Content addressable memory based on phase change material

Abstract

The application belongs to the technical field of optical fiber devices for optical storage, and particularly relates to a content addressable memory based on a phase change material, which comprises a single-wavelength continuous light detection laser module, a wide-spectrum light detection laser module, a pulsed light pumping light source module, an electric pulse generating device, a 2*2 optical fiber coupler input array, a multi-core optical fiber fan-in module, a content addressable memory unit group, a multi-core optical fiber fan-out module, a 2*2 optical fiber coupler output array, a filter group, a photodetector group, a multi-channel detection spectrometer, a 1*n coupler, a photodetector, and a data acquisition module; the output ends of the single-wavelength continuous light detection laser module and the wide-spectrum light detection laser module are connected with the input ends of the 2*2 optical fiber coupler input array. The application can realize an exclusive OR comparison operation in the mode of building a Mach-Zehnder (MZ) interferometer, and provide a new paradigm for high-speed and high-density applications.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber devices for optical storage, and in particular relates to a content addressable memory based on phase change material. Background Art

[0002] Content-addressable memory (CAM) compares an input search word against all rows of stored words in an array in a highly parallel manner. CAM is not only an important component of map-aware applications such as caches, routers, and networks, but also holds great promise in emerging applications such as deep learning and DNA sequence alignment. With the growth of data and mobile connected devices, the demand for high-bandwidth, low-latency, low-power, low-cost, and high-density applications is increasing.

[0003] There are currently some new technologies for designing and implementing CAM. For example, multi-bit CAM based on memristors and FeFETs can increase data density, reduce energy consumption and area; however, due to the limitations of traditional electronic technology, high-speed address lookup remains a challenge. Optical CAM (OE-CAM) based on an integrated silicon photonics platform (Alkabani Y, Miscuglio M, Sorger V J, et al. OE-CAM: ahybrid opto-electronic content addressable memory [J]. IEEE Photonics Journal, 2020, 12 (2): 1-14.) and all-optical CAM (OCAM) based on semiconductor optical amplifiers (Moschos T, Simos S, Vagionas C, et al. An all-optical address look-up table using optical CAM and optical RAM banks [J]. Journal of Lightwave Technology, 2022, 40 (24): 7826-7834.) can be accelerated due to ultrafast transmission of light and are expected to be used in fast routing applications. In addition, CAMs based on phase change materials (PCMs) have also attracted attention. Their integration with silicon photonic components can open up new avenues for light-speed computing and new data center applications (Sevison GA, Farzinazar S, Burrow JA, et al. Phase change dynamics and two-dimensional 4-bit memory in Ge2Sb2Te5 via telecom-band encoding [J]. ACS Photonics, 2020, 7(2): 480-487.). Quashef et al. proposed a CAM architecture based on silicon microring resonators embedded with phase change materials Ge2Sb2Te5 (Quashef MAZ, Alam M K. Ultracompact photonic integrated content addressable memory using phase change materials [J]. Optical and Quantum Electronics, 2022, 54(3): 182.), which can perform high-speed read operations. Summary of the Invention

[0004] The purpose of the present invention is to provide a content-addressable memory based on phase change materials, which can realize XOR comparison operation by building a Mach-Zehnder (MZ) interferometer, providing a new paradigm for high-speed and high-density applications.

[0005] The technical solutions adopted by the present invention are as follows:

[0006] A content-addressable memory based on phase-change materials, comprising a single-wavelength continuous light detection laser module, a broadband light detection laser module, a pulsed light pump light source module, an electric pulse generator, a 2×2 fiber coupler input array, a multi-core fiber fan-in module, a content-addressable memory unit group, a multi-core fiber fan-out module, a 2×2 fiber coupler output array, a filter group, a photodetector group, a multi-channel detection spectrometer, a 1×n coupler, a photodetector, and a data acquisition module;

[0007] The output ends of the single-wavelength continuous light detection laser module and the broadband light detection laser module are connected to the input end of the 2×2 fiber coupler input array, the output end of the electric pulse generating device is connected to the output end of the pulse light pumping light source module, the output end of the pulse light pumping light source module is connected to the input end of the single-wavelength continuous light detection laser module, the single-wavelength continuous light detection laser module passes through the multi-core fiber fan-in module, the output end of the multi-core fiber fan-in module is connected to a content-addressable storage unit group, the output end of the content-addressable storage unit group is connected to the output end of the multi-core fiber fan-out module, and the input end of the multi-core fiber fan-out module is connected to the output end of the 2×2 fiber coupler output array;

[0008] The 2×2 fiber coupler input array, multi-core fiber fan-in module, content addressable storage unit group, and multi-core fiber fan-out module are used for basic functions of addressing comparison by constructing a Mach-Zehnder interferometer.

