OPTICAL COHERENCE DOMAIN REFLECTOMETRY BY SYNTHESIS OF COHERENCE FUNCTION WITH NONLINEARITY COMPENSATION IN FREQUENCY-MODULATION OF A LASER-DIODE

We propose optical coherence domain reflectometry (OCDR) by synthesis of the coherence function for high-spatial-resolution diagnoses of opt ical systems and waveguide devices. By changing the output frequency o f a laser diode using its direct frequency modulation characteristic, the coherence function having a shape of a delta function was synthesi zed. In the basic experiments the reflectivity distribution was measur ed successfully by sweeping the position of the peak. In this paper no nlinearity compensation in the direct frequency modulation is experime ntally demonstrated to improve the resolution. A three-electrode DFB l aser diode with wide-frequency tunable range is introduced as the ligh t source. A spatial resolution of 2-4 mm in air is demonstrated. Furth ermore, the measurement range flexibility of this method is confirmed in the experiments.