices that are easy to obtain. The structure is simple, convenient to implement, and has no additional process difficulty, which is conducive to the miniaturization and civilian use of fiber optic gyroscopes.

[0019] (3) The coherent collapse laser source disclosed in this invention adopts a fully polarization-maintaining optical path structure and outputs linearly polarized light, which can greatly reduce the additional loss caused by polarization mismatch when the source is coupled with the gyroscope Y waveguide. It can be adapted to interference type gyroscopes and resonant type gyroscopes such as fully polarization-maintaining fiber gyroscopes or depolarization gyroscopes. The coherent collapse laser source has a wide range of applications.

[0020] (4) The fiber optic gyroscope driven by the coherent collapse laser source disclosed in this invention, which has the above-mentioned beneficial effects, is low in cost, has good performance, and is easy to miniaturize and commercialize. Attached Figure Description

[0021] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0022] Figure 1 This is a schematic diagram illustrating the implementation principle and optical path structure of the coherent collapse laser source disclosed in this invention.

[0023] Figure 2 This is a schematic diagram of the fiber optic gyroscope based on a coherent collapse laser source disclosed in this invention.

[0024] Figure 3 This is a spectral comparison diagram of the coherent collapse laser obtained by broadening the coherent collapse laser source disclosed in this invention and the initial laser of the semiconductor DFB laser used to obtain the laser source.

[0025] Figure label:

[0026] 1- Semiconductor DFB laser; 2- Temperature control and driving circuit; 3- First polarization-maintaining circulator; 3a- First port of the first polarization-maintaining circulator; 3b- Second port of the first polarization-maintaining circulator; 3c- Third port of the first polarization-maintaining circulator; 4- Polarization-maintaining fiber isolator; 5- Polarization-maintaining coupler; 5a- Bundling end of the polarization-maintaining coupler; 5b- First splitting end of the polarization-maintaining coupler; 5c- Second splitting end of the polarization-maintaining coupler; 6- Second polarization-maintaining circulator; 7- Y-waveguide; 8- Fiber optic ring; 9- Photodetector. Detailed Implementation

[0027] To better understand the above-described objectives, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Furthermore, the present invention can be implemented in other ways different from those described herein; therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0028] Given the high cost and complex implementation methods of current laser spectral broadening solutions, the purpose of this invention is to realize a low-cost, high-performance broadband laser-driven fiber optic gyroscope, and proposes a coherent collapse laser source and a fiber optic gyroscope.

[0029] Lasers are affected by external optical feedback. When the feedback rate varies within the range of -40dB to -10dB, semiconductor lasers will transition from multimode oscillation to a coherent collapse state, resulting in a broadened output laser linewidth, unaffected by the feedback distance. Since current laser research largely focuses on obtaining highly coherent output lasers (narrow-spectrum lasers), this spectral broadening is considered detrimental, leading to limited research and application of this type of coherent collapse laser. However, in fiber optic gyroscopes, broadband light sources can effectively suppress drift caused by parasitic secondary interference, improving system performance. This type of coherent collapse laser source is an ideal light source for fiber optic gyroscopes.

[0030] Example 1

[0031] A specific embodiment of the present invention, such as Figure 1 As shown, a coherent collapse laser source is disclosed, including a semiconductor DFB laser 1, a driving and temperature control circuit 2, a first polarization-maintaining circulator 3, a polarization-maintaining fiber isolator 4, and a polarization-maintaining coupler 5; wherein, the first polarization-maintaining circulator 3 includes a first port 3a, a second port 3b, and a third port 3c; the polarization-maintaining coupler 5 includes a beam-combining end 5a, a first beam-splitting end 5b, and a second beam-splitting end 5c.

[0032] The semiconductor DFB laser 1 is driven by the driving and temperature control circuit 2. The output end of the semiconductor DFB laser 1 is connected to the second port 3b of the first polarization-maintaining circulator. The third port 3c of the first polarization-maintaining circulator is connected to the input end of the polarization-maintaining fiber isolator 4. The output end of the polarization-maintaining fiber isolator 4 is connected to the beam-combining end 5a of the polarization-maintaining coupler. The first beam-splitting end 5b of the polarization-maintaining coupler is the output of the polarization-maintaining broadband laser source based on coherent collapse. The second beam-splitting end 5c of the polarization-maintaining coupler is connected to the first port 3a of the first polarization-maintaining circulator.

