Light emitting chip, optical fiber and light transmission system

Abstract

The invention discloses an optical emission chip, an optical fiber and an optical signal transmission system, and belongs to the field of optical transmission. A light beam emitted by an emission laser can be divided into a first sub-light beam and a second sub-light beam through a first beam splitter; on one hand, the light field mode of the first sub-light beam is converted into a high-order mode and local oscillation light is obtained (so that the local oscillation light can be coupled to a coating layer of the optical fiber for transmission), and on the other hand, information to be transmitted is coupled to the second sub-light beam and signal light is obtained, so that the signal light is coupled to a fiber core of the optical fiber for transmission. And finally, the local oscillation light and the signal light are combined into a light beam to be transmitted by a first beam combiner, so that the light beam to be transmitted is transmitted to a receiving end through different layers of the optical fiber. On one hand, a receiving end does not need to be provided with a laser for generating local oscillation light, on the other hand, local oscillation light and signal light can be transmitted through a single optical fiber, and cost and hardware complexity of an optical transmission system can be reduced at the same time.

Description

Technical Field

[0001] The present invention relates to the field of optical transmission, and particularly to an optical emission chip, an optical fiber, and an optical signal transmission system. Background Art

[0002] Optical transmission systems include two types based on the direct detection principle or the coherent detection principle. Optical transmission systems based on the coherent detection principle have wide applications. However, in the related art, optical transmission systems based on the coherent detection principle usually have high costs or high hardware complexities.

[0003] Therefore, how to provide a solution to the above technical problems is an issue that those skilled in the art need to solve currently. Summary of the Invention

[0004] The objective of the present invention is to provide an optical emission chip, an optical fiber, and an optical signal transmission system. In the present invention, a beam emitted by a transmitting laser is divided into a first sub-beam and a second sub-beam by a first beam splitter. On the one hand, the optical field mode of the first sub-beam is converted into a high-order mode to obtain a local oscillator light (so that the local oscillator light can be coupled to the cladding of the optical fiber for transmission). On the other hand, the information to be transmitted is coupled to the second sub-beam to obtain a signal light, so that the signal light can be coupled to the core of the optical fiber for transmission. Finally, the local oscillator light and the signal light are combined into a beam to be transmitted by a first combiner, so that the beam to be transmitted is transmitted to the receiving end through different layers of the optical fiber. On the one hand, the receiving end does not need to be provided with a laser for generating the local oscillator light. On the other hand, the local oscillator light and the signal light can be transmitted through a single optical fiber, which can reduce the cost and hardware complexity of the optical transmission system at the same time.

[0005] To solve the above technical problems, the present invention provides an optical emission chip, including:

[0006] A first beam splitter for dividing a beam emitted by a transmitting laser into a first sub-beam and a second sub-beam;

[0007] A mode conversion device for converting the optical field mode of the first sub-beam into a high-order mode to obtain a local oscillator light, so that the local oscillator light can be coupled to the cladding of the optical fiber, wherein the cladding of the optical fiber is located outside the core;

[0008] A modulation device for coupling the information to be transmitted to the second sub-beam to obtain a signal light, so that the signal light can be coupled to the core of the optical fiber;

[0009] A first combiner for combining the local oscillator light and the signal light into a beam to be transmitted, so that the beam to be transmitted is transmitted to the receiving end through the optical fiber;

[0010] Wherein, the refractive index of the core of the optical fiber is higher than that of the cladding.

[0011] On the other hand, the modulation device includes an in-phase quadrature modulator, a first beam splitting device, and a first beam combining device;

[0012] The input end of the first beam splitting device is connected to the output end of the first beam splitter. The output end of the first beam splitting device is connected to the input end of the in-phase quadrature modulator. The output end of the in-phase quadrature modulator is connected to the input end of the first beam combining device. The output end of the first beam combining device is connected to the input end of the first beam combiner.

[0013] On the other hand, the first beam splitting device includes a second beam splitter, a third beam splitter, and a fourth beam splitter; the first beam combining device includes a second beam combiner, a third beam combiner, and a fourth beam combiner;

[0014] The input end of the second beam splitter serves as the input end of the first beam splitting device. The first output end of the second beam splitter is connected to the input end of the third beam splitter. The second output end of the second beam splitter is connected to the input end of the fourth beam splitter. The output end of the third beam splitter is connected to the input end of the in-phase modulation unit of the in-phase quadrature modulator. The output end of the fourth beam splitter is connected to the input end of the quadrature modulation unit of the in-phase quadrature modulator. The input end of the third beam combiner is connected to the output end of the in-phase modulation unit. The input end of the fourth beam combiner is connected to the output end of the quadrature modulation unit. The output end of the third beam combiner is connected to the first input end of the second beam combiner. The output end of the fourth beam combiner is connected to the second input end of the second beam combiner. The output end of the second beam combiner serves as the output end of the first beam combining device;

[0015] The in-phase quadrature modulator includes an in-phase modulation unit and a quadrature modulation unit.