[0009] The output ends of the filter group, the multi-channel detection spectrometer, and the 1×n coupler are all connected to the input end of the 2×2 fiber coupler output array, the output end of the photodetector group is connected to the input end of the filter group, the input end of the 1×n coupler is connected to the output end of the photodetector, and the photodetector group and the photodetector are connected to a data acquisition module.

[0010] The single-wavelength continuous light detection laser module and the wide-spectrum light detection laser module emit detection light for monitoring the status of the content-addressable storage unit;

[0011] The single-wavelength continuous light detection laser module includes a continuous light source 1 and a continuous light source 2;

[0012] The broadband light detection laser module includes a broadband light source 1 and a broadband light source 2;

[0013] The pulse light pump light source module includes pulse light source 1, pulse light source 2, pulse light source 3, and pulse light source 4;

[0014] The electric pulse generating device includes a trigger module 1 and a trigger module 2.

[0015] The 2×2 fiber coupler input array includes input contact 1, input contact 2, input contact 3, input contact 4, input contact 5 and input contact 6, and the number of 2×2 fiber couplers is 3n.

[0016] The multi-core fiber fan-in module and the multi-core fiber fan-out module have the same structure, and the 2×2 fiber coupler input array and the 2×2 fiber coupler output array have the same structure;

[0017] The 2×2 optical fiber coupler output array includes output contact 1, output contact 2, output contact 3, output contact 4, output contact 5 and output contact 6.

[0018] The filter group includes a filter module 1, a filter module 2, a filter module 3, and a filter module 4, and is used to filter out light pulses.

[0019] The photoelectric detector group includes detection module 1, detection module 2, detection module 3, and detection module 4, and the number of the photoelectric detectors is 2n, which are used to detect the output continuous light energy.

[0020] The content addressable storage unit group includes a multi-core optical fiber and a phase change material film layer, and the phase change material film layer includes an anti-oxidation film.

[0021] The phase change material film layer is made of a ternary compound of Ge, Sb, and Te and has at least two phases, and is used for reversible switching between the two states under the action of light pulses.

[0022] The technical effects achieved by the present invention are:

[0023] A phase-change material-based content-addressable memory (CAM) based on this invention implements XOR comparison operations by building a Mach-Zehnder (MZ) interferometer, offering a new paradigm for high-speed, high-density applications. In optical packet switching networks, CAM processes optical packet address information, eliminating the need for optoelectronic conversion or coupling between optical fibers and waveguides. Information is transmitted and exchanged directly within the optical fiber, improving optical switching efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of an all-optical multi-bit content addressable memory according to an embodiment of the present invention;

[0025] Figure 2 This is a diagram of a one-bit CAM operation result according to an embodiment of the present invention;

[0026] Figure 3 This is a diagram of the three-bit CAM operation result of an embodiment of the present invention.

[0027] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0028] 1. Single-wavelength continuous light detection laser module; 101. Continuous light source 1; 102. Continuous light source 2; 2. Broad-spectrum light detection laser module; 201. Broad-spectrum light source 1; 202. Broad-spectrum light source 2; 3. Pulsed light pump light source module; 301. Pulsed light source 1; 302. Pulsed light source 2; 303. Pulsed light source 3; 304. Pulsed light source 4; 4. Electric pulse generator; 401. Trigger module 1; 402. Trigger module 2; 5. 2×2 fiber coupler input array; 501. Input contact 1; 502. Input contact 2; 503. Input contact 3; 504. Input contact 4; 505. Input contact 5; 506. Input contact 6; 6. Multi-core fiber fan-in module; 7. Content-addressable storage unit group; 7 01. Multi-core optical fiber; 702. Phase change material film layer; 8. Multi-core optical fiber fan-out module; 9. 2×2 optical fiber coupler output array; 901. Output contact one; 902. Output contact two; 903. Output contact three; 904. Output contact four; 905. Output contact five; 906. Output contact six; 10. Filter group; 1001. Filter module one; 1002. Filter module two; 1003. Filter module three; 1004. Filter module four; 11. Photoelectric detector group; 1101. Detection module one; 1102. Detection module two; 1103. Detection module three; 1104. Detection module four; 12. Multi-channel detection spectrometer; 13. 1×n coupler; 14. Photoelectric detector; 15. Data acquisition module. DETAILED DESCRIPTION

[0029] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is described in detail below with reference to the following examples. It should be understood that the following text is only used to describe one or more specific embodiments of the present invention and does not strictly limit the scope of protection of the present invention.

