A square wave optical signal source generation system and method

Abstract

This invention discloses a square-wave optical signal generation system and method, including a VCSEL laser, a polarization-maintaining beam splitter, and a reflector. The VCSEL laser first possesses excellent linear polarization characteristics. Its emitted beam is first split into TM and TE orthogonal mode beams by the polarization-maintaining beam splitter, where the TE mode is a lasing mode and the TM mode is strongly suppressed. By feeding the TE mode back into the VCSEL resonant cavity, a high-quality square-wave signal is generated, providing a high-quality light source for optical communication, displacement sensing, measurement, and other fields. Simultaneously, the system structure is very simple and easy to implement, greatly reducing the complexity and cost of square-wave optical signal generation.

Description

Technical Field

[0001] This invention belongs to the field of laser technology and relates to a square wave optical signal source generation system and method. Background Technology

[0002] Signal generators play a crucial role in electronic engineering and related fields, with widespread applications in communications, electronic circuits, automatic control, and scientific experiments. The primary function of a signal generator is to produce electrical signals of specific frequencies, amplitudes, and waveforms, providing the necessary input signals for the testing and debugging of equipment and systems. These input signals are not only fundamental to verifying equipment performance but also crucial for ensuring the normal operation of the system.

[0003] Among numerous signal sources, the square wave optical signal source stands out for its unique advantages. The signal generated by a square wave optical signal source possesses extremely clear rising and falling edges, a characteristic that allows it to efficiently transmit digital information through simple "0" and "1" encoding. This characteristic has wide-ranging application value in fields such as digital communication, data processing, and digital circuits. Especially in modern optical communication technology, the generation of square wave optical signals is particularly important. With the continuous increase in data transmission speed and the ongoing advancement of communication technology, the demand for high-speed, stable, and reliable optical signal sources is becoming increasingly urgent. The square wave optical signal source, with its excellent performance, has become one of the core components for realizing high-speed optical communication. It not only meets the needs of high-speed data transmission but also maintains signal stability and reliability in complex communication environments, providing strong support for the development of modern optical communication technology.

[0004] However, the generation of square-wave optical signals faces several technical challenges. Traditional methods for generating square-wave optical signals mainly rely on electronic switches and laser modulation. While these methods are effective to some extent, they often result in complex system structures, high costs, long response times, and insufficient flexibility in practical applications. These problems severely restrict the application of square-wave optical signal sources in high-performance optical communication systems. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems of complex structure, high cost, long response time, and lack of flexibility in practical applications of existing square wave signal generation technology, and to provide a square wave optical signal source generation system and method.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] The first aspect of the present invention provides a square wave optical signal source generation system, including a VCSEL laser, a polarization maintaining beam splitter, and a reflector;

[0008] The beam emitted by the VCSEL laser is split into a TM mode beam and a TE mode beam by a polarization-maintaining beam splitter; a mirror is set in the propagation path of the TE mode beam; after being reflected by the mirror, the TE mode beam is coupled into the resonant cavity of the VCSEL laser to realize the square wave optical signal output.

[0009] Furthermore, a beam splitter is provided between the polarization-maintaining beam splitter and the VCSEL laser. The beam splitter divides the beam reflected by the VCSEL laser into two beams. One beam propagates to the polarization-maintaining beam splitter, and the other beam is output through an optical isolator.

[0010] Furthermore, a collimator is provided between the beam splitter and the VCSEL laser.

[0011] Furthermore, the beam splitter splits the beam in a 50:50 ratio.

[0012] Furthermore, the optical isolator operates in TE mode.

[0013] Furthermore, a collimator is provided on the propagation path of the output beam of the optical isolator.

[0014] A second aspect of the present invention provides a method for generating a square wave optical signal source, comprising the following steps:

[0015] S1, split the beam emitted by the VCSEL laser to obtain the first beam and the second beam;

[0016] S2, the second beam is polarized and split to obtain a TM mode beam and a TE mode beam;

[0017] S3 reflects the TE mode beam back through a mirror and couples it into the VCSEL resonant cavity via optical feedback to achieve square wave optical signal output.

[0018] Furthermore, the optical feedback distance can be adjusted as needed.

[0019] Furthermore, the TE mode beam is reflected back through a mirror and coupled into the VCSEL resonant cavity via optical feedback to achieve square wave optical signal output, specifically as follows:

[0020] By adjusting the length of the external feedback cavity, the relaxation oscillation frequency of the TE mode beam and the external cavity feedback frequency resonate. The relaxation oscillation is excited by optical feedback and phase locking is achieved, thereby realizing the square wave signal output.

