Deep sea hydrothermal liquid cold spring nozzle flow velocity measuring instrument based on optical Doppler and use method of instrument

The invention discloses a deep sea hydrothermal/cold spring nozzle flow velocity measuring instrument based on optical Doppler and a use method of the instrument, and relates to the technical field of deep sea flow velocity measurement. Comprising a pressure-resistant packaging shell and a sapphire flat lens arranged at the left end of the pressure-resistant packaging shell, a laser light source is arranged at the right end in the pressure-resistant packaging shell, an interference light path and a signal processing module are arranged at the left end of the laser light source, and the laser light source is a single-frequency narrow-linewidth green optical fiber laser. According to the invention, the defects in the prior art are overcome, the accurate flow velocity can be obtained at the position about one meter in front of the submarine hydrothermal solution/cold spring nozzle, the resolution of the flow velocity reaches 0.01 m/s, the system design is optimized to be integrated into an integrated detection d