Temperature-insensitive silicon-based hybrid fully-integrated active optical frequency laser regeneration relay chip, optical frequency transmission system and method

Abstract

The invention discloses a temperature-insensitive silicon-based hybrid integrated active optical frequency laser regeneration relay chip, which is suitable for a photon integrated optical frequency cascade transmission system. The chip can carry out on-chip regeneration amplification on a received previous-stage optical signal, and outputs an optical frequency signal with a stable phase to a next stage. According to the invention, the low-loss passive silicon-based waveguide is extremely low, and strict length matching is carried out on the out-of-band waveguide path in the chip, so that out-of-band phase noise caused by temperature change can be effectively inhibited, and the environmental adaptability of the chip is improved. Meanwhile, by means of advanced processes such as micro transfer printing, heterogeneous hybrid integration is carried out on a high-efficiency on-chip frequency shifter and a polarization controller which are realized on the basis of high-electro-optical coefficient materials such as thin-film lithium niobate, so that the on-chip optical frequency laser regeneration relay chip with complete functions is constructed. The chip has the advantages of being compact in structure, low in power consumption, high in environmental adaptability and the like, and is suitable for construction of a next-generation miniaturized optical frequency transfer network.

Description

Technical Field

[0001] This invention relates to the fields of photonic integration technology and optical frequency transfer technology, and particularly to a temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration relay chip, optical frequency transfer system, and method. Background Technology

[0002] Constructing ultra-long-distance ground-based optical frequency networks is of great significance, as it will drive the evolution of time-frequency synchronization systems from traditional microwave atomic clocks to high-precision optical clocks, thereby expanding their application potential in fields such as crustal movement monitoring, tidal effect research, and gravitational wave detection. To extend the optical frequency transmission distance and improve the system's adaptability to high-noise links, a cascaded transmission architecture based on laser regeneration relays has emerged. In traditional laser regeneration relay interferometers, temperature changes introduce out-of-band phase noise in the non-common-mode path. This noise is linearly correlated with temperature changes and accumulates with the increase in the number of cascaded segments, severely degrading the long-term stability of the system. Although online out-of-band phase noise detection and compensation can be used to suppress it, this further increases system power consumption and complexity. See […]. Qiu Z, Zhou Z, Hu L, et al. Temperature-induced noise-insensitive laser repeater station for optical frequency transfer[J]. IEEE Transactions on Instrumentation and Measurement, 2025.] The photonic integration technology developed in recent years has provided an ideal solution to the above problems. By integrating micrometer-scale interferometer structures onto waveguides, not only can intrinsic delay errors be significantly reduced, but more importantly, the on-chip waveguide path can easily achieve precise out-of-band length matching, which is beneficial for building temperature-insensitive system designs. However, the photonic integrated optical frequency transfer laser regeneration repeaters reported so far have only achieved the integration of passive silicon dioxide waveguides; key active devices (such as lasers, frequency shifters, and polarization controllers) have not yet been miniaturized. See [ Akatsuka T, Goh T, Imai H, et al. Optical frequency distribution using laser repeater stations with planar lightwave circuits[J]. Optics express, 2020, 28(7): 9186-9197. Based on high-performance material platforms such as thin-film lithium niobate, and leveraging their excellent electro-optic effects, high-efficiency on-chip key active devices can be realized. See [ Lin Z, Lin Y, Li H, et al. High-performance polarization management devices based on thin-film lithium niobate[J]. Light: Science&Applications, 2022, 11(1): 93. Therefore, hybrid heterogeneous integration of silicon-based waveguides with functional platforms such as thin-film lithium niobate is the core technological approach to realizing a fully functional, integrated optical frequency transmission photonic integrated chip. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing optical frequency laser regeneration repeater systems, such as large size, high environmental sensitivity, and low integration of key active components, and to provide a temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration repeater chip architecture and design method. This scheme structurally suppresses on-chip out-of-band phase noise introduced by temperature variations by strictly matching the length of the out-of-band waveguide path in the silicon-based passive interferometer. Simultaneously, based on advanced hybrid integration processes such as micro-transfer printing, a frequency shifter and polarization controller implemented on a thin-film lithium niobate platform are heterogeneously integrated with the silicon-based interferometer, thereby constructing an integrated, full-function on-chip laser regeneration repeater chip for cascaded optical frequency transmission.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: A temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration repeater chip is characterized in that it includes: a silicon-based passive waveguide layer and a thin-film lithium niobate active waveguide layer stacked together, wherein the silicon-based passive waveguide layer and the thin-film lithium niobate active waveguide layer achieve optical signal coupling through multiple vertically arranged interlayer couplers; The silicon-based passive waveguide layer integrates a first distributed feedback laser gain chip, a first self-injection locked external cavity, a first directional coupler, a second directional coupler, a third directional coupler, a fourth directional coupler, a first end-face coupler, a second end-face coupler, a fifth directional coupler, a first multimode interferometer, a third end-face coupler, a sixth directional coupler, a seventh directional coupler, a second multimode interferometer, a fourth end-face coupler, a third multimode interferometer, a fourth multimode interferometer, a fifth multimode interferometer, a fifth end-face coupler, a sixth end-face coupler, a sixth multimode interferometer, a seventh multimode interferometer, an eighth multimode interferometer, a seventh end-face coupler, and an eighth end-face coupler. The thin-film lithium niobate active waveguide layer integrates a first frequency shifter, a second frequency shifter, a first polarization controller, and a third frequency shifter; The laser output port of the first distributed feedback laser gain chip is optically connected to the input port of the first self-injected locked external cavity. The output port of the first self-injected locked external cavity is optically connected to the first port of the first frequency shifter through the first interlayer coupler. The second port of the first frequency shifter is optically connected to the combining port of the first directional coupler through the second interlayer coupler. The first branch port of the first directional coupler is optically connected to the combining port of the second directional coupler, and the second branch port of the first directional coupler is optically connected to the combining port of the sixth directional coupler. The first branch port of the second directional coupler is optically connected to the combining port of the third directional coupler, and the second branch port of the second directional coupler is connected to the combining port of the third multimode interferometer. The first and second branch ports of the third multimode interferometer are respectively connected to the second branch port of the fifth multimode interferometer and the first branch port of the fourth multimode interferometer; The combining port of the fifth multimode interferometer is connected to the output port of the fifth end-face coupler, and the first splitting port of the fifth multimode interferometer is connected to the second splitting port of the fourth multimode interferometer; the input port of the fifth end-face coupler is connected to an external photodetector for bidirectional optical frequency comparison beat frequency testing; the combining port of the fourth multimode interferometer is connected to the output port of the sixth end-face coupler, and the input port of the sixth end-face coupler is connected to an external short optical fiber or an external frequency shifter for bidirectional optical frequency comparison testing. The first branch port of the third fixed coupler is connected to the second branch port of the second multimode interferometer, and the second branch port of the third fixed coupler is connected to the first branch port of the fourth directional coupler. The combining port of the fourth directional coupler is connected to the first port of the second frequency shifter via the third interlayer coupler, and the second port of the second frequency shifter is connected to the output port of the first end-face coupler via the fourth interlayer coupler; the second splitting port of the fourth directional coupler is connected to the first splitting port of the second multimode interferometer; the input port of the first end-face coupler is connected to an external transmission link for sending optical frequency signals to the next-level link; the combining port of the second multimode interferometer is connected to the output port of the fourth end-face coupler, and the input port of the fourth end-face coupler is connected to an external photodetector for next-level link locking. The first branch port of the sixth directional coupler is connected to the combining port of the sixth multimode interferometer, and the second branch port of the sixth directional coupler is connected to the combining port of the seventh directional coupler. The first and second branch ports of the sixth multimode interferometer are respectively connected to the second branch port of the seventh multimode interferometer and the first branch port of the eighth multimode interferometer. The first branch port and the combining port of the seventh multimode interferometer are respectively connected to the second branch port of the eighth multimode interferometer and the output port of the seventh end-face coupler. The input port of the seventh end-face coupler is connected to an external short optical fiber or an external frequency shifter for bidirectional optical frequency comparison testing. The combining port of the eighth multimode interferometer is connected to the output port of the eighth end-face coupler. The input port of the eighth end-face coupler is connected to an external photodetector for bidirectional optical frequency comparison beat frequency testing. The first branch port and the second branch port of the seventh directional coupler are respectively connected to the first branch port of the fifth directional coupler and the second branch port of the first multimode interferometer. The first branch port and the combining port of the first multimode interferometer are respectively connected to the second branch port of the fifth directional coupler and the output port of the third end face coupler. The input port of the third end face coupler is connected to an external photodetector to achieve on-chip regenerated laser locking. The combining end of the fifth directional coupler is connected to the first port of the third frequency shifter through the sixth inter-layer coupler. The second port of the third frequency shifter is connected to the first port of the first polarization controller. The second port of the first polarization controller is connected to the output port of the second end-face coupler through the fifth inter-layer coupler. The input port of the second end-face coupler is connected to an external transmission link for receiving the optical frequency signal transmitted from the previous stage.

