Optical coherence domain reflectometry by synthesis of coherence function

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Abstract
Reflectometry by synthesis of optical coherence function using a laser diode as a light source for high resolution measurements of optical systems and waveguide devices is proposed. This method has no mechanical moving parts. The oscillation frequency of the laser diode is controlled by the injection current with an appropriate waveform and the coherence function, which corresponds to the time-averaged spectrum shape, is synthesized. The principle that includes three types of synthesized coherence function is presented. The basic experiments of the three methods have been successfully carried out and the resolution about 10 mm in air is demonstrated using an ordinary Fabry-Perot-type single-mode laser diode. The performance deterioration factors of the most promising method are also discussed, in which a coherence function with a delta-function-like shape along the optical path is synthesized to obtain the reflectivity distribution directly.