A single-pumped four-wave mixing light source

Abstract

The application discloses a single-pump four-wave mixing light source, which utilizes a light source spectrum widening technology generated by a third-order nonlinear effect in an optical fiber, and achieves spectrum conversion and light power transfer by injecting high-power pump light into a high-nonlinear optical fiber, so as to realize a wide-spectrum light source and high output power. The spectrum width and the power are related to the pump light source power and the parameters of the nonlinear optical fiber, and the light source power has no upper limit in theory. As a light source, the application can improve the detection precision of a high-precision fiber interferometer.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic gyroscopes and fiber optic interferometers, and particularly relates to a method and application of generating a single-pump four-wave mixing light source, which can be used as a new type of light source in high-precision fiber optic interferometers to further improve the detection accuracy of fiber optic interferometers. Background Technology

[0002] Fiber optic gyroscopes, used as fiber optic interferometers for angular velocity measurement, initially employed helium-neon lasers and semiconductor lasers as their light sources. The application of broadband light sources such as SLD (Silicon-Density Fiber Optic) and erbium-doped fiber optic sources has further improved the angular velocity measurement accuracy of fiber optic gyroscopes. However, in high-precision fiber optic gyroscopes, the relative intensity noise caused by the spectral width of the light source accounts for over 90%. Therefore, further increasing the spectral width of the light source is crucial for reducing relative intensity noise and improving gyroscope accuracy.

[0003] Another method to improve the accuracy of fiber optic gyroscopes is to increase the optical path size; however, as the fiber loop length increases, fiber attenuation leads to insufficient detection power. In the field of precise time measurement worldwide, the highest-precision fiber optic gyroscope reported domestically and internationally currently achieves a zero-bias stability of 10. -6 At the ° / h level, the Earth's rotation angular velocity is measured with high precision to accurately calculate the Earth's rotation period. The fiber optic interferometer in this application can have a fiber optic loop length of up to 20km or more, and the optical power propagation attenuation can reach more than 5dB. Considering that the signal power reaching the detection end is reduced after the attenuation of the entire link, it will directly affect the detection signal-to-noise ratio and thus affect the calculation accuracy of the interferometer. Summary of the Invention

[0004] The technical problem solved by this invention is to address the issues of wide spectrum and high power of light sources in fiber optic interferometers. This invention discloses a method for generating a single-pump four-wave mixing light source and its application, in order to improve the spectral width and output power of light sources used in existing fiber optic interferometers.

[0005] The technical solution of the present invention is: a single-pump four-wave mixing light source module, comprising: a tunable continuous laser, a polarization-maintaining fiber, a fiber amplifier, a polarization-maintaining fiber, a fiber circulator, and a nonlinear fiber;

[0006] The laser light generated by the tunable continuous laser is amplified by a fiber amplifier after passing through a polarization-maintaining fiber. The amplified light then passes through the polarization-maintaining fiber again and is input to the port of a fiber circulator, from which it is output. The optical signal output from the port of the fiber circulator is input to a nonlinear fiber for four-wave mixing. The light output from the nonlinear fiber passes through the port of the fiber circulator and is output to the port of the fiber circulator. The light output from the port passes through the polarization-maintaining fiber again and is input to the port of the fiber circulator, then through the nonlinear fiber connected to the port, and finally output from the port of the fiber circulator. The light output from the port of the fiber circulator is input to the fiber coupling system of an external fiber optic gyroscope or fiber interferometer. After passing through the fiber coupling system, the light enters the fiber loop, generating an interference effect, and is output through the fiber coupling system for signal demodulation processing.

[0007] The tunable continuous laser has an adjustable wavelength with an adjustment accuracy better than 10 pm and an output power better than 10 mW.

[0008] The fiber amplifier has a gain better than 20dB and an output power better than 0.5W.

[0009] The nonlinear optical fiber has a nonlinear coefficient better than 10 / W / km and a zero-dispersion wavelength of 1550nm.

