A device for reducing spontaneous emission of light at the same wavelength as a signal

Abstract

The utility model relates to the technical field of optical fiber laser, concretely is a kind of device for reducing with signal same wavelength spontaneous emission light, including first collimator, polarized light prism, optical rotatory component, attenuation component and reflector being sequentially arranged along light path, and second collimator opposite with polarized light prism side face.The device for reducing with signal same wavelength spontaneous emission light, by the structure and parameter of each component of reasonable setting, utilize polarization characteristics and the mode of multiple attenuation, can effectively reduce with signal same wavelength spontaneous emission light, application test in laser radar scene shows that when not using the device, radar test signal-to-noise ratio is-3dB, signal is submerged in noise, cannot measure useful signal;After using the device, after spontaneous emission light attenuation, radar test signal-to-noise ratio reaches 18dB, has obvious improvement, significantly improves system performance, ensures the normal work of system under weak signal light scene.

Description

Technical Field

[0001] This utility model relates to the field of fiber laser technology, specifically to a device for reducing spontaneous emission light of the same wavelength as the signal. Background Technology

[0002] Fiber optic amplifiers are widely used in fiber lasers and communications. In fiber lasers, they amplify optical power to increase output power. In communications, optical fiber amplifiers (EDFAs) amplify optical signals in transmission links to extend transmission distances. The core working principle of fiber optic amplifiers is to amplify signal light using stimulated emission of rare-earth elements, such as erbium-doped or ytterbium-doped fibers. However, spontaneous emission inevitably occurs during stimulated emission. Suppressing spontaneous emission is a key technology for improving the signal-to-noise ratio of optical communication and laser systems. Common solutions suppress spontaneous emission in three ways: reducing the source of spontaneous emission, limiting the amplification process, and directly attenuating spontaneous emission. The source of spontaneous emission light mainly depends on the parameter design and length optimization of the doped fiber. The main solution to limit the amplification of spontaneous emission light is to insert filters between amplifier stages, attenuating the spontaneous emission light after each amplification stage to prevent it from being amplified in subsequent stages. The main solution for attenuating spontaneous emission light is to use filters to filter out light other than the signal light. The above solutions can effectively suppress most spontaneous emission light, but they cannot filter out spontaneous emission light with the same wavelength as the signal light. Spontaneous emission light with the same wavelength as the signal light is very weak and has little impact in ordinary application scenarios. However, in special application scenarios such as lidar, the signal light is extremely weak and submerged in noise. At this time, the impact of spontaneous emission light is very obvious, and in severe cases, it can directly render the system unusable. Utility Model Content

[0003] To achieve the above objectives, the present invention provides the following technical solution: a device for reducing spontaneous emission light of the same wavelength as a signal, comprising a first collimator, a polarizing beam splitter, a light-rotating component, an attenuation component, and a reflector arranged sequentially along the optical path, and a second collimator opposite to the side of the polarizing beam splitter; the attenuation component is composed of N polarizers stacked together, and the transmission axis of each polarizer is aligned.

[0004] Furthermore, the output optical axis of the first collimator is aligned with the input optical axis of the polarizing beam splitter. The polarizing beam splitter is used to transmit the horizontal polarization component in the incident light along the straight-through direction to the optical rotation component, and to reflect the vertical polarization component coming from the direction of the optical rotation component (103) along the vertical direction to the second collimator.

[0005] Furthermore, the optical rotation component includes a magnetic element and an optical rotation crystal, with the magnetic element surrounding the outside of the optical rotation crystal.

[0006] Furthermore, the optical rotation angle of the optical rotation component is 45°.

[0007] Furthermore, the polarizer in the attenuation component is placed at a 45° angle to the optical axis.

[0008] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0009] This device for reducing spontaneous emission light of the same wavelength as the signal effectively reduces spontaneous emission light of the same wavelength by rationally setting the structure and parameters of each component and utilizing polarization characteristics and multiple attenuation methods. Application tests in lidar scenarios show that without this device, the radar test signal-to-noise ratio is -3dB, and the signal is submerged in noise, making it impossible to measure the useful signal. After using this device to attenuate the spontaneous emission light, the radar test signal-to-noise ratio reaches 18dB, showing a significant improvement and significantly enhancing system performance, ensuring the normal operation of the system in scenarios with weak signal light. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of this utility model;

[0011] Figure 2 This is a schematic diagram of the optical path of a lidar.

[0012] In the figure: 101, first collimator; 102, polarizing beam splitter; 103, optical rotation component; 104, attenuation component; 105, mirror; 106, second collimator. Detailed Implementation

[0013] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0014] Please see Figure 1-2 This embodiment of a device for reducing spontaneous emission light of the same wavelength as a signal includes a first collimator 101, a polarizing beam splitter 102, an optical rotation component 103, an attenuation component 104 and a reflector 105 arranged sequentially along the optical path, and a second collimator 106 opposite to the side of the polarizing beam splitter 102. The attenuation component 104 is composed of N polarizers stacked together, and the transmission axis of each polarizer is in the same direction.

