US 6,616,353 B1 · Laser intensity noise suppression using unbalanced interferometer modulation

Abstract

An external modulation optical communication system suppressing the intensity noise of a semiconductor laser source by making substantially different optical path lengths for the optical paths in the interferometric modulator. Noise reduction is dependent on the correlation between intensity noise and frequency noise of the semiconductor laser. The interferometer path delay difference forms an optical filter that transforms frequency fluctuations into intensity fluctuations that are out of phase with the laser intensity fluctuations. The intensity modulation induced by frequency noise can be out of phase with the optical source intensity fluctuations, leading to total intensity noise at the output of the optical link which is lower than the laser intensity noise. Because the optical interferometer is already present for optical modulation, the optical filter realized by the unequal path delays of the interferometer does not add optical loss. A high correlation between intensity and frequency noise of the optical source is required for substantial intensity noise reduction.

Claims11

Dependent claims

An optical system for reducing the intensity noise of an optical source comprising:

a source of radiation, said radiation having a wavelength and a phase correlated intensity noise;
an interferometer comprising:
an input port in optical communication with said source;
a first optical path in optical communication with said input port and having a first optical path length;
a second optical path in optical communication with said input port and having a second optical path length, said second optical path length differing from said first optical path length by a predetermined optical path length difference substantially greater than said wavelength;
and
an output port in optical communication with said first and second optical paths;
and
a modulator disposed in said second optical path and having a modulator electrical input, said modulator generating an optical phase delay in response to a modulator drive signal received at said modulator electrical input,
wherein said interferometer provides an optical signal having reduced phase correlated intensity noise at said output port in response to said radiation and said predetermined optical path length difference, said predetermined optical path length difference selected to substantially reduce said phase correlated intensity noise.

7 more elements

Dependencies are inferred from the claim text.

Laser intensity noise suppression using unbalanced interferometer modulation

Life of this patent

Laser intensity noise suppression using unbalanced interferometer modulation

Life of this patent

Abstract

Claims11