An ASE light source and fiber-optic gyroscope capable of stabilizing average wavelength

Abstract

The application relates to the technical field of navigation instruments, in particular to an ASE light source and a fiber-optic gyroscope capable of stabilizing average wavelength, which adopts a double-path backward light path structure with large power, wide spectral width and relatively stable average wavelength, contains a double-stage erbium-doped fiber structure in the light path, reduces the temperature sensitivity of the average wavelength of the output light of the ASE light source by adjusting the lengths of the two erbium-doped fiber sections, is designed with a long-period fiber grating in the light path, the average wavelength of the reflectivity peak of the long-period fiber grating and the average wavelength of the output light of the ASE light source both increase with the increase of temperature, the average wavelength drift caused by temperature is reduced, is designed with a Lyot depolarizer in the light path, the Lyot depolarizer is arranged behind a pump laser, the influence of the polarization of the output light of the pump laser on the average wavelength of the output light of the ASE light source is reduced, and in addition, is designed with a Faraday rotating mirror, the polarization state of the reflected light of the Faraday rotating mirror is orthogonal to the polarization state of the incident light, the influence of the polarization of the output light of the pump laser on the average wavelength of the output light of the ASE light source is further reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of navigation instruments, in particular to an ASE light source capable of stabilizing average wavelength and a fiber-optic gyroscope. BACKGROUND

[0002] Nowadays, the ASE light source is widely applied in high-precision fiber-optic gyroscopes due to its high output optical power and wide spectral width. In the fiber-optic gyroscope, the stability of the average wavelength of the light source output light greatly affects the important performance index of the gyroscope, i.e. the zero bias stability. Therefore, improving the average wavelength stability of the ASE light source output light is an important demand in the development process of high-precision fiber-optic gyroscope technology. The average wavelength stability of the ASE light source output light is mainly related to temperature, erbium-doped fiber length, pump laser output optical power, wavelength stability and polarization of the pump laser output light, among which the most influential factors are temperature and polarization of the pump source laser output light.

[0003] At present, the average wavelength stability of the laser is improved mainly by optimizing the erbium-doped fiber length and controlling the wavelength stability and power stability of the pump source laser output light. However, only this method cannot effectively reduce the influence of temperature and pump source polarization on the average wavelength of the light source output light. The influence of temperature on the average wavelength is about 1ppm / ℃, and the working temperature interval of a common high-precision gyroscope is generally about 100℃, so the change amount of the average wavelength caused by temperature can reach 100ppm, and the influence of various polarization states of the pump source output light on the average wavelength of the light source output light can also reach 100ppm. Therefore, both of them have a non-negligible influence on the average wavelength stability of the ASE light source output light, which also leads to the reduction of the precision of the fiber-optic gyroscope. SUMMARY

[0004] The problem solved by the present application is to provide an ASE light source capable of stabilizing average wavelength, which can improve the average wavelength stability of the ASE light source output light and thus guarantee the precision of the high-precision fiber-optic gyroscope.

[0005] To achieve the above object, the present application adopts the following technical scheme:

[0006] On the one hand, the present application provides an ASE light source capable of stabilizing average wavelength, which comprises a 980nm LD pump laser, a pump laser driving device, a Lyot depolarizer, a 1x2 polarization-maintaining fiber coupler, a first wavelength division multiplexer, a second wavelength division multiplexer, a first erbium-doped fiber, a second erbium-doped fiber, a Faraday rotator mirror, a long-period fiber grating and an optical isolator.

[0007] The pump laser driver device is connected with an external power source at one end and with the LD pump laser at the other end, for injecting current and controlling temperature of the LD pump laser;

[0008] The LD pump laser is connected with the Lyot depolarizer, the Lyot depolarizer is connected with the 1x2 polarization maintaining fiber coupler, the 1x2 polarization maintaining fiber coupler is connected with the input ends of the first and second wavelength division multiplexers respectively, for the output light of the LD pump laser to pass through the Lyot depolarizer, the output light of the Lyot depolarizer to be randomly and uniformly distributed in all possible polarization states, and the output light of the Lyot depolarizer to pass through the 1x2 fiber coupler again, the 1x2 fiber coupler to split the light at a ratio of 50:50, so as to serve as a light splitting device and to evenly distribute the light power to the input ends of the first and second wavelength division multiplexers;