[0005] The silicon-based passive waveguide layer is based on any one of silicon-on-insulator, silicon nitride, or silicon dioxide platforms; the thin-film lithium niobate active waveguide layer is based on a lithium niobate-on-insulator platform; the silicon-based passive waveguide layer and the thin-film lithium niobate active waveguide layer are heterogeneously integrated through a micro-transfer printing process.

[0006] Multiple specific waveguide paths in the silicon-based passive waveguide layer satisfy a preset length matching relationship to suppress non-common-mode phase noise caused by temperature changes; the length matching relationship includes: The waveguide length between the seventh directional coupler and the first multimode interferometer is equal to the sum of the waveguide lengths between the fifth directional coupler and the first multimode interferometer, and the waveguide lengths between the seventh directional coupler and the fifth directional coupler; the waveguide length between the third directional coupler and the second multimode interferometer is equal to the sum of the waveguide lengths between the fourth directional coupler and the second multimode interferometer, and the waveguide lengths between the third directional coupler and the fourth directional coupler; the waveguide length between the second directional coupler and the fourth directional coupler is equal to the waveguide length between the second directional coupler and the third multimode interferometer; The waveguide length between the fourth and fifth multimode interferometers is equal to the sum of the waveguide lengths between the third and fifth multimode interferometers and between the third and fourth multimode interferometers; the waveguide length between the sixth directional coupler and the sixth multimode interferometer is equal to the waveguide length between the sixth and fifth directional couplers; the waveguide length between the seventh and eighth multimode interferometers is equal to the sum of the waveguide lengths between the sixth and seventh multimode interferometers and between the sixth and eighth multimode interferometers.

[0007] The first, second, and third frequency shifters are electro-optic phase modulators based on thin-film lithium niobate waveguides and traveling-wave electrodes; the first polarization controller is an electro-optic polarization controller based on thin-film lithium niobate waveguides and a multi-electrode structure.

[0008] The first distributed feedback laser gain chip is externally bonded to a first self-injected locked external cavity on a silicon-based platform on the silicon-based passive waveguide layer via flip-chip bonding to generate an on-chip narrow linewidth laser signal, which can serve as an on-chip regenerated laser.

[0009] The working principle of this invention is as follows: The signal is coupled to the upper thin-film lithium niobate waveguide via the first interlayer coupler, then frequency-shifted by the first frequency shifter and coupled back to the silicon-based waveguide via the second interlayer coupler. The first frequency shifter is used for phase locking of the regenerated laser. After the frequency-shifted signal is split by the first directional coupler, a small portion serves as the return signal for locking in the next-level link. This portion is first split by the sixth directional coupler, and a small portion is used for bidirectional optical frequency comparison testing, entering the bidirectional comparison test structure composed of the sixth, seventh, and eighth multimode interferometers. The majority of the light enters the seventh directional coupler, with a portion serving as the reference signal light for the regenerated laser, and the other portion sequentially passing through the fifth directional coupler, the sixth interlayer coupler, the third frequency shifter, the first polarization controller, the fifth interlayer coupler, and the second end-face coupler before being coupled back to the next-level link. The optical signal transmitted from the previous stage sequentially passes through the second end-face coupler, the fifth inter-layer coupler, the first polarization controller, the third frequency shifter, the sixth inter-layer coupler, and the fifth directional coupler before being coupled to the first multimode interferometer. It is then coupled to an external photodetector via the third end-face coupler. The result, after phase discrimination with the reference signal of the locally regenerated laser, is used to lock the wavelength of the narrow-linewidth laser, which is composed of the first distributed feedback laser gain chip and the first self-injected locked external cavity, through a phase-locked loop and other methods. Simultaneously, the first frequency shifter is used to achieve phase locking of the regenerated laser. Once the loop is locked, the received optical signal from the previous stage can achieve regeneration and amplification at both the frequency and phase levels within the chip. After the regenerated laser locks, most of the optical signal after passing through the first directional coupler is used to transmit to the next-level link. Before entering the transmission link, a portion of the light is used for bidirectional optical frequency comparison testing via the second directional coupler. This testing section consists of a fifth multimode interferometer, a fourth multimode interferometer, and a third multimode interferometer. The majority of the remaining light enters the third directional coupler, a small portion directly enters the second multimode interferometer as a local reference optical signal for locking the next-level link, and the majority of the remaining light enters the next-level transmission link via the fourth directional coupler, the third inter-layer coupler, the second frequency shifter, the fourth inter-layer coupler, and the first end-face coupler. Following a similar process, the regenerated laser in the next-level relay chip is transmitted back via the transmission link through the first end-face coupler, the fourth inter-layer coupler, the second frequency shifter, the third inter-layer coupler, and the fourth directional coupler to the second multimode interferometer. The fourth end-face coupler is used to couple to an external photodetector to detect the phase noise introduced by the next-level transmission link. The second frequency shifter is controlled by a phase-locked loop or other means to lock the next-level link, thus enabling the function of sending a phase-stable optical frequency signal to the next-level link. Therefore, based on the above process, the relay chip can receive, regenerate and amplify the optical signal transmitted from the previous link, while sending a phase-stable optical frequency signal to the next level. It can meet the application requirements of cascaded optical frequency transmission systems and has the advantages of full integration of key active components.

[0010] The present invention also provides an optical frequency transmission system, characterized in that it includes the above-mentioned temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration repeater chip, wherein: The first chip, acting as the master chip, has its first end-face coupler optically connected to the second end-face coupler of the second chip, acting as the slave chip, via a first optical fiber link, to construct a unidirectional optical frequency transmission main path; the second end-face coupler of the master chip is optically connected to the upstream link or the source end to receive the input optical frequency signal. The first end-face coupler of the slave chip is optically connected to the downstream link or terminal to output the regenerated optical frequency signal.

[0011] Furthermore, the slave chip also includes a third photodetector and a second phase-locked loop. The third photodetector is optically connected to the third end face coupler of the slave chip and is used to detect the beat frequency signal of the optical signal from the master chip and the locally regenerated laser from the slave. The second phase-locked loop generates a control signal based on the beat frequency signal and feeds back to control the first distributed feedback laser gain chip and / or the first frequency shifter of the slave chip to achieve frequency and phase locking between the slave regenerated laser and the received signal.

[0012] Furthermore, the master chip also includes a first photodetector and a first phase-locked loop. The first photodetector is optically connected to the fourth end face coupler of the master chip and is used to detect the beat frequency signal between the return optical signal from the slave chip and the local reference light of the master chip. The first phase-locked loop generates a control signal based on the beat frequency signal and feeds back to control the second frequency shifter of the master chip to compensate for the phase noise introduced by the first optical fiber link.

[0013] The present invention also provides a method for cascading optical frequency signals using the above-described optical frequency transmission system, characterized in that it includes: Master-end regeneration locking step: In the master-end chip, the frequency and phase of the regenerated laser generated by the first distributed feedback laser gain chip are locked to the input optical frequency signal from the upper-level link received via the second end-face coupler using the first frequency shifter and the external phase-locked loop connected to the third end-face coupler. Link forward transmission and slave regeneration steps: The locked master-end regenerated laser is sent to the slave chip via the first end face coupler and the first optical fiber link; In the slave chip, the frequency and phase of the regenerated laser generated by the slave chip itself are locked to the received optical signal from the master chip using the third frequency shifter and the external phase-locked loop connected to the eleventh end face coupler. Link Reverse Locking and Noise Compensation Steps: The regenerated laser locked by the slave chip is transmitted back to the master chip via the second end-face coupler and the first optical fiber link; in the master chip, the second frequency shifter and the external phase-locked loop connected to the fourth end-face coupler are used to generate a control signal to drive the second frequency shifter based on the beat frequency signal of the transmitted signal and the local reference light, thereby compensating for the phase noise introduced by the first optical fiber link and completing the phase locking of the first optical fiber link; Stable Transmission Steps: After completing the link reverse locking and noise compensation steps, the master chip continuously outputs a phase-stable optical frequency signal to the slave chip through the first optical fiber link.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1) This invention provides a laser regeneration relay chip architecture for a fully integrated active optical frequency cascade transmission system, which can realize the hybrid full integration of key active devices and passive interferometers in laser regeneration relay.

