Apparatus for time phase encoding
Through the combination of laser, equal-arm interferometer and unequal-arm interferometer, the light intensity is monitored using a single test port, and the driving amplitude of the phase modulator is only required to modulate, which solves the problems of high complexity and error in the existing technology and achieves high efficiency The time phase encoding improves the accuracy and code formation rate.
Patent Information
- Application Number
- CN202420715359.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-09
- Publication Date
- 2024-12-17
- Estimated Expiration
- 2034-04-09
AI Technical Summary
The existing QKD system based on time phase encoding has high complexity, high control difficulty, low operating efficiency, and is difficult to avoid errors caused by fiber coupling on the test port, and has low accuracy.
Using a combination of laser, equal arm interferometer and unequal arm interferometer, the light intensity of the unequal arm interferometer is monitored through a single test port, and only the driving piezoelectric amplitude of the first phase modulator is required to be modulated, reducing the control complexity. And it is made on lithium niobate film through a hybrid integrated optical waveguide process to achieve efficient time coding.
The control process is simplified, the operation efficiency is improved, the fiber coupling error is avoided, and the code formation and accuracy are improved.
Smart Images
Figure CN222192378U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of quantum communication, and in particular to a device for time phase coding. Background Art
[0002] The Quantum Key Distribution (QKD) system is currently the most widely used quantum secure communication device, which can securely negotiate keys in the presence of eavesdropping to ensure the security of communication. The QKD system encodes based on the quantum state information carried by photons. Among them, the most common encoding methods are phase encoding, polarization encoding, and time phase encoding. The current QKD system based on time phase encoding has the following main defects:
[0003] (1) It is necessary to modulate both the driving voltage amplitude and the driving voltage delay, resulting in high system complexity, great control difficulty and low operating efficiency;
[0004] (2) Two test ports are required to monitor the pulse light intensity output by the long and short arms of the unequal-arm interferometer. It is difficult to avoid the error caused by the optical fiber coupling of the two test ports, and the accuracy is low. Summary of the invention
[0005] The embodiment of the utility model provides a device for time phase encoding, so as to at least partially solve the defects in the prior art.
[0006] In order to achieve the above-mentioned purpose, the device for time phase encoding provided by the embodiment of the utility model adopts the following technical solution:
[0007] The device for time phase encoding provided by the embodiment of the utility model includes:
[0008] The laser has an output end optically connected to an input end of the first equal-arm interferometer, and is used to prepare and output a first pulse light.
[0009] The first equal-arm interferometer includes a first fiber coupler MMI1, a first thermo-optical modulator TOM1, a first phase modulator CDM1 and a second fiber coupler MMI2, wherein the first equal-arm interferometer is used to generate a second pulse light that can be used for time encoding based on the first pulse light, and the second pulse light includes multiple groups of two pulse lights with a first fixed phase difference.
[0010] An unequal-arm interferometer comprises a second equal-arm interferometer, a second phase modulator CDM2 and a third fiber coupler MMI3, wherein the unequal-arm interferometer is used to generate a third pulse light that can be used for phase encoding based on the first pulse light, and the third pulse light signal comprises multiple groups of two continuous pulse lights with a second fixed phase difference.
[0011] The output end of the first equal-arm interferometer is optically connected to the input end of the unequal-arm interferometer.
[0012] In some examples, the first output end of the first fiber coupler MMI1 is optically connected to the input end of the first thermo-optical modulator TOM1, and the second output end of the first fiber coupler MMI1 is optically connected to the input end of the first phase modulator CDM1. The output end of the first thermo-optical modulator TOM1 is optically connected to the first input end of the second fiber coupler MMI2, and the output end of the first phase modulator CDM1 is optically connected to the second input end of the second fiber coupler MMI2.
[0013] In some examples, the first output end of the second fiber coupler MMI2 is optically connected to the long arm of the unequal-arm interferometer, and the first output end of the second fiber coupler MMI2 is optically connected to the input end of the second phase modulator CDM2. The output end of the second phase modulator CDM2 is optically connected to the input end of the second thermo-optic modulator TOM2. The output end of the second thermo-optic modulator TOM2 is optically connected to the first input end of the third fiber coupler MMI3. The long arm of the unequal-arm interferometer is optically connected to the second input end of the third fiber coupler MMI3.