[0033] Preferably, since the RIN (relative intensity noise) of the coherent collapse laser is related to the driving current, and the RIN increases with the increase of the driving current, under the premise of ensuring the stable operation of the semiconductor DFB laser 1, the driving current output by the temperature control and driving circuit 2 is greater than the threshold current of the semiconductor DFB laser 1.

[0034] Preferably, the splitting ratio of the first beam-splitting end 5b of the polarization-maintaining coupler is m%, and the splitting ratio of the second beam-splitting end 5c of the polarization-maintaining coupler is n%. The splitting ratio m:n of the polarization-maintaining coupler 5 is 90:10 to 98:2.

[0035] Specifically, the laser output from the semiconductor DFB laser 1 passes sequentially through the second port 3b of the first polarization-maintaining circulator, the third port 3c of the first polarization-maintaining circulator, the polarization-maintaining fiber isolator 4, and the polarization-maintaining coupler 5. The polarization-maintaining coupler 5 splits the laser into two beams. When the second beam-splitting end 5c of the polarization-maintaining coupler is not connected to the first port 3a of the first polarization-maintaining circulator, the output from the first beam-splitting end 5b of the polarization-maintaining coupler is the initial laser of the semiconductor DFB laser 1, which has a narrow spectrum and initial intrinsic linewidth. When the second beam-splitting end 5c of the polarization-maintaining coupler is connected to the first port 3a of the first polarization-maintaining circulator, the feedback light passes through the first port 3a of the first polarization-maintaining circulator and is injected into the semiconductor DFB laser 1 through the second port 3b of the first polarization-maintaining circulator, inducing the semiconductor DFB laser 1 to enter a coherent collapse state, thus broadening the intrinsic laser spectrum. At this time, the output from the first beam-splitting end 5b of the polarization-maintaining coupler is the desired coherent collapse laser.

[0036] The semiconductor DFB laser 1 can be a model with a built-in isolator, but the required feedback power is greater, which affects the final output power. Therefore, preferably, the semiconductor DFB laser 1 has no built-in isolator, the output is linearly polarized light, and the output pigtail is a polarization-maintaining fiber.

[0037] Preferably, taking into account both noise and beamwidth, the splitting ratio m:n of the polarization-maintaining coupler 5 is 93:7.

[0038] Preferably, the driving current output by the temperature control and driving circuit 2 is twice the threshold current of the semiconductor DFB laser 1.

[0039] It should be noted that the semiconductor DFB laser 1 is a common commercial semiconductor DFB laser. The polarization-maintaining fiber isolator 4 enables unidirectional laser output, preventing external light from affecting the stability of the light source.

[0040] Figure 3 To compare the spectra of the coherent collapse laser obtained by broadening the coherent collapse laser source disclosed in this invention with the initial laser from the semiconductor DFB laser used to obtain the laser source, the following is presented: Figure 3It can be seen that the initial laser with an intrinsic linewidth of about 1 MHz was broadened to tens of GHz.

[0041] Compared with existing technologies, the coherent collapse laser source disclosed in this invention utilizes self-injected light to induce the laser to enter the coherent collapse state, broadening the laser spectrum to tens of GHz. It does not involve high-bandwidth optoelectronic modulators or complex multi-stage amplification circuits, providing a feasible technical approach for the development of broadband laser-driven fiber optic gyroscope sources. It has good broadening effect and low application cost. The source structure adopts a full optical path feedback structure, which does not require complex optoelectronic modulation. All the components used are common optical components that are easy to obtain. The structure is simple, convenient to implement, and has no additional process difficulty, which is conducive to the miniaturization and civilian application of fiber optic gyroscopes.

