阅读说明：本技术 一种线性相位调制实现pam4调制码的光芯片 (Optical chip for realizing PAM4 modulation code through linear phase modulation ) 是由 孔祥君 高军毅 于 2019-09-30 设计创作，主要内容包括：本发明涉及一种线性相位调制实现PAM4调制码的光芯片,包括分波的等分Y分支光波导、合波的等分Y分支光波导、两个作为线性电光相位调制臂的电光调制光波导,分波的等分Y分支光波导的输入端通过输入模场耦合光波导与光源相连接导通,两个电光调制光波导对应连接导通分波的等分Y分支光波导的两个输出端与合波的等分Y分支光波导的两个输入端,合波的等分Y分支光波导的输出端连接有输出模场耦合光波导；每个电光调制光波导上均设置有控制线性相位变化的与外接射频信号源相连接的相位控制电极。该发明使用一个激光光源,通过线性相位调制就可实现PAM4调制码型,集成度高,实现方式简单,成本低,体积小,应用范围更广。(The invention relates to an optical chip for realizing PAM4 modulation code by linear phase modulation, which comprises a wave-splitting Y-branch optical waveguide, a wave-combining Y-branch optical waveguide and two electro-optic modulation optical waveguides serving as linear electro-optic phase modulation arms, wherein the input ends of the wave-splitting Y-branch optical waveguides are connected and conducted with a light source through an input mode field coupling optical waveguide; each electro-optical modulation optical waveguide is provided with a phase control electrode which is used for controlling the linear phase change and is connected with an external radio frequency signal source. The invention uses one laser source, can realize PAM4 modulation code pattern through linear phase modulation, and has the advantages of high integration level, simple realization mode, low cost, small volume and wider application range.)

1. The utility model provides an optical chip of PAM4 modulation code is realized to linear phase modulation which characterized in that: the optical waveguide device comprises a wave-splitting equal-splitting Y-branch optical waveguide, a wave-combining equal-splitting Y-branch optical waveguide and two electro-optic modulation optical waveguides serving as linear electro-optic phase modulation arms, wherein the input end of the wave-splitting equal-splitting Y-branch optical waveguide is connected and conducted with a light source through an input mode field coupling optical waveguide, the two output ends of the wave-splitting equal-splitting Y-branch optical waveguide are correspondingly connected and conducted with the input ends of the two electro-optic modulation optical waveguides, the two input ends of the wave-combining equal-splitting Y-branch optical waveguide are correspondingly connected and conducted with the output ends of the two electro-optic modulation optical waveguides, and the output end of the wave-combining equal-splitting Y-; and each electro-optical modulation optical waveguide is provided with a phase control electrode which is used for controlling linear phase change and is connected with an external radio frequency signal source.

2. The optical chip for realizing PAM4 modulation code by linear phase modulation according to claim 1, wherein: and the two output ends of the wave-splitting Y-branch optical waveguide and the two input ends of the wave-combining Y-branch optical waveguide are correspondingly communicated, and static bias electrodes which are used for static compensation and can be electrically connected with an external direct-current power supply are arranged on light paths.

3. The optical chip for realizing PAM4 modulation code by linear phase modulation according to claim 1, wherein: the input mode field coupling optical waveguide, the splitting Y-branch optical waveguide, the electro-optical modulation optical waveguide, the phase control electrode, the combining Y-branch optical waveguide and the output mode field coupling optical waveguide are integrated on the same optical chip.

4. The optical chip for realizing PAM4 modulation code by linear phase modulation according to claim 1, wherein: the input mode field coupling optical waveguide, the wave-splitting Y-branch optical waveguide, the electro-optic modulation optical waveguide, the wave-combining Y-branch optical waveguide and the output mode field coupling optical waveguide are integrally formed lithium niobate thin film optical waveguides.

Technical Field

The invention relates to the field of optical communication, in particular to an optical chip for realizing PAM4 modulation codes by linear phase modulation, which has the advantages of small volume, simple realization mode and high integration level.