[0010] The dispersion coefficient of the nonlinear optical fiber is between -1 ps / (nm*km)@1550nm and 1 ps / (nm*km)@1550nm, and the dispersion slope is less than 0.05 ps / (nm*km). 2 *km)@1550nm.

[0011] The fiber optic circulator has a damage threshold greater than 2W, an isolation of 30dB, and the output fiber is a single-mode polarization-maintaining fiber.

[0012] A method for generating a single-pump four-wave mixing light source includes:

[0013] Set the gain of the fiber amplifier, adjust the current of the tunable continuous laser to regulate the output wavelength, adjust it to the zero-dispersion wavelength of the nonlinear fiber, and use a spectrometer to observe the spectral shape, flatness and spectral width at the output end. When the spectral shape is relatively flat, stop adjusting the tunable continuous laser.

[0014] Adjust the gain current of the fiber optic amplifier to change the gain of the fiber optic amplifier. Use a power meter to measure the output power at the output end. Once the required power is achieved, stop adjusting any parameters of the system.

[0015] Connect to a fiber optic gyroscope or fiber optic interferometer.

[0016] The present invention has the following advantages:

[0017] (1) In this invention, the spectral width of the light source can reach the order of 100 nm, which is superior to the existing erbium-doped fiber spontaneous emission light source and superluminescent diode technology.

[0018] (2) In this invention, the power of the light source is controllable and can reach the level of 100mW. The power of the light source can be increased by increasing the pump light power. Theoretically, there is no upper limit to the power increase.

[0019] (3) In this invention, the spectral type of the light source can be a flat-top light source with good symmetry, which has certain advantages compared with the Gaussian line type of the erbium-doped fiber spontaneous emission light source and the asymmetric line type of the superluminescent diode.

[0020] (4) In this invention, the spectral type, spectral width and output power of the light source are all controllable parameters, and can be flexibly designed as a customized light source according to the needs, with the advantages of adjustable parameters and reduced redundancy. Attached Figure Description

[0021] Figure 1 This invention relates to a method and application for generating a single-pump four-wave mixing light source.

[0022] Figure 2 This is the gain spectrum of a single-pump four-wave mixing broadband light source in an embodiment of the present invention;

[0023] Figure 3 This is an embodiment of the invention showing the change of gain spectrum of a single-pump four-wave mixing broadband light source with pump light frequency.

[0024] Figure 4 This is an embodiment of the invention showing the change of gain spectrum of a single-pump four-wave mixing broadband light source with pump power.

[0025] Figure 5 This is an embodiment of the invention showing how the gain spectrum of a single-pump four-wave mixing broadband light source varies with the length of a nonlinear optical fiber. Detailed Implementation

[0026] This invention discloses a method for generating a single-pump four-wave mixing light source and its application, which can produce a wide spectrum with high power and a flat and symmetrical spectral shape.

[0027] Reference Figure 1 This invention relates to a method for generating a single-pump four-wave mixing light source and its application.

[0028] In this embodiment, the single-pump four-wave mixing broadband light source system is configured as follows: Figure 1 As shown in A; Figure 1The tunable continuous laser 1 in component A is tunable at a wavelength of 1550 nm, with a preferred tuning accuracy of 1 ppm and an output power better than 10 mW. The laser output from tunable laser 1 is amplified by a polarization-maintaining fiber 2 and then input to a fiber amplifier 3. The fiber amplifier 3 preferably has a gain better than 20 dB and an output power better than 0.5 W. The light output from fiber amplifier 3 passes through port 5a of fiber circulator 5 and exits from port 5b. The optical signal output from port 5b of fiber circulator 5 is then fed into a nonlinear fiber 6. The preferred parameters of the nonlinear fiber are: a nonlinear coefficient better than 10 / W / km, a zero-dispersion wavelength of 1550 nm, a dispersion coefficient preferably between -1 ps / (nm*km)@1550 nm and 1 ps / (nm*km)@1550 nm, and a dispersion slope of less than 0.05 ps / (nm*km). 2 *km)@1550nm; The light output from the nonlinear fiber 6 is output from port 7a to port 7b of the fiber optic circulator 7; The light output from port 7b is input again to port 7c of the fiber optic circulator 7 via the polarization-maintaining fiber 8, and the light is input again to port 5b of the fiber optic circulator 5 via the nonlinear fiber 6 connected to 7a, and output from port 5c of the fiber optic circulator 5.