[0014] In some examples, the laser, the first equal-arm interferometer, and the unequal-arm interferometer are fabricated on a lithium niobate film using a hybrid integrated optical waveguide process.
[0015] The device for time phase encoding provided by the embodiment of the utility model has the following beneficial effects:
[0016] (1) By optically connecting the output end of the first equal-arm interferometer with the input end of the unequal-arm interferometer, only the amplitude of the driving piezoelectric of the first phase modulator CDM1 needs to be modulated to obtain the second pulse light that can be used for time encoding. There is no need to modulate the delay of the driving piezoelectric of the first phase modulator CDM1, which reduces the complexity of control and improves the operation efficiency.
[0017] (2) The light intensity of the long arm and the short arm of the unequal-arm interferometer can be detected through one test port to maintain the balance of the light intensity of the two arms of the unequal-arm interferometer. When interference occurs at the receiving end, the interference effect is better, which is beneficial to improving the coding rate. There is no need to use two test ports for detection, which avoids the error caused by optical fiber coupling when using two test ports for detection, thereby improving the accuracy. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0019] Figure 1 A schematic diagram of the composition structure of a device for time phase encoding provided in an embodiment of the utility model. DETAILED DESCRIPTION
[0020] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.
[0021] like Figure 1 As shown, the device for time phase encoding provided by the embodiment of the utility model includes: a laser, an equal-arm interferometer and an unequal-arm interferometer, wherein:
[0022] The laser has an output end optically connected to an input end of the first equal-arm interferometer, and is used to prepare and output a first pulse light.
[0023] Specifically, the laser is a coaxially packaged single-mode DFB laser. This type of laser does not require a built-in semiconductor cooler TEC, and the packaging form and structure are relatively simple, which can further save space and cost and is conducive to integration.
[0024] The first equal-arm interferometer, whose output end is optically connected to the input end of the unequal-arm interferometer, includes a first fiber coupler MMI1, a first thermo-optical modulator TOM1, a first phase modulator CDM1 and a second fiber coupler MMI2, wherein the first equal-arm interferometer is used to generate a second pulse light that can be used for time encoding based on the first pulse light, and the second pulse light includes multiple groups of two pulse lights with a first fixed phase difference.
[0025] In some examples, the first output end of the first fiber coupler MMI1 is optically connected to the input end of the first thermo-optical modulator TOM1, and the second output end of the first fiber coupler MMI1 is optically connected to the input end of the first phase modulator CDM1. The output end of the first thermo-optical modulator TOM1 is optically connected to the first input end of the second fiber coupler MMI2, and the output end of the first phase modulator CDM1 is optically connected to the second input end of the second fiber coupler MMI2.
[0026] Specifically, the first equal-arm interferometer is a Mach-Zehnder interferometer, and the pulse light utilization rate of the interferometer of this type of structure is high. The first phase modulator CDM1 and the first thermo-optical modulator TOM1 are respectively arranged on two different arms of the equal-arm interferometer, the first phase modulator CDM1 is used to adjust the phase of the pulse light input into one arm of the first equal-arm interferometer, and the first thermo-optical modulator TOM1 is used to fine-tune the phase of the pulse light input into the other arm of the equal-arm interferometer to compensate for the phase drift caused by environmental changes, which is conducive to reducing the bit error rate.
[0027] By optically connecting the output end of the first equal-arm interferometer with the input end of the unequal-arm interferometer, it is only necessary to modulate the amplitude of the driving piezoelectric of the first phase modulator CDM1 to obtain a second pulse light that can be used for time encoding. There is no need to modulate the delay of the driving piezoelectric of the first phase modulator CDM1, which reduces the complexity of control and improves operating efficiency.
