Patent ID: 6912338

Claim:
An optical signal noise reduction device to reduce noise of binary optical signals, comprising: a first nonlinear optical loop mirror switch comprising a first optical ring fiber having high nonlinear optical characteristics, a first optical coupler connected to the first optical ring fiber, and a second optical coupler connected to the first optical ring fiber; and an optical control pulse generator to generate a train of optical control signals having a pulse repeating frequency the same as a train of pulse signals, with the first optical coupler inputting the train of pulse signals to the first optical ring fiber, and the second optical coupler inputting the train of optical control signals to the first optical ring fiber, wherein the input pulse signals are input into the first optical ring fiber in a propagating direction of clock-wise (CW) and counter-clock-wise (CCW) through the first optical coupler, and the optical control signals are input into the first optical ring fiber in a propagating direction of CW or CCW through the second optical coupler, where the first optical coupler outputs only optical pulse signals that are synchronized with the optical control signals train from the first optical ring fiber; and a second non-linear optical loop mirror switch comprising a second optical fiber ring having high nonlinear optical characteristics, a third optical coupler connected to the second optical ring fiber, and an output fiber connected to the third optical coupler, wherein the output of the first optical coupler and the input of the third optical coupler are connected to each other, wherein the third optical coupler inputs the optical pulse signals, output from the first coupler, into the second optical ring fiber in a propagating direction of CW and CCW, with a coupling rate of the third optical coupler to optical pulses propagating in directions of CW and CCW is slightly different so that an optical transparency of pulses propagating in the directions of CW and CCW at the third coupler are different, and wherein in the first nonlinear loop mirror switch noise contained in signals input into the first nonlinear loop mirror switch is reduced with corresponding interference of the optical control signals and the input signals, and noise contained in signals output from the first optical coupler to the third optical coupler is reduced with corresponding interference of signals in a direction of CW and CCW signals in the second nonlinear loop mirror switch, such that the third optical coupler outputs optical signals with reduced noise.