Stimulated Brillouin scattering (SBS) suppression in an optical communications system

A method of reducing noise caused by a beat between a stimulated Brillouin scattering (SBS) suppression tone and a radio frequency (RF) information signal distortion out of band spectrum, while transmitting an optical signal through optical fiber, the method comprising:

• receiving a radio frequency (RF) information-carrying signal;
• applying one or more dithering signals to a first frequency signal having a first frequency signal that is higher than that of the RF information-carrying signal, thereby generating a dithered higher frequency signal which is a SBS suppression higher frequency dither signal;
• splitting the higher frequency dither signal, a first portion of the dithered higher frequency signal for directly modulating a light source and a second portion of the dithered higher frequency signal for adjustment by a phase and gain adjustment circuit;
• adjusting a gain and phase of the second portion of the dithered higher frequency signal by adjusting the gain to modify a signal amplitude and adjusting the phase to be out of phase with the dithered higher frequency signal of the first portion of the dithered signal modulating the light beam for cancelling noise caused by the beat between the SBS suppression tone and RF information signal distortion out of band spectrum, by externally intensity modulating the light beam emitted from the light source with both the adjusted second portion of the dithered higher frequency signal and with a radio frequency (RF) information carrying signal;
• and
• coupling into the optical fiber the light beam modulated with the RF information-carrying signal.

An optical transmitter for stimulated Brillouin scattering suppression in an optical transmission system, the method comprising:

• a signal generator for generating a dithered higher frequency signal by applying one or more dithering signals to a generated signal;
• a splitter for splitting the dither signal, a first portion of the dithered higher frequency signal for directly modulating a light source and a second portion of the dithered higher frequency signal for adjustment by a phase and gain adjustment circuit;
• a light source for emitting a light beam while said light source is directly modulated via the first portion of the dithered higher frequency signal;
• the phase and gain control circuit for adjusting at least one of a gain or a phase of the second portion of the dithered higher frequency signal;
• an external modulator for externally intensity modulating the light beam emitted from the light source with both the adjusted second portion of the dithered higher frequency signal and with a radio frequency (RF) information carrying signal,
• wherein the frequency of the direct modulating signal for SBS suppression is at least twice the frequency of the highest RF information-carrying signal frequency;
• and
• a coupler for coupling into the optical fiber the light beam modulated with the RF information-carrying signal.