Content addressable memory based on phase change material

Abstract

The invention 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. Comprising a single-wavelength continuous light detection laser module, a wide-spectrum light detection laser module, a pulse light pump light source module, an electric pulse generation device, a 2 * 2 optical fiber coupler input array, a multi-core optical fiber fan-in module, a content addressable storage unit group, a multi-core optical fiber fan-out module, a 2 * 2 optical fiber coupler output array, a filter group and a photoelectric detector group, the system comprises a multi-channel detection spectrometer, a 1 * n coupler, a photoelectric detector and a data acquisition module. The output end of the single-wavelength continuous light detection laser module and the output end of the wide-spectrum light detection laser module are connected with the input end of the 2 * 2 optical fiber coupler input array. According to the invention, the XOR comparison operation can be realized by building the Mach-Zehnder (MZ) interferometer, and a new normal form is provided for high-speed and high-density application.

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 the input search word with all rows of the stored word in an array in a highly parallel manner. CAM is not only an important part of mapping-aware applications such as caches, routers, and networks, but also has great prospects in emerging applications such as deep learning and DNA sequence alignment. With the increase in 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 some new technologies to design and implement CAM. For example, multi-bit CAM based on memristors and FeFETs can increase data density, reduce energy consumption and area; but due to the limitations of traditional electronic technology, high-speed address lookup is still challenging. Optical CAM (OE-CAM) (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.) based on integrated silicon photonics platform and all-optical CAM (OCAM) (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.) based on semiconductor optical amplifiers can be accelerated due to ultra-fast transmission of light, and are expected to be used in fast routing applications. In addition, CAM based on phase change materials (PCMs) has also attracted attention. Its 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 reading 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 solution adopted by the present invention is as follows:

[0006] A content-addressable memory based on phase change material, comprising a single-wavelength continuous light detection laser module, a wide-spectrum light detection laser module, a pulse light pump light source module, an electric pulse generating device, a 2×2 fiber coupler input array, a multi-core fiber fan-in module, a content-addressable storage 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 wide-spectrum 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 the basic function 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 photoelectric detector 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 photoelectric detector, and the photoelectric detector group and the photoelectric detector 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 state 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 comprises broadband light source 1 and 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 comprises a trigger module 1 and a trigger module 2.

[0015] The 2×2 fiber coupler input array includes input contact one, input contact two, input contact three, input contact four, input contact five and input contact six, 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 one, output contact two, output contact three, output contact four, output contact five and output contact six.

[0018] The filter group includes filter module 1, filter module 2, filter module 3 and filter module 4, which are 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 reversibly switching between the two states under the action of light pulses.

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

[0023] The present invention provides a content addressable memory based on phase change material, which realizes XOR comparison operation by building a Mach-Zehnder (MZ) interferometer, and provides a new paradigm for high-speed and high-density applications. In an optical packet switching network, CAM processes optical packet address information, and does not require photoelectric conversion / coupling between optical fiber and waveguide. Information is directly transmitted and exchanged in the optical fiber, which can improve the efficiency of optical switching. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 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 1 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 listed 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. Pulse light pump light source module; 301. Pulse light source 1; 302. Pulse light source 2; 303. Pulse light source 3; 304. Pulse light source 4; 4. Electric pulse generating device; 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 specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific embodiments of the present invention, and does not strictly limit the scope of protection of the specific claims 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 wide-spectrum light detection laser module 2, a pulse 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 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, 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 state of the content addressable storage unit;

[0035] The single-wavelength continuous light detection laser module 1 includes a continuous light source 1 101 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 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 ; it has a different wavelength from the single-wavelength continuous light detection laser module 1 , and is controlled by an 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 one 1001, filter module two 1002, filter module three 1003, and filter module four 1004, which are used to filter out light pulses to prevent affecting the detection results and damaging subsequent detection devices. The number is 2n, and the number is 2n.

[0043] The photoelectric detector group 11 includes detection module one 1101, detection module two 1102, detection module three 1103, and detection module four 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, and the number of channels is n; the 1×n coupler 13 integrates the final signal.

[0045] The content addressable storage unit group 7 includes a multi-core optical fiber 701 and a phase change material film layer 702, and the phase change material film layer 702 includes an anti-oxidation film. The light pulse acts on the phase change material by evanescent field coupling; a single content addressable storage unit group 7 includes a storage unit and a search unit, and the storage unit and the search unit include two side cores of the multi-core optical fiber 701, the phase change material film layer 702 and the anti-oxidation film; the multi-core optical fiber 701 with a core number of 2n can realize n-bit content addressable storage.

[0046] 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 to reversibly switch between the two states under the action of light pulses. The optical properties (reflectivity and transmittance) between different phases are different. The phase change material film layer 702 and the anti-oxidation film are combined with the side of the optical fiber by radio frequency magnetron sputtering; the anti-oxidation film is made of indium tin oxide and silicon dioxide to prevent the phase change material film layer from being oxidized 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 amorphous GST has high transmittance). 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 storage 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 storage 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 storage data (Match). Taking -20dB as the reference value, a certain tolerance rate is allowed.

[0048] The above gives the result of XOR comparison of a single CAM. In practical applications, a CAM array is needed. 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, and the matching degree is 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, and the matching degree is 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 completely matching state with the search information, the output value is the lowest, and the matching degree is 100%; when the search information is "001", 2 bits of data are in a matching state, and the matching degree is 66.7%; when the search information is "011", only the data of CAM unit 1 matches, and the matching degree is 33.3%; when the search data is "111", the data of the CAM units do not match, and the matching degree 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 sulfur-based 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 above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A content addressable memory based on phase change material, characterized in that: It comprises a single-wavelength continuous light detection laser module (1), a wide-spectrum light detection laser module (2), a pulse 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 a 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.

2. The content addressable memory based on phase change material according to claim 1, characterized in that: 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 optical fiber coupler output array (9); the output end of the photoelectric detector 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 photoelectric detector (14); and the photoelectric detector group (11) and the photoelectric detector (14) are connected to a data acquisition module (15).

3. The content addressable memory based on phase change material according to claim 1, characterized in that: 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).

4. 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.

5. The content addressable memory based on phase change material according to claim 1, characterized in that: The multi-core optical fiber fan-in module (6) and the multi-core optical fiber fan-out module (8) have the same structure, and the 2×2 optical fiber coupler input array (5) and the 2×2 optical 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).

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

7. The content addressable memory based on phase change material according to claim 1, characterized in that: The photoelectric detector group (11) comprises 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.

8. The content addressable memory based on phase change material according to claim 1, characterized in that: 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.

9. The content addressable memory based on phase change material according to claim 8, characterized in that: 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 reversibly switching between the two states under the action of a light pulse.

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