[0016] On the other hand, the emission laser includes a distributed feedback laser.

[0017] On the other hand, the mode conversion device includes an input waveguide, a mode coupling structure, a cladding region, and an output waveguide;

[0018] The input waveguide is used to input the first sub-beam so as to introduce the first sub-beam into the mode conversion device;

[0019] The mode coupling structure is used to couple the first sub-beam between different waveguide modes through its own waveguide structure and refractive index distribution, and excite high-order modes by using the phase matching condition;

[0020] The cladding region is used to change the effective refractive index of the waveguide mode to meet the phase matching condition required for mode conversion;

[0021] The output waveguide is used to output the local oscillator light obtained through mode conversion from the mode conversion device.

[0022] To solve the above technical problems, the present invention also provides an optical fiber, which includes a core, a cladding layer, and a coating layer;

[0023] The cladding layer is located between the core and the coating layer;

[0024] The core is used to couple and transmit the signal light in the beam to be transmitted;

[0025] The cladding layer is used to couple and transmit the local oscillator light in the beam to be transmitted;

[0026] The coating layer is used to protect the core and the cladding layer;

[0027] Wherein, the refractive index of the core is higher than that of the cladding layer, and the beam to be transmitted is generated by the optical emission chip as described above.

[0028] On the other hand, the cladding layer includes a plurality of sub-cladding layers;

[0029] Specifically, the cladding layer is used to couple and transmit the local oscillator light in the beam to be transmitted through its multiple sub-cladding layers;

[0030] Wherein, the refractive index of the sub-cladding layer close to the core is higher than that of the sub-cladding layer far from the core.

[0031] On the other hand, the cladding layer includes a first sub-cladding layer and a second sub-cladding layer;

[0032] The diameter of the core is in a first diameter range, the first sub-cladding layer is in a second diameter range, and the second sub-cladding layer is in a third diameter range;

[0033] The first diameter range includes 7 microns to 15 microns, the second diameter range includes 7 microns to 90 microns to 200 microns, and the third diameter range includes 7 microns to 150 microns to 500 microns.

[0034] To solve the above technical problems, the present invention also provides an optical transmission system, which includes the optical emission chip as described above, the optical fiber as described above, and further includes:

[0035] An emission laser connected to the optical emission chip, which is used to generate a beam;

[0036] An optical receiving device connected to the output end of the optical fiber, which is used to perform coherent demodulation on the signal in the beam to be transmitted.

[0037] On the other hand, the optical receiving device includes a mode demultiplexer, a power amplification module, and an integrated coherent receiver;

[0038] The mode demultiplexer is used to demultiplex the signal light and the local oscillator light;

[0039] The power amplification module is used to amplify the power of the signal light and the local oscillator light;

[0040] The integrated coherent receiver is used to perform coherent demodulation based on the signal light and the local oscillator light after power amplification to obtain the information to be transmitted.

[0041] Beneficial effects: The present invention provides an optical emission chip. Considering that the beams obtained from the same light source naturally have relatively low phase noise, and through the conversion of the optical field mode, the non-interfering transmission of two beams of light in different layers of the same optical fiber can be achieved. Therefore, in the present invention, the beam emitted by the emission laser can be divided into a first sub-beam and a second sub-beam by a first beam splitter. On the one hand, the optical field mode of the first sub-beam is converted into a high-order mode to obtain the local oscillator light (so that the local oscillator light can be coupled to the cladding layer of the optical fiber for transmission), and on the other hand, the information to be transmitted is coupled to the second sub-beam to obtain the signal light, so that the signal light can be coupled to the core of the optical fiber for transmission. Finally, the local oscillator light and the signal light are combined into the beam to be transmitted by the first combiner, so that the beam to be transmitted is transmitted to the receiving end through different layers of the optical fiber; on the one hand, the receiving end does not need to be provided with a laser for generating the local oscillator light, and on the other hand, the local oscillator light and the signal light can be transmitted through a single optical fiber, which can reduce the cost and hardware complexity of the optical transmission system at the same time.

