Method and apparatus for optical delivery fiber having cladding with absorbing regions

An apparatus comprising:

• an optical delivery fiber having a plurality of cladding layers for the delivery of an optical signal, the delivery fiber including a first segment having a substantially transparent core and an attenuating cladding waveguide, wherein the attenuating cladding waveguide of the first segment includes a pump-wavelength-absorbing dopant, and wherein the pump-wavelength-absorbing dopant includes at least one element selected from the group consisting of transition metals and rare-earth elements, and;
• an amplifying fiber segment spliced to a first end of the first segment of the delivery fiber, wherein the amplifying segment includes an amplifying core having a dopant that absorbs pump light and amplifies signal light, wherein the amplifying core is surrounded by a cladding layer that forms a pump-wavelength waveguide;
• a second segment spliced to a second end of the first segment that is opposite the first end of the first segment, wherein a concentration of a pump-wavelength dopant in the second segment is higher than a concentration of the pump-wavelength dopant in the first segment;
• and
• a third segment spliced to a far end of the second segment relative to the first segment, wherein a concentration of pump-wavelength dopant in the third segment is higher than the concentration of the pump-wavelength dopant in the second segment.

An apparatus comprising:

• an optical delivery fiber having a plurality of cladding layers for the delivery of an optical signal, the delivery fiber including a first segment having a substantially transparent core and an attenuating cladding waveguide;
• an amplifying fiber segment spliced to a first end of the first segment of the delivery fiber, wherein the amplifying segment includes an amplifying core having a dopant that absorbs pump light and amplifies signal light, wherein the amplifying core is surrounded by a cladding layer that forms a pump-wavelength waveguide;
• a second segment spliced to a second end that is opposite the first end of the first segment, wherein a concentration of a pump-wavelength dopant in the second segment is higher than a concentration of a pump-wavelength dopant in the first segment;
• and
• a third segment spliced to a far end of the second segment relative to the first segment, wherein a concentration of pump-wavelength dopant in the third segment is higher than the concentration of the pump-wavelength dopant in the second segment, wherein a concentration of a signal-wavelength dopant in the second segment is higher than a concentration of a signal-wavelength dopant in the third segment.

An apparatus comprising:

• an optical delivery fiber having a plurality of cladding layers for the delivery of an optical signal, the delivery fiber including a first segment having a substantially transparent core and an attenuating cladding waveguide;
• an amplifying fiber segment spliced to a first end of the first segment of the delivery fiber, wherein the amplifying segment includes an amplifying core having a dopant that absorbs pump light and amplifies signal light, wherein the amplifying core is surrounded by a cladding layer that forms a pump-wavelength waveguide;
• a second segment spliced to a second end that is opposite the first end of the first segment, wherein a concentration of a pump-wavelength dopant in the second segment is higher than a concentration of a pump-wavelength dopant in the first segment;
• and
• a third segment spliced to a far end of the second segment relative to the first segment, wherein a concentration of pump-wavelength dopant in the third segment is higher than the concentration of the pump-wavelength dopant in the second segment, wherein a concentration of a signal-wavelength dopant in the first segment is higher than a concentration of a signal-wavelength dopant in the third segment.

A method comprising:

• providing a continuous length of fiber that includes a delivery fiber having a core and a gain fiber having a core, the delivery fiber operatively coupled to the gain fiber;
• delivering pump light into the core of the gain fiber over a length of the core of the gain fiber;
• amplifying a signal wavelength in the core of the gain fiber;
• and
• dumping pump light at a first rate over a distributed length of a first segment of the delivery fiber and dumping pump light at a second rate over a distributed length of a second segment of the delivery fiber, wherein the first rate is lower than the second rate, wherein the providing of the delivery fiber includes providing a plurality of cladding layers surrounding the core including a pump-light-guiding inner cladding having a pump-light-absorbing dopant that is concentrated in the inner cladding, wherein the dumping of pump light further includes absorbing the pump light in the pump-light-absorbing dopant, and wherein the pump-light-absorbing dopant includes at least one element selected from the group consisting of transition metals and rare-earth elements.

An apparatus comprising:

• a continuous length of fiber that includes a delivery fiber having a core and a gain fiber having a core, the delivery fiber operatively coupled to the gain fiber;
• means for delivering pump light into the core of the gain fiber over a length of the core of the gain fiber;
• means for amplifying a signal wavelength in the core of the gain fiber;
• and
• means for dumping pump light at a first rate over a distributed length of a first segment of the delivery fiber and means for dumping pump light at a second rate over a distributed length of a second segment of the delivery fiber, wherein the first rate is lower than the second rate, wherein the means for dumping of pump light further includes dopant means for absorbing the pump light, and wherein the dopant means includes at least one element selected from the group consisting of transition metals and rare-earth elements.