[0042] Example 2

[0043] The optical path structure in Example 1 uses a self-injected feedback form composed of a first polarization-maintaining circulator 3, a polarization-maintaining fiber isolator 4, and a polarization-maintaining coupler 5. This is only one implementation method. Another possible method is to use a 1×2 polarization-maintaining coupler with a suitable splitting ratio and add a reflector to one of the beam splitting ends. The core of this method is to allow feedback light of appropriate power (feedback rate -40dB to -10dB) to enter the semiconductor DFB laser and induce coherent collapse, thereby achieving laser spectrum broadening.

[0044] A specific embodiment of the present invention discloses a coherent collapse laser source, including a semiconductor DFB laser 1, a driving and temperature control circuit 2, a polarization maintaining coupler 5, and a reflector; wherein, the polarization maintaining coupler 5 includes a beam-combining end 5a, a first beam-splitting end 5b, and a second beam-splitting end 5c.

[0045] The semiconductor DFB laser 1 is driven by the driving and temperature control circuit 2. The output end of the semiconductor DFB laser 1 is connected to the beam combining end 5a of the polarization-maintaining coupler. The first beam splitting end 5b of the polarization-maintaining coupler is the output of the polarization-maintaining broadband laser source based on coherent collapse. The second beam splitting end 5c of the polarization-maintaining coupler is connected to a reflector, which is connected to the semiconductor DFB laser 1. The reflector is used to allow feedback light with a feedback rate range of -40dB to -10dB to enter the semiconductor DFB laser 1, inducing coherent collapse in the semiconductor DFB laser 1, thereby achieving laser spectrum broadening.

[0046] It should be noted that the background technology uses a coating method on the end face of the optical fiber, while embodiment 2 uses an optical feedback method of optical fiber coupler + mirror; in addition, the laser used in the background technology is a multi-mode laser; the present invention uses a single-mode laser.

[0047] Example 3

[0048] A specific embodiment of the present invention discloses a fiber optic gyroscope, which is driven by a coherent collapse laser source provided in either embodiment 1 or embodiment 2 of the present invention. Specifically, it includes various fiber optic gyroscopes such as an interferometric polarization-maintaining fiber optic gyroscope, an interferometric polarization-degrading fiber optic gyroscope, and a resonant fiber optic gyroscope.

[0049] Compared with existing technologies, the coherent collapse laser source disclosed in this invention adopts a fully polarization-maintaining optical path structure and outputs linearly polarized light. This can greatly reduce the additional losses caused by polarization mismatch when the source is coupled with the gyroscope's Y-waveguide. It can be adapted to interferometric gyroscopes such as interferometric fully polarization-maintaining fiber gyroscopes or interferometric depolarizing fiber gyroscopes and resonant fiber gyroscopes. The coherent collapse laser source has a wide range of applications. Fiber gyroscopes driven by the coherent collapse laser source disclosed in this invention have low cost, good performance, and are easy to miniaturize and commercialize.

[0050] Example 4

[0051] A specific embodiment of the present invention discloses an interferometric fiber optic gyroscope, which is driven by a coherent collapse laser source provided in Embodiment 1 of the present invention, such as... Figure 2 As shown, it includes a semiconductor DFB laser 1, a temperature control and driving circuit 2, a first polarization-maintaining circulator 3, a polarization-maintaining fiber isolator 4, a polarization-maintaining fiber coupler 5, a second polarization-maintaining circulator 6, a Y-waveguide 7, a fiber optic ring 8, and a photodetector 9.

[0052] Example 5

[0053] In one specific embodiment of the present invention, a fiber optic gyroscope is disclosed. This fiber optic gyroscope is driven by the coherent collapse laser source provided in Embodiment 1 of the present invention. The difference from Embodiment 4 is that this fiber optic gyroscope uses a 2×2 coupler instead of the second polarization-maintaining circulator 6.

