Choi Hae Young, Mudhana Gopinath, Park Kwan Seob, Paek Un-Chul, Lee Byeong Ha
Department of Information and Communications, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-Gu, Gwangju, 500-712, South Korea.
Opt Express. 2010 Jan 4;18(1):141-9. doi: 10.1364/OE.18.000141.
We propose and demonstrate a cross-talk free simultaneous measurement system for temperature and external refractive index (ERI) implemented by dual-cavity Fabry-Perot (FP) fiber interferometer. The sensing probe consists of two cascaded FP cavities formed with a short piece of multimode fiber (MMF) and a micro-air-gap made of hollow core fiber (HOF). The fabricated sensor head was ultra-compact; the total length of the sensing part was less than 600 mum. Since the reflection spectrum of the composite FP structures is given by the superposition of each cavity spectrum, the spectrum measured in the wavelength domain was analyzed in the Fourier or spatial frequency domain. The experimental results showed that temperature could be determined independently from the spatial frequency shift without being affected by the ERI, while the ERI could be also measured solely by monitoring the intensity variation in the spatial frequency spectrum. The ERI and the temperature sensitivities were approximately 16 dB/RIU for the 1.33-1.45 index range, and 8.9 nm/ degrees C at low temperature and 14.6 nm/ degrees C at high temperature, respectively. In addition, it is also demonstrated that the proposed dual-cavity FP sensor has potential for compensating any power fluctuation that might happen in the input light source.
我们提出并演示了一种由双腔法布里 - 珀罗（FP）光纤干涉仪实现的用于温度和外部折射率（ERI）的无串扰同时测量系统。传感探头由两个级联的FP腔组成，这两个腔由一小段多模光纤（MMF）和一个由空心光纤（HOF）制成的微气隙形成。所制作的传感器头超紧凑；传感部分的总长度小于600微米。由于复合FP结构的反射光谱由每个腔的光谱叠加给出，因此在波长域测量的光谱在傅里叶或空间频率域进行分析。实验结果表明，温度可以独立于空间频率偏移来确定，而不受ERI的影响，同时ERI也可以仅通过监测空间频率谱中的强度变化来测量。在1.33 - 1.45的折射率范围内，ERI灵敏度约为16 dB/RIU，在低温下温度灵敏度为8.9 nm/℃，在高温下为14.6 nm/℃。此外，还证明了所提出的双腔FP传感器具有补偿输入光源中可能出现的任何功率波动的潜力。
