Real-time measurement system for overlapping reflection signals of fiber Bragg gratings using high-speed wavelength-swept laser
Real-time measurement system for overlapping reflection signals of fiber Bragg gratings using high-speed wavelength-swept laser
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DOI：
10.1117/1.oe.61.7.076114
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发表时间：
2022-07
影响因子：
1.3
通讯作者：
Tatsuya Yamaguchi;Akira Nakamoto;Y. Shinoda
中科院分区：
文献类型：
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作者：
Tatsuya Yamaguchi;Akira Nakamoto;Y. Shinoda
摘要。我们提出了一种防止光纤布拉格光栅（fbg）反射信号重叠的实时测量系统。该系统结合了采用傅立叶域锁模（FDML）的波长扫描激光器和具有三条光路的缓冲级，实现了304.2 kHz的高速测量速率。使用高速扫波长激光器的系统受到光纤传输时间（延迟）的影响。延迟会导致测量不准确、难以区分光纤光栅反射信号、光纤光栅反射信号重叠等问题。为了防止这些问题，我们介绍了一种用光纤开关对波长扫描激光器进行脉冲调制的方法。这种方法允许通过提取和识别在特定波长的光纤光栅的反射信号来校正延迟。通过识别所有fbg的反射信号，可以确定重叠信号。因此，我们设计了一种测量方法，该方法使用光纤开关在一个光纤光栅的波长区域用来自激光波长扫光的重叠信号遮蔽光。这种方法抑制了重叠，并且只允许提取和解调其他fbg的反射信号。该系统使用波长扫频激光器进行双向前向和后向扫描，使得阴影光纤光栅信号可以在任意扫描方向解调。我们证明了使用三缓冲FDML激光器的系统可以同时测量安装在任意距离上的fbg的应变或振动。
Abstract. We propose a real-time measurement system that prevents overlapping reflection signals in fiber Bragg gratings (FBGs). The system combines a wavelength-swept laser using Fourier domain mode-locking (FDML) and a buffer stage with three optical paths to obtain a high-speed measurement rate of 304.2 kHz. Systems using high-speed wavelength-swept lasers are affected by the propagation time (delay) of the optical fiber. The delay causes problems such as inaccurate measurements, difficulty in distinguishing FBG reflection signals, and overlapping FBG reflection signals. To prevent these problems, we introduce a method for pulse modulation of a wavelength-swept laser by a fiber switch. This method allows for correction of delays by extracting and identifying only the reflection signal of the FBG at a specific wavelength. By identifying the reflection signals of all FBGs, the overlapping signals can be determined. Accordingly, we devise a measurement method that uses a fiber switch to shade light in the wavelength region of one FBG with overlapping signals from the wavelength-swept light of the laser. This method suppresses overlapping and allows only the reflection signal of the other FBGs to be extracted and demodulated. The proposed system uses bidirectional forward and backward scans with the wavelength-swept laser, such that the shaded FBG signals can be demodulated with either scanning direction. We demonstrate that the system using a three-buffered FDML laser can simultaneously measure the strain or vibration of FBGs installed at arbitrary distances.