  We utilize various techniques to characterize the residual phase modulation
of a fiber-based Mach-Zehnder electro-optical intensity modulator. A heterodyne
technique is used to directly measure the phase change due to a given change in
intensity, thereby determining the chirp parameter of the device. This chirp
parameter is also measured by examining the ratio of sidebands for sinusoidal
amplitude modulation. Finally, the frequency chirp caused by an intensity pulse
on the nanosecond time scale is measured via the heterodyne signal. We show
that this chirp can be largely compensated with a separate phase modulator. The
various measurements of the chirp parameter are in reasonable agreement.

Atomic Physics;Optics