[0029] Figure 1 In B, by Figure 1 The light output from system port 5c shown in Figure A is input 11 to the fiber optic coupling system 12 of the fiber optic gyroscope or fiber optic interferometer. After passing through the fiber optic coupling system 12, the light enters the fiber optic loop 13 to generate an interference effect. The light is then output through the fiber optic coupling system 12 for signal demodulation processing.

[0030] In this embodiment, the steps of a single-pump four-wave mixing light source generation method are as follows:

[0031] Step S1: Set the gain of fiber amplifier 3 to 25dB and adjust... Figure 1 The current of the tunable continuous laser 1 in A is adjusted to adjust the output wavelength. The adjustment range is around 1550nm, which is near the zero-dispersion wavelength of the nonlinear fiber 6. The spectral shape, flatness and spectral width of the spectrum are observed at the output end using a spectrometer. When the spectral shape is relatively flat, the adjustment of the tunable continuous laser 1 is stopped.

[0032] Step S2: Adjust the gain current of fiber optic amplifier 3 to change the gain of fiber optic amplifier 3. Use a power meter to measure the output power at the output end. Stop adjusting any system parameters after the requirement is met.

[0033] Step S3, will Figure 1 A's system according to Figure 1 Connect the fiber optic gyroscope or fiber optic interferometer using method B.

[0034] Based on the above embodiments, the single-pump four-wave mixing broadband light source generation method and system will be described in detail below with reference to a specific example.

[0035] Figure 2 The image shows the gain spectrum of a single-pump four-wave mixing broadband light source according to an embodiment of the present invention.

[0036] Tunable laser 1, with a set wavelength of 1549.98 nm, has an output power of 0.5 W after amplification by fiber amplifier 3. The nonlinear fiber 6 has a nonlinear coefficient of 10.8 W / km and a dispersion slope of 0.015 ps / (nm). 2 *km)@1550nm, the nonlinear fiber 6 has a length of 300m.

[0037] Figure 3 This illustrates how the gain spectrum of a single-pump four-wave mixing broadband light source varies with the pump light frequency in an embodiment of the present invention.

[0038] The wavelengths of the tunable laser 1 are set to 1540.00nm, 1550.00nm and 1560.00nm respectively, and the output power after amplification by the fiber amplifier 3 is 0.5W.

[0039] The nonlinear coefficient of nonlinear fiber 6 is 10.8 W / km, and the dispersion slope is 0.015 ps / (nm). 2 *km), the nonlinear optical fiber 6 has a length of 300m.

[0040] Figure 3 This indicates that by only changing the wavelength of the pump light tuned laser 1, the gain spectrum shape of the single-pump four-wave mixing broadband light source remains unchanged, the gain remains unchanged, and the spectrum shifts with the wavelength of the tuned laser 1.

[0041] Figure 4 This illustrates how the gain spectrum of a single-pump four-wave mixing broadband light source varies with pump power in an embodiment of the present invention.

[0042] The wavelength of the tunable laser 1 is set to 1549.90nm, and the output power after amplification by the fiber amplifier 3 is set to 0.5W, 1.0W and 1.5W respectively.

[0043] The nonlinear coefficient of nonlinear fiber 6 is 10.8 W / km, and the dispersion slope is 0.015 ps / (nm). 2 *km), the nonlinear optical fiber 6 has a length of 300m.