[0054] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A coherent collapse laser source, characterized in that, The device includes a semiconductor DFB laser (1), a driving and temperature control circuit (2), a first polarization-maintaining circulator (3), a polarization-maintaining fiber isolator (4), and a polarization-maintaining coupler (5); wherein the first polarization-maintaining circulator (3) includes a first port (3a), a second port (3b), and a third port (3c); the polarization-maintaining coupler (5) includes a beam-combining end (5a), a first beam-splitting end (5b), and a second beam-splitting end (5c). The semiconductor DFB laser (1) is driven by the driving and temperature control circuit (2). The output end of the semiconductor DFB laser (1) is connected to the second port (3b) of the first polarization-maintaining circulator. The third port (3c) of the first polarization-maintaining circulator is connected to the input end of the polarization-maintaining fiber isolator (4). The output end of the polarization-maintaining fiber isolator (4) is connected to the beam-combining end (5a) of the polarization-maintaining coupler. The first beam-splitting end (5b) of the polarization-maintaining coupler is the output of the polarization-maintaining broadband laser source based on coherent collapse. The second beam-splitting end (5c) of the polarization-maintaining coupler is connected to the first port (3a) of the first polarization-maintaining circulator.

2. The coherent collapse laser source according to claim 1, characterized in that, The driving current output by the temperature control and driving circuit (2) is greater than the threshold current of the semiconductor DFB laser (1).

3. The coherent collapse laser source according to claim 2, characterized in that, The splitting ratio of the first beam splitter (5b) of the polarization-maintaining coupler is m%, and the splitting ratio of the second beam splitter (5c) of the polarization-maintaining coupler is n%. The splitting ratio m:n of the polarization-maintaining coupler (5) is 90:10 to 98:

2.

4. The coherent collapse laser source according to claim 3, characterized in that, The laser output from the semiconductor DFB laser (1) passes sequentially through the second port (3b) of the first polarization-maintaining circulator, the third port (3c) of the first polarization-maintaining circulator, the polarization-maintaining fiber isolator (4), and the polarization-maintaining coupler (5). It is split into two beams by the polarization-maintaining coupler (5). When the second beam splitting end (5c) of the polarization-maintaining coupler is not connected to the first port (3a) of the first polarization-maintaining circulator, the output of the first beam splitting end (5b) of the polarization-maintaining coupler is the initial laser of the semiconductor DFB laser (1). When the second beam splitting end (5c) of the polarization-maintaining coupler is connected to the first port (3a) of the first polarization-maintaining circulator, the feedback light passes through the first port (3a) of the first polarization-maintaining circulator and is injected into the semiconductor DFB laser (1) through the second port (3b) of the first polarization-maintaining circulator, inducing the semiconductor DFB laser (1) to enter the coherent collapse state and complete the broadening of the intrinsic laser spectrum. At this time, the output of the first beam splitting end (5b) of the polarization-maintaining coupler is the coherent collapse laser.

5. The coherent collapse laser source according to claim 4, characterized in that, The semiconductor DFB laser (1) has no built-in isolator, the output is linearly polarized light, and the output pigtail is a polarization-maintaining fiber.

6. The coherent collapse laser source according to claim 5, characterized in that, The polarization maintaining coupler (5) has a splitting ratio m:n of 93:

7.

7. The coherent collapse laser source according to claim 6, characterized in that, The driving current output by the temperature control and driving circuit (2) is twice the threshold current of the semiconductor DFB laser (1).

8. The coherent collapse laser source according to claim 7, characterized in that, The spectrum of the initial laser has an intrinsic linewidth of 100 kHz to 20 MHz; the spectrum of the coherent collapse laser has a linewidth of 10 GHz to 50 GHz.

9. A fiber optic gyroscope, characterized in that, The fiber optic gyroscope is driven by a coherent collapse laser source as described in any one of claims 1 to 8.

10. A fiber optic gyroscope, characterized in that, The fiber optic gyroscope is an interferometric fiber optic gyroscope, driven by a coherent collapse laser source as described in any one of claims 1 to 8, comprising a semiconductor DFB laser (1), a temperature control and driving circuit (2), a first polarization-maintaining circulator (3), a polarization-maintaining fiber isolator (4), a polarization-maintaining coupler (5), a second polarization-maintaining circulator (6), a Y-waveguide (7), a fiber optic ring (8), and a photodetector (9).

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