[0015] 2) Through rigorous theoretical derivation, this invention establishes the length matching design criteria for out-of-band paths in on-chip passive laser regeneration relay interferometers, effectively suppressing phase noise introduced by temperature changes from a structural perspective, and enabling the chip to have extremely low thermal sensitivity.

[0016] 3) This invention can compress the optical frequency laser regeneration relay composed of traditional fiber optic devices from the centimeter or even meter level to the millimeter or even micrometer level in a photonic integrated chip. Under the premise of achieving the same function, it has the outstanding advantages of small size, low power consumption and high stability.

[0017] 4) This invention integrates silicon-based waveguides with functional materials such as thin-film lithium niobate in a hybrid heterogeneous manner, enabling the chip to simultaneously possess low transmission loss and high-efficiency electro-optic modulation capabilities, thus providing a feasible technical path for constructing a high-performance, high-stability fully integrated optical frequency transmission system. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration relay chip provided in an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of a cascaded optical frequency transfer system architecture based on the chip provided in an embodiment of the present invention.

[0020] In the diagram: 0 - First distributed feedback laser gain chip; 1 - First self-injection locking external cavity; 2 - First directional coupler; 3 - Second directional coupler; 4 - Third directional coupler; 5 - Fourth directional coupler; 6 - First end-face coupler (for sending optical frequency signals to the next stage link); 7 - Second end-face coupler (for receiving optical frequency signals transmitted from the previous stage); 8 - Fifth directional coupler; 9 - First multimode interferometer; 10 - Third end-face coupler (for on-chip regenerated laser locking); 11 - Sixth directional coupler; 12 - Seventh directional coupler; 13 - Second multimode interferometer; 14 - Fourth end-face coupler (for locking the next stage link); 15 - Third multimode interferometer; 16 - Fourth multimode interferometer; 17 - Fifth multimode interferometer; 18 - Fifth end-face coupler (for bidirectional optical frequency comparison beat frequency testing); 19 - Sixth end-face coupler (for bidirectional optical frequency comparison testing); 20 - Sixth multimode interferometer; 21 - 22 - 8th Multimode Interferometer; 23 - 7th End-face Coupler (for bidirectional optical frequency comparison testing); 24 - 8th End-face Coupler (for bidirectional optical frequency comparison beat frequency testing); 25 - 1st Interlayer Coupler; 26 - 1st Frequency Shifter; 27 - 2nd Interlayer Coupler; 28 - 3rd Interlayer Coupler; 29 - 2nd Frequency Shifter; 30 - 4th Interlayer Coupler; 31 - 5th Interlayer Coupler; 32 - 1st Polarization Controller; 33 - 3rd Frequency Shifter; 34 - 6th Interlayer Coupler; 001 - Master relay chip; 002 - Fiber optic link; 003 - Slave relay chip The main components inside the master relay chip 001 are marked as follows: 100 - First distributed feedback laser gain chip; 101 - First self-injection locked external cavity; 102 - First directional coupler; 103 - Second directional coupler; 104 - Third directional coupler; 105 - Fourth directional coupler; 106 - First end-face coupler; 107 - Second end-face coupler; 108 - Fifth directional coupler; 109 - First multimode interferometer; 110 - Third end-face coupler; 111 - Sixth directional coupler; 112 - Seventh directional coupler; 113 - Second multimode interferometer; 114 - Fourth end-face coupler; 115 - Third multimode interferometer; 116 - Fourth multimode interferometer; 117 - Fifth multimode interferometer; 118 - Fifth end-face coupler; 119 - Sixth end-face coupler; 120 - Sixth multimode interferometer; 121 - Seventh multimode interferometer; 122 - Eighth multimode interferometer; 123 - Seventh end-face coupler; 124 - Eighth end-face coupler; 125 - First interlayer coupler; 126 - First phase modulator (used as first frequency shifter); 127 - Second interlayer coupler; 128 - Third interlayer coupler; 129 - Second phase modulator (used as second frequency shifter); 130 - Fourth interlayer coupler; 131 - Fifth interlayer coupler; 132 - First polarization controller; 133 - Third phase modulator (used as third frequency shifter); 134 - Sixth interlayer coupler; 135 - First photodetector; 136 - First phase-locked loop; 137 - First sawtooth wave generator; 138 - First acousto-optic frequency shifter (external test device); 139 - First signal generator; 140 - Second photodetector; 141 - Second sawtooth wave generator; Key internal components of repeater chip 003 are marked as follows: 300 - Second distributed feedback laser gain chip; 301 - Second self-injection locked external cavity; 302 - Eighth directional coupler; 303 - Ninth directional coupler; 304 - Tenth directional coupler; 305 - Eleventh directional coupler; 306 - Ninth end-face coupler; 307 - Tenth end-face coupler; 308 - Twelfth directional coupler; 309 - Ninth multimode interferometer; 310 - Eleventh end-face coupler; 311 - Thirteenth directional coupler; 312 - Fourteenth directional coupler; 313 - Tenth multimode interferometer; 314 - Twelfth end-face coupler; 315 - Eleventh multimode interferometer; 316 - Twelfth multimode interferometer; 317 - Thirteenth multimode interferometer; 318 - Thirteenth end-face coupler; 319 - Fourteenth end-face coupler; 320 - Fourteenth multimode interferometer; 321 - 322 - 16th Multimode Interferometer; 323 - 15th End-face Coupler; 324 - 16th End-face Coupler; 325 - 7th Interlayer Coupler; 326 - 4th Phase Modulator (used as 1st Frequency Shifter); 327 - 8th Interlayer Coupler; 328 - 9th Interlayer Coupler; 329 - 5th Phase Modulator (used as 2nd Frequency Shifter); 330 - 10th Interlayer Coupler; 331 - 11th Interlayer Coupler; 332 - 2nd Polarization Controller; 333 - 6th Phase Modulator (used as 3rd Frequency Shifter); 334 - 12th Interlayer Coupler; 335 - 3rd Photodetector; 336 - 2nd Phase-Locked Loop; 337 - 3rd Sawtooth Wave Generator; 338 - 4th Sawtooth Wave Generator; 339 - 4th Photodetector. Detailed Implementation

[0021] The present invention will be further described below with reference to the embodiments and accompanying drawings. The embodiments are implemented based on the technical solutions of the present invention, and detailed implementation methods and specific workflows are given. However, the scope of protection of the present invention is not limited to the following embodiments.

[0022] like Figure 1 As shown, the temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration repeater chip of the present invention adopts an advanced silicon-based thin-film lithium niobate (Si-TFLN) heterogeneous hybrid integrated architecture, including: Silicon Layer: All passive devices, including end couplers (EC), directional couplers (DC), multimode interferometers (MMI), and self-injection locked external cavities (SIL), are fabricated on this layer using standard CMOS-compatible processes (such as electron beam lithography and dry etching).

[0023] TFLN Active Layer: Contains three independent functional unit blocks (corresponding to...) Figure 1 (The three dashed boxes in the image). Each functional unit integrates an electro-optic frequency shifter (PM / FS) and a polarization controller (PC) based on an X-cut or Z-cut TFLN thin film, and is equipped with a coplanar waveguide (CPW) electrode (IC) to apply the RF drive signal. These TFLN unit blocks are bonded to designated locations on the silicon substrate with submicron precision using micro-transfer technology, and low-loss vertical coupling between the silicon-based waveguide and the TFLN waveguide is achieved through an inverse tapered mode converter.