[0028] Among them, Figure 1 As shown, the phase difference of the pulse light output by the two arms of the first equal-arm interferometer is adjusted to 0 or π through the first phase modulator CDM1. After the first pulse light passes through the first fiber coupler MMI1, the pulse light output by the laser is divided into two pulse lights, and the two pulse lights are respectively input into the upper arm and the lower arm of the equal-arm interferometer. When the phase difference of the pulse light output by the upper arm and the lower arm of the first equal-arm interferometer is 0, due to the characteristics of the second fiber coupler, the pulse light input into the short arm of the unequal-arm interferometer is offset. At this time, the pulse light output by the first equal-arm interferometer is only input into the long arm of the unequal-arm interferometer. Conversely, when the phase difference of the pulse light output by the upper arm and the lower arm of the first equal-arm interferometer is π, the pulse light output by the first equal-arm interferometer is only input into the short arm of the unequal-arm interferometer. Since the pulse light output by the long arm and the short arm of the unequal-arm interferometer has a delay difference, the pulse light output by the first equal-arm interferometer can be used for time encoding. Specifically, the time code of the pulse light input to the long arm of the unequal-arm interferometer is set to Z0, and the time code of the pulse light input to the short arm of the unequal-arm interferometer is set to Z1.
[0029] The unequal-arm interferometer includes a second equal-arm interferometer, a second phase modulator CDM2 and a third fiber coupler MMI3, wherein the unequal-arm interferometer is used to generate a third pulse light that can be used for phase encoding based on the first pulse light, and the third pulse light signal includes multiple groups of two continuous pulse lights with a second fixed phase difference.
[0030] The first output end of the third fiber coupler MMI3 is a test port. The light intensity of the long arm and the short arm of the unequal-arm interferometer can be detected through one test port to maintain the balance of the light intensity of the two arms of the unequal-arm interferometer. When interference occurs at the receiving end, the interference effect is better, which is beneficial to improving the coding rate. There is no need to use two test ports for detection, which avoids the error caused by fiber coupling when using two test ports for detection, and has a higher accuracy rate.
[0031] In some examples, the first output end of the second fiber coupler is optically connected to the long arm of the unequal-arm interferometer, and the first output end of the second fiber coupler is optically connected to the input end of the second phase modulator CDM2. The output end of the second phase modulator CDM2 is optically connected to the input end of the second thermo-optic modulator TOM2. The output end of the second thermo-optic modulator TOM2 is optically connected to the first input end of the third fiber coupler MMI3. The long arm of the unequal-arm interferometer is optically connected to the second input end of the third fiber coupler.
[0032] Specifically, the second equal-arm interferometer and the second phase modulator CDM2 are arranged on the short arm of the unequal-arm interferometer. Among them, a second thermo-optical modulator TOM2 is arranged on one arm of the second equal-arm interferometer. The second thermo-optical modulator TOM2 is used to adjust the arm length difference between the two arms of the unequal-arm interferometer to balance the light intensity of the pulse light output by the two arms of the unequal-arm interferometer. When the phase difference of the pulse light output by the two arms of the first equal-arm interferometer is adjusted to π / 2 by the first phase modulator CDM1, due to the characteristics of the second optical fiber coupler, the pulse light output by the first equal-arm interferometer is simultaneously input into the two arms of the unequal-arm interferometer. By adjusting the voltage across the second phase modulator CDM2, the pulse light output by the two arms of the unequal-arm interferometer has a fixed phase difference. Among them, under the X basis vector, the phase encoding of two consecutive pulse lights with a fixed phase difference of 0 is represented by X0, and the phase encoding of two consecutive pulse lights with a fixed phase difference of π is represented by X1; under the Y basis vector, the phase encoding of two consecutive pulse lights with a fixed phase difference of 0 is represented by Y0, and the phase encoding of two consecutive pulse lights with a fixed phase difference of π is represented by Y1.
[0033] In some examples, the laser, the first equal-arm interferometer, and the unequal-arm interferometer are fabricated on a lithium niobate film using a hybrid integrated optical waveguide process.
[0034] Specifically, in optoelectronic integrated chips, hybrid integrated optical waveguide technology can be used to achieve the integration of multiple modules. Based on lithium niobate film, lasers, first equal-arm interferometers and unequal-arm interferometers are integrated on the same chip, which is conducive to achieving a highly integrated and miniaturized chip structure. Due to the high dielectric constant of lithium niobate film, the transmission loss is small.
