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14 February 2018 Highly sensitive method of temperature sensing by using heterodyne detection
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In this paper, we propose temperature sensing method by using optical beating. When temperature changes, a peak wavelength of the sensing laser varies slightly. However, with limitation of the optical spectrum analyzer’s (OSA) spectral resolution (sub-nm), it is hard to measure the exact quantity of the wavelength variation. Therefore, we used electrical spectrum analyzer (ESA) and two lasers to obtain the wavelength shift. We used DFB-LD (distributed feedback laser diode) and TLS (tunable laser source) to get beating signal. Each of laser has 1550 nm of wavelength, -20 dBm of intensity and 108 of Q factor. We varied temperature by 0.1 °C from 17.4 °C to 18.4 °C using TEC (temperature controller). We observed 0.01 nm/°C of wavelength change through OSA and 9.5 GHz/°C of beating frequency change through ESA. With this result, we verified that we can measure relative temperature change with having ultra-fine resolution of 9.5×10-7 °C theoretically for the ESA resolution bandwidth of 1 kHz. This detecting ability can be applied to highly sensitive temperature sensor.
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Eudum Kim, Sun-Ho Kim, Jun-Hee Park, Su-Jin Jeon, Ji-Hoon Kim, Mi Jung, and Young-Wan Choi "Highly sensitive method of temperature sensing by using heterodyne detection", Proc. SPIE 10551, Optical Data Science: Trends Shaping the Future of Photonics, 105510N (14 February 2018);

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