[0024] The laser output port of the first distributed feedback laser gain chip 0 is connected to the input port of the first self-injection locked external cavity 1. The output port of the first self-injection locked external cavity 1 is connected to the input port of the first interlayer coupler 25. The output port of the first interlayer coupler 25 is connected to the first port of the first frequency shifter 26. The second port of the first frequency shifter 26 is connected to the output port of the second interlayer coupler 27. The input port of the second interlayer coupler 27 is connected to the combining port of the first directional coupler 2. The first branch port and the second branch port of the first directional coupler 2 are respectively connected to the combining port of the second directional coupler 3 and... The sixth directional coupler 11 is connected to the combining port; the first and second branch ports of the second directional coupler 3 are respectively connected to the combining port of the third directional coupler 4 and the combining port of the third multimode interferometer 15; the first and second branch ports of the third multimode interferometer 15 are respectively connected to the second branch port of the fifth multimode interferometer 17 and the first branch port of the fourth multimode interferometer 16; the combining port and the first branch port of the fifth multimode interferometer 17 are respectively connected to the output port of the fifth end-face coupler 18 and the second branch port of the fourth multimode interferometer 16; the output of the fifth end-face coupler 18... The input port is connected to an external photodetector for bidirectional optical frequency comparison beat frequency testing. The combining port of the fourth multimode interferometer 16 is connected to the output port of the sixth end-face coupler 19. The input port of the sixth end-face coupler 19 is connected to an external short optical fiber or an external frequency shifter for bidirectional optical frequency comparison testing. The first and second branch ports of the third fixed coupler 4 are respectively connected to the second branch port of the second multimode interferometer 13 and the first branch port of the fourth directional coupler 5. The first branch port and combining port of the second multimode interferometer 13 are respectively connected to the second branch port of the fourth directional coupler 5 and the fourth end-face coupler 19. The output port of the fourth end-face coupler 14 is connected to the output port of the fourth directional coupler 5, and the input port of the third inter-layer coupler 28 is connected to the first port of the second frequency shifter 29. The second port of the second frequency shifter 29 is connected to the output port of the fourth inter-layer coupler 30, and the input port of the fourth inter-layer coupler 30 is connected to the output port of the first end-face coupler 6. The input port of the first end-face coupler 6 is connected to the external transmission link for sending optical frequency signals to the next level link.The first and second branch ports of the sixth directional coupler 11 are respectively connected to the combining port of the sixth multimode interferometer 20 and the combining port of the seventh directional coupler 12. The first and second branch ports of the sixth multimode interferometer 20 are respectively connected to the second branch port of the seventh multimode interferometer 21 and the first branch port of the eighth multimode interferometer 22. The first branch port and combining port of the seventh multimode interferometer 21 are respectively connected to the second branch port of the eighth multimode interferometer 22 and the output port of the seventh end-face coupler 23. The input port of the seventh end-face coupler 23 is connected to an external short optical fiber or an external frequency shifter for bidirectional optical frequency comparison testing. The combining port of the eighth multimode interferometer 22 is connected to the output port of the eighth end-face coupler 24. The input port of the eighth end-face coupler 24 is connected to an external photodetector for bidirectional optical frequency comparison beat frequency testing. The first and second branch ports of the seventh directional coupler 12 are respectively connected to the combining port of the sixth multimode interferometer 20 and the combining port of the seventh directional coupler 12. The first branch port of the fifth directional coupler 8 is connected to the second branch port of the first multimode interferometer 9. The first branch port and the combining port of the first multimode interferometer 9 are respectively connected to the second branch port of the fifth directional coupler 8 and the output port of the third end-face coupler 10. The input port of the third end-face coupler 10 is connected to an external photodetector for on-chip regenerated laser locking. The combining port of the fifth directional coupler 8 is connected to the input port of the sixth interlayer coupler 34. The output port of the sixth interlayer coupler 34 is connected to the first port of the third frequency shifter 33. The second port of the third frequency shifter 33 is connected to the first port of the first polarization controller 32. The second port of the first polarization controller 32 is connected to the output port of the fifth interlayer coupler 31. The input port of the fifth interlayer coupler 31 is connected to the output port of the second end-face coupler 7. The input port of the second end-face coupler 7 is connected to an external transmission link for receiving optical frequency signals transmitted from the previous stage.

[0025] Its core workflow and technical principles are as follows: On-chip laser generation and narrow linewidth reduction: By bonding the first distributed feedback laser gain chip 0 to the first self-injection locked external cavity 0 on the silicon waveguide, an on-chip regenerated laser signal with narrow linewidth and low phase noise is generated and output.

[0026] Uplink signal reception and regeneration locking: The input optical signal from the upstream link enters the chip via the second end-face coupler 7, and then passes sequentially through the fifth inter-layer coupler 21, the first polarization controller 32, the third frequency shifter 33, and the sixth inter-layer coupler 34. It then interferes with a reference beam split from the locally regenerated laser at the first multimode interferometer 9. The interference signal is output to an external photodetector via the third end-face coupler 10 for phase detection. The generated error signal is fed back through a phase-locked loop to control the wavelength of the first distributed feedback laser gain chip 0 and the phase of the first frequency shifter 26, thereby locking the frequency and phase of the locally regenerated laser to the received uplink signal, achieving signal "regeneration".

[0027] Downlink Signal Transmission and Link Locking: Most of the power of the regenerated laser is used to transmit to the next-level link. This signal passes sequentially through the first directional coupler 2, the second directional coupler 3, the third directional coupler 4, and the fourth directional coupler 5, and is coupled to the thin-film lithium niobate waveguide via the third interlayer coupler 28. After frequency shifting by the second frequency shifter 29, it is output to the external fiber optic link via the fourth interlayer coupler 30 and the first end-face coupler 6. Simultaneously, a small portion of light is split from this transmission path and interferes with the optical signal returned from the next-level link at the second multimode interferometer 13. The resulting beat frequency signal is output to the external detector via the fourth end-face coupler 14. This signal carries double the phase noise introduced by the next-level link. Through phase-locked loop feedback control of the second frequency shifter 29, phase noise compensation and locking of the next-level transmission link are achieved, thereby outputting a phase-stable optical frequency signal.

[0028] Two-way performance monitoring structure: The chip integrates two sets of symmetrical two-way optical frequency comparison test structures (related to devices 15-19 and devices 20-24 respectively). By comparing the local signal with the peer signal looped back through the external short optical fiber and discrete frequency shifter, the final residual phase noise of the system can be extracted and evaluated online, which is used to monitor the actual performance of the cascaded transmission system.

