US 6,389,195 B1 · Dynamic fiber loop-mirror filter based on pump-induced saturable gain or saturable absorber gratings

Abstract

An all-fiber, optically-tunable, narrowband optical loop-mirror filter (10) that makes use of a loop-mirror (24). The optical filter (10) includes a coupler (12), including two input fiber ports (14, 16) and two output fiber ports (18, 20) that are connected together to form the loop-mirror (24). A saturable medium (22) is positioned in the loop-mirror (24), and can be either a saturable absorber medium or a saturable gain medium. A potentially broadband optical input signal to be filtered and a pump are applied to the input ports (14, 16) of the coupler (12). The counter propagating signals in the loop-mirror (24) generated by the input signal and the pump create two standing wave interference patterns in the saturable medium (22). Depending on whether the input signal and the pump are applied to the same input port (14, 16) or different input ports (14, 16) determines whether the two standing wave interference patterns are in phase with each other or Ξ radians out of phase with each other. If the saturable medium (22) is a saturable gain medium, then the peaks of the pump standing wave interference pattern bleach the gain of the filter (22) at the peak locations, preventing amplification of the input signal at these locations. Likewise, if the saturable medium (22) is a saturable absorber medium, the peaks of the pump interference pattern bleach the absorption of the saturable medium (22) at the peak locations, leaving rest of the saturable medium (22) to provide saturation. Therefore, the filter (10) can be either a bandpass filter or a notch filter.

Claims30

Dependent claims

A loop-mirror filter for filtering an optical input signal, said filter comprising:

a coupler responsive to the optical input signal and an optical pump;
a loop-mirror including a first end and a second end connected to the coupler, said coupler coupling the pump and the input signal into the loop-mirror and creating a pump interference pattern from the pump travelling through the loop-mirror and a signal interference pattern from the input signal travelling through the loop-mirror;
and
a saturable medium positioned in the loop-mirror, said pump pattern creating a pump standing wave interference pattern in the saturable medium and said input signal interference pattern creating an input signal standing wave interference pattern in the saturable medium, said input signal standing wave interference pattern interacting with the pump standing wave interference pattern in the saturable medium to filter the optical input signal.

1 more element

A method of filtering an optical signal, said method comprising the steps of:

applying an optical input signal to a coupler;
applying an optical pump to the coupler;
generating a first set of counter-propagating waves from the input signal in a fiber loop connected to the coupler;
generating a second set of counter-propagating waves from the pump in the fiber loop;
generating an input signal standing wave interference pattern in a saturable medium positioned within the fiber loop from the first set of counter-propagating waves;
generating a pump standing wave interference pattern in the saturable medium from the second set of counter-propagating waves;
and
filtering the input signal from the interaction of the input signal standing wave interference pattern and the pump standing wave interference pattern in the saturable medium, said input signal interference pattern and said pump interference pattern being formed of substantially the same optical frequencies.

5 more elements

Dependencies are inferred from the claim text.

Dynamic fiber loop-mirror filter based on pump-induced saturable gain or saturable absorber gratings

Life of this patent

Dynamic fiber loop-mirror filter based on pump-induced saturable gain or saturable absorber gratings

Life of this patent

Abstract

Claims30