High-extinction-ratio fiber acousto-optic modulator and fiber sensing system

Abstract

The utility model discloses a kind of high extinction ratio optical fiber acoustooptic modulator and optical fiber sensing system, the modulator includes base, input end optical fiber collimator, acoustooptic medium, polarized light splitting prism, two output end optical fiber collimator, matching network and radio frequency socket.Acoustooptic medium is bonded with transverse wave transducer on sound passing surface, and it is connected with radio frequency socket by matching network.Working, radio frequency signal drives transducer to excite transverse wave ultrasonic wave in acoustooptic medium, so that incident laser occurs abnormal bragg diffraction.0 order light and 1st order diffraction light after diffraction are respectively coupled to the first output end optical fiber collimator and second output end optical fiber collimator output after being separated by polarized light splitting prism.The structure effectively increases two light beams separation angle, significantly suppresses 0 order light crosstalk, realizes high extinction ratio in single device, with compact structure, low insertion loss, small power consumption advantage.

Description

Technical Field

[0001] This utility model relates to the field of optoelectronic technology, specifically to a high extinction ratio fiber optic acousto-optic modulator and fiber optic sensing system. Background Technology

[0002] Distributed fiber optic sensing systems utilize optical fibers as both the signal transmission medium and sensing unit, enabling continuous sensing of the spatial distribution and changes in external parameters along the fiber over long distances and large areas. Among these, distributed fiber optic sensing systems based on phase-sensitive optical time-domain reflectometers (OTDRs) have become an important branch of distributed fiber optic sensing technology due to their advantages such as wide sensing range, high spatial resolution, compact structure, and rapid response. Currently, this technology is widely used in fields such as power monitoring, perimeter security, oil and gas exploration, and seismic wave detection.

[0003] The fiber optic acousto-optic modulator is the core component of an OTDR, requiring the optical pulses entering the sensing fiber to have a sufficiently high extinction ratio. Otherwise, significant crosstalk will occur between sensing signals, affecting sensing accuracy. Currently, the extinction ratio limit for a single acousto-optic modulator is 60 dB. Typically, two fiber optic acousto-optic modulators are cascaded to improve the extinction ratio; however, this method significantly increases the product size, insertion loss, and power consumption, hindering the development of fiber optic sensing systems towards low power consumption and miniaturization, thus limiting further applications. Utility Model Content

[0004] In view of the above-mentioned shortcomings of the existing technology, the purpose of this utility model is to provide a fiber optic acousto-optic modulator with a high extinction ratio, which solves the problems of large size, complex structure, high insertion loss and high power consumption of the existing acousto-optic modulator.

[0005] Furthermore, an optical fiber sensing system including the aforementioned modulator is provided.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A high extinction ratio fiber optic acousto-optic modulator includes a base and the following components mounted on the base: an input fiber optic collimator, an acousto-optic medium, a polarizing beam splitter, a first output fiber optic collimator, a second output fiber optic collimator, a matching network, and an RF socket disposed on one side of the base. The acousto-optic medium is located in the output optical path of the input fiber collimator, and the relative position of the output angle of the input fiber collimator and the light-transmitting surface of the acousto-optic medium satisfies the anomalous Bragg diffraction condition; a transverse wave transducer is bonded to the acoustic surface of the acousto-optic medium, the transverse wave transducer is electrically connected to the matching network through a wire, and the matching network is electrically connected to the radio frequency socket through a wire. The polarization beam splitter is located in the light output path of the acousto-optic medium and is used to spatially separate the 0th order light and the 1st order diffracted light output after anomalous Bragg diffraction of the acousto-optic medium and couple them to the first output fiber collimator and the second output fiber collimator, respectively.

[0007] Furthermore, the input fiber collimator is used to receive horizontally polarized incident light.

[0008] Furthermore, the 0th-order light maintains a horizontal polarization state and is transmitted by the polarization beam splitter to the first output fiber collimator for output, while the 1st-order diffracted light becomes a vertical polarization state and is reflected by the polarization beam splitter to the second output fiber collimator for output.

