Optical low-coherence reflectometer for measuring WDM components

We developed an optical low coherence reflectometer (OLCR) that is specialized for measuring wavelength dependent reflectances from wavelength division multiplexed components. The system is a complex OLCR (uses fringes and Fourier transform spectroscopy to obtain phase information) and is superior to conventional (envelope detection) OLCR in that reflected phase information can be used to resolve the reflectance amplitudes within narrow spectral windows. The system also contains several improvements over previous complex OLCR configurations, including a copropagating reference signal for minimum fringe degradation and a polarization diversity detection scheme. We used the system to measure internal reflections from several arrayed-waveguide gratings.