Recursive optical delay line filter with neutralization

An optical delay line filter comprising:

• an optical loop provided with a first and second directional coupler, wherein a first optical signal circulates through the optical loop between a first directional coupler and a second directional coupler, and wherein each of the first and second directional couplers extract a percentage of light from the first optical signal each time the first optical signal passes through each of the first and second directional couplers, thereby generating a series of positive and negative signals;
• a photodetector, the photodetector receiving the extracted light from the first and second directional couplers;
• and
• an impulse cancellation line, the impulse cancellation line providing a second optical signal to the photodetector, the second optical signal canceling a first positive signal in the series of positive signals.

A method for filtering an optical signal comprising the steps of:

• circulating the optical signal through a first and second directional coupler;
• extracting a percentage of light from the optical signal each time the optical signal passes through each of the first and second directional couplers, thereby generating a series of positive and negative signals;
• and
• canceling a first positive signal in the series of positive signals.

An optical delay line filter comprising:

• an optical splitter receiving an optical signal and providing a first optical output and a second optical output;
• an optical loop having an optical path;
• a first directional coupler having a first port, a second port, a third port, and a fourth port, the first port receiving the first optical output, the third port and the fourth port adapted to provide a portion of the optical path;
• a second directional coupler having a first port, a second port, and a third port, the first port and the second port adapted to provide a portion of the optical path;
• a photodetector in communication with the second port of the first directional coupler and the third port of the second directional coupler;
• and
• an impulse cancellation line coupling said second optical output to the photodetector.