Wide linear dynamic range optical modulator

DETAILED DESCRIPTION The present invention provides a novel and improved optical modulator having linear modulation characteristics over a wide dynamic range.
Thus, the present invention avoids the degraded performance caused by inherent input current to output intensity nonlinearities of the conventional light emitting device because the optical signal generated by the light emitting device of the present invention remains at a constant amplitude.
In the preferred embodiment the present invention is an optical amplitude modulator including signal generation means and tunable filter means.
The signal generation means is typically a wavelength stabilized narrowband optical source for generating an optical signal.
The generated optical signal enters the tunable filter means, typically an electrooptically active waveguide which shares a common optical axis with the signal generation means.
The filter means is capable of varying its wavelength response in response to the variation of an input electrical filter control signal.
The filter means receives the optical signal and the control signal so as to vary the amplitude of the input optical signal.
The filter thus provides an output amplitude modulated optical signal.
The apparatus may further include, located between and sharing a common optical axis with the signal generation means and the filter means, optical isolator means.
The optical isolator means is for preventing optical signals reflected from or otherwise originating at the filter means which travel toward the signal generation means from impinging on the signal generation means.
The present invention generates an amplitude, i.
e.
intensity, modulated optical signal by passing a fixed amplitude, fixed wavelength, input optical signal through an optical filter having an electrically variable wavelength response.
The optical filter has a Bragg-like grating corrugated surface tailored to provide the filter with a linear wavelength response.
The filter response is characterized by a very linear (constant, non-zero) region over wavelength