[0009] Furthermore, an antireflective film is coated on the light-transmitting surface of the acousto-optic medium.

[0010] Furthermore, the acousto-optic medium is tellurium dioxide crystal.

[0011] An optical fiber sensing system includes the aforementioned acousto-optic modulator.

[0012] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a high extinction ratio fiber optic acousto-optic modulator. By cleverly utilizing the polarization state rotation caused by anomalous Bragg diffraction and combining it with a polarizing beam splitter, a high extinction ratio optical switching function is achieved. Specifically, after a horizontally polarized incident laser undergoes anomalous Bragg diffraction with a transverse wave ultrasonic wave in an acousto-optic medium, its 0th-order light retains its original horizontal polarization state, while the 1st-order diffracted light rotates to a vertical polarization state. The polarizing beam splitter then, based on this orthogonal polarization difference, transmits the 0th-order light (horizontally polarized) to the first output fiber collimator and reflects the 1st-order diffracted light (vertically polarized) to the second output fiber collimator. This design significantly increases the separation angle between the 1st-order and 0th-order light, effectively reducing the probability of the 0th-order light entering the second output fiber collimator, thereby improving the extinction ratio, reducing signal crosstalk of the 0th-order light, and enhancing the accuracy of sensing. Compared to the traditional method of cascading two fiber optic acousto-optic modulators, this invention has a simpler structure, significantly reduced size, insertion loss, and power consumption, and lower cost. At the same time, it can achieve an extinction ratio of up to 80dB, laying a solid foundation for the development of fiber optic sensing systems towards miniaturization and low power consumption. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the high extinction ratio fiber optic acousto-optic modulator of this utility model; Figure 2 This is a schematic diagram of the optical path of the high extinction ratio fiber optic acousto-optic modulator of this utility model.

[0014] In the figure, 1-base, 2-input fiber collimator, 3-acoustic-optic medium, 4-polarizing beam splitter, 5-first output fiber collimator, 6-second output fiber collimator, 7-matching network, 8-RF socket, 9-transverse wave transducer. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings. Example

[0016] like Figure 1 As shown, this utility model provides a high extinction ratio fiber optic acousto-optic modulator, including a base 1, and the following components mounted on the base 1: an input fiber optic collimator 2, an acousto-optic medium 3, a polarizing beam splitter 4, a first output fiber optic collimator 5, a second output fiber optic collimator 6, a matching network 7, and an RF socket 8 disposed on one side of the base 1. The acousto-optic medium 3 is located on the output optical path of the input fiber collimator 2, and the relative position of the output angle of the input fiber collimator 2 and the light-transmitting surface of the acousto-optic medium 3 satisfies the anomalous Bragg diffraction condition; a transverse wave transducer 9 is bonded to the acoustic surface of the acousto-optic medium 3, and the transverse wave transducer 9 is electrically connected to the matching network 7 through a wire, and the matching network 7 is electrically connected to the radio frequency socket 8 through a wire. The polarization beam splitter 4 is located in the light output path of the acousto-optic medium 3, and is used to spatially separate the 0th order light and the 1st order diffracted light output after anomalous Bragg diffraction of the acousto-optic medium 3, and couple them to the first output fiber collimator 5 and the second output fiber collimator 6 respectively.

[0017] In specific implementation, the input fiber collimator 2 is used to receive horizontally polarized incident light. The 0th-order light maintains its horizontal polarization state and is transmitted by the polarizing beam splitter 4 to the first output fiber collimator 5 for output. The 1st-order diffracted light becomes vertically polarized and is reflected by the polarizing beam splitter 4 to the second output fiber collimator 6 for output. Its optical path diagram is as follows: Figure 2 As shown.

[0018] In practice, an antireflection film is coated on the light-transmitting surface of the acousto-optic medium 3. This can significantly reduce insertion loss and improve the overall optical efficiency of the device.

