DFB fiber laser static strain sensor based on beat frequency interrogation with a reference fiber laser locked to a FBG resonator

Abstract

We report on a high-resolution static strain sensor developed with distributed feedback (DFB) fiber laser. A reference FBG resonator is used for temperature compensation. Locking another independent fiber laser to the resonator using the Pound-Drever-Hall technique results in a strain power spectral density better than S_ε(f) = (4.6 × 10^-21) ε²/Hz in the frequency range from 1 Hz to 1 kHz, corresponding to a minimum dynamic strain resolution of 67.8 pε/√Hz. This frequency stabilized fiber laser is proposed to interrogate the sensing DFB fiber laser by the beat frequency principle. As a reasonable DFB fiber laser setup is realized, a narrow beat frequency line-width of 3.23 kHz and a high beat frequency stability of 0.036 MHz in 15 minutes are obtained in the laboratory test, corresponding to a minimum static strain resolution of 270 pε. This is the first time that a sub-0.5 nε level for static strain measurement using DFB fiber laser is demonstrated.

Michelson interferometer composite cavity fiber laser sensor with radio frequency interrogation

“…When one longitudinal mode jumps, the other modes can still generate the BFS in two phases, so the BFS is relatively stable. This demodulation method realizes sensing by detecting the BFS, which is carried out in the electrical domain and has high stability [14][15][16][17] .…”

Orthogonal Demodulation Pound–Drever–Hall Technique for Ultra-Low Detection Limit Pressure Sensing

“…The PDH technique utilizes the lock-in technique that can avoid the influence of light intensity perturbation to generate a higher signal-to-noise ratio (SNR) discriminating signal. Due to the high sensitivity and SNR [2,3,4] of PDH technique, studies on vibration detection [5], strain sensing [5,6,7,8,9], microcavity gyroscope [4,10], particle detection [11,12], and pressure tuning and sensing [13] have been published. Up to now, PDH sensing demodulation is processed by the lock-in technique, and the modulated output is directly mixed with the local oscillation, which also drives the phase modulator.…”

High-Resolution Temperature Sensor Based on Single-Frequency Ring Fiber Laser via Optical Heterodyne Spectroscopy Technology

“…For an optical fiber sensor that is based on SFFL with such a narrow linewidth, tiny wavelength shift, or more specifically, frequency shift cannot be resolved with the conventional optical spectrum analyzer (OSA) or scanning FPI, which have a resolution that is far big enough to make full use of the benefits of a narrow linewidth. Therefore, measuring the shift of the beat frequency between the eigen-polarization modes of a SFFL itself [ 14 ] or between the SFFL under test and an external narrow-linewidth fiber laser [ 15 ] is an effective way to exploit the characteristic of a narrow-linewidth SFFL. A temperature sensor that is based on dual-polarization single-frequency distributed feedback (DFB) fiber laser was reported to achieve a temperature resolution of 0.04 °C, through measuring both the polarization beat frequency and the absolute wavelength of one polarization [ 16 ].…”

“…However, further improvement on temperature resolution was constrained by limited beat-frequency shift for the longitudinal mode in different polarization states. Recently, a high-resolution static strain sensor that was based on single-frequency DFB fiber laser was reported with optical heterodyne spectroscopy technology, in which a reference laser with fixed-frequency was applied to interrogate the sensor [ 15 ]. It offers a promising solution for higher sensitivity and resolution, while the thermal effects in the phase-shifted FBG-based cavity have the potential problems of grating dephasing when they are employed in temperature sensing [ 18 ].…”