[0029] The derivation is performed using two temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration repeater chips as the master and slave ends, respectively. Subsequent derivations utilize subscripts. as well as To distinguish the relevant parameters in the master and slave relay chips The first distributed feedback laser gain chip 0, located at the main end, is coupled to the first self-injection locked external cavity 1 on the silicon-based platform via external bonding or other methods. When the laser output is in a self-injection locked state, it can compress the linewidth of the broadband distributed feedback laser, outputting a narrow-linewidth, low-phase-noise optical frequency signal as the light source to be transmitted. Assume its angular frequency and initial phase are respectively... as well as The signal is coupled to the upper thin-film lithium niobate waveguide by the first interlayer coupler 25, and after passing through the first frequency shifter 26, it generates an angular frequency of . After frequency shifting, the light is coupled back into the silicon waveguide via the second interlayer coupler 27. After passing through the first directional coupler 2 and the second directional coupler 3, a small portion of the light is used for regenerated laser phase locking and bidirectional optical frequency comparison testing. The majority of the light passes sequentially through the third directional coupler 4 and the fourth directional coupler 5, and is then coupled to the upper lithium niobate waveguide via the third interlayer coupler 28. After passing through the second frequency shifter 29, an angular frequency of [value missing] is generated. After frequency shifting, the signal is coupled back into the silicon waveguide by the fourth inter-layer coupler 30, and then coupled to the external transmission link via the first end-face coupler 6. The second frequency shifter 29 here can lock the phase noise of the transmission link through a phase-locked loop or similar method. When the optical frequency signal reaches the temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration relay chip (which is the slave end) via the transmission link, it passes sequentially through the second end-face coupler 7, the fifth inter-layer coupler 31, the first polarization controller 32, the third frequency shifter 33, and the sixth inter-layer coupler 34. After being split by the fifth directional coupler 8, a portion of the light passes through the first multimode interferometer 9 and the third end-face coupler 10 before being coupled to the external photodetector. This signal can be represented as: in, This indicates the frequency shift angle of the third frequency shifter 33. The phase fluctuation generated by the signal source driving the third frequency shifter 33 Phase noise introduced to the transmission link, The phase noise introduced by the waveguide path between device 1 and device 2 exhibits bidirectional reciprocity and superposition, i.e., , Assume that the angular frequency and initial phase of the regenerated laser generated by the first distributed feedback laser gain chip 0 and the first self-injection locked external cavity 1 in the end chip are respectively... For and After passing sequentially through the first interlayer coupler 25, the first frequency shifter 26, and the second interlayer coupler 27, a small portion of the light is transmitted through the first directional coupler 2 to the sixth directional coupler 11. A small portion of this light is used for bidirectional optical frequency comparison testing, while the remaining portion reaches the seventh directional coupler 12. Subsequently, a small portion of this light is coupled to an external photodetector via the first multimode interferometer 9 and the third end-face coupler 10, serving as a reference signal for the regenerated laser. Its beat frequency signal with the received signal can be written as: in, The phase ripple introduced by the signal source driving the first frequency shifter 26. To eliminate phase noise introduced by the RF source in each relay station, the signal... With angular frequency After phase detection and locking at the reference frequency, we can obtain: After phase locking, the regenerated laser sequentially passes through the seventh directional coupler 12, the fifth directional coupler 8, the sixth interlayer coupler 34, the third frequency shifter 33, the first polarization controller 32, the fifth interlayer coupler 31, and the second end-face coupler 7 before being transmitted back to the main relay chip via a transmission link. It then sequentially passes through the first end-face coupler 6, the fourth interlayer coupler 30, the second frequency shifter 29, the third interlayer coupler 28, and the fourth directional coupler 5 in the main relay chip before entering the second multimode interferometer 13. Finally, it is coupled to the external photodetector by the fourth end-face coupler 14. The signal expression can be written as: In the main end, a small portion of the light from the optical signal to be transmitted, after passing through the third fixed coupler 4, is coupled to the photodetector via the second multimode interferometer 13 and the fourth end-face coupler 14. The resulting beat frequency signal can be expressed as: Signal With twice the phase noise introduced by the transmission link. Lock it to an angular frequency of After obtaining the reference frequency, we can get: in, This represents the residual phase noise after loop locking. The first two terms on the right-hand side of the equation represent the out-of-band phase noise introduced by this structure. Assume the wavelength path length between device 1 and device 2 is... To suppress this type of noise, the relevant waveguide length needs to meet the following conditions: Once the link is locked, the signal from the regenerated laser in the slave chip reaching the sixth directional coupler 11 can be expressed as: To evaluate the performance of the cascaded transmission system based on this laser regeneration relay chip, a structure for bidirectional optical frequency comparison testing was designed into the architecture. In the main chip, after the optical signal to be transmitted is transmitted to the second directional coupler 3, a small portion of the light sequentially passes through the third multimode interferometer 15, the fifth multimode interferometer 17, and the fifth end-face coupler 18 to be coupled to an external photodetector, serving as the bidirectional comparison test reference signal in the main chip. This reference signal can be written as: After the regenerated laser light from the end chip is split by the sixth directional coupler 11, a small portion of the light is sequentially coupled to the external drive at an angular frequency of 20 through the sixth multimode interferometer 20, the seventh multimode interferometer 21, and the seventh end-face coupler 23. The discrete fiber optic frequency shifter. After passing through this frequency shifter and the sixth end-face coupler 19 in the main chip, it sequentially passes through the fourth multimode interferometer 16, the fifth multimode interferometer 17, and the fifth end-face coupler 18 before being coupled to an external photodetector, and then to a reference signal. After taking the beat frequency, we can obtain: in, This refers to the phase noise introduced into the short fiber containing the discrete fiber frequency shifter. Similarly, after the regenerated laser signal in the slave chip is split by the sixth directional coupler 11, a small portion of the light passes sequentially through the sixth multimode interferometer 20, the eighth multimode interferometer 22, and the eighth end-face coupler 24 before being coupled to an external photodetector. This serves as the reference signal for the bidirectional comparison test in the slave end, and can be written as: The signal light to be transmitted in the master chip is split by the second directional coupler 3, and then sequentially coupled to the external discrete fiber frequency shifter via the third multimode interferometer 15, the fourth multimode interferometer 16, and the sixth end-face coupler 19. It is then transmitted to the slave chip, where it sequentially passes through the seventh multimode interferometer 21, the eighth multimode interferometer 22, and the eighth end-face coupler 24 before being coupled to the external photodetector, which then interacts with the reference signal. The beat frequency result can be expressed as: Signal and Subtracting and dividing by a coefficient of 2 eliminates the phase noise introduced by the short fiber in which the discrete fiber frequency shifter is located, and effectively extracts the residual phase noise of the system. Under the above processing, the resulting evaluation signal expression is: To eliminate out-of-band phase noise introduced during bidirectional optical frequency comparison testing, the waveguide length design must meet the following conditions: Figure 2 This is a complete relay link formed by cascading two chips of the present invention, one as the master end and the other as the slave end. As shown in the figure, it illustrates an embodiment of an optical frequency transmission system based on fiber optic link 2, using two laser regeneration chips as the master end 1 and the slave end 3 of the transmission system, respectively.