An apparatus comprising:

• an optical delivery fiber having a plurality of cladding layers for the delivery of an optical signal, the delivery fiber including
• a first segment having
• a substantially transparent core, an attenuating cladding waveguide, and an outer cladding that surrounds the attenuating cladding waveguide, wherein the substantially transparent core has a substantially unchanging core diameter in the first segment,
• wherein the attenuating cladding waveguide has a substantially unchanging cladding diameter in the first segment, wherein the attenuating cladding waveguide includes a first absorbing region having a first dopant that includes at least one element selected from the group consisting of transition metals and rare-earth elements, and that absorbs pump light in the attenuating cladding waveguide of the first segment, wherein the first absorbing region that is in the attenuating cladding waveguide does not surround the core in a continuous annular manner,
• wherein the attenuating cladding waveguide includes a second absorbing region having a second dopant, and wherein the second dopant is different than the first dopant.

A method comprising:

• providing a delivery fiber having a first segment that has
• a core having a substantially unchanging core diameter in the first segment,
• a plurality of cladding layers surrounding the core including a pump-light-guiding inner cladding that surround the core and an outer cladding that surrounds the inner cladding,
• wherein the inner cladding has a substantially unchanging inner-cladding diameter in the first segment, wherein the inner cladding includes a first absorbing region having a first dopant that absorbs pump light and includes at least one element selected from the group consisting of transition metals and rare-earth elements, wherein the first dopant is not in a continuous annular distribution surrounding the core, wherein the inner cladding includes a second absorbing region having a second dopant that absorbs light, and wherein the second dopant is different than the first dopant;
• providing a gain fiber having a core, the delivery fiber operatively coupled to the gain fiber;
• delivering pump light into the core of the gain fiber over a length of the core of the gain fiber;
• amplifying a signal wavelength in the core of the gain fiber;
• and
• dumping pump light over a distributed length of the first segment of the delivery fiber, wherein the dumping of pump light further comprises absorbing the pump light in the first region of pump-light-absorbing dopant, and wherein the absorbing of the pump light is concentrated in at least one non-annular portion of the inner cladding surrounding the core in the first segment.

An apparatus comprising:

• a delivery fiber having a first segment that has
• a core having a substantially unchanging core diameter in the first segment, and
• a plurality of cladding layers surrounding the core including a pump-light-guiding inner cladding that surround the core and an outer cladding that surrounds the inner cladding, wherein the inner cladding has a substantially unchanging inner-cladding diameter in the first segment;
• a gain fiber having a core, the delivery fiber operatively coupled to the gain fiber;
• means for delivering pump light into the core of the gain fiber over a length of the core of the gain fiber;
• means for amplifying a signal wavelength in the core of the gain fiber;
• and
• means for dumping light over a distributed length of the first segment of the delivery fiber, wherein the means for dumping light further comprises a first dopant means for absorbing pump light, wherein the first dopant means includes at least one element selected from the group consisting of transition metals and rare-earth elements, and wherein the first dopant means is located in the inner cladding and does not surround the core in a continuous annular manner, wherein the means for dumping light further includes a second dopant means for absorbing light, wherein the second dopant means is different than the first dopant means, and wherein the second dopant means is located in the inner cladding.

An apparatus comprising:

• a continuous length of optical delivery fiber having a plurality of cladding layers for the delivery of an optical signal, the continuous length of delivery fiber including
• a first segment having a substantially transparent core and an attenuating cladding waveguide doped with a first concentration of an absorbing dopant that absorbs light of a first predetermined wavelength, and
• a second segment having a substantially transparent core and an attenuating cladding waveguide doped with a second concentration of an absorbing dopant that absorbs light of the first predetermined wavelength, wherein the second concentration is higher than the first concentration, wherein the first segment is closer to a signal-input end of the delivery fiber than is the second segment, wherein the first predetermined wavelength is a pump wavelength,
• wherein the absorbing dopant in the first segment and the absorbing dopant in the second
• segment are both a first absorbing dopant,
• wherein the attenuating cladding waveguide of the first segment is also doped with a second absorbing dopant that absorbs light of a second predetermined wavelength, and the attenuating cladding waveguide of the second segment is also doped with the second absorbing dopant that absorbs light of the second predetermined wavelength,
• wherein the second predetermined wavelength is a signal wavelength, and
• wherein a concentration of the second dopant in the attenuating cladding waveguide of the second segment is lower than a concentration of the second dopant in the attenuating cladding waveguide of the first segment.

A method comprising:

• providing a continuous length of fiber that includes a delivery fiber having a core and a gain fiber having a core, the delivery fiber operatively coupled to the gain fiber;
• delivering pump light into the core of the gain fiber over a length of the core of the gain fiber;
• amplifying a signal wavelength in the core of the gain fiber;
• dumping pump light over a distributed length of the delivery fiber;
• and
• actively cooling at least a portion of the delivery fiber at a location on the delivery fiber where the dumping of pump light occurs.

An apparatus comprising:

• a continuous length of fiber that includes a delivery fiber having a core and a gain fiber having a core, the delivery fiber operatively coupled to the gain fiber;
• means for delivering pump light into the core of the gain fiber over a length of the core of the gain fiber;
• means for amplifying a signal wavelength in the core of the gain fiber;
• means for dumping pump light over a distributed length of the delivery fiber;
• and
• means for actively cooling at least a portion of the delivery fiber at a location on the delivery fiber where the means for dumping pump light is located.