[0044] Figure 4 This indicates that by only changing the output power of fiber amplifier 3, the gain spectrum of the single-pump four-wave mixing broadband light source increases with the increase of pump power, and the gain spectral width widens with the increase of pump power.

[0045] Figure 5 This paper illustrates how the gain spectrum of a single-pump four-wave mixing broadband light source varies with the length of a nonlinear optical fiber in an embodiment of the present invention.

[0046] The wavelength of the tunable laser 1 is set to 1549.90nm, and the output power after amplification by the fiber amplifier 3 is set to 0.5W.

[0047] The nonlinear coefficient of nonlinear fiber 6 is 10.8 W / km, and the dispersion slope is 0.015 ps / (nm). 2 The lengths of the nonlinear optical fibers 6 are set to 300m, 600m and 900m respectively (*km).

[0048] Figure 5 This indicates that by only changing the length of the nonlinear fiber 6, the gain spectrum of the single-pump four-wave mixing broadband light source increases with the increase of the length of the nonlinear fiber 6, while the gain spectrum width and shape remain unchanged.

[0049] according to Figure 2 , Figure 3 , Figure 4 and Figure 5 The pattern shown allows for adjustment of the output of a single-pump four-wave mixing broadband light source optical system to meet the light source requirements of fiber optic gyroscopes or fiber optic interferometers.

[0050] In summary, this invention presents a single-pump four-wave mixing broadband light source. First, the broadband light source is generated using the four-wave mixing effect of a nonlinear optical fiber, resulting in a flat spectral profile. Second, the power of the single-pump four-wave mixing broadband light source can be controlled by the pump light power and the length of the nonlinear optical fiber, theoretically with no upper limit. Finally, the spectral width of the single-pump four-wave mixing light source can be controlled by the pump light power. These three adjustment methods offer significant advantages over traditional fiber optic interferometer light sources. The application of this single-pump four-wave mixing broadband light source to a fiber optic gyroscope is a first-time proposal and represents an innovative application method.

[0051] The above description is only the best specific embodiment of the present invention, but the protection scope 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 technical scope disclosed in the present invention should be included within the protection scope of the present invention.

[0052] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A single-pumped four-wave mixing light source module, characterized by, It comprises: a tunable continuous laser, a polarization maintaining optical fiber, a fiber amplifier, a fiber circulator and a nonlinear fiber; the laser output by the tunable continuous laser is input to the fiber amplifier for power amplification after passing through the polarization maintaining optical fiber; the amplified light is input to the first port (5a) of the first fiber circulator after passing through the polarization maintaining optical fiber, and is output from the second port (5b) of the first fiber circulator; the light signal output from the second port (5b) of the first fiber circulator is input to the nonlinear fiber for four-wave mixing; the light output from the nonlinear fiber is output to the second port (7b) of the second fiber circulator through the first port (7a) of the second fiber circulator; the light output from the second port (7b) of the second fiber circulator is input to the third port (7c) of the second fiber circulator of the fiber circulator again through the polarization maintaining optical fiber, and is input to the second port (5b) of the first fiber circulator again through the nonlinear fiber connected with the first port (7a) of the second fiber circulator, and is finally output from the third port (5c) of the first fiber circulator; the light output from the third port (5c) of the first fiber circulator of the fiber circulator is input to the fiber coupling system of the external fiber-optic gyroscope or fiber interferometer, the light enters the fiber loop after passing through the fiber coupling system to produce interference effect, and is output through the fiber coupling system for signal demodulation processing.

2. A single pump four wave mixing light source module as claimed in claim 1, wherein, The tunable continuous laser is wavelength tunable.

3. A single pump four wave mixing light source module as claimed in claim 1, wherein, The nonlinear optical fiber has a dispersion coefficient between -1 ps / (nm*km)@1550 nm and 1 ps / (nm*km)@1550 nm and a dispersion slope less than 0.05 ps / (nm 2 *km)@1550 nm.

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