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Development of a fully automated Fibre Interferometer

Author(s): G. Lakshminarayanan, Shanti Bhattacharya, C. A. Khansa and A. Prabhakar
Affiliation(s): Department of Electrical Engineering, Indian Institute of Technology Madras

Topic: 2. Development of Optical Measurement Systems
Presentation: Oral

Fibre interferometry has many advantages, especially in the 1550nm region. In this wavelength region, not only are components easily available, but also they are typically inexpensive. This means that it is easy to have a completely optical system right up to a fibre pigtailed photodetector for detecting the output interference signal. Having such a system means minimum or no alignment of components is necessary. However, a fibre interferometer is far more sensitive to environmental disturbances than a free space one. Even a small movement of the fibre, will result in fluctuation of the interference output, as will thermal fluctuations. It, therefore, becomes important to have some form of stabilisation for the interferometer. Without stabilisation, the phase fluctuates through 2p causing the output intensity to vary through its entire gamut of values. In this paper, we present initial results on a completely automated dual wavelength fibre interferometer, which can be used for height measurement. The various parts of the interferometer such as the multi-wavelength erbium doped fibre source developed specifically for this interferometer, the optical calibration that was carried out to arrive at the best configuration and the electrical control required for the stabilisation will all be presented in detail.