[0042] The present invention also provides an optical fiber and an optical transmission system, which have the same beneficial effects as the above optical emission chip. Description of the Drawings

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the related technologies and embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0044] Figure 1 It is a schematic structural diagram of an optical emission chip provided by the present invention;

[0045] Figure 2 It is a schematic structural diagram of an optical fiber provided by the present invention;

[0046] Figure 3 It is a schematic structural diagram of an optical transmission system provided by the present invention;

[0047] Figure 4 It is a schematic structural diagram of an integrated coherent receiver provided by the present invention. Detailed implementation mode

[0048] The core of the present invention is to provide an optical emission chip, an optical fiber, and an optical signal transmission system. In the present invention, a beam emitted by a transmitting laser is divided into a first sub-beam and a second sub-beam by a first beam splitter. On the one hand, the optical field mode of the first sub-beam is converted into a high-order mode to obtain a local oscillator light (so that the local oscillator light can be coupled to the cladding of the optical fiber for transmission). On the other hand, the information to be transmitted is coupled to the second sub-beam to obtain a signal light, so that the signal light can be coupled to the core of the optical fiber for transmission. Finally, the local oscillator light and the signal light are combined into a beam to be transmitted by a first combiner, so that the beam to be transmitted is transmitted to the receiving end through different layers of the optical fiber. On the one hand, the receiving end does not need to be provided with a laser for generating local oscillator light. On the other hand, the local oscillator light and the signal light can be transmitted through a single optical fiber, which can reduce the cost and hardware complexity of the optical transmission system at the same time.

[0049] In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0050] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of an optical emission chip provided by the present invention. The optical emission chip includes:

[0051] A first beam splitter 1 for dividing a beam emitted by a transmitting laser into a first sub-beam and a second sub-beam;

[0052] A mode conversion device 2 for converting the optical field mode of the first sub-beam into a high-order mode to obtain a local oscillator light, so that the local oscillator light can be coupled to the cladding of the optical fiber, wherein the cladding of the optical fiber is located outside the core;

[0053] A modulation device 3 for coupling the information to be transmitted to the second sub-beam to obtain a signal light, so that the signal light can be coupled to the core of the optical fiber;

[0054] A first combiner 4 for combining the local oscillator light and the signal light into a beam to be transmitted, so that the beam to be transmitted is transmitted to the receiving end through the optical fiber;

[0055] Wherein, the refractive index of the core of the optical fiber is higher than that of the cladding.

[0056] Specifically, considering the technical problems in the above background art and also considering that the light beams obtained from the same light source naturally have relatively low phase noise, and the non-interfering transmission of two light beams in different layers of the same optical fiber can be achieved through the conversion of the optical field mode. Therefore, in the embodiments of the present invention, two sub-beams are desired to be obtained based on the light beams generated by the same light source, and then the local oscillator light and the signal light with different optical field modes are obtained through the conversion of the optical field mode, so as to couple the local oscillator light and the signal light to different layers of the optical fiber for transmission. On the one hand, the requirement for setting a laser (for generating the local oscillator light) at the receiving end is avoided. On the other hand, the synchronous transmission of the local oscillator light and the signal light can be achieved through a single optical fiber, which can significantly reduce the structural complexity and cost of the optical transmission system.

[0057] Specifically, based on the above considerations, in the embodiments of the present invention, first, the light beam emitted by the transmitting laser can be divided into a first sub-beam and a second sub-beam by the first beam splitter 1, so as to obtain the local oscillator light and the modulation light through the first sub-beam and the second sub-beam subsequently. Generally, the first sub-beam and the second sub-beam obtained by splitting the light beam emitted by the transmitting laser have the same frequency and a stable phase correlation basis. Since they are from the same laser source, the influence of internal noise sources such as frequency and phase fluctuations on the two light beams is consistent, and no additional phase noise caused by light source differences will be generated. The optical field modes of the first sub-beam and the second sub-beam obtained by splitting the light beam generated by the transmitting laser are usually the fundamental mode, and the light beam of the fundamental mode tends to be transmitted by the core with a high refractive index in the optical fiber, while the light beam of the higher-order mode tends to be transmitted by the cladding with a low refractive index in the optical fiber. Therefore, in the embodiments of the present invention, the optical field mode of the first sub-beam can be converted into a higher-order mode by the mode conversion device 2 to obtain the local oscillator light, so that the local oscillator light can be coupled to the cladding of the optical fiber and transmitted by the cladding. On the other hand, the information to be transmitted can be coupled to the second sub-beam by the modulation device 3 to obtain the signal light without the need for optical field mode conversion. In this case, the signal light will be coupled to the core of the optical fiber. Since they can be transmitted by different layers of the optical fiber, the local oscillator light and the signal light will not interfere with each other during the transmission process, thus realizing the transmission of the local oscillator light and the signal light by a single optical fiber.

[0058] Among them, the fundamental mode of the signal light can be various, for example, it can be the fundamental mode of TE0, etc. The embodiments of the present invention do not make any limitations here.

