<title>High-resolution strain sensing by locking lasers to fiber Bragg gratings</title>

<title>Multiplexed FBG sensors and their applications</title>

“…A different situation is when the system is working in a "lock-in' mode where the laser wavelength is locked to a particular point (e.g., the peak) of the reflection spectrum by a closed feedback loop [44,45]. In this case, the effect of the interferometric signal is to affect the lock-in accuracy and the use of low-pass filter may not help.…”

<title>Performance of a time-division-multiplexed fiber Bragg grating sensor array with a tunable laser source</title>

“…a(t)= 2. + coswt (5) where m ' the amplitude of the wavelength modulation and A is an average wavelength that can be tuned (swept) over a certain wavelength range.…”

“…A multiplexed array of FBG sensors sharing the same tunable laser and/or the same signal processing unit would greatly reduce the cost in terms of cost per sensor. The other advantage of using laser sources may be the higher power level for improving signal to noise ratio and for multiplexing a large number of sensors using TDM or a combination of WDM and TDM techniques [4][5][6][7]. However, as the coherence length of the laser is long, the leakage waves from other channels in a TDM system due to the limited extinction ratio of the optical pulse modulation may interfere with the signal wave and result in unwanted interferometric signals.…”

Experimental investigation of a 4‐FBG TDM sensor array with a tunable laser source

“…There has been considerable research interest recently in using tunable lasers for interrogating fiber Bragg grating (FBG) sensors [1][2][3][4][5]. Compared with other configurations that use broadband sources and wavelength filtering devices, the use of laser sources provides a much higher optical power level within a narrow spectral width and thus improves the signal-to-noise ratio.…”

“…The first category is the analytical ABCs that approximate the continuous one-way wave equation at the boundary, for example, the Engquist-Majda-Mur condition [1,2]. The second category involves with the perfectly matched layer (PML) ABCs [3] that match plane waves at the boundary. In the PML ABCs, several PML layers must be employed for sufficiently accurate results.…”