Improved Pound-Drever-Hall Techniques for High Resolution Optical Fiber Grating Sensors

The interrogation technology plays a key role in high resolution fiber grating sensors. Due to the high sensitivity and quick response, the Pound-Drever-Hall (PDH) technique is one of the most successful interrogation methods in the high resolution fiber grating sensor systems. However, the traditional PDH technique can only interrogate one sensing element with limited measurement range, and can't fully exploit the capability of optical fiber sensors. To break through this limitation, lots of efforts have been put to improve the PDH technique. This article reviews the recent improvements on PDH technique towards large measurement range and low probe power interrogation. Sideband interrogation method and high order PDH technique are proposed to expand the measurement range without tuning the laser frequency; In order to enable low probe power interrogation, which is essential in multiplexed sensing, coherent PDH and active PDH techniques are developed. Those improvements will promote the further development of PDH technique and provide powerful tools for high-resolution sensing applications.