[0021] Furthermore, by adjusting the optical feedback distance, the relaxation oscillation frequency of the TE mode beam and the external cavity optical feedback frequency are made to resonate.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention discloses a square-wave optical signal generation system. Utilizing the orthogonal polarization characteristics of a laser, this invention successfully separates the beam emitted by a VCSEL laser into two independent beams: a TM mode and a TE mode. This design not only ensures the purity of both beam modes but also provides a foundation for subsequent modulation. By placing a reflector on the propagation path of the TE mode beam, a feedback modulation loop is formed. This structure facilitates multiple reflections of the beam within the cavity, increasing the interaction time between the beam and the gain medium, thereby improving the laser's stability and output efficiency. An optical isolator is placed on the probe beam path to achieve mode selection; by selecting the TE mode output, a square-wave signal is generated. The laser system of this invention has a compact structure, and the connections between the components are simple and clear, making it easy to integrate with other optical elements or systems. This design not only improves the system's flexibility but also facilitates subsequent expansion and upgrades. Compared with traditional square-wave optical signal sources, the components used in this invention are relatively simple and low-cost, thus achieving higher cost-effectiveness.

[0024] Furthermore, the beam splitter divides the reflected light into two paths, reducing signal loss and interference on a single path. In particular, the path output through the optical isolator can serve as an independent monitoring channel for evaluating the performance of the VCSEL laser and beam integrity. This design helps ensure the quality of the beam entering the polarization-maintaining beam splitter, thereby improving the quality of the final generated square wave optical signal. The beam splitting achieved through the beam splitter makes system maintenance and debugging more intuitive and convenient. When system calibration or troubleshooting is required, the beam output from the optical isolator can be used for rapid location and analysis, effectively shortening maintenance time and reducing maintenance costs.

[0025] Furthermore, the beam splitter precisely divides the beam reflected by the VCSEL laser into two beams in a 50:50 ratio, ensuring that each beam has the same intensity and stability. The system does not require additional optical attenuators or amplifiers to balance the intensity of the optical signals, thereby reducing the complexity and cost of the system.

[0026] Furthermore, this invention discloses a method for generating a square-wave optical signal source. A beam from a VCSEL laser is uniformly split into two beams using a beam splitter, providing a reliable foundation for subsequent polarization beam splitting and optical feedback. The second beam is polarized using a polarization-maintaining beam splitter, precisely separating the TM and TE mode beams. This not only improves the utilization rate of the optical signal but also provides necessary polarization state control for the subsequent optical feedback process. The TE mode beam is reflected back using a mirror and coupled into the VCSEL resonant cavity through optical feedback, realizing the output of a square-wave optical signal. During this process, the optical feedback distance can be adjusted as needed. By adjusting the length of the external feedback cavity, resonance between the relaxation oscillation frequency of the TE mode beam and the external cavity feedback frequency is achieved. This resonance mechanism not only excites relaxation oscillations but also achieves phase locking, thereby ensuring the stability and consistency of the square-wave optical signal. Through precise optical feedback control and phase-locking mechanisms, a high-quality square-wave optical signal is successfully output. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a structural diagram of a square wave optical signal source generation system according to an embodiment of the present invention;

[0029] Figure 2 The input-output curves of the laser in two linear polarization modes in an embodiment of the present invention are shown.

[0030] Figure 3 This is an embodiment of the present invention showing the TE mode square wave time-domain optical output;

[0031] Figure 4 The spectrum of the time-domain optical signal measured in an embodiment of the present invention;

[0032] Figure 5 This is a block diagram of a square wave optical signal source generation method according to an embodiment of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and marked in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0037] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0038] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0039] The present invention is described in further detail below with reference to the accompanying drawings:

[0040] See Figure 1 The present invention provides a square wave optical signal generation system, including a VCSEL laser, a polarization maintaining beam splitter and a reflector;

[0041] The beam emitted by the VCSEL laser is split into a TM mode beam and a TE mode beam by a polarization-maintaining beam splitter (PBS). A reflector M is placed along the propagation path of the TE mode beam. After being reflected by the reflector M, the TE mode beam is coupled into the resonant cavity of the VCSEL laser to achieve square wave optical signal output. A beam splitter (BS) is placed between the polarization-maintaining beam splitter (PBS) and the VCSEL laser. The beam splitter (BS) splits the beam reflected by the VCSEL laser into two beams. One beam propagates to the polarization-maintaining beam splitter (PBS), and the other beam is output through an optical isolator (ISO). The beam splitter (BS) is configured with a 50:50 beam splitting ratio; the optical isolator (ISO) is in TE mode. A collimator (L) is placed between the beam splitter (BS) and the VCSEL laser. A collimator (L) is placed along the propagation path of the output beam of the optical isolator (ISO). After being split by the beam splitter (BS), the beam passes through the optical isolator (ISO) and the collimator (L) in sequence before entering the photodetector.