[0059] The present invention provides an optical emission chip. Considering that the beams obtained from the same light source naturally have relatively low phase noise, and two beams of light can be transmitted without interference in different layers of the same optical fiber through the conversion of the optical field mode, in the present invention, the beam emitted by the emission laser can be divided into a first sub-beam and a second sub-beam by a first beam splitter. On the one hand, the optical field mode of the first sub-beam is converted into a high-order mode to obtain a local oscillator light (so that the local oscillator light can be coupled to the cladding layer of the optical fiber for transmission). On the other hand, the information to be transmitted is coupled to the second sub-beam to obtain a signal light, so that the signal light can be coupled to the core of the optical fiber for transmission. Finally, the local oscillator light and the signal light are combined into a beam to be transmitted by a first combiner, so that the beam to be transmitted is transmitted to the receiving end through different layers of the optical fiber. On the one hand, the receiving end does not need to be provided with a laser for generating the local oscillator light. On the other hand, the local oscillator light and the signal light can be transmitted through a single optical fiber, which can reduce the cost and hardware complexity of the optical transmission system at the same time.

[0060] Based on the above embodiments:

[0061] As an optional embodiment, the modulation device 3 includes an in-phase quadrature modulator, a first beam splitting device, and a first combining device;

[0062] The input end of the first beam splitting device is connected to the output end of the first beam splitter 1, the output end of the first beam splitting device is connected to the input end of the in-phase quadrature modulator, the output end of the in-phase quadrature modulator is connected to the input end of the first combining device, and the output end of the first combining device is connected to the input end of the first combiner 4.

[0063] Specifically, the in-phase quadrature modulator can select a commercial modulator chip based on materials such as lithium niobate (LiNbO3), silicon-based (Si), or silicon nitride (SiN), which have good electro-optic effects and stability. The first beam splitting device and the first combining device can adopt beam splitters and combiners manufactured based on planar optical waveguide technology, which have high optical path integration and stable performance.

[0064] Specifically, in terms of circuit connection, high-precision optical fibers or optical waveguides can be used to connect the output end of the first beam splitter 1 to the input end of the first beam splitting device to ensure low-loss transmission of optical signals. The output end of the first beam splitting device is connected to the input end of the in-phase quadrature modulator, the output end of the in-phase quadrature modulator is connected to the input end of the first combining device, and the output end of the first combining device is connected to the input end of the first combiner 4, all of which are accurately connected through appropriate optical interfaces to ensure accurate introduction of optical signals into each component. In terms of parameter setting and debugging, the parameters such as the bias voltage and modulation rate of the in-phase quadrature modulator can be set according to the overall design requirements of the optical emission chip. The optical signal power, spectrum and other indicators at each connection point are monitored and debugged through instruments such as an optical power meter and a spectrum analyzer to ensure the normal operation of the modulation device 3.

[0065] Specifically, the modulation device 3 in the embodiments of the present invention has the advantages of simple structure, low cost, and strong stability.

[0066] Of course, in addition to this specific form, the modulation device 3 can also be in other specific forms, which are not limited in the embodiments of the present invention.

[0067] As an alternative embodiment, the first beam splitting device includes a second beam splitter, a third beam splitter, and a fourth beam splitter; the first beam combining device includes a second beam combiner, a third beam combiner, and a fourth beam combiner;

[0068] The input end of the second beam splitter serves as the input end of the first beam splitting device. The first output end of the second beam splitter is connected to the input end of the third beam splitter, and the second output end of the second beam splitter is connected to the input end of the fourth beam splitter. The output end of the third beam splitter is connected to the input end of the in-phase modulation unit of the in-phase quadrature modulator, and the output end of the fourth beam splitter is connected to the input end of the quadrature modulation unit of the in-phase quadrature modulator. The input end of the third beam combiner is connected to the output end of the in-phase modulation unit, and the input end of the fourth beam combiner is connected to the output end of the quadrature modulation unit. The output end of the third beam combiner is connected to the first input end of the second beam combiner, and the output end of the fourth beam combiner is connected to the second input end of the second beam combiner. The output end of the second beam combiner serves as the output end of the first beam combining device;

[0069] The in-phase quadrature modulator includes an in-phase modulation unit and a quadrature modulation unit.

[0070] Specifically, the first beam splitting device and the first beam combining device in the embodiments of the invention have the advantages of simple structure and low cost. In terms of component selection, the first, second, third, and fourth beam splitters and the first, second, third, and fourth beam combiners can adopt fused biconical taper type or microelectromechanical system type beam splitters / combiners. The former has lower cost and mature technology; the latter can achieve high-precision optical path control. The in-phase modulation unit and the quadrature modulation unit can select the structure of a dual parallel Mach-Zehnder modulator (DP-MZM, Dual - Parallel Mach - Zehnder Modulator) integrated on the same chip to implement the in-phase and quadrature modulation functions. In terms of optical path construction, optical fibers or optical waveguides can be used to connect each beam splitter, beam combiner, and modulation unit in sequence. For example, an optical signal output from the second beam splitter is processed by the third beam splitter and then connected to the input end of the in-phase modulation unit, and the other path is processed by the fourth beam splitter and then connected to the input end of the quadrature modulation unit; the output signals of the in-phase modulation unit and the quadrature modulation unit are respectively connected to the third beam combiner and the fourth beam combiner, and then their output signals are connected to the second beam combiner. In terms of performance optimization, the transmission efficiency of optical signals between components can be optimized by adjusting parameters such as the splitting ratio of the beam splitter and the coupling efficiency of the beam combiner. Using phase control technology to ensure phase matching between the in-phase modulation unit and the quadrature modulation unit and improve the modulation accuracy.