[0030] The main terminal 1 consists of a first distributed feedback laser gain chip 100, a first self-injection locked external cavity 101, a first directional coupler 102, a second directional coupler 103, a third directional coupler 104, a fourth directional coupler 105, a first end-face coupler 106, a second end-face coupler 107, a fifth directional coupler 108, a first multimode interferometer 109, a third end-face coupler 110, a sixth directional coupler 111, a seventh directional coupler 112, a second multimode interferometer 113, a fourth end-face coupler 114, a third multimode interferometer 115, a fourth multimode interferometer 116, a fifth multimode interferometer 117, and a fifth end-face coupler. 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139 ...8, 139, The system comprises an optical phase modulator 138, a first signal generator 139, a second photodetector 140, and a second sawtooth wave generator. The laser output port of the first distributed feedback laser gain chip 100 is connected to the input port of the first self-injection locked external cavity 101. The output port of the first self-injection locked external cavity 101 is connected to the input port of the first interlayer coupler 125. The output port of the first interlayer coupler 125 is connected to the first port of the first phase modulator 126. The RF modulation port and the second port of the first phase modulator 126 are respectively connected to the second interlayer coupler. The output port of the second interlayer coupler 127 is connected to the output port of the second sawtooth wave generator 141. The input port of the second interlayer coupler 127 is connected to the combining port of the first directional coupler 102. The first branch port and the second branch port of the first directional coupler 102 are respectively connected to the combining port of the second directional coupler 103 and the combining port of the sixth directional coupler 111. The first branch port and the second branch port of the second directional coupler 103 are respectively connected to the combining port of the third directional coupler 104 and the combining port of the third multimode interferometer 115.The first and second branch ports of the third multimode interferometer 115 are respectively connected to the second branch port of the fifth multimode interferometer 117 and the first branch port of the fourth multimode interferometer 116. The combining port and the first branch port of the fifth multimode interferometer 117 are respectively connected to the output port of the fifth end-face coupler 118 and the second branch port of the fourth multimode interferometer 116. The input port of the fifth end-face coupler 118 is connected to the optical input port of the second photodetector 140. The RF output port of the second photodetector 140 is used for bidirectional optical frequency comparison testing. The combining port of the fourth multimode interferometer 116 is connected to the output port of the sixth end-face coupler 119. The input port of the sixth end-face coupler 119 is connected to the first port of the first acousto-optic frequency shifter 138. The RF modulation port and the second port of the first acousto-optic frequency shifter 138 are respectively connected to the output port of the first signal generator 139 and the short optical fiber for bidirectional optical frequency comparison testing. The first and second branch ports of the third directional coupler 104 are respectively connected to the second branch port of the second multimode interferometer 113 and the first branch port of the fourth directional coupler 105. The first branch port and the combining port of the second multimode interferometer 113 are respectively connected to the second branch port of the fourth directional coupler 105 and the output port of the fourth end-face coupler 114. The input port of the fourth end-face coupler 114 is connected to the optical input port of the first photodetector 135. The RF output port of the first photodetector 135 is connected to the input port of the first phase-locked loop 136. The output port of the first phase-locked loop 136 is connected to the feedback control port of the first sawtooth wave generator 137. The output port of the first sawtooth wave generator 137 is connected to the second phase modulator 12. The RF modulation port of 9 is connected; the combining port of the fourth directional coupler 105 is connected to the input port of the third inter-layer coupler 128, the output port of the third inter-layer coupler 128 is connected to the first port of the second phase modulator 129, the second port of the second phase modulator 129 is connected to the output port of the fourth inter-layer coupler 130, the input port of the fourth inter-layer coupler 130 is connected to the output port of the first end-face coupler 106, and the input port of the first end-face coupler 106 is connected to the first port of the optical fiber link 2, for transmitting optical frequency signals to the next level link;The first and second branch ports of the sixth directional coupler 111 are respectively connected to the combining port of the sixth multimode interferometer 120 and the combining port of the seventh directional coupler 112. The first and second branch ports of the sixth multimode interferometer 120 are respectively connected to the second branch port of the seventh multimode interferometer 121 and the first branch port of the eighth multimode interferometer 122. The first branch port and combining port of the seventh multimode interferometer 121 are respectively connected to the second branch port of the eighth multimode interferometer 122 and the output port of the seventh end-face coupler 123. The input port of the seventh end-face coupler 123 is connected to an external short optical fiber or an external phase modulator for bidirectional optical frequency comparison testing. The combining port of the eighth multimode interferometer 122 is connected to the output port of the eighth end-face coupler 124. The first and second branch ports of the seventh directional coupler 112 are respectively connected to the fifth directional coupler 112. The first branch port of 08 is connected to the second branch port of the first multimode interferometer 109. The first branch port and the combining port of the first multimode interferometer 109 are respectively connected to the second branch port of the fifth directional coupler 108 and the output port of the third end-face coupler 110. The combining port of the fifth directional coupler 108 is connected to the input port of the sixth inter-layer coupler 134. The output port of the sixth inter-layer coupler 134 is connected to the first port of the third phase modulator 133. The second port of the third phase modulator 133 is connected to the first port of the first polarization controller 132. The second port of the first polarization controller 132 is connected to the output port of the fifth inter-layer coupler 131. The input port of the fifth inter-layer coupler 131 is connected to the output port of the second end-face coupler 107. The input port of the second end-face coupler 107 is connected to the previous stage transmission link for receiving the optical frequency signal transmitted from the previous stage. The slave end 3 comprises a second distributed feedback laser gain chip 300, a second self-injection locked external cavity 301, an eighth directional coupler 302, a ninth directional coupler 303, a tenth directional coupler 304, an eleventh directional coupler 305, a ninth end-face coupler 306, a tenth end-face coupler 307, a twelfth directional coupler 308, a ninth multimode interferometer 309, an eleventh end-face coupler 310, a thirteenth directional coupler 311, a fourteenth directional coupler 312, a tenth multimode interferometer 313, a twelfth end-face coupler 314, an eleventh multimode interferometer 315, a twelfth multimode interferometer 316, a thirteenth multimode interferometer 317, a thirteenth end-face coupler 318, and a fourteenth end-face coupler 319. The system comprises the following components: a fourteenth multimode interferometer 320, a fifteenth multimode interferometer 321, a sixteenth multimode interferometer 322, a fifteenth end-face coupler 323, a sixteenth end-face coupler 324, a seventh interlayer coupler 325, a fourth phase modulator 326, an eighth interlayer coupler 327, a ninth interlayer coupler 328, a fifth phase modulator 329, a tenth interlayer coupler 330, an eleventh interlayer coupler 331, a second polarization controller 332, a sixth phase modulator 333, a twelfth interlayer coupler 334, a third photodetector 335, a second phase-locked loop 336, a third sawtooth wave generator 337, a fourth sawtooth wave generator 338, and a fourth photodetector 339; the second distributed feedback laser gain chip. The laser output port of 300 is connected to the input port of the second self-injection locked external cavity 301. The output port of the second self-injection locked external cavity 301 is connected to the input port of the seventh interlayer coupler 325. The output port of the seventh interlayer coupler 325 is connected to the first port of the fourth phase modulator 326. The second port of the fourth phase modulator 326 is connected to the output port of the eighth interlayer coupler 327. The input port of the eighth interlayer coupler 327 is connected to the combining port of the eighth directional coupler 302. The first branch port and the second branch port of the eighth directional coupler 302 are respectively connected to the combining port of the ninth directional coupler 303. The first and second branch ports of the ninth directional coupler 303 are connected to the combined port of the tenth directional coupler 304 and the combined port of the eleventh multimode interferometer 315, respectively; the first and second branch ports of the eleventh multimode interferometer 315 are connected to the second branch port of the thirteenth multimode interferometer 317 and the first branch port of the twelfth multimode interferometer 316, respectively; the combined port and the first branch port of the thirteenth multimode interferometer 317 are connected to the output port of the thirteenth end face coupler 318 and the second branch port of the twelfth multimode interferometer 316, respectively.The combining port of the twelfth multimode interferometer 316 is connected to the output port of the fourteenth end-face coupler 319. The first and second branch ports of the tenth directional coupler 304 are respectively connected to the second branch port of the tenth multimode interferometer 313 and the first branch port of the eleventh directional coupler 305. The first branch port and combining port of the tenth multimode interferometer 313 are respectively connected to the second branch port of the eleventh directional coupler 305 and the output port of the twelfth end-face coupler 314. The combining port of the eleventh directional coupler 305 is connected to the input port of the ninth interlayer coupler 328. The output port of the ninth interlayer coupler 328 is connected to the first port of the fifth phase modulator 329. The second port of the fifth phase modulator 329 is connected to the output port of the tenth interlayer coupler 330. The input port of the tenth interlayer coupler 330 is connected to the output port of the ninth end-face coupler 306. The first branch port of the thirteenth directional coupler 311 is connected to... The first and second branch ports are respectively connected to the combining port of the fourteenth multimode interferometer 320 and the combining port of the fourteenth directional coupler 312. The first and second branch ports of the fourteenth multimode interferometer 320 are respectively connected to the second branch port of the fifteenth multimode interferometer 321 and the first branch port of the sixteenth multimode interferometer 322. The first branch port and the combining port of the fifteenth multimode interferometer 321 are respectively connected to the second branch port of the sixteenth multimode interferometer 322 and the combining port of the fourteenth directional coupler 312. The output port of the fifteenth end-face coupler 323 is connected to the input port of the fifteenth end-face coupler 323, which is connected to an external short optical fiber or an external phase modulator for bidirectional optical frequency comparison testing. The combining port of the sixteenth multimode interferometer 322 is connected to the output port of the sixteenth end-face coupler 324, and the input port of the sixteenth end-face coupler 324 is connected to the optical input port of the fourth photodetector 339. The radio frequency output port of the fourth photodetector 339 is used for bidirectional optical frequency comparison beat frequency testing.The first and second branch ports of the fourteenth directional coupler 312 are respectively connected to the first branch port of the twelfth directional coupler 308 and the second branch port of the ninth multimode interferometer 309. The first branch port and the combining port of the ninth multimode interferometer 309 are respectively connected to the second branch port of the twelfth directional coupler 308 and the output port of the eleventh end-face coupler 310. The input port of the eleventh end-face coupler 310 is connected to the optical input port of the third photodetector 335. The RF output port of the third photodetector 335 is connected to the input port of the second phase-locked loop 336. The first and second output ports of the second phase-locked loop 336 are respectively connected to the current drive port of the second distributed feedback laser gain chip 300 and the feedback control port of the third sawtooth wave generator 337. The output port of the third sawtooth wave generator 337 is connected to the RF modulation port of the fourth phase modulator 326; the combining terminal of the twelfth directional coupler 308 is connected to the input port of the twelfth interlayer coupler 334; the output port of the twelfth interlayer coupler 334 is connected to the first port of the sixth phase modulator 333; the second port and the RF modulation port of the sixth phase modulator 333 are respectively connected to the first port of the second polarization controller 332 and the output port of the fourth sawtooth wave generator 338; the second port of the second polarization controller 332 is connected to the output port of the eleventh interlayer coupler 331; the input port of the eleventh interlayer coupler 331 is connected to the output port of the tenth end-face coupler 307; and the input port of the tenth end-face coupler 307 is connected to the second port of the optical fiber link 2. In this embodiment, the master end 1 is located at one end of the optical fiber link 2, and the slave end 3 is located at the other end of the optical fiber link 2. Furthermore, in this embodiment, the frequency shifter employs a high-efficiency on-chip architecture based on a phase modulator and sawtooth wave linear phase modulation. The sawtooth wave signal can be provided by any signal generator, or it can be generated by a sawtooth wave conversion device composed of a sine wave generator and a nonlinear transmission line. The optical frequency cascade transfer method using the aforementioned temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration repeater chip is as follows: In the derivation of the working principle, subscripts are used as well as To distinguish the relevant parameters in the master and slave relay chips, and considering the out-of-band waveguide path, a strict length match was achieved. The first distributed feedback laser gain chip 100 located at master end 1 is coupled to the first self-injected locked external cavity 101 on the silicon-based platform via external bonding or other methods. When the laser output is in a self-injected locked state, the linewidth of the broadband distributed feedback laser can be compressed, outputting a narrow-linewidth, low-phase-noise optical frequency signal as the light source to be transmitted. Assume its angular frequency and initial phase are respectively... as well as The signal is coupled to the upper thin-film lithium niobate waveguide by the first interlayer coupler 125, and after passing through the first phase modulator 126, it is generated by the second sawtooth wave generator 141 with an angular frequency of [value missing]. Driven by a sawtooth wave signal, thus generating an angular frequency of The frequency is shifted, and then the signal is coupled back into the silicon waveguide via the second interlayer coupler 127. After passing through the first directional coupler 102 and the second directional coupler 103, a small portion of the light is used for regenerated laser phase locking and bidirectional optical frequency comparison testing, while the majority of the light passes through the third directional coupler 104 and the fourth directional coupler 105, and is coupled to the upper lithium niobate waveguide via the third interlayer coupler 128. After passing through the second phase modulator 129, the first sawtooth wave generator 137 generates an angular frequency of [value missing]. Driven by a sawtooth wave signal, thus generating an angular frequency of The frequency shifter 129 is used to couple the signal back into the silicon waveguide via the fourth inter-layer coupler 130, and then to the fiber optic link 2 via the first end-face coupler 106. The second frequency shifter 129 here, through the first phase-locked loop 136, can lock the phase noise introduced into the fiber optic link 2. When the optical frequency signal reaches the slave end 3 via the fiber optic link 2, it passes sequentially through the tenth end-face coupler 307, the eleventh inter-layer coupler 331, the second polarization controller 332, the sixth phase modulator 333, and the twelfth inter-layer coupler 334, and is then split by the twelfth directional coupler 308. A portion of the light passes through the ninth multimode interferometer 309 and the eleventh end-face coupler 310 before being coupled to the third photodetector 335. This signal can be represented as: in, This indicates the frequency shift angle of the third frequency shifter 33. The phase fluctuation generated by the signal source driving the third frequency shifter 33 Phase noise introduced to the transmission link. Assume that the angular frequency and initial phase of the regenerated laser generated from end 3 by the second distributed feedback laser gain chip 300 and the second self-injection locked external cavity 301 are respectively... For and After passing sequentially through the seventh interlayer coupler 325, the fourth phase modulator 326, and the eighth interlayer coupler 327, a small portion of the light is transmitted through the eighth directional coupler 302 to the thirteenth directional coupler 311. A small portion of this light is used for bidirectional optical frequency comparison testing, while the remaining portion reaches the fourteenth directional coupler 312. Subsequently, a small portion of this light is coupled through the ninth multimode interferometer 309 and the eleventh end-face coupler 310 to the third photodetector 335, serving as a reference signal for the regenerated laser from end 3. Its beat frequency signal with the received signal can be written as: in, The phase ripple introduced by the third sawtooth wave generator 337, which drives the fourth phase modulator 326, is addressed. To eliminate phase noise introduced by the radio frequency source in each relay station, the signal... With angular frequency After phase detection and locking at the reference frequency, we can obtain: The phase-locked regenerated laser sequentially passes through the fourteenth directional coupler 312, the twelfth directional coupler 308, the twelfth interlayer coupler 334, the sixth phase modulator 333, the second polarization controller 332, the eleventh interlayer coupler 331, and the tenth end-face coupler 307 before being transmitted back to the main end 1 via fiber optic link 2. It then sequentially passes through the first end-face coupler 106, the fourth interlayer coupler 130, the second frequency shifter 129, the third interlayer coupler 128, and the fourth directional coupler 105 in the relay chip of the main end 1 before entering the second multimode interferometer 113. Finally, it is coupled to the first photodetector 135 by the fourth end-face coupler 114. The signal expression can be written as: In the main terminal 1, a small portion of the light from the optical signal to be transmitted, after passing through the third fixed coupler 104, is coupled to the first photodetector 135 via the second multimode interferometer 113 and the fourth end-face coupler 114. The resulting beat frequency signal can be expressed as: Signal With twice the phase noise introduced by fiber link 2. Lock it to an angular frequency of... After obtaining the reference frequency, we can get: in, This represents the residual phase noise after loop locking. When the link is locked, the signal after the regenerated laser from terminal 3 reaches the thirteenth directional coupler 311 can be expressed as: To evaluate the performance of the cascaded transmission system based on this laser regeneration relay chip, a structure for bidirectional optical frequency comparison testing was designed into the architecture. In the main terminal 1, after the optical signal to be transmitted is transmitted to the second directional coupler 103, a small portion of the light sequentially passes through the third multimode interferometer 115, the fifth multimode interferometer 117, and the fifth end-face coupler 118 to be coupled to an external photodetector, serving as the bidirectional comparison test reference signal in the main terminal, which can be written as: The regenerated laser light from the end-3 chip is split by the thirteenth directional coupler 311, and a small portion of the light is sequentially coupled to an external drive with an angular frequency of [missing value] through the fourteenth multimode interferometer 320, the fifteenth multimode interferometer 321, and the fifteenth end-face coupler 323. The first acousto-optic frequency shifter 138. After passing through the first acousto-optic frequency shifter 138 and the sixth end-face coupler 119 in the main terminal 1 chip, it sequentially passes through the fourth multimode interferometer 116, the fifth multimode interferometer 117, and the fifth end-face coupler 118 before being coupled to the second photodetector 140, and is connected to the reference signal. After taking the beat frequency, we can obtain: in, The phase noise is introduced into the short optical fiber where the first acousto-optic frequency shifter 138 is located. Similarly, after the regenerated laser signal in end 3 is split by the thirteenth directional coupler 311, a small portion of the light passes sequentially through the fourteenth multimode interferometer 320, the sixteenth multimode interferometer 322, and the sixteenth end-face coupler 324 before being coupled to the fourth photodetector 339 as a reference signal for bidirectional comparison testing in end 3. This can be written as: The signal light to be transmitted in the master end 1 is split by the second directional coupler 103, and then coupled to the first acousto-optic frequency shifter 138 via the third multimode interferometer 115, the fourth multimode interferometer 116, and the sixth end-face coupler 119. It is then transmitted to the slave end 3, where it is coupled to the fourth photodetector 339 via the fifteenth multimode interferometer 321, the sixteenth multimode interferometer 322, and the sixteenth end-face coupler 324. This photodetector is then coupled to the reference signal. The beat frequency result can be expressed as: Signal and After subtracting and dividing by a coefficient of 2, the phase noise introduced by the short optical fiber where the first acousto-optic frequency shifter 138 is located can be eliminated, and the residual phase noise of the system can be effectively extracted.

