A tunable optoelectronic oscillator based on a dml-soa laser chip

Abstract

The application discloses a tunable optoelectronic oscillator based on a DML-SOA laser chip and belongs to the technical field of semiconductor processes. The tunable optoelectronic oscillator comprises a self-feedback laser, the self-feedback laser encapsulates a DML-SOA laser and an optical isolator in a butterfly tube shell, and is sequentially connected with an optical time delay line and an optoelectronic detector through an optical path, the optoelectronic detector is connected with an electrical amplifier through an electric circuit, the electrical amplifier is connected with an electrical coupler through an electric circuit, one of the electrical coupler is connected with a Bias-T through an electric circuit, the other of the electrical coupler is used as a microwave signal output, and a direct-current power supply is connected with the Bias-T and the self-feedback laser simultaneously. The tunable optoelectronic oscillator has the characteristics of compact structure, high signal-to-noise ratio and low phase noise, can realize a P-1 oscillation phenomenon with adjustable frequency interval through simple electrical injection tuning, and has a wide application prospect in the field of optoelectronic integration and microwave signal generation.

Description

Technical Field

[0001] This 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 Technology

[0002] Opto-oscillators (OOs) have enormous potential applications in optical sensing, radar, and wireless communication, providing an ideal solution for generating high-frequency, low-phase-noise signals. For example, in radar systems, they are used for frequency synthesis and microwave signal generation. In 5G wireless communication, OOs can provide high-stability and tunable frequency output, meeting the frequency synthesis requirements between small base stations and base stations in 5G networks. However, traditional OOs typically require external modulators for RF loading and complex optical loops for optical feedback, which not only increases system complexity but also leads to larger size and higher power consumption. To address these issues, researchers have recently attempted to combine light sources with amplifiers to simplify the system. However, current solutions still have many limitations, especially in frequency tuning, system integration, and size optimization. Furthermore, in traditional solutions, to achieve tunable microwave output from an OO, the wavelength of the laser source is typically tuned to tune the filter peak of the photonic microwave filter. This is combined with a microwave phase shifter to achieve wide-range continuous tuning of the OO, which increases system complexity and the requirements for the light source. Another approach is to adjust the bias voltage of the electrical phase shifter [Ke ren, et al. Fine Frequency Tunable Optoelectronic Oscillator Based on Electrical Phase Shifter] to change the phase of the oscillation frequency in the cavity, which is equivalent to changing the cavity time delay, ultimately achieving a change in the cavity oscillation frequency. However, the tunable frequency range is too narrow, only about 5.5 MHz. Summary of the Invention

[0003] The purpose of this invention is to provide a tunable optoelectronic oscillator based on a DML-SOA laser chip, achieving a more compact and stable system structure through a monolithically integrated DML-SOA chip. The on-chip DML provides a direct RF optoelectronic converter, realizes the SOA with optical feedback amplification, and provides tunable P-1 oscillation, enabling tunable photonic microwave signal output.

[0004] To achieve the above objectives, this invention provides a tunable optoelectronic oscillator based on a DML-SOA laser chip, comprising a self-feedback laser. The self-feedback laser encapsulates a monolithically integrated DML-SOA laser and an optical isolator in a butterfly-shaped housing, which are sequentially connected to an optical delay line and a photodetector via an optical path. The photodetector converts the optical signal into an electrical signal and connects it to an electrical amplifier via a circuit. The electrical amplifier amplifies the signal and connects it to an electrical coupler via a circuit. One path of the electrical coupler is connected to a Bias-T via a circuit, and the microwave signal is reloaded onto the DML section of the DML-SOA laser through the Bias-T to form an optoelectronic loop. The other path of the electrical coupler serves as the microwave signal output. A DC power supply is simultaneously connected to the Bias-T and the SOA section of the DML-SOA laser.

[0005] Preferably, the DML-SOA laser is a monolithic integrated structure, comprising a DML section and an SOA section. The DML section directly modulates the RF circuit signal via direct modulation, while the SOA section, acting as optical amplification feedback, enables tunable P-1 oscillation, providing a simple method for generating high-frequency optical microwaves, unlike other solutions that rely on external fiber optic loops for tunable optical feedback. This approach achieves high integration and eliminates the need for mechanical optical attenuators to control feedback strength; the solution can be implemented simply through electrical injection tuning.

[0006] Preferably, the DC power supply and the Bias-T are connected to the SOA section. On the one hand, they provide electrical injection gain for the DML to realize the lasing of the laser and control the bias position of the DML directly modulated laser to achieve the target tuning effect. On the other hand, they supply power to the SOA section to realize tunable amplification feedback to achieve P-1 oscillation and complete tunable microwave signal output.