[0009] The first wavelength division multiplexer is connected with the first erbium-doped fiber and the long-period fiber grating respectively, for the first wavelength division multiplexer to deliver 980nm pump light into the first erbium-doped fiber and to excite signal light with a wavelength of 1550nm, and then to separate and output the backward signal light into the long-period fiber grating;

[0010] The second wavelength division multiplexer is connected with the erbium-doped fiber and the second erbium-doped fiber respectively, and the second erbium-doped fiber is connected with the Faraday rotator mirror, for the second wavelength division multiplexer to deliver 980nm pump light into the second erbium-doped fiber and to excite signal light with a wavelength of 1550nm, and then for the backward signal light to pass through the first and second wavelength division multiplexers and to be output into the long-period fiber grating;

[0011] The long-period fiber grating is connected with the optical isolator, for the modulated transmitted light of the long-period fiber grating to be incident on the optical isolator, and for the output light to be highly polarized linearly polarized light.

[0012] Further, the ASE light source with stable average wavelength described above, the pump laser driver device comprises: a current driving and temperature control module;

[0013] The current driving is used for injecting current into the LD pump laser;

[0014] The temperature control module is used for controlling the temperature of the LD pump laser.

[0015] Further, the ASE light source with stable average wavelength described above further comprises: an indicator light module;

[0016] The indicator light module is used for showing the working state of the ASE light source.

[0017] Further, the ASE light source with stable average wavelength described above further comprises a switch module.

[0018] The switch module is arranged between the pump laser driver and an external power supply.

[0019] In another aspect, the application provides an optical fiber gyroscope comprising the ASE light source with stable average wavelength described above.

[0020] The application has the following advantages:

[0021] The double-pass backward light path structure with large power, wide spectral width and stable average wavelength is adopted, and a two-stage erbium-doped fiber structure with more flexible structure is included in the light path design, so that the temperature sensitivity of the average wavelength of the ASE light source output light can be reduced by adjusting the lengths of the two erbium-doped fibers. A long-period fiber grating is also designed in the light path, and the average wavelength of the reflectivity peak of the long-period fiber grating and the average wavelength of the output light of the ASE light source both increase with the increase of temperature, so that the transmission light signal of the long-period fiber grating is filtered, and the average wavelength drift caused by temperature is reduced.

[0022] A Lyot depolarizer is also designed in the light path and arranged after the pump laser to reduce the influence of the polarization of the output light of the pump laser on the average wavelength of the output light of the ASE light source. In addition, a Faraday rotating mirror is designed, and the polarization state of the reflected light is orthogonal to that of the incident light, so that the influence of the polarization of the output light of the pump laser on the average wavelength of the output light of the ASE light source can be further reduced. In a temperature range of about 100℃ (-45℃-70℃), the average wavelength drift of the conventional ASE light source is in the order of 200ppm, and the ASE light source designed in the application can reduce the average wavelength drift to the order of 20ppm. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0024] Figure 1 is a light path schematic diagram provided by an embodiment of the ASE light source with stable average wavelength of the application;

[0025] Figure 2 is a graph of the average wavelength of a conventional ASE light source changing with temperature provided by an embodiment of the ASE light source with stable average wavelength of the application;

[0026] Figure 3 Figure 2 is a graph showing the average wavelength of the ASE light source provided by an embodiment of the present application as a function of temperature.

[0027] Figure 1 In the figure, 1 is a pump laser driving device, 2 is an LD pump laser, 3 is a Lyot depolarizer, 4 is a 1x2 optical fiber coupler, 5 is a first wavelength division multiplexer, 6 is a first erbium-doped fiber, 7 is a second wavelength division multiplexer, 8 is a second erbium-doped fiber, 9 is a Faraday rotator mirror, 10 is a long period fiber grating, and 11 is an optical isolator. DETAILED DESCRIPTION

[0028] In order to make the objects, technical solutions, and advantages of the present application clearer, the technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0029] Figure 1 Figure 1 is a schematic diagram of an optical path of an ASE light source provided by an embodiment of the present application. Please refer to Figure 1 The embodiment can include:

[0030] an LD pump laser of 980 nm, a pump laser driving device, a Lyot depolarizer, a 1x2 polarization-maintaining optical fiber coupler, a first wavelength division multiplexer, a second wavelength division multiplexer, a first erbium-doped fiber, a second erbium-doped fiber, a Faraday rotator mirror, a long period fiber grating, and an optical isolator;

[0031] One end of the pump laser driving device is connected with an external power supply, and the other end is connected with the LD pump laser, for injecting current and controlling temperature for the LD pump laser;

[0032] The LD pump laser is connected with the Lyot depolarizer, the Lyot depolarizer is connected with the 1x2 polarization-maintaining optical fiber coupler, the 1x2 polarization-maintaining optical fiber coupler is respectively connected with the input ends of the first wavelength division multiplexer and the second wavelength division multiplexer, for the output light of the LD pump laser to pass through the Lyot depolarizer, the output light of the Lyot depolarizer to be randomly and uniformly distributed in all possible polarization states, and the output light of the Lyot depolarizer to pass through the 1x2 optical fiber coupler again, the splitting ratio of the 1x2 optical fiber coupler being 50:50, so as to serve as a light splitting device to average the light power and distribute it to the input ends of the first wavelength division multiplexer and the second wavelength division multiplexer;

[0033] The first wavelength division multiplexer is connected with the first erbium-doped fiber and the long-period fiber grating respectively, and is used for transmitting the 980nm pump light into the first erbium-doped fiber by the first wavelength division multiplexer, exciting the signal light with the wavelength of 1550nm, and separating and outputting the backward signal light into the long-period fiber grating;

[0034] The second wavelength division multiplexer is connected with the erbium-doped fiber and the second erbium-doped fiber respectively, the second erbium-doped fiber is connected with the Faraday rotator mirror, and is used for transmitting the 980nm pump light into the second erbium-doped fiber by the second wavelength division multiplexer, exciting the signal light with the wavelength of 1550nm, and outputting the backward signal light into the long-period fiber grating through the first wavelength division multiplexer and the second wavelength division multiplexer;

[0035] The long-period fiber grating is connected with the optical isolator, and is used for outputting the highly polarized linearly polarized light after the transmission light modulated by the long-period fiber grating is incident to the optical isolator.

[0036] It can be understood that the pump laser driver device is composed of a temperature control system and a constant current system, is connected with the LD pump laser with the output light wavelength of 980nm, and provides the injection current and the temperature control for the LD pump laser. The output light of the LD pump laser passes through a Lyot depolarizer, the output light of the Lyot depolarizer is randomly and uniformly distributed in all possible polarization states, the output light signal of the Lyot depolarizer passes through a 1×2 optical fiber coupler, the 4-splitting ratio of the 1×2 optical fiber coupler is 50:50, and the 1×2 optical fiber coupler is used as a light splitting device to average the light power to two output ends. One output end of the 1×2 optical fiber coupler is connected with the first wavelength division multiplexer, and the other output end is connected with the second wavelength division multiplexer.

[0037] In the two input ports of the first wavelength division multiplexer, the input port connected with the 1×2 optical fiber coupler has the working wavelength of 980±10nm, and the input port connected with the long-period fiber grating 10 has the working wavelength of 1550±30nm. In the two input ports of the second wavelength division multiplexer, the input port connected with the 1×2 optical fiber coupler has the working wavelength of 980±10nm, and the input port connected with the first erbium-doped fiber has the working wavelength of 1550±30nm.

[0038] The first wavelength division multiplexer transmits 980nm pump light into the first erbium-doped fiber and excites signal light with a wavelength of about 1550nm, and then separates the backward signal light and outputs it into the long-period fiber grating. The second wavelength division multiplexer also transmits 980nm pump light into the second erbium-doped fiber and excites signal light with a wavelength of about 1550nm, and then separates the backward signal light and outputs it into the long-period fiber grating 10. The forward signal light excited by the two erbium-doped fibers is reflected by the Faraday rotator mirror, and the polarization state of the reflected signal light is orthogonal. Finally, the signal light is separated by the two wavelength division multiplexers and output into the long-period fiber grating.

[0039] The signal light is transmitted through the long-period fiber grating, which is modulated by the grating transmittance. Since the reflection peak of the long-period fiber grating and the average wavelength of the ASE light source output light both increase with the increase of temperature, the signal light can be temperature-compensated to reduce the temperature sensitivity of the average wavelength of the output light.

