Technical Characteristics and Application Prospects of 1535nm and 1550nm Lasers in the Field of Ranging
In the invisible infrared spectrum, although 1535nm and 1550nm lasers differ by only 15nm, they exhibit significant differences in performance and application. Both lasers fall within the eye-safe wavelength range (1400–1600 nm), meaning they do not penetrate the eye to the retina and cause permanent damage, while also avoiding the strongest radiation zone of sunlight in the atmosphere. This makes them core light sources for modern optoelectronic technology.
In the field of laser ranging, infrared wavelength laser technology is pushing the limits of measurement accuracy and distance. Among them, the 1535 nm and 1550 nm near-infrared lasers, despite differing by only 15 nm, exhibit significant differences in physical properties, technical implementation, and application scenarios. Their widespread application in the field of ranging is profoundly reshaping the technological landscape in core areas such as autonomous driving, industrial surveying, fiber optic communications, and military reconnaissance.
1. 1550nm Laser: The Gold Standard for Long-Range Ranging
Eye Safety and Power Advantages
The core advantage of 1550nm lasers in the field of ranging is first reflected in their eye safety. Due to the strong absorption of this wavelength by the moisture in the cornea and lens of the human eye, it cannot reach the fragile retina. According to international laser safety standards (IEC 60825), the maximum permissible exposure (MPE) for 1550nm lasers is over 10 times that of 905nm lasers, enabling the safe use of higher power outputs. This characteristic enables 1550nm laser radar to achieve higher peak power under the same safety conditions—typical values can reach the kilowatt level (e.g., 1kW instantaneous power), far exceeding the hundred-watt level limitation of 905nm lasers. The power advantage directly translates into longer effective detection ranges. Under standard test conditions with a 10% reflectivity, 1550nm laser radar can achieve detection ranges exceeding 250 meters, while 905nm products are typically limited to ranges between 150 and 200 meters.
Outstanding transmission characteristics and material challenges
The 1550 nm wavelength is located in the lowest loss window (0.15-0.19 dB/km) of quartz fiber, offering greater transmission advantages than 1535 nm (0.17 dB/km) and 1310 nm (0.35 dB/km). This characteristic makes it an indispensable choice in fiber optic ranging systems and long-distance communications. In free-space transmission, the 1550nm laser exhibits a smaller beam divergence angle, enabling it to maintain higher energy density over long distances and improve echo signal quality.
However, 1550nm lasers face significant material challenges. Their core light source is based on the indium phosphide (InP) material system, which requires indium gallium arsenide (InGaAs) detectors for compatibility. The crustal abundance of indium is only 0.05 ppm, comparable to silver, and its rarity leads to high costs. According to industry analysis, the cost of InP lasers is more than five times that of GaAs-based 905 nm solutions, constituting the primary obstacle to large-scale application.
The Duality of Weather Adaptability
1550 nm lasers exhibit complex characteristics in terms of weather adaptability. On the one hand, their long wavelength characteristics give them stronger haze penetration capabilities, making them significantly superior to 905 nm lasers in dusty and smoky environments. On the other hand, however, water molecules strongly absorb 1550 nm lasers (absorption peak at approximately 1450 nm), causing their performance to decline significantly in rainy weather. Field tests indicate that under heavy rain conditions, the detection range of 1550nm laser radar may plummet from 500 meters to 50 meters, creating a “water curtain effect.” Technological advancements using frequency-modulated continuous wave (FMCW) and power compensation algorithms are addressing this issue.
2. Comparison and Analysis of Application Scenarios in the Distance Measurement Field
In-vehicle LiDAR: Balancing Safety and Cost
In the field of autonomous driving, 1550nm LiDAR has become the preferred choice for high-end vehicles due to its ultra-long detection range. The Tudao Falcon LiDAR (1550nm) achieves a maximum detection range of 500 meters and can still reach 250 meters under 10% reflectivity conditions, far exceeding the 150-200 meter range of 905nm radar. This feature is critical in high-speed scenarios—when traveling at 120 km/h, the braking distance is approximately 130 meters, and the detection margin provided by 1550nm lidar significantly enhances safety. Its ultra-high resolution of 0.06° × 0.06° ensures that a pedestrian at 200 meters is fully covered by the point cloud.
The 1535nm lidar stands out due to its temperature stability and system simplification advantages. Its solid-state design eliminates the need for complex temperature control, maintaining stability in extreme cold or heat, significantly enhancing device reliability. This feature, combined with moderate cost (lower than the 1550nm solution), makes the 1535nm lidar highly promising for mid-range vehicles and industrial applications.
Industrial surveying and special application scenarios
1535nm lasers demonstrate unique value in industrial precision surveying. Their low-noise characteristics ensure purer signals in high-precision terrain scanning, improving point cloud quality. The wavelength's penetration characteristics through industrial materials also make it excel in specific material measurements.
The 1550nm laser is indispensable in fiber optic ranging systems. Its ultra-low fiber loss characteristics (0.15dB/km) make it an ideal choice for long-distance distributed fiber optic measurement, widely applied in pipeline monitoring, perimeter security, and other fields. In military ranging applications, the 1550nm laser's atmospheric penetration capability and stealthiness (difficult to detect by the enemy) make it the standard configuration for portable laser rangefinders.
Advantages in Special Applications
Medical Ranging: 1550nm lasers are used in optical coherence tomography (OCT) systems to achieve micron-level depth measurements of internal biological tissue structures.
Aerospace: 1550nm laser radar is used for satellite rendezvous and docking ranging and deep space exploration, with its long-range capabilities meeting the demands of space missions.
Complex Industrial Environments: 1535nm lasers maintain stability in extreme environments such as high-temperature workshops, making them suitable for the steel and metallurgy industries.
4. Technical Challenges and Development Trends
Core Bottlenecks and Breakthrough Directions
The cost challenges faced by 1550 nm lasers are gradually being alleviated through technological innovation. Power enhancement of 1535nm lasers is a current research priority. By improving energy conversion efficiency through erbium-ytterbium co-doping technology, the next-generation products aim to increase peak power to the kilowatt level. Optoelectronic integration is another key direction—integrating drive circuits, control logic, and laser chips into a single module to enhance reliability and reduce size.
5. Summary: Complementary Development Shaping the Future of Ranging
1535nm and 1550nm lasers exhibit clear differentiated roles in the ranging field. The 1550nm laser maintains a dominant position in high-end automotive radar, ultra-long-range fiber sensing, and satellite ranging applications due to its ultra-long detection range and mature fiber amplification technology. With the maturation of InP production processes and advancements in silicon photonics integration technology, its cost barriers are expected to gradually ease, expanding its application boundaries.
The 1535nm wavelength leverages the advantages of erbium-doped fiber gain peaks and exceptional temperature stability to establish a unique competitive edge in industrial precision surveying, unmanned aerial vehicle systems, and military equipment operating in wide temperature ranges. Its system simplification and compact design characteristics make it particularly suitable for applications sensitive to space and power consumption.
Over the next five years, we may witness the deepening of a landscape where 1535nm focuses on medium-to-short-range high-stability applications and 1550nm dominates ultra-long-range transmission. As FMCW technology matures and multi-wavelength fusion systems become more widespread, the advantages of both lasers will be further leveraged, jointly driving laser ranging technology to new heights in terms of accuracy, distance, and reliability. This will provide a solid technological foundation for autonomous driving, aerospace, industrial intelligence, and national defense security. In this silent “wavelength competition,” there are no absolute winners—only the optimal solution tailored to specific scenarios. This is precisely the charm of optical technology.