[0007] Preferably, the electrical coupler is a 1×2 electrical coupler, one of which serves as the final microwave output signal and the other 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 the jumper wire after the DML-SOA laser and the optical isolator are packaged.

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

[0010] Preferably, the optical isolator is located at the light output port of the DML-SOA laser or is directly encapsulated inside the laser tube of the DML-SOA laser.

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

[0012] Therefore, the tunable optoelectronic oscillator based on a DML-SOA laser chip with the above-described structure has the following beneficial effects:

[0013] (1) Based on the InP semiconductor process platform, this invention realizes the monolithic integration of the core part of the tunable optoelectronic oscillator, which also greatly simplifies the system, reduces costs, and improves yield. The laser gain and direct modulation section (DML) and the tunable optical amplification feedback section (SOA) are monolithically integrated.

[0014] (2) The DML part in this invention realizes the direct modulation of the radio frequency circuit signal through direct modulation, which eliminates the external laser, polarization controller and external modulator in the traditional scheme. 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 size and increases the system stability.

[0015] (3) The SOA portion in this invention serves as optical amplification feedback, enabling tunable P-1 oscillations with adjustable frequency intervals. This provides a simple method for generating high-frequency optical microwaves, unlike other schemes that use external fiber optic loops to achieve tunable optical feedback. This approach achieves high integration and eliminates the need for mechanical optical attenuators to control the feedback strength; it can be implemented simply through electrical injection tuning.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a tunable optoelectronic oscillator system based on a DML-SOA chip according to the present invention;

[0018] Figure 2 This is a schematic diagram of the P-1 oscillation phenomenon of the DML-SOA chip in this embodiment;

[0019] Figure 3 This is a schematic diagram of the spectrum of the P-1 oscillation phenomenon of the DML-SOA chip in this embodiment;

[0020] Figure 4 This is a schematic diagram of the microwave signal output of the tunable optoelectronic oscillator in this embodiment;

[0021] Figure 5 This is a schematic diagram representing the microwave signal phase noise of the tunable optoelectronic oscillator in this embodiment. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0024] Example

[0025] See Figure 1 This invention provides a tunable optoelectronic oscillator based on a DML-SOA laser chip, comprising a self-feedback laser. The self-feedback laser encapsulates a monolithically integrated DML-SOA laser and an optical isolator in a butterfly-shaped housing, sequentially connected to an optical delay line and a photodetector via an optical path. The photodetector converts the optical signal into an electrical signal and connects it to an electrical amplifier via a circuit. The electrical amplifier amplifies the signal and connects it to an electrical coupler via a circuit. One path of the electrical coupler is connected to a bias-T via a circuit, and the bias-T (DC biaser) reloads the microwave signal onto the DML section of the DML-SOA laser, forming an optoelectronic loop. The other path of the electrical coupler serves as the microwave signal output. A DC power supply is connected to both the bias-T and the SOA section of the DML-SOA laser. The DC power supply is a DC bias power supply.

[0026] The optical isolator is located at the output port of the DML-SOA laser to prevent optical reflections from external systems from entering the laser and affecting its lasing mode. Furthermore, the optical isolator can be directly packaged inside the laser tube of the DML-SOA laser, achieving a high degree of integration.

[0027] The optical delay line connects directly to the jumper cable encapsulating the DML-SOA laser and optical isolator. The optical delay line uses single-mode fiber, FBG fiber, or other optical delay devices.

[0028] The photodetector is directly connected to the optical delay line to convert optical signals into electrical microwave signals. Beat frequencies are generated within the photodetector by lasers of different wavelengths. An electrical amplifier is directly connected to the photodetector to achieve low-noise amplification of the microwave signal.

[0029] The DML-SOA laser is a monolithic integrated structure comprising a DML section and an SOA section. The DML section directly modulates the RF circuit signal via direct modulation, while the SOA section, acting as optical amplification feedback, enables tunable P-1 oscillation, providing a simple method for generating high-frequency optical microwaves, unlike other solutions that rely on external fiber optic loops for tunable optical feedback. This approach achieves high integration and eliminates the need for mechanical optical attenuators to control feedback strength; it can be achieved through simple electrical injection tuning.

[0030] The DC power supply and Bias-T are connected to the SOA section. On the one hand, they provide electrical injection gain for DML to realize laser lasing and control the position of Bias-T of the DML direct-tuned laser to achieve target tuning effect. On the other hand, they supply power to the SOA section to realize tunable amplification feedback to achieve P-1 oscillation and complete tunable microwave signal output.

