Optical homodyne frequency domain reflectometer using an external cavity semiconductor laser

An external cavity traveling-wave semiconductor ring laser with narrow linewidth is used as a light source for research in frequency domain reflectometry. The optical frequency of the laser is linearly chirped by an intra-cavity phase modulator. The time-delayed reflection signal is mixed with a reference signal to produce a microwave frequency that indicates the position of the reflection. For optical fiber measurement, a spatial resolution of 30 m and a one-way dynamic range of 28 dB for Rayleigh backscattered light have been achieved.<
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