[0030] like Figure 1-Figure 3 As shown, a content-addressable memory based on phase change material includes a single-wavelength continuous light detection laser module 1, a broadband light detection laser module 2, a pulsed light pump light source module 3, an electric pulse generating device 4, a 2×2 fiber coupler input array 5, a multi-core fiber fan-in module 6, a content-addressable storage unit group 7, a multi-core fiber fan-out module 8, a 2×2 fiber coupler output array 9, a filter group 10, a photodetector group 11, a multi-channel detection spectrometer 12, a 1×n coupler 13, a photodetector 14, and a data acquisition module 15;

[0031] The output ends of the single-wavelength continuous light detection laser module 1 and the broadband light detection laser module 2 are connected to the input end of the 2×2 fiber coupler input array 5, the output end of the electric pulse generating device 4 is connected to the output end of the pulse light pumping light source module 3, the output end of the pulse light pumping light source module 3 is connected to the input end of the single-wavelength continuous light detection laser module 1, the single-wavelength continuous light detection laser module 1 passes through the multi-core fiber fan-in module 6, the output end of the multi-core fiber fan-in module 6 is connected to the content-addressable storage unit group 7, the output end of the content-addressable storage unit group 7 is connected to the output end of the multi-core fiber fan-out module 8, and the input end of the multi-core fiber fan-out module 8 is connected to the output end of the 2×2 fiber coupler output array 9;

[0032] The 2×2 fiber coupler input array 5, the multi-core fiber fan-in module 6, the content addressable storage unit group 7, and the multi-core fiber fan-out module 8 are used for the basic function of addressing comparison by constructing a Mach-Zehnder interferometer.

[0033] The output ends of the filter group 10, the multi-channel detection spectrometer 12, and the 1×n coupler 13 are all connected to the input end of the 2×2 fiber coupler output array 9, the output end of the photodetector group 11 is connected to the input end of the filter group 10, the input end of the 1×n coupler 13 is connected to the output end of the photodetector 14, and the photodetector group 11 and the photodetector 14 are connected to the data acquisition module 15.

[0034] The single-wavelength continuous light detection laser module 1 and the wide-spectrum light detection laser module 2 emit detection light for monitoring the status of the content-addressable storage unit;

[0035] The single-wavelength continuous light detection laser module 1 includes a continuous light source 101 and a continuous light source 2 102;

[0036] The broadband light detection laser module 2 includes a broadband light source 1 201 and a broadband light source 2 202;

[0037] The pulse light pump light source module 3 includes pulse light source 1 301 , pulse light source 2 302 , pulse light source 3 303 and pulse light source 4 304 . It has a different wavelength from the single-wavelength continuous light detection laser module 1 and is controlled by the electric pulse generator 4 to emit pulse light.

[0038] The electric pulse generating device 4 includes a trigger module 1 401 and a trigger module 2 402 .

[0039] All light source groups enter the multi-core fiber fan-in module 6 through the 2×2 fiber coupler input array 5. The 2×2 fiber coupler input array 5 includes input contact 1 501, input contact 2 502, input contact 3 503, input contact 4 504, input contact 5 505 and input contact 6 506, and the number of 2×2 fiber couplers is 3n.

[0040] The multi-core fiber fan-in module 6 and the multi-core fiber fan-out module 8 have the same structure, and the 2×2 fiber coupler input array 5 and the 2×2 fiber coupler output array 9 have the same structure;

[0041] The 2×2 fiber coupler output array 9 includes output contact one 901 , output contact two 902 , output contact three 903 , output contact four 904 , output contact five 905 and output contact six 906 .

[0042] The filter group 10 includes filter module 1 1001, filter module 2 1002, filter module 3 1003, and filter module 4 1004, which are used to filter out light pulses to prevent them from affecting the detection results and damaging subsequent detection devices. The number is 2n. The number is 2n.