Claims

1. A temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration repeater chip, characterized in that, include: A silicon-based passive waveguide layer and a thin-film lithium niobate active waveguide layer are stacked together, and the silicon-based passive waveguide layer and the thin-film lithium niobate active waveguide layer achieve optical signal coupling through multiple vertically arranged interlayer couplers; The silicon-based passive waveguide layer integrates a first distributed feedback laser gain chip (0), a first self-injection locked external cavity (1), a first directional coupler (2), a second directional coupler (3), a third directional coupler (4), a fourth directional coupler (5), a first end-face coupler (6), a second end-face coupler (7), a fifth directional coupler (8), a first multimode interferometer (9), a third end-face coupler (10), a sixth directional coupler (11), a seventh directional coupler (12), a second multimode interferometer (13), a fourth end-face coupler (14), a third multimode interferometer (15), a fourth multimode interferometer (16), a fifth multimode interferometer (17), a fifth end-face coupler (18), a sixth end-face coupler (19), a sixth multimode interferometer (20), a seventh multimode interferometer (21), an eighth multimode interferometer (22), a seventh end-face coupler (23), and an eighth end-face coupler (24). The thin-film lithium niobate active waveguide layer integrates a first frequency shifter (26), a second frequency shifter (29), a first polarization controller (32), and a third frequency shifter (33). The laser output port of the first distributed feedback laser gain chip (0) is optically connected to the input port of the first self-injection locked external cavity (1). The output port of the first self-injection locked external cavity (1) is optically connected to the first port of the first frequency shifter (26) through the first interlayer coupler (25). The second port of the first frequency shifter (26) is optically connected to the combining port of the first directional coupler (2) through the second interlayer coupler (27). The first branch port of the first directional coupler (2) is optically connected to the combining port of the second directional coupler (3), and the second branch port of the first directional coupler (2) is optically connected to the combining port of the sixth directional coupler (11). The first branch port of the second directional coupler (3) is optically connected to the combining port of the third directional coupler (4), and the second branch port of the second directional coupler (3) is connected to the combining port of the third multimode interferometer (15). The first and second branch ports of the third multimode interferometer (15) are respectively connected to the second branch port of the fifth multimode interferometer (17) and the first branch port of the fourth multimode interferometer (16); The combining port of the fifth multimode interferometer (17) is connected to the output port of the fifth end-face coupler (18), and the first split port of the fifth multimode interferometer (17) is connected to the second split port of the fourth multimode interferometer (16); the input port of the fifth end-face coupler (18) is connected to an external photodetector for bidirectional optical frequency comparison beat frequency testing; the combining port of the fourth multimode interferometer (16) is connected to the output port of the sixth end-face coupler (19), and the input port of the sixth end-face coupler (19) is connected to an external short optical fiber or an external frequency shifter for bidirectional optical frequency comparison testing; The first branch port of the third fixed coupler (4) is connected to the second branch port of the second multimode interferometer (13), and the second branch port of the third fixed coupler (4) is connected to the first branch port of the fourth directional coupler (5). The combining port of the fourth directional coupler (5) is connected to the first port of the second frequency shifter (29) through the third interlayer coupler (28), and the second port of the second frequency shifter (29) is connected to the output port of the first end-face coupler (6) through the fourth interlayer coupler (30); the second split port of the fourth directional coupler (5) is connected to the first split port of the second multimode interferometer (13); the input port of the first end-face coupler (6) is connected to an external transmission link for sending optical frequency signals to the next-level link; the combining port of the second multimode interferometer (13) is connected to the output port of the fourth end-face coupler (14), and the input port of the fourth end-face coupler (14) is connected to an external photodetector for locking the next-level link. The first branch port of the sixth directional coupler (11) is connected to the combining port of the sixth multimode interferometer (20), and the second branch port of the sixth directional coupler (11) is connected to the combining port of the seventh directional coupler (12). The first and second branch ports of the sixth multimode interferometer (20) are respectively connected to the second branch port of the seventh multimode interferometer (21) and the first branch port of the eighth multimode interferometer (22). The first branch port and the combining port of the seventh multimode interferometer (21) are respectively connected to the second branch port of the eighth multimode interferometer (22) and the output port of the seventh end-face coupler (23). The input port of the seventh end-face coupler (23) is connected to an external short optical fiber or an external frequency shifter for bidirectional optical frequency comparison testing. The combining port of the eighth multimode interferometer (22) is connected to the output port of the eighth end-face coupler (24). The input port of the eighth end-face coupler (24) is connected to an external photodetector for bidirectional optical frequency comparison beat frequency testing. The first branch port and the second branch port of the seventh directional coupler (12) are respectively connected to the first branch port of the fifth directional coupler (8) and the second branch port of the first multimode interferometer (9). The first branch port and the combined port of the first multimode interferometer (9) are respectively connected to the second branch port of the fifth directional coupler (8) and the output port of the third end face coupler (10). The input port of the third end face coupler (10) is connected to an external photodetector to realize on-chip regenerated laser locking. The combining end of the fifth directional coupler (8) is connected to the first port of the third frequency shifter (33) through the sixth interlayer coupler (34). The second port of the third frequency shifter (33) is connected to the first port of the first polarization controller (32). The second port of the first polarization controller (32) is connected to the output port of the second end-face coupler (7) through the fifth interlayer coupler (31). The input port of the second end-face coupler (7) is connected to the external transmission link to receive the optical frequency signal transmitted from the previous stage.

