Apparatus for protecting powered optical amplifiers
View Patent ↗The present application is directed to an optical apparatus including an optical waveguide configured to receive an optical signal at an input wavelength. The apparatus also includes one or more optical pump sources connected to transmit pump light to the optical gain medium for the optical gain medium to amplify the optical signal. The apparatus also includes an optical feedback loop for a protection wavelength that includes the optical gain medium and at least a portion of the optical waveguide. A round-trip optical gain of the optical feedback loop is higher at an optical wavelength of the pump light than at the input wavelength less than unity in the presence of the optical signal. In addition, the round-trip gain of the optical feedback loop is greater than or equal to unity in the absence of the optical signal.
1. An optical apparatus, comprising:
an optical waveguide configured to receive an optical signal at an input wavelength, the optical waveguide including an optical gain medium;
one or more optical pump sources connected to transmit pump light to the optical gain medium such that the optical gain medium is able to amplify the optical signal; and
an optical feedback loop for a protection wavelength that includes the optical gain medium and at least a portion of the optical waveguide,
wherein a round-trip gain of the optical feedback loop for the protection wavelength is less than unity in the presence of the optical signal, and
wherein the round-trip gain of the optical feedback loop for the protection wavelength is greater then equal or equal to unity in the absence of the optical signal.
2. The apparatus of claim 1 , wherein the input wavelength is within a range that includes one of an Original, Extended, Short, Conventional, Long or Ultra-long optical telecommunication optical bands.
3. The apparatus of claim 1 , wherein the wavelength of the pump light is different from the wavelength of the input wavelength by at least about 20 percent.
4. The apparatus of claim 1 , wherein the optical gain medium includes a rare-earth doped optical fiber.
5. The apparatus of claim 1 , wherein the optical gain medium includes a semiconductor optical amplifier.
6. The apparatus of claim 1 , wherein the optical feedback loop includes a first reflector physically connected to the optical waveguide on an input side of the optical gain medium and a second reflector connected to an output side of the gain medium, wherein the first reflector has a higher reflectivity than the second reflector at the wavelength of the protection light.
7. The apparatus of claim 6 , wherein the first and second reflectors reflect light more weakly at the wavelength of the optical signal than at the wavelength of the protection light.
8. The apparatus of claim 5 , wherein at least one of the first and second reflectors is coupled to the optical waveguide by another optical waveguide located to not receive the optical signal.
9. The apparatus of claim 8 , wherein the another optical waveguide tails is coupled to the optical waveguide configured to receive the optical signal by a wavelength division multiplexer.
10. The apparatus of claim 8 , wherein the another optical waveguide further includes a variable optical attenuator.
11. The apparatus of claim 8 , wherein a variable optical attenuator is located between each of the reflectors and the optical waveguide.
12. The apparatus of claim 1 , further includes an optical isolator located in-between the optical feedback loop and an input port for the input light.
13. The apparatus of claim 1 , further includes an optical power dump optically connected to the optical waveguide at a location between the optical feedback loop and an optical output port of the apparatus.
14. The apparatus of claim 1 , wherein the optical feedback loop is part of a ring laser that further includes:
a second optical waveguide coupled to a first coupling junction on the first optical waveguide located in-between an input source and the gain medium;
a third optical waveguide coupled to a second coupling junction on the first optical waveguide located in-between an optical output port and the optical gain medium; and
a band pass filter coupling the second optical waveguide to the third optical waveguide.
15. The apparatus of claim 14 , further including an isolator in the third optical waveguide located in-between the second coupling junction and the band pass filter.
16. The apparatus of claim 14 , wherein the first and second coupling junctions include wavelength division multiplexers.
17. The apparatus of claim 14 , the third optical waveguide is coupled to a power dump coupled to a coupling junction located in-between the band pass filter and the second coupling junction.
18. A method, comprising:
providing an optical waveguide having an optical gain medium therein, to amplify an optical signal input into the optical waveguide, the optical waveguide including an optical feedback loop for a protection wavelength; and
coupling a source of pump light to the optical waveguide such that the pump light is able to cause the gain medium to amplify an optical signal input into the optical waveguide;
wherein a round-trip gain of the optical feedback loop for the protection wavelength is less than unity in the presence of the optical signal, and
wherein the round-trip gain of the optical feedback loop for the protection wavelength is greater than or equal to unity in the absence of the optical signal.
19. A method, comprising:
forming a laser cavity, including: passing a pump light, emitted from a pump source, through an optical feedback loop that includes an optical gain medium that can absorb the pump light and emit light at a protection wavelength, wherein:
the optical feedback loop includes at least a portion of a waveguide pathway that is configured to receive an input light at an input wavelength configured to carry an optical signal,
a maximum round-trip gain of light within the optical feedback loop occurs at a protection wavelength,
the protection wavelength is different from the input wavelength, and a net round trip gain in amplitude of the emitted light at the protection wavelength through the optical feedback loop is greater than or equal to one in the absence of the input light.
20. The apparatus of claim 1 , wherein at least two optical pumps sources are positioned on opposite ends of the optical feedback loop to transmit pump light.