CHINESE JOURNAL OF PHYSICS VOL. 38, NO. 3-I JUNE 2000

Heterodyne Interferometric Measurement of the Thermo-Optic
Coefficient of Single Mode Fiber

Springfield Chang^1,2, Chia-Chen Hsu$^{3,\dagger}$, Tzer-Hsiang Huang³, Wei-Ching Chuang¹,
Yu-Sheng Tsai¹, Jen-Yu Shieh¹, and Chung-Yee Leung<sup>2

1</sup>Department of Electro-optics Engineering, National Huwei Institute of Tchnology,

Huwei, Taiwan 632, R.O.C.

²Institute of Optical Sciences, National Central University, Chung-Li, Taiwan 320, R.O.C.

³Department of Physics, National Chung Cheng University, Ming-Hsiung, Taiwan 621, R.O.C.
(Received January 3, 2000)

The thermo-optic coefficient of a single mode fiber is determined by a heterodyne interferometric technique. The heterodyne beat signal, resulting from the beating of the carrier and two side-band frequencies, is related to the phase shift difference between the carrier and the side-band waves in a fiber Fabry-Perot interferometer. This phase shift difference is determined with a phase sensitive detection technique and is found to be temperature dependent. From the temperature dependence, the thermo-optic coefficient of the single mode fiber is determined to be 9.2 x 10^-6 C^-1. The experimental result agrees well with a theoretical simulation using the temperature dependent Sellmeier equation for fused silica.

PACS. 42.81.Cn - Fiber testing and measurement of fiber parameters.
PACS. 78.20.Ci $\,$- Optical constants.
PACS. 78.20.Nv - Thermooptical and photothermal effects.

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