1. Introduction In the late 1950s, the rapid development of materials technology, semiconductor technology, laser technology, microelectronics technology, and optical technology greatly promoted the development of optoelectronic technology, leading to widespread attention. It has seen significant applications, particularly in the military, such as in lidar and anti-laser guided weapon systems. Simultaneously, in specialized industrial sectors like fiber optic communication, precision measurement, precision manufacturing, and parts inspection, optoelectronic technology has been applied to varying degrees in production processes, resulting in substantial efficiency improvements. However, current optoelectronic technology remains cutting-edge. Many existing optoelectronic products have complex principles and stringent manufacturing requirements, leading to high costs that are not affordable for ordinary users. Therefore, this paper develops and designs an optoelectronic control device using a microcontroller combined with optoelectronic technology. Similar to an infrared remote control device, this device uses a laser as its signal carrier, and the transmitted signal can be specially modulated. Its simple principle and low cost make it accessible to ordinary users. 2. Basic Principles The basic principle of this system is the combination of microcontroller technology and photoelectric detection technology. Its detection principle block diagram is shown in Figure 1. The system uses a microcontroller to control the power supply. The microcontroller automatically generates a series of ordered power pulses based on the information entered by the user, and uses these power pulses to control the semiconductor laser. The laser emitted by the semiconductor laser is thus a series of laser pulse waves, which are the signal waves carrying the user's information. When the photodetector detects this laser signal wave, it converts it into a series of continuous electrical pulse waves. However, the signal obtained at this time is very weak and irregular. Furthermore, due to stray light and external interference, the electrical signal here is also mixed with some useless interference signals. Therefore, these signals cannot be used directly. They must be amplified and denoised by a preamplifier circuit. The processed signal can then directly drive the microcontroller to work, performing decoding and discrimination processing. Through comparison and discrimination, the microcontroller determines which processing to perform and then generates a control signal to start the control device. 3 Key Technologies 3.1 Encoding Technology/Laser Modulation Technology Laser modulation generally modulates the frequency or amplitude of a laser. This method combines encoding technology with laser modulation technology for comprehensive compilation. The AT89C51 is selected as the control module due to its wide application, high stability, and cost-effectiveness, making it the preferred microcontroller for this system. The specific encoding and modulation process is as follows: First, the microcontroller is configured to power on for 40μs if a binary code "1" is detected, and power off for 40μs if "0" is detected. Then, the process is repeated cyclically after detecting the entire binary code. This forms a periodic pulse. When the user enters the number 1998, its binary code is 11111001110. The microcontroller then controls the pulse signal timing control signal as shown in Figure 2. Considering that the receiving end also uses a microcontroller, a communication protocol is also required. This method is used here. Under normal circumstances, the signal level is low. When transmission is needed, four sets of 10μs signals are transmitted first. The control signal is transmitted only after these signals are completed. 3.2 Selection of Photoelectric Detection Devices Currently, commonly used photoelectric detection devices in photoelectric detection technology include photomultiplier tubes, avalanche diodes, photodiodes, phototransistors, PIN diodes, photoresistors, photocells, and CCD arrays, among other semiconductor devices. Table 1 can be used as a reference for comparison and selection of photoelectric detection devices. Table 1 shows that the photodiode is the most ideal choice. Its spectral response range meets the requirements of this system. It has advantages such as good linearity, low applied voltage, low dark current, small size, high stability, and low price. Its output current is small, and its photosensitive area is small. The light-receiving area can be increased by designing a preamplifier circuit and installing optical equipment. Therefore, the photodiode is selected as the photoelectric detection device for this system. When connecting the detection equipment, it is important to ensure that the photodiode operates normally in reverse bias. Its general detection circuit is shown in Figure 3, and the small-signal equivalent circuit of this circuit is shown in Figure 4. 3.3 Frequency Response Analysis of the Detection Circuit To achieve maximum power output at a given input illuminance, RL = Rb and g < 0. Here, Cj is the photodiode junction capacitance, Rg is the internal resistance, and Se is the photocurrent. RL is the input resistance of the preamplifier circuit. In the design, considering the need to obtain sufficient signal power and voltage from the photodiode, RL and Rb cannot be too small. According to its small-signal equivalent circuit, excessively large RL and Rb will cause high-frequency cutoff, frequency drop, and reduced bandwidth. Frequency response is a major factor to consider in photoelectric detection circuits; it is necessary to achieve the best linearity and frequency distortion while ensuring the required detection sensitivity. Therefore, the detection circuit can be designed based on the above analysis. 3.4 Noise Handling and Preamplifier Circuit Design The key part of the photoelectric detection circuit lies in the design of the preamplifier circuit and noise handling. Various external disturbances and internal noise exist in actual photoelectric detection circuits. External disturbances include random fluctuations and additional optical modulation, end current in the optical transmission medium, background undulations, stray light incidence, and electromagnetic interference affecting the detection circuit. These disturbances can be addressed by stabilizing the radiation source, removing stray light, and selecting polarizers. Internal noise is mainly generated by semiconductor devices within the detection circuit. This noise primarily manifests as thermal noise and can be eliminated through capacitive coupling. Therefore, to reduce external disturbances, a microcontroller is used to control the semiconductor laser and generate an ordered laser pulse signal, significantly reducing the impact of external disturbances on the system. To reduce the influence of internal thermal noise and improve the signal-to-noise ratio at the amplifier output, a noise-free bias amplifier circuit is selected, as shown in Figure 5. The value of C2 is chosen such that its reactance is less than Rb at minimum operating efficiency, allowing the thermal noise generated by Ra and Rb to bypass to ground through C2. This results in only a small amount of noise generated by Rd. For ease of calculation and determination of specific resistor and capacitor parameters, a small-signal equivalent analysis was performed on this circuit. The general equivalent processing involves treating various devices as equivalent mean square (or effective) current sources of the same form. This allows for the establishment of an equivalent noise circuit in a unified manner with other circuit components. Calculations show that this circuit has a high signal-to-noise ratio and meets the system's signal requirements. 3.5 Signal Judgment, Processing, and Control Signal Generation This part mainly involves amplifying and shaping the signal before sending it to the microcontroller for processing. The microcontroller generates a control signal to achieve synchronous control of different devices. To verify the feasibility of this technology, we designed and developed a laser password alarm system. Experiments showed stable performance and convenient operation, proving that this method is highly feasible. 4 Conclusion This system has advantages such as simple principle, system stability, low price, and easy operation, making it more accessible to a wider range of users. By modifying the receiving part with photoelectric shafts or lenses to increase the receiving area, flexible and rapid short-to-medium range communication and control can be achieved. Its intelligence level is relatively high; by simply changing the program within the microcontroller, more other controls can be executed, showing great development potential. In military applications, using this device for external rocket launchers would enable simpler, more optimized, and longer-range operations, eliminating concerns about cable breakage and interference. In civilian applications, it can be used in security devices, making them more intelligent and user-friendly, such as security doors and safes. In industrial applications, it can be used to control large, modular equipment or different operational steps on the same production line. Utilizing the flexible programmable nature of microcontrollers, its application range is further broadened.