Demonstration of Phase Correlation Between the Spectral Lines of a Broadband Fiber Laser

The spectrally broadened output of an erbium-doped fiber laser generated by intra-cavity four-wave mixing is passed through a demultiplexer yielding multiple narrow-linewidth spectral sources. These spectral lines are tested for their phase correlation by providing two such spectral lines simultaneously as input to the fiber-optic Mach-Zehnder-based interferometer, and studying the interference. Significant phase correlation is obtained which is not limited by the wavelength separation between the spectral lines. Comparison with the results from two standard narrow-linewidth lasers as well as two broadband non-laser sources aid in the interpretation of the spectral visibility data.