[0040] The transmitted light modulated by the long-period fiber grating is incident on the optical isolator, and the output light is highly polarized linearly polarized light, which can meet the high polarization requirement of the full polarization high-precision fiber-optic gyroscope for the light source output light. If it is a mixed polarization or depolarization high-precision fiber-optic gyroscope, a depolarizer can be added after the optical isolator to make the light source a non-polarized or low-polarized light source, so as to reduce the polarization-related error of the gyroscope. The optical isolator 11 also prevents the backward transmission of signal light in the rear-end optical path or the backward transmission of reflected light in the optical path from entering the light source, so as to avoid causing the lasing of the broadband light source.

[0041] Preferably, the pump laser driving device comprises: a current driving and temperature control module;

[0042] The current driving is used for injecting current into the LD pump laser.

[0043] The temperature control module is used for controlling the temperature of the LD pump laser.

[0044] It can be understood that the current driving and temperature control module keep the injection current of the LD pump laser unchanged, so as to stabilize the output optical power of the LD pump laser, thereby reducing the influence of the output optical power of the LD pump laser on the stability of the average wavelength of the ASE light source output light.

[0045] Preferably, it further comprises: an indicator light module;

[0046] The indicator light module is used for displaying the working state of the ASE light source.

[0047] Preferably, it further comprises: a switch module;

[0048] The switch module is arranged between the pump laser driving device and the external power supply.

[0049] In a specific embodiment, the application designs an optical path containing a dual-polarization structure, specifically: the splitting ratio of the 1x2 fiber coupler in the optical path is 50:50, which is used as a power divider, the first output end of which is connected with a first wavelength division multiplexer, the first wavelength division multiplexer is connected with a first section of erbium-doped fiber, the second output end of the 1x2 fiber coupler is connected with a second wavelength division multiplexer at the other end of the first section of erbium-doped fiber, and the second wavelength division multiplexer is connected with a second section of erbium-doped fiber. There are two sections of erbium-doped fiber for spontaneous emission gain, and the fiber lengths at both ends are variable. The lengths of the two sections of fiber are named as L1 and L2, respectively, and in the optical path, there is always a set of (L1, L2) values that can make the temperature sensitivity of the average wavelength of the output light of the ASE light source lowest.

[0050] In a specific embodiment, the embodiment is designed with a long-period fiber grating, the average wavelength of the reflectivity peak of which increases with the increase of temperature. As shown in Figure 2 and Figure 3 , the average wavelength of the output light of the ASE light source also increases with the increase of temperature, so that the transmission light signal of the long-period fiber grating is filtered by the grating and used as temperature compensation, which can reduce the average wavelength drift caused by temperature. In a temperature change of 100℃, the stability of the average wavelength can be improved from the order of 100ppm to about 10ppm or less.

[0051] In a specific embodiment, the application is designed with a Lyot depolarizer between the pump laser and the 1x2 fiber coupler, which is formed by two high-birefringence fibers with a length ratio of 1:2 and is fused at an angle of 45°, which can reduce the average wavelength drift of the output light of the ASE light source caused by the polarization of the output light of the pump laser to less than 10ppm.

[0052] In a specific embodiment, the application is also designed with a Faraday rotating mirror, the polarization state of the reflected light of which is orthogonal to that of the incident light, which can also further reduce the influence of the polarization of the output light of the pump laser on the average wavelength of the output light of the ASE light source.

[0053] The application also provides a fiber-optic gyroscope comprising the ASE light source with stable average wavelength of any one of the above.

[0054] It can be understood that the same or similar parts in the above embodiments can be mutually referred to, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0055] It should be noted that in the description of the application, the terms "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the application, unless otherwise specified, "a plurality of" means at least two.

[0056] Any procedural or methodological descriptions in flow charts or otherwise described herein can be understood to represent modules, segments, or portions of code that include executable instructions for implementing specific logic functions or steps, and the scope of preferred embodiments of the present application includes additional implementations that can not be in the order shown or discussed, including performing functions in a substantially simultaneous manner, or in reverse order according to the functionality involved, as will be understood by those skilled in the art to which embodiments of the present application pertain.

