Temperature Sensor Based on Self-Interference of a Single Long-Period Fiber Grating

Byeong Ha LEE, Youngjoo CHUNG, Won-Taek HAN, Un-Chul PAEK

Summary :

A novel temperature sensor device based on a conventional long-period fiber grating but having an improved sensing resolution is presented. By forming a reflector at one cleaved end of the fiber embedding a long-period grating, a fine interference fringe pattern was obtained within the conventional broadband resonant spectrum of the grating. Due to the fine internal structure of the reflection spectrum of the proposed device, the accuracy in reading the temperature-induced resonant wavelength shift was improved. The formation of the self-interference fringe is analyzed and its properties are discussed in detail. The performance of the proposed device is analyzed by measuring the resonant wavelength shift of the device placed in a hot oven under varying temperature. The rate of the fringe shift is measured to be 551 pm/. The rms deviation is 10 pm over a 100 dynamic range, which corresponds to 0.2 in rms temperature deviation. The thermal variation of the differential effective index of the fiber is calculated to be (0.3 0.1)10^-6/ by comparing the analytic calculations with the experimental results. The interference fringe shift is revealed to be inversely proportional to the differential effective group index of the fiber, which implies that the shifting rate strongly depends on the type of fibers and also on the order of the involved cladding mode.

• Publication: IEICE TRANSACTIONS on Electronics Vol.E83-C No.3 pp.287-292
• Publication Date: 2000/03/25
• Type of Manuscript: Special Section PAPER (Special Issue on Optical Fiber Sensors)
• Category: Physical and Mechanical Sensors

Authors

Byeong Ha LEE
Youngjoo CHUNG
Won-Taek HAN
Un-Chul PAEK

Keyword

fiber grating,  long-period fiber grating,  fiber sensor,  cascaded fiber grating,  temperature sensor