[0071] Certainly, in addition to the specific structures in the embodiments of the present invention, the first beam combining device and the first beam splitting device may also be of other specific structures, which are not limited in the embodiments of the present invention.

[0072] As an alternative embodiment, the emitting laser includes a distributed feedback laser.

[0073] Specifically, the distributed feedback laser (DFB, Distributed Feedback Laser) has the advantages of low cost and strong stability. In terms of selection, a distributed feedback laser that meets the design specifications of the optical emission chip can be selected, such as a DFB laser with a wavelength in the communication band of 1310 nm or 1550 nm, an output power of 0 dBm to 10 dBm, and a linewidth less than 10 MHz, so as to meet the requirements of wavelength, power, and spectral purity for optical signal emission.

[0074] Certainly, in addition to this specific type, the emitting laser may also be other types of narrow linewidth lasers to reduce costs, which are not limited in the embodiments of the present invention.

[0075] As an alternative embodiment, the mode conversion device 2 includes an input waveguide, a mode coupling structure, a cladding region, and an output waveguide;

[0076] The input waveguide is used to input the first sub-beam so as to introduce the first sub-beam into the mode conversion device 2;

[0077] The mode coupling structure is used to couple the first sub-beam between different waveguide modes through its own waveguide structure and refractive index distribution, and excite high-order modes by using the phase matching condition;

[0078] The cladding region is used to change the effective refractive index of the waveguide mode to meet the phase matching condition required for mode conversion;

[0079] The output waveguide is used to output the local oscillator light obtained by mode conversion from the mode conversion device 2.

[0080] Specifically, the mode conversion device 2 in the embodiments of the present invention belongs to a mode conversion device 2 based on the waveguide mode conversion principle, and has the advantages of simple structure, low cost, and strong stability. The input waveguide therein can provide a stable optical input port; the mode coupling structure can be of various types. For example, it can be an asymmetric mode coupler, which can be composed of a sub-wavelength grating waveguide and a strip multi-mode waveguide, etc. Through a specific waveguide structure and refractive index distribution, the input light is coupled between different waveguide modes, and the high-order mode is excited by using the phase matching condition; the cladding region can include an upper cladding and a lower cladding, and by setting cladding materials with different refractive indices, the effective refractive index of the waveguide mode can be changed to meet the phase matching condition required for mode conversion, so as to realize the regulation of the mode conversion function; while the output waveguide can export the light after mode conversion from the mode conversion device 2 and connect to the subsequent optical signal processing module.

[0081] Of course, in addition to this specific structure, the mode conversion device 2 can also be of other specific structure types, which are not limited in the embodiments of the present invention.

[0082] Please refer to Figure 2 , Figure 2 which is a schematic structural diagram of an optical fiber provided by the present invention. The optical fiber includes a core, a cladding, and a coating layer;

[0083] The cladding is located between the core and the coating layer;

[0084] The core is used to couple and transmit the signal light in the beam to be transmitted;

[0085] The cladding is used to couple and transmit the local oscillator light in the beam to be transmitted;

[0086] The coating layer is used to protect the core and the cladding;

[0087] Among them, the refractive index of the core is higher than that of the cladding, and the beam to be transmitted is generated by the optical emission chip in the foregoing embodiments.

[0088] Specifically, the embodiments of the present invention provide an optical fiber adapted to the foregoing optical emission chip. Different from traditional optical fibers, the cladding of this optical fiber can be used to couple and transmit the local oscillator light in the beam to be transmitted, and the core is used to couple and transmit the signal light in the beam to be transmitted, so that the local oscillator light and the signal light are transmitted in different layers of the optical fiber, preventing the local oscillator light and the signal light from interfering with each other due to being too close during the transmission in the same optical fiber.

[0089] Among them, different layers of the optical fiber can be coaxially designed. The core and the cladding layer can be made of pure silica glass, or some auxiliary materials (such as high-purity silica, polymer materials, fluoride glass, tellurite glass, etc.) can be doped to improve the refractive index. The coating layer can protect the surface of the optical fiber from damage and improve its mechanical strength. The material of the coating layer can be acrylic resin, polyimide, metal, etc., which is not limited in the embodiments of the present invention.