[0035] The basic principle of the present invention is described above in conjunction with specific embodiments. However, it should be pointed out that the advantages, strengths, effects, etc. mentioned in the present invention are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present invention. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation. The above details do not limit the present invention to be implemented by adopting the above specific details.
[0036] Each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system embodiment, since it basically corresponds to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.
[0037] The block diagrams of the devices, apparatuses, equipment, and systems disclosed in the present utility model are only illustrative examples and are not intended to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these devices, apparatuses, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", and the like are open words, referring to "including but not limited to", and can be used interchangeably with them. The words "or" and "and" used here refer to the words "and / or" and can be used interchangeably with them, unless the context clearly indicates otherwise. The word "such as" used here refers to the phrase "such as but not limited to", and can be used interchangeably with it.
[0038] The method and apparatus disclosed in the present utility model may be implemented in many ways. For example, the method and apparatus disclosed in the present utility model may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above order of steps for the method is for illustration only, and the steps of the method disclosed in the present utility model are not limited to the order specifically described above, unless otherwise specifically stated. In addition, in some embodiments, the present utility model may also be implemented as a program recorded in a recording medium, which includes machine-readable instructions for implementing the method disclosed in the present utility model. Therefore, the present utility model also covers a recording medium storing a program for executing the method disclosed in the present utility model.
[0039] It should also be noted that in the apparatus, equipment and method disclosed in the present utility model, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be regarded as equivalent schemes disclosed in the present utility model. The above description of the disclosed aspects is provided to enable any technician in the field to make or use the present utility model. Various modifications to these aspects are very obvious to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the present utility model. Therefore, the present utility model is not intended to be limited to the aspects shown here, but to the widest range consistent with the principles and novel features disclosed herein.
[0040] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments disclosed in the utility model to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.
[0041] It is understandable that the related features in the above methods and devices can be referenced to each other. In addition, the "first", "second" and the like in the above embodiments are used to distinguish the embodiments, but do not represent the advantages and disadvantages of the embodiments.
[0042] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.
[0043] It should be noted that the above embodiments do not limit the present invention in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation shall fall within the protection scope of the present invention.
Claims
1. A device for time phase encoding, characterized in that include: A laser, used for preparing and outputting a first pulse light, wherein an output end is optically connected to an input end of a first equal-arm interferometer; The first equal-arm interferometer comprises a first optical fiber coupler MMI1, a first thermo-optical modulator TOM1, a first phase modulator CDM1 and a second optical fiber coupler MMI2; An unequal-arm interferometer, comprising a second equal-arm interferometer, a second phase modulator CDM2 and a third optical fiber coupler MMI3; The output end of the first equal-arm interferometer is optically connected to the input end of the unequal-arm interferometer.
2. The device for time phase encoding according to claim 1, characterized in that: The first output end of the first optical fiber coupler MMI1 is optically connected to the input end of the first thermo-optical modulator TOM1, and the second output end of the first optical fiber coupler MMI1 is optically connected to the input end of the first phase modulator CDM1; The output end of the first thermo-optical modulator TOM1 is optically connected to the first input end of the second optical fiber coupler MMI2, and the output end of the first phase modulator CDM1 is optically connected to the second input end of the second optical fiber coupler MMI2.
3. The device for time phase encoding according to claim 1, characterized in that: The first output end of the second optical fiber coupler MMI2 is optically connected to the long arm of the unequal-arm interferometer, and the first output end of the second optical fiber coupler MMI2 is optically connected to the input end of the second phase modulator CDM2; The output end of the second phase modulator CDM2 is optically connected to the input end of the second thermo-optical modulator TOM2; The output end of the second thermo-optical modulator TOM2 is optically connected to the first input end of the third optical fiber coupler MMI3; the long arm of the unequal-arm interferometer is optically connected to the second input end of the third optical fiber coupler MMI3.
4. The device for time phase encoding according to claim 3, characterized in that: The laser, the first equal-arm interferometer and the unequal-arm interferometer are manufactured on a lithium niobate film by adopting a hybrid integrated optical waveguide process.