Tunable photoelectric oscillator based on DML-SOA laser chip

Abstract

The invention discloses a tunable photoelectric oscillator based on a DML-SOA laser chip, and belongs to the technical field of semiconductor processes. Comprising a self-feedback laser, the self-feedback laser packages a DML-SOA laser and an optical isolator in a butterfly-shaped tube shell, the butterfly-shaped tube shell is sequentially connected with an optical delay line and a photoelectric detector through optical paths, the photoelectric detector is connected with an electric amplifier through a circuit, and the electric amplifier is connected with an electric coupler through a circuit. One path of the electric coupler is connected with the Bias-T through a circuit, the other path of the electric coupler serves as microwave signal output, and the direct-current power source is connected with the Bias-T and the self-feedback laser at the same time. The P-1 oscillator has the advantages of being compact in structure, high in signal-to-noise ratio and low in phase noise, the P-1 oscillation phenomenon with the tunable frequency interval can be achieved only through simple electric injection tuning, and the P-1 oscillator has wide application prospects in the fields of photoelectric integration and microwave signal generation.

Description

Technical Field

[0001] The invention relates to the field of semiconductor process technology, and in particular to a tunable optoelectronic oscillator based on a DML-SOA laser chip. Background Art

[0002] Optoelectronic oscillators have great potential application value in the fields of optical sensing, radar, wireless communication, etc., and provide an ideal solution for the generation of some high-frequency, low-phase noise signals. For example, in radar systems, they are used for frequency synthesis and microwave signal generation. In 5G wireless communications, optoelectronic oscillators can provide high stability and tuned frequency output to meet the frequency synthesis requirements between small base stations and base stations in 5G networks. However, traditional optoelectronic oscillators usually require external modulators to provide RF loading and complex optical circuits to provide optical feedback, which not only increases the complexity of the system, but also leads to large size and high power consumption. In order to solve these problems, researchers have tried to combine light sources with amplifiers to simplify the system in recent years. However, the current technical solutions still have many limitations, especially in frequency tuning, system integration and size optimization. In addition, in order to achieve tunable optoelectronic oscillation microwave output in traditional solutions, the wavelength of the laser light source is generally tuned to tune the filter peak of the photonic microwave filter, and a microwave phase shifter is used at the same time to finally achieve a large range of continuous tuning of the optoelectronic oscillator. This method increases the complexity of the system and the requirements for the light source. Another way is to change the phase of the oscillation frequency in the ring cavity by adjusting the bias voltage of the electrical phase shifter [Ke ren, et.al. Fine Frequency Tunable Optoelectronic Oscillator Based on Electrical Phase Shifter], which is equivalent to changing the ring cavity delay and ultimately changing the ring cavity oscillation frequency. However, the frequency tunable range is too narrow, with a tuning range of only about 5.5MHz. Summary of the invention

[0003] The purpose of the present invention is to provide a tunable optoelectronic oscillator based on a DML-SOA laser chip, which realizes a more compact and stable system structure through a monolithic integrated DML-SOA chip. The on-chip DML provides a direct radio frequency optoelectronic converter, realizes the SOA of optical feedback amplification, provides a tunable P-1 oscillation, and realizes a tunable photon microwave signal output.

[0004] To achieve the above-mentioned purpose, the present invention provides a tunable optoelectronic oscillator based on a DML-SOA laser chip, comprising a self-feedback laser, wherein the self-feedback laser encapsulates a monolithically integrated DML-SOA laser and an optical isolator in a butterfly tube shell and is sequentially connected to an optical delay line and a photodetector through an optical path, wherein the photodetector converts an optical signal into an electrical signal and is connected to an electrical amplifier through a circuit, wherein the electrical amplifier amplifies the signal and is connected to an electrical coupler through a circuit, wherein one path of the electrical coupler is connected to a Bias-T through a circuit, and a microwave signal is reloaded to the DML part of the DML-SOA laser through the Bias-T to form an optoelectronic circuit, and the other path of the electrical coupler is output as a microwave signal, and a DC power supply is simultaneously connected to the Bias-T and the SOA part of the DML-SOA laser.

[0005] Preferably, the DML-SOA laser is a monolithic integrated structure, including a DML part and an SOA part. The DML part realizes direct modulation of the RF loop signal by direct modulation, and the SOA part, as an optical amplification feedback, can realize the frequency-interval-tunable P-1 oscillation phenomenon, thereby providing a simple way to generate optical high-frequency microwaves, which is different from other solutions that realize tunable optical feedback through an external optical fiber loop. Here, high integration is achieved, and no mechanical optical attenuator is required to control the feedback strength. This solution can be achieved by simple electrical injection tuning.

[0006] Preferably, the DC power supply and the Bias-T are connected to the SOA part, on the one hand, providing electrical injection gain for the DML to achieve the lasing of the laser and adjust the bias position of the DML direct-modulated laser to achieve the target tuning effect; on the other hand, power is supplied to the SOA part to realize tunable amplification feedback to achieve P-1 oscillation and complete tunable microwave signal output.