[0042] The square-wave optical signal generation system provided by this invention utilizes a combination of a VCSEL (Vertical-Cavity Surface-Emitting Laser) and a polarization-maintaining beam splitter (PBS) to precisely split the laser beam into TM and TE modes. In particular, the TE mode beam, after being reflected by the mirror M, is coupled back into the resonant cavity of the VCSEL laser. This not only enhances the feedback of the TE mode light but also promotes stable mode selection within the laser cavity, thereby achieving high-quality square-wave optical signal output. This significantly improves the stability and purity of the optical signal, which is particularly important for applications requiring precise control of the optical waveform. The beam splitter BS (50:50 ratio) introduced into the system not only achieves uniform distribution of the VCSEL laser output beam but also guides one path to the PBS for mode separation and feedback, while the other path outputs through the optical isolator ISO, effectively avoiding reflection interference in the optical path and improving the overall efficiency and stability of the system. The TE mode configuration of the optical isolator ISO ensures the mode consistency of the output beam, further enhancing the system performance; the beam splitter BS splits the beam that passes through the optical isolator ISO and collimator L, and finally enters the photodetector, providing a real-time monitoring channel for the system.

[0043] See Figure 5 This invention provides a method for generating a square wave optical signal source, comprising the following steps:

[0044] S1, split the beam emitted by the VCSEL laser to obtain the first beam and the second beam;

[0045] The VCSEL laser is activated, and its continuous beam is split by a beam splitter. The beam splitter is configured to evenly divide the laser beam into two beams, labeled as the first beam and the second beam, respectively. In this embodiment, the first beam is not directly used for generating a square wave signal, but can be used for system monitoring or other purposes. The second beam then proceeds to the next step.

[0046] S2, the second beam is polarized and split to obtain a TM mode beam and a TE mode beam;

[0047] The second beam then enters a polarization-maintaining beam splitter (PBS), which splits it into a TM mode beam and a TE mode beam based on the polarization characteristics of the light. The TM mode beam is strongly suppressed in a certain region. The TE mode beam, on the other hand, is selected for the subsequent feedback process because it is crucial for realizing the square wave optical signal.

[0048] S3 reflects the TE mode beam back through a mirror and couples it into the VCSEL resonant cavity via optical feedback to achieve square wave optical signal output.

[0049] The TE-mode beam is reflected back through mirror M, forming an external feedback loop. The position and angle of mirror M are precisely adjusted to ensure that the TE-mode beam can be efficiently recoupled into the resonant cavity of the VCSEL laser. To precisely control the feedback process, the length of the external feedback cavity is adjusted to match the relaxation oscillation frequency of the TE-mode beam. This determines whether the external cavity feedback frequency and the relaxation oscillation frequency can resonate; when they resonate, the optical feedback will excite relaxation oscillations, and through a phase-locked mechanism, the laser output will exhibit stable square wave characteristics.

[0050] The square-wave optical signal generation method of this invention efficiently separates the beam emitted by a VCSEL laser into two independent beams: TM mode and TE mode, through beam splitting and polarization beam splitting steps. This polarization separation not only ensures the purity of the two beam modes but also provides a foundation for subsequent polarization control. By placing a reflector in the propagation direction of the TE mode beam to realize a feedback modulation loop, the interaction time between the beam and the gain medium is increased, thereby improving the stability and output efficiency of the laser. Simultaneously, the design of the external ring cavity helps suppress laser noise and fluctuations; an optical isolator is placed in the probe optical path to achieve mode selection, thus enabling fine control of the laser output. The components used in this method are relatively simple and easy to integrate, ensuring the flexibility and scalability of the system. By adjusting the parameters of the external ring cavity and the rotation angle of the half-wave plate, further control and optimization of the laser output can be achieved.

[0051] To further illustrate the advantages of the present invention, Figure 2The input-output curves of the laser in this embodiment of the invention for two linear polarization modes show that the threshold of the TE mode is much lower than that of the TM mode. Specifically, the TE mode begins to output significant optical power with a lower input current, while the TM mode requires a higher input current to achieve the same output power level. This result verifies the low threshold characteristic of the TE mode in VCSEL lasers. The lower threshold of the TE mode is mainly due to its optical field distribution being more well-matched to the cavity structure of the VCSEL laser, resulting in more efficient energy conversion and lower optical loss. In contrast, the optical field distribution of the TM mode is less well-matched to the cavity structure, thus requiring a higher input current to overcome optical loss and reach the threshold.