2. The temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration repeater chip according to claim 1, characterized in that, The silicon-based passive waveguide layer is based on any one of silicon-on-insulator, silicon nitride, or silicon dioxide platforms; the thin-film lithium niobate active waveguide layer is based on a lithium niobate-on-insulator platform; the silicon-based passive waveguide layer and the thin-film lithium niobate active waveguide layer are heterogeneously integrated through a micro-transfer printing process.

3. The temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration repeater chip according to claim 1, characterized in that, Multiple specific waveguide paths in the silicon-based passive waveguide layer satisfy a preset length matching relationship to suppress non-common-mode phase noise caused by temperature changes; the length matching relationship includes: The waveguide length between the seventh directional coupler (12) and the first multimode interferometer (9) is equal to the sum of the waveguide lengths between the fifth directional coupler (8) and the first multimode interferometer (9) and between the seventh directional coupler (12) and the fifth directional coupler (8); the waveguide length between the third directional coupler (4) and the second multimode interferometer (13) is equal to the sum of the waveguide lengths between the fourth directional coupler (5) and the second multimode interferometer (13) and between the third directional coupler (4) and the fourth directional coupler (5); the waveguide length between the second directional coupler (3) and the fourth directional coupler (5) is equal to the waveguide length between the second directional coupler (3) and the third multimode interferometer (15); the fourth multimode interferometer (9)... The waveguide length between the multimode interferometer (16) and the fifth multimode interferometer (17) is equal to the sum of the waveguide lengths between the third multimode interferometer (15) and the fifth multimode interferometer (17) and between the third multimode interferometer (15) and the fourth multimode interferometer (16); the waveguide length between the sixth directional coupler (11) and the sixth multimode interferometer (20) is equal to the waveguide length between the sixth directional coupler (11) and the fifth directional coupler (8); the waveguide length between the seventh multimode interferometer (21) and the eighth multimode interferometer (22) is equal to the sum of the waveguide lengths between the sixth multimode interferometer (20) and the seventh multimode interferometer (21) and between the sixth multimode interferometer (20) and the eighth multimode interferometer (22).

4. The temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration repeater chip according to claim 1, characterized in that, The first frequency shifter (26), the second frequency shifter (29) and the third frequency shifter (33) are electro-optic phase modulators based on thin-film lithium niobate waveguides and traveling wave electrodes; the first polarization controller (32) is an electro-optic polarization controller based on thin-film lithium niobate waveguides and multi-electrode structures.

5. The temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration repeater chip according to claim 1, characterized in that, The first distributed feedback laser gain chip (0) is externally bonded to the first self-injected locked external cavity (1) on the silicon-based passive waveguide layer via flip-chip bonding to generate an on-chip narrow linewidth laser signal, which can be used as an on-chip regenerated laser.

6. An optical frequency transmission system, characterized in that, It comprises at least two temperature-insensitive silicon-based hybrid fully integrated active optical frequency laser regeneration repeater chips as described in any one of claims 1 to 5, wherein: The first chip serves as the master chip, and its first end-face coupler (6) is optically connected to the second end-face coupler (7) of the second chip, which serves as the slave chip, through the first optical fiber link to construct a unidirectional optical frequency transmission main path; the second end-face coupler (7) of the master chip is optically connected to the upper-level link or the source end to receive the input optical frequency signal; The first end face coupler (6) of the slave chip is optically connected to the lower-level link or terminal to output the regenerated optical frequency signal.

7. The optical frequency transmission system according to claim 6, characterized in that, The slave chip also includes a third photodetector (335) and a second phase-locked loop (336). The third photodetector (335) is optically connected to the third end face coupler (10) of the slave chip and is used to detect the beat frequency signal of the optical signal from the master chip and the locally regenerated laser from the slave. The second phase-locked loop (336) generates a control signal based on the beat frequency signal and feeds back to control the first distributed feedback laser gain chip (300) and / or the first frequency shifter (326) of the slave chip to achieve frequency and phase locking between the slave regenerated laser and the received signal.

8. The optical frequency transmission system according to claim 7, characterized in that, The master chip also includes a first photodetector (135) and a first phase-locked loop (136). The first photodetector (135) is optically connected to the fourth end face coupler (114) of the master chip and is used to detect the beat frequency signal between the return optical signal from the slave chip and the local reference light of the master chip. The first phase-locked loop (136) generates a control signal based on the beat frequency signal and feeds back to control the second frequency shifter (129) of the master chip to compensate for the phase noise introduced by the first optical fiber link.

9. A method for cascading optical frequency signal transmission using the optical frequency transmission system according to any one of claims 6 to 8, characterized in that, include: Master-end regeneration locking step: In the master-end chip, the frequency and phase of the regenerated laser generated by the first distributed feedback laser gain chip (0) are locked to the input optical frequency signal from the upper-level link received via the second end-face coupler (7) using the first frequency shifter (26) and the external phase-locked loop connected to the third end-face coupler (10). Link forward transmission and slave regeneration steps: The locked master-end regenerated laser is sent to the slave chip via the first end face coupler (6) and the first optical fiber link; In the slave chip, the frequency and phase of the regenerated laser generated by the slave chip itself are locked to the received optical signal from the master chip using the third frequency shifter (33) and the external phase-locked loop connected to the eleventh end face coupler (310); Link Reverse Locking and Noise Compensation Steps: The regenerated laser locked by the slave chip is transmitted back to the master chip via the second end-face coupler (307) and the first optical fiber link; In the master chip, the second frequency shifter (29) and the external phase-locked loop connected to the fourth end-face coupler (114) are used to generate a control signal to drive the second frequency shifter (29) based on the beat frequency signal of the transmitted signal and the local reference light, to compensate for the phase noise introduced by the first optical fiber link and complete the phase locking of the first optical fiber link; Stable Transmission Steps: After completing the link reverse locking and noise compensation steps, the master chip continuously outputs a phase-stable optical frequency signal to the slave chip through the first optical fiber link.

Images