[0090] Specifically, based on a single optical fiber in the embodiments of the present invention, the local oscillator light and the signal light generated by the same laser at the transmitting end can be synchronously transmitted to the receiving end. On the one hand, there is no need to set a laser at the receiving end to generate the local oscillator light. On the other hand, there is no need to perform long-distance transmission of the local oscillator light and the signal light through two optical fibers, which directly simplifies the structure of the optical transmission system and reduces the cost.

[0091] As an alternative embodiment, the cladding layer includes a plurality of sub-cladding layers;

[0092] The cladding layer is specifically used to couple and transmit the local oscillator light in the to-be-transmitted light beam through its multiple sub-cladding layers;

[0093] Among them, the refractive index of the sub-cladding layer close to the core is higher than that of the sub-cladding layer far from the core.

[0094] Specifically, through the design of multiple sub-cladding layers, the transmission position of the local oscillator light can be made farther away from the core, thereby further reducing the mutual interference between the local oscillator light and the signal light during the transmission in the same optical fiber and improving the accuracy of information transmission.

[0095] In addition, as an alternative embodiment, the optical fiber may further include an isolation layer;

[0096] The isolation layer is located between the core and the cladding layer, and the refractive index of the isolation layer is between that of the core and the cladding layer.

[0097] Specifically, considering that the local oscillator light is transmitted in the cladding layer and the signal light is transmitted in the core, there is mutual interference between them, mainly due to the coupling of the optical fields and the interaction of different mode lights. By adding an isolation layer, the local oscillator light and the signal light can be physically separated, reducing the optical field overlap area and reducing the crosstalk between modes. By selecting a suitable isolation layer material to form a specific gradient distribution of its refractive index with the core and the cladding layer, the penetration and interaction of the optical fields can be effectively blocked. For example, using a low-refractive-index material as the isolation layer can limit the propagation range of light in the core and the cladding layer, reducing the leakage and mutual interference of light energy.

[0098] Specifically, various materials can be selected for the isolation layer. For example, they can be: (1) Silica aerogel: It has an extremely low density and refractive index, and can effectively prevent the penetration of the optical field between the core and the cladding. Its nano-porous structure can reduce the propagation speed of light and reduce inter-mode coupling. In the field of optical communication, the low refractive index characteristic of aerogel makes it a potential isolation layer material, which can reduce the mutual interference between the signal light and the local oscillator light. (2) Fluoride glass: Such as ZrF4-BaF2-LaF3-AlF3-NaF series glass, fluoride glass has a low refractive index and good optical uniformity, low absorption of infrared light, and can reduce optical transmission loss. When used in the optical fiber isolation layer, it can reduce the interaction between different mode lights while ensuring low-loss transmission of optical signals. (3) Polymer materials: Such as polytetrafluoroethylene, polymer materials are easy to process and form, and the refractive index can be controlled by adjusting the molecular structure. Polytetrafluoroethylene has chemical stability and a low refractive index, can provide isolation for the optical fiber, reduce the interference between the local oscillator light and the signal light, and can be customized according to requirements. The embodiments of the present invention are not limited herein.

[0099] Among them, the refractive index of the isolation layer is relatively low and is between the core and the cladding. The relatively low refractive index can reduce the leakage of the optical field to the cladding when the signal light is totally reflected and transmitted in the core; while the refractive index higher than that of the cladding can limit the propagation of the local oscillator light in the cladding and prevent it from penetrating into the core. Such a refractive index gradient distribution can physically separate the two kinds of light and reduce mutual interference. For example, if the refractive index of the core is 1.46 and the refractive index of the cladding is 1.44, the refractive index of the isolation layer can be designed between 1.44 and 1.46. The specific value can be precisely optimized according to the specific application scenario and optical performance requirements of the optical fiber. The embodiments of the present invention are not limited herein.

[0100] As an alternative embodiment, the cladding includes a first sub-cladding and a second sub-cladding;

[0101] The diameter of the core is in a first diameter range, the first sub-cladding is in a second diameter range, and the second sub-cladding is in a third diameter range;

[0102] The first diameter range includes 7 μm to 15 μm, the second diameter range includes 7 μm to 90 μm to 200 μm, and the third diameter range includes 7 μm to 150 μm to 500 μm.

[0103] Specifically, Figure 2 R in c is the diameter of the core, R cl1 is the diameter of the first sub-cladding, R cl2 is the diameter of the second sub-cladding, R f is the diameter of the coating layer.

[0104] Specifically, through the design of two sub-cladding layers, the local oscillator light can be coupled to the vicinity of the interface between the first sub-cladding layer and the second sub-cladding layer for transmission, thereby increasing the distance between the local oscillator light and the signal light in the optical fiber, reducing the mutual interference between the two, and improving the information transmission accuracy.