[0052] Figure 3 The TE mode square wave time-domain optical output of this invention is shown in the embodiment of the invention. Since the photodetector used is of AC type, it can be seen that the time-domain optical signal oscillates around 0 with a period of 7 ns and the amplitude is consistent throughout. This indicates that the square wave optical signal generated by this invention has high reliability and consistency in the time domain.

[0053] Figure 4 The spectrum of the time-domain optical signal measured in this embodiment of the invention is 7.6 GHz, which is the relaxation oscillation frequency of the square wave. Harmonics are distributed near the center frequency, and the interval between the harmonics corresponds to the reciprocal of the feedback duration. It can be seen that the square wave optical signal generated by this invention has good stability and good spectral characteristics.

[0054] In summary, this invention generates an initial beam using a VCSEL laser and precisely splits it into TM and TE modes using a polarization-maintaining beam splitter. The TE mode beam, after reflection by a mirror, is recoupled into the resonant cavity of the VCSEL laser. This process enhances the optical feedback of the TE mode, thereby effectively generating a square-wave optical signal. This design not only improves the generation efficiency of the optical signal but also ensures its stability and purity. A beam splitter is placed between the VCSEL laser and the polarization-maintaining beam splitter, enabling precise control and distribution of the laser beam. The beam splitter divides the beam into two beams in a 50:50 ratio; one beam is used to generate a square-wave optical signal, while the other is output through an optical isolator for monitoring or other applications. This design not only improves the system's flexibility but also ensures uniform beam distribution and efficient utilization. A collimator in the system facilitates precise beam calibration and shaping, ensuring the stability and consistency of the beam during propagation. Furthermore, the use of an optical isolator effectively prevents optical signal reflection and interference, further improving the system's stability and reliability. The optical isolator is designed in TE mode, meaning it only allows TE mode optical signals to pass through. This design helps to further purify the TE mode optical signal and reduce interference from other modes, thereby improving the purity and quality of the square wave optical signal. A collimator is also placed on the output beam propagation path of the optical isolator, which not only ensures the stability and consistency of the output beam but also facilitates subsequent beam processing and applications. Furthermore, the system design and implementation are highly scalable, allowing for adjustments and optimizations based on actual application requirements to meet the needs of different scenarios. The components used in this method are relatively simple and easy to integrate, providing strong assurance for the system's flexibility and scalability. By adjusting the parameters of the external annular cavity and the rotation angle of the half-wave plate, further control and optimization of the laser output can be achieved, meeting diverse needs in different application scenarios.

[0055] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A square wave optical signal generation system, characterized in that, Includes VCSEL laser, polarization-maintaining beam splitter, and reflector; The beam emitted by the VCSEL laser is split into a TM mode beam and a TE mode beam by a polarization-maintaining beam splitter. A mirror is placed in the propagation path of the TE mode beam. After being reflected by the mirror, the TE mode beam is coupled into the resonant cavity of the VCSEL laser. By adjusting the length of the external feedback cavity, the relaxation oscillation frequency of the TE mode beam and the external cavity feedback frequency resonate. The relaxation oscillation is excited by optical feedback and phase locking is achieved, thereby realizing the square wave signal output. A beam splitter is placed between the polarization-maintaining beam splitter and the VCSEL laser. The beam splitter splits the beam reflected by the VCSEL laser into two beams. One beam propagates to the polarization-maintaining beam splitter, and the other beam is output through an optical isolator.

2. The square wave optical signal generation system according to claim 1, characterized in that, A collimator is provided between the beam splitter and the VCSEL laser.

3. The square wave optical signal generation system according to claim 1, characterized in that, The beam splitter splits the beam in a 50:50 ratio.

4. The square wave optical signal generation system according to claim 1, characterized in that, The optical isolator is in TE mode.

5. The square wave optical signal generation system according to claim 1, characterized in that, A collimator is provided on the propagation path of the output beam of the optical isolator.

6. A method for generating a square wave optical signal source, based on the square wave optical signal source generation system of claim 1, characterized in that, Includes the following steps: S1, split the beam emitted by the VCSEL laser to obtain the first beam and the second beam; S2, the second beam is polarized and split to obtain a TM mode beam and a TE mode beam; S3 reflects the TE mode beam back through a mirror and couples it into the VCSEL resonant cavity via optical feedback to achieve square wave optical signal output.

7. The method for generating a square wave optical signal source according to claim 6, characterized in that, The optical feedback distance can be adjusted as needed.

8. The method for generating a square wave optical signal source according to claim 6, characterized in that, By adjusting the optical feedback distance, the relaxation oscillation frequency of the TE mode beam and the external cavity optical feedback frequency can be made to resonate.

Images