[0015] The first collimator 101 outputs horizontally polarized light, which passes directly through the polarizing beam splitter 102 and then enters the optical rotation component 103.

[0016] The optical rotation component 103 includes a magnetic element and a built-in optical rotation crystal. The magnetic element generates positive and negative magnetic fields according to the direction of the magnetic poles to control the optical rotation direction of the magneto-optical crystal to be clockwise or counterclockwise, and its optical rotation angle is 45°.

[0017] After horizontally polarized light enters the optical rotator 103, its polarization direction is rotated by 45°, and then it enters the attenuation component 104.

[0018] The optical axes of the N polarizers of the attenuation component 104 are all placed at 45°, which is the same as the polarization direction of the linearly polarized light output by the optical rotation component 103. Since the spontaneous emission light is unpolarized light, its power is attenuated by 50% after passing through each polarizer, while the signal light is linearly polarized light and passes through the polarizer with almost no attenuation.

[0019] The 45° polarized light output from the attenuation component 104 is reflected by the reflector 105 and then passes through the attenuation component 104 again, where the spontaneous emission light is attenuated once more before entering the optical rotator 103. At this point, the polarization direction of the light is rotated again by 45° within the optical rotator 103, becoming vertically polarized light. This vertically polarized light enters the polarizing beam splitter 102, is refracted 90°, passes through the side, and finally enters the second collimator 106 for output.

[0020] The attenuation coefficient of this device for spontaneously emitted light is: Where N is the number of polarizers in the attenuation component 104. Since the light signal passes through the attenuation component 104 twice, it is attenuated 2N times. The polarizing beam splitter 102 has the same attenuation effect on spontaneous emission light. The light signal passes through twice, so the total number of attenuations is 2N+2.

[0021] like Figure 2 As shown, in the constructed lidar optical path, the seed source wavelength is selected as 1535nm, which is the spontaneous emission peak of the gain fiber, where the spontaneous emission light power is the highest. This device is connected between the fiber amplifier and the circulator to attenuate the spontaneous emission light. Without this device, the radar test signal-to-noise ratio is -3dB, and the signal is submerged in noise, making it impossible to measure the useful signal. After using this device, the radar test signal-to-noise ratio reaches 18dB, showing significant improvement.

[0022] The working principle of the above embodiments is as follows:

[0023] The first collimator outputs horizontally polarized signal light, which can pass directly through the polarizing beam splitter. After entering the optical rotator, the horizontally polarized light is rotated 45° by the magnetic field generated by its magnetic element and the built-in optical rotator crystal. Finally, the light is output as 45° polarized light to the attenuation component. The attenuation component consists of N polarizers with the optical axis of the polarizers at 45°, which is consistent with the polarization direction of the linearly polarized light output by the optical rotator. Therefore, the linearly polarized light can pass through the attenuation component with almost no attenuation. The spontaneous emission light is attenuated by 50% for each polarizer it passes through. After passing through N polarizers, the first attenuation is completed. The 45° polarized light output by the attenuation component is reflected by a mirror and passes through the attenuation component again. The spontaneous emission light passes through N polarizers again, completing the second attenuation. After passing through a total of 2N polarizers, the light that passes through the attenuation component again enters the optical rotator. The polarization direction is rotated 45° again, changing from 45° polarized light to vertically polarized light. After entering the polarizing beam splitter, the vertically polarized light is refracted 90° and output from the side, finally entering the second collimator to complete the signal light output.

[0024] The entire workflow is now complete, and anything not described in detail in this specification is existing technology known to those skilled in the art.

[0025] It should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0026] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device for reducing spontaneous emission light of the same wavelength as a signal, characterized in that: It includes a first collimator (101), a polarizing beam splitter (102), an optical rotation component (103), an attenuation component (104), and a reflector (105) arranged sequentially along the optical path, as well as a second collimator (106) opposite to the side of the polarizing beam splitter (102); The attenuation component (104) is composed of N polarizers stacked together, with the transmission axis of each polarizer in the same direction.

2. A device for reducing spontaneous emission light of the same wavelength as a signal according to claim 1, characterized by: The output optical axis of the first collimator (101) is aligned with the input optical axis of the polarizing beam splitter (102). The polarizing beam splitter (102) is used to transmit the horizontal polarization component in the incident light along the straight-through direction to the optical rotation component (103), and to reflect the vertical polarization component coming from the direction of the optical rotation component (103) along the vertical direction to the second collimator (106).

3. The apparatus of claim 1, wherein: the signal is a light signal; and the device is configured to reduce spontaneous emission of light at the same wavelength as the light signal. The optical rotation component (103) includes a magnetic element and an optical rotation crystal, the magnetic element being surrounded on the outside of the optical rotation crystal.

4. A device for reducing spontaneous emission light of the same wavelength as a signal according to claim 3, characterized by: The optical rotation angle of the optical rotation component (103) is 45°.

5. The apparatus of claim 1, wherein: the signal is a light signal; and the device is configured to reduce spontaneous emission of light at the same wavelength as the light signal. The polarizer in the attenuation component (104) is placed at 45° along its optical axis.

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