[0043] The photoelectric detector group 11 includes detection module 1 1101 , detection module 2 1102 , detection module 3 1103 , and detection module 4 1104 , and the number of photoelectric detectors 14 is 2n, which are used to detect the output continuous light energy, convert the optical signal into an electrical signal, and transmit it to the data acquisition module 15 .

[0044] The multi-channel detection spectrometer 12 detects the signal after MZ interference and searches for a suitable working wavelength. The number of channels is n. The 1×n coupler 13 integrates the final signal.

[0045] The content-addressable storage unit group 7 comprises a multi-core optical fiber 701 and a phase-change material film 702, which includes an anti-oxidation film. Light pulses act on the phase-change material through evanescent field coupling. A single content-addressable storage unit group 7 comprises a storage unit and a search unit, each of which comprises two side cores of the multi-core optical fiber 701, the phase-change material film 702, and the anti-oxidation film. A multi-core optical fiber 701 with 2n cores can achieve n-bit content-addressable storage.

[0046] Phase-change material layer 702 is made of a ternary compound of Ge, Sb, and Te, and has at least two phases. It switches reversibly between these two states in response to light pulses, with different phases exhibiting varying optical properties (reflectivity and transmittance). Phase-change material layer 702 and an anti-oxidation film are bonded to the sides of the optical fiber via radio frequency magnetron sputtering. The anti-oxidation film, made of indium tin oxide and silicon dioxide, protects the phase-change material layer from oxidation when exposed to air.

[0047] An interference optical path is constructed outside the seven-core optical fiber through the fan-in and fan-out module of the seven-core optical fiber, where the length difference between the two arms of the interference optical path is about 10 mm, and the free spectral range FSR = 0.166 nm. Figure 2As shown. Initially, the GST states of the storage unit and the search unit are both amorphous, which means that both inputs of the XOR operation are 1 (the transmittance of the amorphous GST is high). When the detection wavelength is 1530.235nm, the total transmission output is -25.9dB, and the output light is extremely weak, so it is determined that the search data matches the stored data (Match). When the search unit is switched to state 0 (GST is crystalline), the optical path difference of the interference arm increases, and the interference spectrum is red-shifted. When the detection wavelength is 1530.235nm, the total transmission output is -17.5dB, and the transmittance increases, which indicates that the search data does not match the stored data (Mismatch). Similarly, when both the storage unit and the search unit are switched to state 0, the optical path difference of the interference arm decreases, and the interference spectrum is blue-shifted. When the detection wavelength is 1530.235nm, the total transmission output is -25.9dB, and the transmittance is extremely low, which indicates that the search data matches the stored data (Match). Taking -20dB as the reference value, a certain tolerance rate is allowed.

[0048] The above shows the results of the XOR comparison of a single CAM. In practical applications, a CAM array is required. When the normalized total output result is in the range of 0-0.25 (close to 0), it indicates that the output data of the 3-bit CAM unit is completely matched (All Match); when the result is in the range of 0.25-0.5, it indicates that 2 bits of data in the 3-bit CAM unit match, with a matching degree of 66.7%; when the result is in the range of 0.5-0.75, it indicates that 1 bit of data in the 3-bit CAM unit matches, with a matching degree of 33.3%; when the result is in the range of 0.75-1 (close to 1), it indicates that the 3-bit CAM data does not match at all (All Mismatch). Figure 3 (ad) show the output status when the information stored in the three CAM cells is "000", "010", "011" and "111", and the search information is "000", "001", "011" and "111". Take the storage of "000" as an example ( Figure 3 (a) When the search information is "000", the stored information is in a complete match with the search information, the output value is the lowest, and the match is 100%; when the search information is "001", 2 bits of data are in a match state, and the match is 66.7%; when the search information is "011", only the data of CAM unit 1 is matched, and the match is 33.3%; when the search data is "111", the data of all CAM units do not match, and the match is 0%.

[0049] In summary, in this embodiment, an all-optical multi-bit content addressable memory based on phase change material and multi-core optical fiber is proposed. The present invention utilizes a combination of chalcogenide phase change material and optical fiber, and has the advantages of low power consumption, non-volatility, simple structure, and easy combination with other optical devices.

