Fiber optic attenuators and attenuation systems

An attenuation system for attenuating optical energy transmitted through a fiber optic, comprising:

• a controllable attenuator, arranged with respect to a portion of the fiber optic, the portion of the fiber optic having material removed therefrom thereby exposing a surface thereof through which at least some of said optical energy can be controllably extracted, the attenuator including a controllable material formed over said surface for controllably extracting said optical energy according to a changeable stimulus applied to said controllable material which affects the refractive index thereof;
• a level sensing circuit, coupled to said fiber optic, for sensing a level of at least a portion of the optical energy transmitted therein and providing a sensed level stimulus;
• and
• a control circuit coupled to the controllable attenuator for controlling an amount of the changeable stimulus applied to the controllable material in accordance with the sensed level stimulus, received from the level sensing circuit.

A method for controllably attenuating optical energy transmitted through a core of a fiber optic, a portion of the fiber optic having a portion of cladding encasing the core removed therefrom, thereby exposing an evanescent tail of the optical mode field transmitted through the core, the method comprising:

• extracting optical energy from the evanescent tail of the optical mode field using a bulk material, positioned over said portion of the fiber optic, into which the evanescent tail penetrates;
• using a controllable material positioned between the bulk material and the core of the fiber optic to vary a depth of penetration of the evanescent tail into the bulk material, including varying the index of refraction of the controllable material;
• and
• sensing a level of at least a portion of the optical energy transmitted in said fiber optic;
• wherein said using a controllable material includes varying the index of refraction of the controllable material according to the sensed level of at least a portion of the optical energy transmitted in said fiber optic.

A method for controllably attenuating optical energy transmitted through a core of a fiber optic, a portion of the fiber optic having a portion of cladding encasing the core removed therefrom, thereby exposing an evanescent tail of the optical mode field transmitted through the core, the method comprising:

• extracting optical energy from the evanescent tail of the optical mode field using a bulk material, positioned over said portion of the fiber optic, into which the evanescent tail penetrates;
• and
• using a controllable material positioned between the bulk material and the core of the fiber optic to vary a depth of penetration of the evanescent tail into the bulk material including varying the index of refraction of the controllable material;
• wherein a majority of the cladding between an outer radius thereof and the core is removed from the portion of the fiber optic, and wherein:
• said using a controllable material includes varying an effective optical thickness thereof by varying the index of refraction thereof, thereby varying the depth of penetration of the evanescent tail into the bulk material.

A method for controllably attenuating optical energy transmitted through a core of a fiber optic, a portion of the fiber optic having a portion of cladding encasing the core removed therefrom, thereby exposing an evanescent tail of the optical mode field transmitted through the core, the method comprising:

• extracting optical energy from the evanescent tail of the optical mode field using a bulk material, positioned over said portion of the fiber optic, into which the evanescent tail penetrates;
• and
• using a controllable material positioned between the bulk material and the core of the fiber optic to vary a depth of penetration of the evanescent tail into the bulk material, including varying the index of refraction of the controllable material;
• wherein:
• the controllable material has a controllable index of refraction approximately matched to the index of refraction of the cladding;
• and
• the bulk material has a fixed index of refraction higher than the effective mode index of refraction of the fiber optic.

A method for controllably attenuating optical energy transmitted through a core of a fiber optic, a portion of the fiber optic having a portion of cladding encasing the core removed therefrom, thereby exposing an evanescent tail of the optical mode field transmitted through the core, the method comprising:

• extracting optical energy from the evanescent tail of the optical mode field using a bulk material, positioned over said portion of the fiber optic, into which the evanescent tail penetrates;
• and
• using a controllable material positioned between the bulk material and the core of the fiber optic to vary a depth of penetration of the evanescent tail into the bulk material, including varying the index of refraction of the controllable material;
• wherein said using a controllable material includes:
• varying the index of refraction of the controllable material by changing a temperature or voltage stimulus applied thereto.

A method for forming an attenuation system for attenuating optical energy transmitted through a fiber optic, comprising:

• removing material from a portion of the fiber optic thereby exposing a surface thereof through which at least some of said optical energy transmitted therein can be extracted;
• forming a controllable material over the surface for controlling an amount of optical energy extracted from the fiber optic in accordance with refractive index changes induced therein by a changeable stimulus to be applied thereto;
• providing a level sensing circuit, coupled to said fiber optic, for sensing a level of at least a portion of the optical energy transmitted therein and providing a sensed level stimulus;
• and
• providing a control circuit for controlling a value of the changeable stimulus to be applied to the controllable material in accordance with the sensed level stimulus, received from the level sensing circuit.