[0105] Specifically, in terms of the selection of the optical fiber material, the core can use high-purity silica (SiO2) as the core material. Because silica has good optical properties such as low loss and high transparency, it can ensure the efficient transmission of the signal light in the core. To increase the refractive index of the core, elements such as germanium (Ge) can be appropriately doped. For example, doping a certain proportion of germanium in silica can make the refractive index of the core meet the design requirements while ensuring the transmission quality of the signal light. The first sub-cladding layer can use silica doped with a small amount of fluorine (F). The doping of fluorine can reduce the refractive index of silica, making its refractive index lower than that of the core. Such a refractive index difference helps to confine the signal light in the core for transmission and reduce the leakage of the signal light. The second sub-cladding layer can also use silica, but the fluorine content doped can be higher than that of the first sub-cladding layer to further reduce its refractive index, so as to better confine the local oscillator light between the first sub-cladding layer and the second sub-cladding layer and reduce the mutual interference between the local oscillator light and the signal light.

[0106] Specifically, through the above setting of the diameter range, the material consumption of the optical fiber and the optical transmission quality can be balanced.

[0107] Of course, in addition to the above specific settings, the diameter ranges of each layer of the optical fiber can also be other specific types, which are not limited in the embodiments of the present invention.

[0108] Please refer to Figure 3 , Figure 3 which is a schematic structural diagram of an optical transmission system provided by the present invention. The optical transmission system includes an optical emission chip as described in the foregoing embodiments, an optical fiber as described in the foregoing embodiments, and further includes:

[0109] An emission laser connected to the optical emission chip for generating a light beam;

[0110] An optical receiving device connected to the output end of the optical fiber for performing coherent demodulation on the signal in the light beam to be transmitted.

[0111] Specifically, the emission laser can generate an original light beam, so that the optical emission chip can generate a local oscillator light of a high-order mode and a signal light coupled with the information to be transmitted based on the original light beam, and synthesize them into a light beam to be transmitted. The optical receiving device can receive the light beam to be transmitted sent by the optical fiber and perform coherent demodulation on the signal in the light beam to be transmitted.

[0112] As an alternative embodiment, the optical receiving device includes a mode demultiplexer, a power amplification module, and an integrated coherent receiver;

[0113] The mode demultiplexer is configured to demultiplex the signal light and the local oscillator light;

[0114] The power amplification module is configured to amplify the power of the signal light and the local oscillator light;

[0115] The integrated coherent receiver is configured to perform coherent demodulation based on the signal light and the local oscillator light after power amplification to obtain the information to be transmitted.

[0116] Specifically, the mode demultiplexer can demultiplex the signal light and the local oscillator light in the beam to be transmitted, the power amplification module can amplify the power of the signal light and the local oscillator light to improve the sensitivity of coherent detection, and the integrated coherent receiver can perform coherent demodulation based on the signal light and the local oscillator light after power amplification to obtain the information to be transmitted.

[0117] Specifically, for better illustration of the embodiments of the present invention, please refer to Figure 4 , Figure 4 which is a schematic structural diagram of an integrated coherent receiver provided by the present invention.

[0118] Specifically, the optical mixer: is a key component of the ICR (Integrated Coherent Receiver), which mixes the local oscillator light and the signal light. Through the principle of optical interference, the electric fields of the two beams of light interact with each other to generate a beat signal containing signal information, realizing the coherent processing of the optical signal. The low-pass filter: filters the mixed signal to remove high-frequency noise and unnecessary high-frequency components, and only retains the low-frequency baseband signal to improve the signal quality and facilitate subsequent processing. The photodetector: converts the filtered optical signal into an electrical signal, which is a key link in the optoelectronic conversion, and converts the information carried by the optical signal into an electrical signal form for further processing. Other processing units: perform subsequent processing on the electrical signal output by the photodetector. For example, the RTO (Real-time Oscilloscope) can be used to monitor and analyze the signal characteristics. Other processing units may include functional modules such as signal amplification, analog-to-digital conversion, and digital signal processing to achieve the complete demodulation and analysis of the received signal.

[0119] Of course, in addition to this specific structure, the integrated coherent receiver can also be other structures, which are not limited in the embodiments of the present invention.

[0120] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. It should also be noted that in this specification, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the existence of additional identical elements in the process, method, article or device comprising that element.