[0007] Preferably, the electric coupler adopts a 1×2 electric coupler, one of which is used as the final microwave output signal and the other is used as electrical feedback, which is directly loaded onto the DML through the Bias-T to realize the closed loop of the optoelectronic resonator.

[0008] Preferably, the optical delay line is connected to a jumper wire after the DML-SOA laser and the optical isolator are packaged.

[0009] Preferably, the optical delay line adopts one of single-mode optical fiber, FBG optical fiber or other optical delay devices.

[0010] Preferably, the optical isolator is located at the light outlet of the DML-SOA laser or is directly packaged in the laser tube of the DML-SOA laser.

[0011] Preferably, the DC power supply is a DC bias power supply.

[0012] Therefore, the present invention adopts a tunable optoelectronic oscillator based on a DML-SOA laser chip with the above structure, which has the following beneficial effects: (1) The present invention is based on the InP semiconductor process platform and realizes the monolithic integration of the core part of the tunable optoelectronic oscillator, which also greatly simplifies the system, reduces costs and improves the yield rate. The laser gain and direct modulation part (DML) and the tunable optical amplifier feedback part (SOA) are integrated into a single chip.

[0013] (2) The DML part of the present invention realizes direct modulation of the RF loop signal by direct modulation, eliminating the external laser, polarization controller and external modulator in the traditional solution. In addition, since there is no external modulator, the optical loss is smaller and the use of external EDFA can be eliminated, which greatly simplifies the system volume and increases the system stability.

[0014] (3) The SOA part in the present invention acts as an optical amplification feedback, which can realize the P-1 oscillation phenomenon with tunable frequency interval, thus providing a simple way to generate optical high-frequency microwaves, which is different from other schemes that use external optical fiber loops to achieve tunable optical feedback. Here, high integration is achieved, and no mechanical optical attenuator is required to control the feedback intensity. This scheme can be achieved by simple electrical injection tuning.

[0015] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of a tunable optoelectronic oscillator system based on a DML-SOA chip according to the present invention; Figure 2 Schematic diagram of the spectrum of the P-1 oscillation phenomenon of the DML-SOA chip in this embodiment; Figure 3 Schematic diagram of the spectrum of the P-1 oscillation phenomenon of the DML-SOA chip in this embodiment; Figure 4 Schematic diagram of microwave signal output of the tunable optoelectronic oscillator in this embodiment; Figure 5 Schematic diagram of microwave signal phase noise characterization of the tunable optoelectronic oscillator in this embodiment. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0018] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0019] Example See also Figure 1 The present invention provides a tunable optoelectronic oscillator based on a DML-SOA laser chip, including a self-feedback laser, which encapsulates a monolithic integrated DML-SOA laser and an optical isolator in a butterfly tube shell and is connected to an optical delay line and a photodetector in turn through an optical path, the photodetector converts the optical signal into an electrical signal and is connected to an electrical amplifier through a circuit, the electrical amplifier amplifies the signal and is connected to an electrical coupler through a circuit, one of the electrical couplers is connected to a Bias-T through a circuit, and the microwave signal is reloaded to the DML part of the DML-SOA laser through the Bias-T (DC bias device) to form an optoelectronic circuit, the other path of the electrical coupler is used as a microwave signal output, and a DC power supply is connected to the Bias-T and the SOA part of the DML-SOA laser at the same time. The DC power supply is a DC bias power supply.

[0020] The optical isolator is located at the light outlet of the DML-SOA laser to prevent the optical reflection of the external system from entering the laser and affecting the laser's lasing mode. In addition, the optical isolator can be directly packaged in the laser tube of the DML-SOA laser to achieve a higher level of integration.

[0021] The optical delay line is directly connected to the jumper wire after the DML-SOA laser and the optical isolator are packaged. The optical delay line adopts one of single-mode optical fiber, FBG optical fiber or other optical delay devices.

[0022] The photodetector is directly connected to the optical delay line to convert the optical signal into an electrical microwave signal. The beat frequency is generated in the photodetector by lasers of different wavelengths. The electrical amplifier is directly connected to the photodetector to achieve low-noise amplification of the microwave signal.

[0023] The DML-SOA laser is a monolithic integrated structure, including the DML part and the SOA part. The DML part realizes direct modulation of the RF loop signal by direct modulation. The SOA part, as an optical amplification feedback, can realize the P-1 oscillation phenomenon with tunable frequency interval, thus providing a simple way to generate optical high-frequency microwaves, which is different from other solutions that realize tunable optical feedback through external optical fiber loops. Here, high integration is achieved, and there is no need for a mechanical optical attenuator to control the feedback intensity. This solution can be achieved through simple electrical injection tuning.

[0024] The DC power supply and Bias-T are connected to the SOA part. On the one hand, they provide electrical injection gain for the DML to realize the lasing of the laser and adjust the Bias-T position of the DML direct-modulated laser to achieve the target tuning effect; on the other hand, they power the SOA part to realize tunable amplification feedback to achieve P-1 oscillation and complete tunable microwave signal output.

