Switchable-gain optical amplifier
View Patent ↗Methods, systems, and apparatus, including computer programs encoded on computer storage media, for optical communications. One optical amplifier includes an input port; a bar-cross switch optically coupled to the input port; a first gain stage optically coupled between first port of the bar-cross switch and to an output port; and a secondary gain stage optically coupled between a second port and a third port of the bar-cross switch, wherein in a bar-state of the bar-cross switch the secondary gain stage is bypassed and in a cross-state, the secondary gain stage and the first gain stage are applied to an input light beam.
1. An optical amplifier comprising:
an input port;
a bar-cross switch optically coupled to the input port;
a first gain stage optically coupled between a first port of the bar-cross switch and an output port; and
a secondary gain stage optically coupled between a second port and a third port of the bar-cross switch, wherein the secondary gain stage comprises a pump bypass structure coupled around an isolator and including a first pump wavelength WDM;
wherein in a bar-state of the bar-cross switch the secondary gain stage is bypassed and in a cross-state, the secondary gain stage and the first gain stage are applied to an input light beam,
wherein the secondary gain stage comprises a plurality of cascading gain stages, each comprising a separate gain-flattening filter and rare-earth doped fiber, and
wherein one or more of the cascading gain stages uses remnant pump light from a previous stage.
2. The optical amplifier of claim 1 , wherein the secondary gain stage comprises a gain-flattening filter and a rare-earth doped fiber.
3. The optical amplifier of claim 1 , wherein the first gain stage comprises a gain-flattening filter and a rare-earth doped fiber.
4. The optical amplifier of claim 1 , further comprising a controller, wherein the controller controls the state of the bar-cross switch.
5. The optical amplifier of claim 1 , wherein each of the cascading gain stages includes a pump source.
6. An optical amplifier comprising:
an input port;
a bar-cross switch optically coupled to the input port;
a first gain stage optically coupled between a first port of the bar-cross switch and an output port; and
a secondary gain stage optically coupled between a second port and a third port of the bar-cross switch, wherein the secondary gain stage comprises a pump bypass structure coupled around an isolator and including a first pump wavelength WDM;
wherein in a bar-state of the bar-cross switch the secondary gain stage is bypassed and in a cross-state, the secondary gain stage and the first gain stage are applied to an input light beam,
wherein the bar-cross switch is configured to pass both pump light and optical signals such that remnant pump light can be used to pump a rare-earth doped fiber of a subsequent gain stage.
7. The optical amplifier of claim 1 , wherein the amplifier can be applied to S band, C band, and L band optical signals.
8. The optical amplifier of claim 1 , wherein the first gain stage and the secondary gain stage are configured to provide a flat gain over a large gain range.
9. The optical amplifier of claim 1 ,
wherein the secondary gain stage further comprises a pump-bypass structure including an isolator, pump wavelength WDMs, and a by-pass insertion loss point.
10. The optical amplifier of claim 1 , further comprising one or more additional bar-cross switches serially coupled between a first port of the bar-cross switch and the first gain stage, and wherein each of the one or more additional bar-cross switches is coupled to a corresponding secondary gain stage.
11. The optical amplifier of claim 1 , further comprising:
an input photodiode for detecting an input signal power;
an output photodiode for detecting an output signal power; and
electrical communications lines for providing measurements of the input photodiode and the output photodiode to a controller.
12. An optical amplifier, comprising:
an input port;
a wavelength division multiplexing fiber coupled to the input port, a pump source, and to a first port of a first bar-cross switch;
the first bar-cross switch configured to selectively couple a first gain stage based on whether the first bar-cross switch is positioned in a bar-state or a cross-state, the first gain stage including a first gain flattening filter and a first erbium doped optical fiber; and
a second bar-cross switch coupled to an output port of the first bar-cross switch and to an output port of the optical amplifier, wherein the second bar-cross switch is configured to selectively couple a secondary gain stage based on whether the second bar-cross switch is positioned in a bar-state or a cross-state, the secondary gain stage including a second gain flattening filter and a second erbium doped optical fiber,
wherein the respective states of the first bar-cross switch and the second bar-cross switch are selected to provide a particular output gain for the optical amplifier.
13. The optical amplifier of claim 6 , wherein the secondary gain stage comprises a gain-flattening filter and a rare-earth doped fiber.
14. The optical amplifier of claim 6 , wherein the first gain stage comprises a gain-flattening filter and a rare-earth doped fiber.
15. The optical amplifier of claim 6 , further comprising a controller, wherein the controller controls the state of the bar-cross switch.
16. The optical amplifier of claim 6 , wherein the secondary gain stage comprises a plurality of cascading gain stages and wherein each of the cascading gain stages includes a pump source.
17. The optical amplifier of claim 6 , wherein the amplifier can be applied to S band, C band, and L band optical signals.
18. The optical amplifier of claim 6 , further comprising:
an input photodiode for detecting an input signal power;
an output photodiode for detecting an output signal power; and
electrical communications lines for providing measurements of the input photodiode and the output photodiode to a controller.