Background

In the 5G era, higher requirements are required for network transmission rate and higher requirements are required for system capacity, and in order to improve the network capacity of high-speed interconnection and reduce the transmission cost per bit, a 4-level amplitude Modulation (PAM 4) technology is introduced to improve the transmission rate. The PAM4 modulation mode adopts 4 different signal levels for signal transmission, each symbol period can represent logic information (0, 1, 2, 3) of 2 bits, bandwidth utilization efficiency can be effectively improved, and meanwhile, the PAM4 adopts a high-order modulation format, so that the requirement on the performance of an optical device can be reduced, and a balance can be achieved among the performance, cost, power consumption and density of different application occasions. However, in the prior art, two lasers and two modulators are required for generating the PAM4 signal, the requirement on the control accuracy of the device is high, the implementation mode is complex, the cost is relatively high, and the application range is limited.

Disclosure of Invention

Aiming at the existing defects, the invention provides the optical chip for realizing the PAM4 modulation code by linear phase modulation, which has the advantages of small volume, simple realization mode and high integration level.

The technical scheme adopted by the invention for solving the technical problems is as follows:

an optical chip for realizing PAM4 modulation code by linear phase modulation comprises a wave-splitting Y-branch optical waveguide, a wave-combining Y-branch optical waveguide and two electro-optic modulation optical waveguides serving as linear electro-optic phase modulation arms, wherein the input ends of the wave-splitting Y-branch optical waveguides are connected and conducted with a light source through an input mode field coupling optical waveguide, the two output ends of the wave-splitting Y-branch optical waveguide are correspondingly connected and conducted with the input ends of the two electro-optic modulation optical waveguides, the two input ends of the wave-combining Y-branch optical waveguide are correspondingly connected and conducted with the output ends of the two electro-optic modulation optical waveguides, and the output ends of the wave-combining Y-branch optical waveguides are connected with an output mode field coupling optical waveguide; and each electro-optical modulation optical waveguide is provided with a phase control electrode which is used for controlling linear phase change and is connected with an external radio frequency signal source.

Preferably, a static bias electrode for static compensation and electrically connected with an external direct current power supply is arranged on each of light paths through which two output ends of the split Y-branch optical waveguide of the split wave and two input ends of the split Y-branch optical waveguide of the combined wave are correspondingly communicated.

Preferably, the input mode field coupling optical waveguide, the split optical waveguide, the electro-optical modulation optical waveguide, the phase control electrode, the combined optical waveguide, and the output mode field coupling optical waveguide are integrated on the same optical chip.

Preferably, the input mode field coupling optical waveguide, the splitting Y-branch optical waveguide, the electro-optic modulation optical waveguide, the combining Y-branch optical waveguide, and the output mode field coupling optical waveguide are integrally formed lithium niobate thin film optical waveguides.

The invention has the beneficial effects that: the invention only needs one laser light source, external continuous laser is led in through an input mode field coupling optical waveguide and a split Y-branch waveguide of split waves, two paths of light with equal amplitude are formed after the split waves, then the two paths of light are respectively transmitted to the input end of a split Y-branch optical waveguide of combined waves through an electro-optical modulation optical waveguide, and then the signals are led out through an output field coupling optical waveguide after the split Y-branch optical waveguide of the combined waves is combined, so that a complete optical loop is formed. All set up the phase control electrode on every electro-optical modulation optical waveguide, through the amplitude adjustment to external radio frequency signal, produce the adjustment of waveguide medium electric field intensity, because the effect of electro-optical effect makes the refracting index of electro-optical modulation optical waveguide produce corresponding change, lead to the light through two electro-optical modulation optical waveguides to produce the phase difference, when external radio frequency signal amplitude satisfies PAM4 signal waveform, the wave-combining optical waveguide produces interference effect, the light amplitude of output just also forms corresponding PAM4 signal waveform, its implementation is simpler, the cost is lower, the volume can reduce ten to hundred times, the integration improves by a wide margin, its range of application has been enlarged.