[0050] The foregoing is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained herein shall, unless otherwise specified or limited, be implemented in accordance with conventional means in the art.

Claims

1. A content-addressable memory based on phase change material, characterized in that: It includes a single-wavelength continuous light detection laser module (1), a broadband light detection laser module (2), a pulsed light pump light source module (3), an electric pulse generating device (4), a 2×2 fiber coupler input array (5), a multi-core fiber fan-in module (6), a content addressable storage unit group (7), a multi-core fiber fan-out module (8), a 2×2 fiber coupler output array (9), a filter group (10), a photoelectric detector group (11), a multi-channel detection spectrometer (12), a 1×n coupler (13), a photoelectric detector (14), and a data acquisition module (15); The output ends of the single-wavelength continuous light detection laser module (1) and the wide-spectrum light detection laser module (2) are connected to the input end of the 2×2 fiber coupler input array (5); the output end of the electric pulse generating device (4) is connected to the output end of the pulse light pumping light source module (3); the output end of the pulse light pumping light source module (3) is connected to the input end of the single-wavelength continuous light detection laser module (1); the single-wavelength continuous light detection laser module (1) passes through the multi-core fiber fan-in module (6); the output end of the multi-core fiber fan-in module (6) is connected to a content addressable storage unit group (7); the output end of the content addressable storage unit group (7) is connected to the output end of the multi-core fiber fan-out module (8); the input end of the multi-core fiber fan-out module (8) is connected to the output end of the 2×2 fiber coupler output array (9); The 2×2 fiber coupler input array (5), the multi-core fiber fan-in module (6), the content addressable storage unit group (7), and the multi-core fiber fan-out module (8) are used for the basic function of addressing comparison by constructing a Mach-Zehnder interferometer; The output ends of the filter group (10), the multi-channel detection spectrometer (12), and the 1×n coupler (13) are all connected to the input end of the 2×2 fiber coupler output array (9), the output end of the photodetector group (11) is connected to the input end of the filter group (10), the input end of the 1×n coupler (13) is connected to the output end of the photodetector (14), and the photodetector group (11) and the photodetector (14) are connected to the data acquisition module (15); The single-wavelength continuous light detection laser module (1) and the wide-spectrum light detection laser module (2) emit detection light for monitoring the state of the content-addressable storage unit; The single-wavelength continuous light detection laser module (1) comprises a continuous light source 1 (101) and a continuous light source 2 (102); The broadband light detection laser module (2) comprises a broadband light source 1 (201) and a broadband light source 2 (202); The pulse light pump light source module (3) comprises a pulse light source 1 (301), a pulse light source 2 (302), a pulse light source 3 (303), and a pulse light source 4 (304); The electric pulse generating device (4) comprises a trigger module 1 (401) and a trigger module 2 (402); The content addressable storage unit group (7) comprises a multi-core optical fiber (701) and a phase change material film layer (702), wherein the phase change material film layer (702) comprises an anti-oxidation film; The phase change material film layer (702) is made of a ternary compound of Ge, Sb, and Te and has at least two phases, and is used for reversible switching between the two states under the action of light pulses.

2. The content addressable memory based on phase change material according to claim 1, characterized in that: The 2×2 fiber coupler input array (5) includes input contact one (501), input contact two (502), input contact three (503), input contact four (504), input contact five (505) and input contact six (506), and the number of 2×2 fiber couplers is 3n.

3. The content addressable memory based on phase change material according to claim 1, characterized in that: The multi-core fiber fan-in module (6) and the multi-core fiber fan-out module (8) have the same structure, and the 2×2 fiber coupler input array (5) and the 2×2 fiber coupler output array (9) have the same structure; The 2×2 optical fiber coupler output array (9) includes output contact one (901), output contact two (902), output contact three (903), output contact four (904), output contact five (905) and output contact six (906).

4. The content addressable memory based on phase change material according to claim 1, characterized in that: The filter group (10) comprises a filter module 1 (1001), a filter module 2 (1002), a filter module 3 (1003), and a filter module 4 (1004), and is used to filter out light pulses.

5. The content addressable memory based on phase change material according to claim 1, characterized in that: The photoelectric detector group (11) includes a detection module one (1101), a detection module two (1102), a detection module three (1103), and a detection module four (1104), and the number of the photoelectric detectors (14) is 2n, which are used to detect the output continuous light energy.

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