[0031] The electrical coupler uses a 1×2 electrical coupler, with one path serving as the final microwave output signal and the other path serving as electrical feedback. It is directly loaded onto the DML via Bias-T to achieve a closed loop for the optoelectronic resonator.

[0032] See Figure 2 and 3 These are schematic diagrams of the spectrum and frequency signals of the P-1 oscillation generated under the action of optical amplification feedback.

[0033] Figure 2 This is a schematic diagram of the spectral signal of the P-1 oscillation generated under the action of optical amplification feedback. Under the action of optical self-feedback, some nonlinear phenomena occur, causing the optical resonant frequency to split. 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 approximately 0.1 nm and a corresponding frequency interval of approximately 12.5 GHz. Therefore, if the signal is received by PD beat frequency, a 12.5 GHz microwave signal can be generated.

[0034] Figure 3 This diagram illustrates the spectrum of the P-1 oscillation generated by optical amplification feedback. It shows a 12.5 GHz microwave signal, produced by beating between two adjacent wavelengths received by the PD. Additionally, a lower-power 25 GHz microwave signal exists, generated by beating between alternating wavelengths.

[0035] Figure 4 This diagram illustrates the microwave signal output of a tunable optoelectronic oscillator at different frequencies. Through optical amplification feedback, by tuning the intensity ratio of the optical feedback, P-1 oscillations with different wavelength intervals can be generated, thus producing microwave signals of different frequencies. The signal outputs at different frequencies all exhibit a signal-to-noise ratio exceeding 40 dB, demonstrating excellent signal quality.

[0036] Figure 5 This diagram illustrates the phase noise of the microwave signal from a tunable opto-oscillator. The phase noise reaches a minimum of −121.8 dBc / Hz at a 10 kHz frequency offset, and is below −110.7 dBc / Hz at other frequency offsets, demonstrating good microwave signal quality.

[0037] Therefore, this invention employs a tunable opto-oscillator based on a DML-SOA laser chip, as described above. By directly loading a radio frequency signal onto a directly modulated laser (DML) and using a semiconductor optical amplifier (SOA) to generate self-feedback amplification, a wavelength-interval-tunable P-1 oscillation is produced, thereby achieving a wavelength-interval-tunable opto-oscillation output. This opto-oscillator eliminates the need for an external modulator and external optical loop feedback, greatly simplifying the system structure and reducing its size. By adjusting the current injection ratio of the DML and SOA, the P-1 Period-One oscillation mode can be tuned, thus achieving a tunable microwave signal output with a wavelength interval of 12GHz to 13GHz. This system features a compact structure, high signal-to-noise ratio, and low phase noise. This invention has broad application prospects in the fields of optoelectronic integration and microwave signal generation.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A tunable optoelectronic oscillator based on a DML-SOA laser chip, characterized in that, The system includes a self-feedback laser, which encapsulates a DML-SOA laser and an optical isolator in a butterfly-shaped housing and connects them sequentially to an optical delay line and a photodetector via an optical path. The photodetector is connected to an electrical amplifier via a circuit, and the electrical amplifier is connected to an electrical coupler via a circuit. One path of the electrical coupler is connected to a Bias-T via a circuit, and the other path of the electrical coupler serves as a microwave signal output. A DC power supply is connected to both the Bias-T and the self-feedback laser. The DML-SOA laser is a monolithic integrated structure, including a DML part and an SOA part. The DML part achieves direct modulation of the radio frequency circuit signal through direct modulation. The SOA part serves as optical amplification feedback and can achieve P-1 oscillation with tunable frequency intervals, which can be achieved through simple electrical injection tuning. The DC power supply and the Bisa-T are connected to the SOA section to provide electrical injection gain for the DML and power the SOA section. The electrical coupler is a 1×2 electrical coupler, one of which serves as the final microwave output signal and the other as electrical feedback, which is directly applied to the DML through the Bias-T. The optical isolator is located at the output port of the DML-SOA laser or is directly encapsulated inside the laser tube of the DML-SOA laser; The optical delay line is connected to the jumper wire after the DML-SOA laser and the optical isolator are packaged. The DML part realizes direct modulation of the radio frequency circuit signal through direct modulation, eliminating the need for external laser, polarization controller and external modulator in the traditional solution. The optical delay line uses one of the following: single-mode fiber, FBG fiber, or other optical delay devices. The DC power supply is a DC bias power supply.

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