Drawings

FIG. 1 is a schematic structural diagram of an embodiment of the present invention;

part names and serial numbers in the figure: 1-split Y-branch optical waveguide of 1-split wave, 2-split Y-branch optical waveguide of composite wave, 3-electro-optical modulation optical waveguide, 4-input mode field coupling optical waveguide, 5-output mode field coupling optical waveguide, 6-phase control electrode, 7-static bias electrode.

Detailed Description

To more clearly illustrate the objects, technical solutions and advantages of the embodiments of the present invention, the present invention will be further described in detail with reference to the accompanying drawings and embodiments, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without inventive step, are within the scope of the present invention.

In the embodiment of the present invention, as shown in fig. 1, an optical chip for realizing PAM4 modulation code by linear phase modulation includes a splitting Y-branch optical waveguide 1, a combining Y-branch optical waveguide 2, and two electro-optic modulation optical waveguides 3 as linear electro-optic phase modulation arms, wherein the input end of the splitting Y-branch optical waveguide 1 is connected and conducted with a light source through an input mode field coupling optical waveguide 4, the two output ends of the splitting Y-branch optical waveguide 1 are correspondingly connected and conducted with the input ends of the two electro-optic modulation optical waveguides 3, the two input ends of the combining Y-branch optical waveguide 2 are correspondingly connected and conducted with the output ends of the two electro-optic modulation optical waveguides 3, and the output end of the combining Y-branch optical waveguide 1 is connected with an output mode field coupling optical waveguide 5, so as to connect the splitting Y-branch optical waveguide 1, the electro-optic modulation optical waveguides 3, and the two electro-optic modulation optical waveguides 3 to form a, The equal Y-branch optical waveguides 2 of the combined wave are connected in sequence and are mutually light-guided, the equal Y-branch optical waveguides 1 of the split wave are used as the split wave, that is, the equal Y-branch optical waveguides 1 of the split wave are provided with an input end and two output ends, the input end of the equal Y-branch optical waveguides is coupled with a single continuous laser light source through an input mode field coupling optical waveguide 4, the light emitted by the single continuous laser light source forms two paths of light with equal amplitude through the split wave of the equal Y-branch optical waveguides 1 of the split wave after entering through the input mode field coupling optical waveguide 4, the two paths of light are transmitted to the corresponding electro-optical modulation optical waveguides 3, the equal Y-branch optical waveguides 2 of the combined wave are used for the combined wave, that is, the equal Y-branch optical waveguides are provided with two input ends and one output ends, the two input ends are correspondingly connected with the output ends of the two electro-optical modulation optical waveguides 3, so, then, after wave combination is carried out through the halved Y-branch optical waveguide 2 of the wave combination, signals are led out through the output field coupling optical waveguide 5 to form a complete optical loop; here, each of the electro-optical modulation optical waveguides 3 is provided with a phase control electrode 6 connected with an external radio frequency signal source for controlling linear phase change, the adjustment of the electric field intensity of a waveguide medium is generated by adjusting the amplitude of an external radio frequency signal, the refractive index of the electro-optical modulation optical waveguide 3 is correspondingly changed under the action of an electro-optical effect by changing the voltage on the phase control electrode 6, so that the light passing through the two electro-optical modulation optical waveguides 3 generates a phase difference, when the amplitude of the external radio frequency signal meets the PAM4 signal waveform, the wave combining optical waveguide generates an interference effect, the output light intensity also forms a corresponding PAM4 signal waveform, and the modulation principle is as follows:

setting the amplitude of input light to be 3A and the optical phase difference in the first electro-optical modulation optical waveguide and the second electro-optical modulation optical waveguide to be theta; after the wave division, the light amplitude in each channel is 1.5A, and the light intensity at the time point t in the two optical waveguides can be respectively written as E₁(t)＝1.5Asin(ωt),E₂(t)＝1.5Asin(ωt+θ)

The light intensity after the superposition is E (t) ═ E₁(t)+E₂(t)＝1.5Asin(ωt)+1.5Asin(ωt+θ)

E(t)＝3Asin(ωt+θ/2)cos(θ/2)

The values of θ were taken as 180 °, 141.06 °, 96.38 ° and 0 °, respectively, and the results after finishing were as shown in table 1:

TABLE 1

Where E (t) is the light intensity, A is the unit light amplitude value, t is the time, ω is the angular frequency, and θ is the optical phase difference in the two electro-optically modulated optical waveguides.