[0019] In a specific implementation, the acousto-optic medium 3 is tellurium dioxide (TeO2) crystal. Tellurium dioxide crystal has an extremely high figure of merit in acousto-optics, enabling it to achieve extremely high diffraction efficiency with extremely low radio frequency drive power, thereby reducing device power consumption and improving device performance.

[0020] Working principle: The radio frequency signal is transmitted to the matching network 7 through the radio frequency socket 8, driving the transducer 9 to excite transverse wave ultrasonic waves in the acousto-optic medium 3, thereby causing anomalous Bragg diffraction of the horizontally polarized incident laser beam calibrated by the input fiber collimator 2. After diffraction, the 0th order light retains its original horizontal polarization state, while the polarization state of the 1st order diffracted light is rotated to vertical polarization. The polarization beam splitter 4 utilizes the orthogonal polarization characteristics to effectively separate the two beams: the 0th order light is transmitted to the first output fiber collimator 5, while the 1st order diffracted light is reflected to the second output fiber collimator 6, thus completing the optical modulation.

[0021] The method for optical modulation using the above-mentioned acousto-optic modulator includes the following steps: (1) The horizontally polarized incident light is coupled into the acousto-optic medium through the input fiber collimator; (2) Transverse wave ultrasound is excited in the acousto-optic medium by transverse wave transducer, causing the incident light to undergo anomalous Bragg diffraction; first-order diffracted light is generated and is vertically polarized light; (3) Use a polarizing beam splitter to separate the 0th order horizontally polarized light from the 1st order diffracted vertically polarized light; and transmit and couple the 0th order horizontally polarized light to the output of the first output fiber collimator, and reflect and couple the 1st order diffracted vertically polarized light to the output of the second output fiber collimator, thus completing the optical modulation.

[0022] In practice, by adjusting the angle of the polarizing beam splitter, the power of the output first-order diffracted vertically polarized light can be maximized.

[0023] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of this utility model that do not depart from the spirit and scope of this technical solution should be covered within the scope of the claims of this utility model.

Claims

1. A high extinction ratio fiber optic acousto-optic modulator, characterized in that, Includes a base, and the following components mounted on the base: an input fiber collimator, an acousto-optic medium, a polarizing beam splitter, a first output fiber collimator, a second output fiber collimator, a matching network, and an RF socket disposed on one side of the base. The acousto-optic medium is located in the output optical path of the input fiber collimator, and the relative position of the output angle of the input fiber collimator and the light-transmitting surface of the acousto-optic medium satisfies the anomalous Bragg diffraction condition; a transverse wave transducer is bonded to the acoustic surface of the acousto-optic medium, the transverse wave transducer is electrically connected to the matching network through a wire, and the matching network is electrically connected to the radio frequency socket through a wire. The polarization beam splitter is located in the light output path of the acousto-optic medium and is used to spatially separate the 0th order light and the 1st order diffracted light output after anomalous Bragg diffraction of the acousto-optic medium and couple them to the first output fiber collimator and the second output fiber collimator, respectively.

2. The high extinction ratio fiber optic acousto-optic modulator according to claim 1, characterized in that, The input fiber collimator is used to receive horizontally polarized incident light.

3. The high extinction ratio fiber optic acousto-optic modulator according to claim 2, characterized in that, The 0th-order light remains horizontally polarized and is transmitted by the polarizing beam splitter to the first output fiber collimator. The 1st-order diffracted light becomes vertically polarized and is reflected by the polarizing beam splitter to the second output fiber collimator.

4. The high extinction ratio fiber optic acousto-optic modulator according to claim 1, characterized in that, An antireflective film is coated on the light-transmitting surface of the acousto-optic medium.

5. The high extinction ratio fiber optic acousto-optic modulator according to claim 1, characterized in that, The acousto-optic medium is tellurium dioxide crystal.

6. A fiber optic sensing system, characterized in that, Includes the acousto-optic modulator described in any one of claims 1 to 5.

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