Generation of a variable carrier frequency for laser doppler vibrometers based on an optical phase-locked loop
State of the Art/Motivation
- Variable offset frequency cannot be achieved in the employment of conventional acoustooptic devices (e.g. Bragg cells). And the limited highest frequency of acoustooptic devices impose restrictions on its widespread application.
- Given the limitation of the relation between the carrier frequency and vibration frequency, conventional LDVs with acoustooptic devices are hardly applied for different measurements with a relatively large variation of vibration frequency.
- Disadvantages of conventional LDV in volume and price are against the portable tendency for instrument
- The feasibility and design criteria of employment of OPLL have been proofed preliminarily. The result has indicated the advantages of LDVs with a structure of OPLL in the generation of a variable carrier frequency and its alluring prospects.
- Investigation of the relation on the parameter of OPLL and LDV properties and building a relevant mathematical model as well as find an optimal solution with minimum noise.
- Establishment of experimental platform and realization of the variable carrier frequency generation.
- Variable carrier frequency generation in MHz with two diode lasers via frequency-offset-lock in a heterodyne optical phase-lock loop (OPLL).
- Building a mathematical model to explore the effect of the parameter in OPLL for LDV properties.
- Based on the change rule of LDV parameters (e.g. PSD of photocurrent) making decisions on the structure and devices of OPLL.
- Setting up an experimental platform for generation of the variable carrier frequency.