In a further improvement, as shown in fig. 1, a static bias electrode 7 for static compensation and electrically connected to an external dc power supply is disposed on a light path where two output ends of the split Y-branch optical waveguide 1 and two input ends of the combined Y-branch optical waveguide 2 are correspondingly communicated. Since the electro-optical modulation optical waveguide 3 is connected between the output end of the splitting Y-branch optical waveguide 1 and the input end of the combining Y-branch optical waveguide 2 and conducts the light to form an optical path, the static bias electrode 7 can be arranged at any position on the output end of the splitting Y-branch optical waveguide 1, the electro-optical modulation optical waveguide 3 and the input end of the combining Y-branch optical waveguide 2, so that the tiny deviation of the refractive index caused by the electro-optical modulation optical waveguide 3 in the production process can be solved, and the tiny deviation can be eliminated by applying a direct current bias on the bias electrode. At this time, the static bias electrode 7 and the phase control electrode 6 are both independently arranged and are isolated from the corresponding optical waveguide through insulating layers arranged on the upper surface and the lower surface of the optical waveguide, the direction of the electrodes is parallel to the optical waveguide, and the electrodes and the optical waveguide are integrated on the same optical chip during manufacturing. The external direct current power supply on the static bias electrode 7 is an independently adjusted direct current power supply, and can be independently adjusted without influence, and the static bias electrode 7 which is independently arranged can conveniently realize the static fine adjustment of the signal phase on the light path, thereby ensuring good extinction ratio.

In a further improvement, as shown in fig. 1, in order to make the light propagation smoother and avoid interference, the input mode field coupling optical waveguide 4, the split equal Y-branch optical waveguide 1, the electro-optical modulation optical waveguide 3, the phase control electrode 6, the combined equal Y-branch optical waveguide 2, and the output mode field coupling optical waveguide 7 are integrated on the same optical chip. The input mode field coupling optical waveguide 4, the splitting Y-branch optical waveguide 1, the electro-optical modulation optical waveguide 3, the combining Y-branch optical waveguide 2 and the output mode field coupling optical waveguide 7 are integrally formed lithium niobate thin film optical waveguides, that is, the lithium niobate thin film optical waveguides are integrally formed on the same substrate and can be conducted by light, the structure is simplified, the substrate can be made of different crystal materials, such as glass, lithium niobate, lithium tantalate, gallium arsenide, monocrystalline silicon and other multilayer composite materials, and preferably thin film lithium niobate with good electro-optical characteristics is used as the substrate to manufacture the lithium niobate thin film optical waveguides, so that the volume of the lithium niobate thin film optical waveguides is reduced, and the production of miniaturized products is facilitated. The phase control electrode 6 is separated from the corresponding electro-optical modulation optical waveguide 3 by the insulating layers arranged on the upper and lower surfaces of the optical waveguide, the electrode direction is parallel to the electro-optical modulation optical waveguide, and the electrode and the electro-optical modulation optical waveguide are integrated on the same optical chip during manufacturing. When light passes through the electro-optical modulation optical waveguide 3, the phase amplitude of the light after passing through the electro-optical modulation optical waveguide 3 is changed by modulating the phase control electrode 6, and finally the light is output after being multiplexed by the halved Y-branch optical waveguide 2 of the multiplexed wave, when the amplitude of an external radio frequency signal meets the PAM4 signal waveform, the output light amplitude also forms a corresponding complete PAM4 signal waveform, and finally the PAM4 signal is output by coupling the output mode field with the optical waveguide.

It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.