[0025] The electric coupler uses a 1×2 electric coupler, one of which is used as the final microwave output signal and the other is used as electrical feedback, which is directly loaded onto the DML through the Bias-T to realize the closed loop of the optoelectronic resonator.

[0026] See Figure 2 and 3 They are respectively schematic diagrams of the spectrum and frequency signal of the P-1 oscillation generated under the action of optical amplification feedback.

[0027] Figure 2 This is a schematic diagram of the spectrum signal of P-1 oscillation generated by optical amplification feedback. Under the action of optical self-feedback, some nonlinear phenomena occur, resulting in the splitting of the optical resonance frequency. It can be seen that two pairs of sub-frequency peaks are symmetrically generated on both sides of the main frequency, with a wavelength interval of about 0.1nm and a corresponding frequency interval of about 12.5GHz. Therefore, if the signal is received through the PD beat frequency, a 12.5GHz microwave signal can be generated.

[0028] Figure 3 The schematic diagram of the spectrum signal of P-1 oscillation generated by optical amplification feedback shows that a 12.5 GHz microwave signal can be generated, which is generated by the beat frequency of two adjacent wavelengths received by the PD. In addition, there is a 25 GHz microwave signal with lower power, which is generated by the beat frequency between the alternate wavelengths.

[0029] Figure 4This is a schematic diagram of the output of microwave signals of a tunable optoelectronic oscillator at different frequencies. Under the action of optical amplification feedback, by tuning the intensity ratio of optical feedback, P-1 oscillations of different wavelength intervals can be generated, that is, microwave signals of different frequencies can be generated. The signal outputs of different frequencies all have a signal-to-noise ratio of more than 40dB, showing good signal quality.

[0030] Figure 5 The figure is a schematic diagram of the phase noise of the microwave signal of the tunable optoelectronic oscillator. The phase noise at a frequency offset of 10kHz is as low as −121.8dBc / Hz, and the phase noise at other frequency offsets is lower than −110.7dBc / Hz, showing good microwave signal quality.

[0031] Therefore, the present invention adopts the above-mentioned tunable optoelectronic oscillator based on the DML-SOA laser chip, directly loads the radio frequency signal onto the direct modulated laser DML, and uses the semiconductor optical amplifier SOA to generate self-feedback amplification to generate P-1 oscillation with tunable wavelength interval, thereby realizing optoelectronic oscillation output with tunable wavelength interval. The optoelectronic oscillator does not require feedback from an external modulator and an external optical circuit, which greatly simplifies the system structure and reduces the system volume. By adjusting the current injection ratio of the DML and the SOA, the P-1Period-One oscillation mode can be tuned, thereby realizing tunable microwave signal output with a wavelength interval of 12 GHz to 13 GHz. The system has the characteristics of compact structure, high signal-to-noise ratio and low phase noise. The present invention has broad application prospects in the fields of optoelectronic integration and microwave signal generation.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A tunable optoelectronic oscillator based on a DML-SOA laser chip, characterized in that: The invention comprises a self-feedback laser, wherein the self-feedback laser encapsulates a DML-SOA laser and an optical isolator in a butterfly tube shell, and is sequentially connected to an optical delay line and a photodetector through an optical path, the photodetector is connected to an electric amplifier through a circuit, the electric amplifier is connected to an electric coupler through a circuit, one path of the electric coupler is connected to a Bias-T through a circuit, the other path of the electric coupler is output as a microwave signal, and a direct current power supply is simultaneously connected to the Bias-T and the self-feedback laser.

2. The tunable optoelectronic oscillator based on a DML-SOA laser chip according to claim 1, characterized in that: The DML-SOA laser is a monolithic integrated structure, including a DML part and an SOA part. The DML part realizes direct modulation of the radio frequency loop signal by direct modulation, and the SOA part serves as optical amplification feedback.

3. The tunable optoelectronic oscillator based on a DML-SOA laser chip according to claim 2, characterized in that: The DC power supply and the Bias-T are connected to the SOA part, and are used to provide electrical injection gain for the DML and power the SOA part.

4. The tunable optoelectronic oscillator based on a DML-SOA laser chip according to claim 2, characterized in that: The electric coupler adopts a 1×2 electric coupler, one of which is used as the final microwave output signal, and the other is used as electrical feedback, which is directly loaded onto the DML through the Bias-T.

5. The tunable optoelectronic oscillator based on a DML-SOA laser chip according to claim 1, characterized in that: The optical delay line is connected to the jumper wire after the DML-SOA laser and the optical isolator are packaged.

6. The tunable optoelectronic oscillator based on a DML-SOA laser chip according to claim 1, characterized in that: The optical delay line adopts one of single-mode optical fiber, FBG optical fiber or other optical delay devices.

7. The tunable optoelectronic oscillator based on a DML-SOA laser chip according to claim 1, characterized in that: The optical isolator is located at the light outlet of the DML-SOA laser or is directly packaged in the laser tube of the DML-SOA laser.

8. The tunable optoelectronic oscillator based on a DML-SOA laser chip according to claim 1, characterized in that: The DC power supply is a DC bias power supply.

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