Objective  The ocean is an important link in the global carbon cycle, carbon is transferred along the ocean's food chain starting with phytoplankton photosynthesis and exists as particulate organic carbon (POC). The measurement of the ocean's ability to store carbon will be greatly influenced by the discovery of its particulate organic carbon content. The realization of ocean particulate matter profiling can clarify the key processes of its formation, evolution and transport, which is of great significance to regional and global ecological research and climate problem solution. It will help human beings to better understand the ocean and explore its deep resources. Half of the current contribution to ocean observation data comes from satellite remote sensing, a technique that allows simultaneous observation of large areas, but lacks access to ocean profile information. The performance of the oceanic particulate organic carbon concentration profile detection system based on high spectral resolution technology is simulated and analyzed because lidar can detect profile information based on the change in optical properties caused by phytoplankton in clear ocean waters.

  Methods  High Spectral Resolution Lidar (HSRL) is a type of lidar that uses narrowband filters (or filters) to achieve spectral separation by taking advantage of the difference in the magnitude of the spectral width of particle scattering and molecular scattering in the backscattering spectrum of the echo signal (Fig.1). HSRL technology is the current preferred solution for the development of particle detection lidar. The simulation software (Fig.2) is used to obtain the ocean water parameters combined with the preset lidar system parameters (Tab.1), and then the lidar equation is used to simulate the return profile photoelectron number. Utilizing an iodine molecular absorption cell as a filter, the transmission window of the oceanic water column, and the laser's engineering design are combined to analyze the detection system's optimal operating wavelength under various loading platforms.

  Results and Discussions  When the detection requirement of a single detection system with a signal-to-noise ratio of 5 is met, simulation results reveal that the detection depth in the 50 dB dynamic range of the oceanic water column averages at 80 m (Fig.4). Depending on the return spectrum (Fig.5, Fig.7) and filtering capabilities of the filter, the best center wavelength for lidar operation in various usage scenarios can be chosen. The absorption line of the iodine molecule absorption cell near 532 nm can be used as the working wavelength to be selected. The optimal operating center wavelength of the shipboard platform needs to consider the transmission characteristics of the laser in seawater (Tab.2). The optimal operating center wavelength of the airborne platform needs to take into account the atmospheric transmission characteristics of the laser (Tab.3). According to the filter's ability to absorb the meter scattered signal in the echo spectrum, and the stability requirements, the most effective working wavelength for airborne detection systems and shipborne detection systems is 532.292 8 nm and 532.245 1 nm.

  Conclusions   Because the development of a lidar system is a time-consuming and difficult project, it is essential to simulate and optimize the system parameters early on to ensure the viability and usability of the lidar system. The water body has an effect on the maximum detectable depth of lidar, according to simulation results. The actual ocean exploration can choose the appropriate sea area to obtain better results. The determination of the optimal operating wavelength for high spectral resolution lidar based on iodine molecular absorption cell can provide a reference for the subsequent construction of practical systems.