[0057] It should be understood that portions of the present application can be realized with hardware, software, firmware or a combination thereof. In the above embodiments, a plurality of steps or methods can be realized as software or firmware to be executed by a suitable instruction-executing system and stored in a storage. For example, if realized with hardware, and as in another embodiment, any one or a combination of the following technologies known in the art can be used: discrete logic circuitry having logic gates for implementing logic functions on data signals, application specific integrated circuits having appropriate combinational logic gates, programmable gate arrays (PGA), field programmable gate arrays (FPGA), and the like.

[0058] Those skilled in the art can understand that all or part of the steps carried out by the above-mentioned embodiments can be completed by programs instructing relevant hardware, and the programs can be stored in a computer-readable storage medium, and when executed, include one or a combination of steps of the method embodiments.

[0059] In addition, each functional unit in each embodiment of the present application can be integrated in one processing module, or each unit can be physically present separately, or two or more units can be integrated in one module. The above-mentioned integrated module can be realized in the form of hardware or in the form of a software functional module. When the integrated module is realized in the form of a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0060] The above-mentioned storage medium can be a read-only memory, a magnetic disk or an optical disk, etc.

[0061] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0062] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and that variations, modifications, substitutions and changes can be made by those skilled in the art without departing from the scope of the present application.

Claims

1. An ASE light source with a stable average wavelength, characterized in that, It comprises: 980nm LD pump laser, pump laser drive device, Lyot depolarizer, 1x2 polarization maintaining fiber coupler, first wavelength division multiplexer, second wavelength division multiplexer, first erbium-doped fiber, second erbium-doped fiber, Faraday rotator mirror, long period fiber grating and optical isolator; One end of the pump laser drive device is connected with an external power supply, and the other end is connected with the LD pump laser, which is used for injecting current and controlling the temperature of the LD pump laser; The LD pump laser is connected with the Lyot depolarizer, the Lyot depolarizer is connected with the 1x2 polarization maintaining fiber coupler, the 1x2 polarization maintaining fiber coupler is connected with the input end of the first wavelength division multiplexer and the second wavelength division multiplexer respectively, which is used for the output light of the LD pump laser to pass through the Lyot depolarizer, the output light of the Lyot depolarizer will be uniformly distributed in all possible polarization states, and the output light of the Lyot depolarizer passes through the 1x2 polarization maintaining fiber coupler again, the splitting ratio of the 1x2 polarization maintaining fiber coupler is 50:50, which is used as a light splitting device to average the optical power to the input end of the first wavelength division multiplexer and the second wavelength division multiplexer; The first wavelength division multiplexer is connected with the first erbium-doped fiber and the long period fiber grating respectively, which is used for the first wavelength division multiplexer to deliver 980nm pump light to the first erbium-doped fiber, excite signal light with a wavelength of 1550nm, and then separate the backward signal light and output it to the long period fiber grating; The second wavelength division multiplexer is connected with the first erbium-doped fiber and the second erbium-doped fiber respectively, and the second erbium-doped fiber is connected with the Faraday rotator mirror, which is used for the second wavelength division multiplexer to deliver 980nm pump light to the second erbium-doped fiber, excite signal light with a wavelength of 1550nm, and then the backward signal light passes through the first wavelength division multiplexer and the second wavelength division multiplexer and is output to the long period fiber grating; The long period fiber grating is connected with the optical isolator, which is used for the transmission light modulated by the long period fiber grating to be incident on the optical isolator, and the output light is highly polarized linearly polarized light; The temperature sensitivity of the average wavelength of the ASE light source is reduced by adjusting the length of the first erbium-doped fiber and the second erbium-doped fiber.

2. The stable average wavelength ASE light source of claim 1, wherein, The pump laser drive device comprises a current drive and a temperature control module; The current drive is used for injecting current into the LD pump laser; The temperature control module is used for controlling the temperature of the LD pump laser.

3. The stable average wavelength ASE light source of claim 2, wherein, It further comprises: An indicator light module; The indicator light module is used for indicating the working state of the ASE light source.

4. The stable average wavelength ASE light source of claim 3, wherein, It further comprises: A switch module; The switch module is arranged between the pump laser drive device and the external power supply.

5. An optical fiber gyroscope, characterized by The ASE light source with stable average wavelength comprises any one of claims 1-4.

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