[0121] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. An optical emission chip, characterized in that, Comprising: A first beam splitter for splitting the beam emitted by the transmitting laser into a first sub-beam and a second sub-beam; A mode conversion device for converting the optical field mode of the first sub-beam into a high-order mode to obtain a local oscillator light, so that the local oscillator light is coupled to the cladding of the optical fiber, wherein the cladding of the optical fiber is located outside the core; A modulation device for coupling the information to be transmitted to the second sub-beam to obtain a signal light, so that the signal light is coupled to the core of the optical fiber; A first beam combiner for combining the local oscillator light and the signal light into a beam to be transmitted, so that the beam to be transmitted is transmitted to the receiving end through the optical fiber; Wherein, the refractive index of the core of the optical fiber is higher than that of the cladding.

2. The optical emission chip according to claim 1, wherein The modulation device includes an in-phase quadrature modulator, a first beam splitting device and a first beam combining device; The input end of the first beam splitting device is connected to the output end of the first beam splitter, the output end of the first beam splitting device is connected to the input end of the in-phase quadrature modulator, the output end of the in-phase quadrature modulator is connected to the input end of the first beam combining device, and the output end of the first beam combining device is connected to the input end of the first beam combiner.

3. The optical emission chip according to claim 2, wherein The first beam splitting device includes a second beam splitter, a third beam splitter and a fourth beam splitter; the first beam combining device includes a second beam combiner, a third beam combiner and a fourth beam combiner; The input end of the second beam splitter serves as the input end of the first beam splitting device, the first output end of the second beam splitter is connected to the input end of the third beam splitter, the second output end of the second beam splitter is connected to the input end of the fourth beam splitter, the output end of the third beam splitter is connected to the input end of the in-phase modulation unit of the in-phase quadrature modulator, the output end of the fourth beam splitter is connected to the input end of the quadrature modulation unit of the in-phase quadrature modulator, the input end of the third beam combiner is connected to the output end of the in-phase modulation unit, the input end of the fourth beam combiner is connected to the output end of the quadrature modulation unit, the output end of the third beam combiner is connected to the first input end of the second beam combiner, the output end of the fourth beam combiner is connected to the second input end of the second beam combiner, and the output end of the second beam combiner serves as the output end of the first beam combining device; The in-phase quadrature modulator includes an in-phase modulation unit and a quadrature modulation unit.

4. The optical emission chip according to claim 1, characterized in that, The transmitting laser includes a distributed feedback laser.

5. The optical emission chip according to any one of claims 1 to 4, characterized in that, The mode conversion device includes an input waveguide, a mode coupling structure, a cladding region and an output waveguide; The input waveguide is used to input the first sub-beam so as to introduce the first sub-beam into the mode conversion device; The mode coupling structure is used to couple the first sub-beam between different waveguide modes through its own waveguide structure and refractive index distribution, and excite a high-order mode by using the phase matching condition; The cladding region is used to change the effective refractive index of the waveguide mode to meet the phase matching condition required for mode conversion; The output waveguide is used to output the local oscillator light obtained through mode conversion from the mode conversion device.

6. An optical fiber, characterized in that, Including a core, a cladding and a coating layer; The cladding is located between the core and the coating layer; The core is used to couple and transmit the signal light in the beam to be transmitted; The cladding layer is used to couple and transmit the local oscillator light in the beam to be transmitted; The coating layer is used to protect the core and the cladding layer; Wherein, the refractive index of the core is higher than that of the cladding layer, and the beam to be transmitted is generated by the optical emission chip according to any one of claims 1 to 5.

7. The optical fiber according to claim 6, characterized in that, The cladding layer includes a plurality of sub-cladding layers; The cladding layer is specifically used to couple and transmit the local oscillator light in the beam to be transmitted through its plurality of sub-cladding layers; Wherein, the refractive index of the sub-cladding layer closer to the core is higher than that of the sub-cladding layer farther from the core.

8. The optical fiber according to claim 7, characterized in that, The cladding layer includes a first sub-cladding layer and a second sub-cladding layer; The diameter of the core is in a first diameter range, the first sub-cladding layer is in a second diameter range, and the second sub-cladding layer is in a third diameter range; The first diameter range includes 7 microns to 15 microns, the second diameter range includes 7 microns to 90 microns to 200 microns, and the third diameter range includes 7 microns to 150 microns to 500 microns.

9. An optical transmission system, characterized in that, Comprising the optical emission chip according to any one of claims 1 to 5, the optical fiber according to any one of claims 6 to 8, further comprising: An emission laser connected to the optical emission chip for generating a beam; An optical receiving device connected to the output end of the optical fiber for performing coherent demodulation on the signal in the beam to be transmitted.

10. The optical transmission system according to claim 9, wherein The optical receiving device includes a mode demultiplexer, a power amplification module, and an integrated coherent receiver; The mode demultiplexer is used to demultiplex the signal light and the local oscillator light; The power amplification module is used to amplify the power of the signal light and the local oscillator light; The integrated coherent receiver is used to perform coherent demodulation according to the power-amplified signal light and local oscillator light to obtain the information to be transmitted.

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