Abstract

Frequency-modulated continuous-wave (FMCW) reflectometry, which is composed of a frequency-swept light source and an imbalanced two-beam interferometer, is frequently used to characterize the optical waveguide devices.^1-3 A laser diode is often used as the frequency-swept light source because its optical frequency can be easily changed by modulating the injection current. However, it is difficult to achieve linear optical frequency sweep by linearly modulating the injection current because the optical frequency change of the laser lags behind the injection current change due to thermal resistance of the laser. The faster the injection current changes, the larger the optical frequency change lags. As a result, the reflection profile is blurred and the spatial resolution is degraded. Here we describe a high resolution FMCW reflectometry using a laser diode with linearized optical frequency sweep by using a digital signal processor (DSP).

© 1995 IEEE