Method and apparatus for reduction of optical coupling between pump lasers and photodetectors in optical amplifiers
View Patent ↗In a first aspect, the present invention comprises an optical filter comprising a fiber having a core and a cladding and a light-absorbing coating applied onto a portion of the fiber cladding, the coating attenuating loosely bound cladding modes. In another aspect, the invention comprises a fiber amplifier apparatus comprising fibers for delivering pump laser light and for monitoring signal light and at least one photodetector optically coupled to a monitoring fiber, wherein either an optical filter is disposed between a monitoring fiber and a photodetector or at least one of the fibers has a core and a cladding and a light-absorbing coating applied onto a portion of the fiber cladding. A method in accordance with the present invention includes providing an optical amplifier having fibers for delivering pump laser light and for monitoring signal light, and applying a light-absorbing coating onto a portion of one of said fibers.
1. An optical amplifier comprising:
an optical gain medium connected to an input optical fiber and an output optical fiber;
an optical coupler connected to the optical gain medium between the input and output optical fibers;
a pump member optically coupled to the optical gain medium via a first filter member to deliver a pump laser light to the optical gain medium, the first filter member including a first length portion and a second length portion, wherein the second length portion is proximate a location where the pump member is optically coupled to the first filter member and a light-absorbing coating is applied to the second length portion and is not applied to the first length portion; and
a photodetector optically coupled to the optical coupler via a second filter member, wherein the photodetector receives an optical signal and produces an electrical signal proportional to the optical signal.
2. The optical amplifier of claim 1 , wherein the second portion of the first filter member is proximate a location where the pump member is optically coupled to the first filter member.
3. The optical amplifier of claim 1 , wherein the first filter member comprises a core and a cladding surrounding the core, wherein the light-absorbing coating is disposed upon a portion of the cladding such that the light absorbing coating attenuates a light propagating through the cladding.
4. The optical amplifier of claim 1 , wherein the first filter member comprises a core and a cladding with a protective coating, wherein the light-absorbing coating is disposed upon a portion of the protective coating such that the light absorbing coating attenuates a light propagating through the protective coating.
5. The optical amplifier of claim 1 , wherein the first filter member comprises a core and a cladding surrounding the core, wherein the light-absorbing coating is disposed upon a portion of the cladding such that the light absorbing coating reduces light leaking from an adjacent fiber from entering the first filter member.
6. The optical amplifier of claim 1 , wherein the light-absorbing coating is marking ink.
7. The optical amplifier of claim 1 , wherein the second filter member has a light absorbing coating applied only to a portion of its length proximate a location where the photodetector is optically coupled to the second filter member.
8. The optical amplifier of claim 7 , wherein the second filter member comprises a core and a cladding surrounding the core, wherein the light-absorbing coating is disposed upon a portion of the cladding such that the light absorbing coating attenuates a light propagating through the cladding.
9. The optical amplifier of claim 7 , wherein the second filter member comprises a core and a cladding with a protective coating, wherein the light-absorbing coating is disposed upon a portion of the protective coating such that the light absorbing coating attenuates a light propagating through the protective coating.
10. The optical amplifier of claim 7 , wherein the first filter member comprises a core and a cladding surrounding the core, wherein the light-absorbing coating is disposed upon a portion of the cladding such that the light absorbing coating reduces light leaking from an adjacent fiber from entering the first filter member.
11. The optical amplifier of claim 7 , wherein the light-absorbing coating marking fluid.
12. The optical amplifier of claim 1 , wherein the input fiber delivers an optical signal to the optical gain medium and the optical coupler directs a portion of the optical signal to the second filter member.
13. An optical amplifier comprising:
an optical gain medium connected to an input optical fiber and an output optical fiber;
an optical coupler connected to the optical gain medium between the input and output optical fibers;
a first filter member configured to optically couple a pump member to the optical coupler, the first filter member having a first length portion and a second length portion, wherein the second portion is proximate a location where the pump member is optically coupled to the first filter member and a light-absorbing coating is applied to the second length portion and is not applied to the first length portion; and
a second filter member configured to optically couple a photodetector to the optical coupler, wherein the second filter member has a light-absorbing coating applied only to a portion of its length proximate a location where the photodetector is optically coupled to the second filter member.
14. The optical amplifier of claim 13 , wherein each filter member comprises a core and a cladding surrounding the core, wherein the light-absorbing coating is disposed upon a portion of the cladding such that the light absorbing coating attenuates a light propagating through the cladding.
15. The optical amplifier of claim 13 , wherein each filter member comprises a core and a cladding with a protective coating, wherein the light-absorbing coating is disposed upon a portion of the protective coating such that the light absorbing coating attenuates a light propagating through the protective coating.
16. The optical amplifier of claim 13 , wherein each filter member comprises a core and a cladding surrounding the core, wherein the light-absorbing coating is disposed upon a portion of the cladding such that the light absorbing coating reduces light leaking from an adjacent fiber from entering the first filter member.
17. The optical amplifier of claim 13 , wherein the light-absorbing coating marking fluid.
18. The optical amplifier of claim 13 , wherein the pump member delivers a pump laser light to the optical gain medium.
19. The optical amplifier of claim 13 , wherein the photodetector receives an optical signal and produces an electrical signal proportional to the optical signal.
20. An optical amplifier comprising:
an optical gain medium connected to an input optical fiber and an output optical fiber;
an optical coupler connected to the optical gain medium between the input and output optical fibers;
a photodetector configured to receive an optical signal and produce an electrical signal proportional to the optical signal;
a filter member configured to optically couple the photodetector to the optical coupler, the filter member having a first length portion and a second length portion, wherein the second portion is proximate a location where the photodetector is optically coupled to the filter member and a light-absorbing coating is applied to the second length portion and is not applied to the first length portion; and
a pump member configured to deliver a pump laser light to the optical gain medium.
21. The optical amplifier of claim 20 , further comprising a second filter member configured to optically couple the pump member to the optical gain medium, wherein the second filter member includes a first length portion and a second length portion, wherein the second portion is proximate a location where the pump member is optically coupled to the second filter member and a light-absorbing coating is applied to the second length portion and is not applied to the first length portion.
22. The optical amplifier of claim 20 , wherein the input fiber delivers an optical signal to the optical gain medium and the optical coupler directs a portion of the optical signal to the photodetector.
23. The optical amplifier of claim 22 , wherein the filter member is configured to allow the transmission of the optical signal to the photodector.
24. The optical amplifier of claim 23 , wherein the transmission of the optical signal to the photodetector is between 1527-1565 nm.
25. The optical amplifier of claim 22 , wherein the photodetector is configured to produce an electrical signal proportional to the optical signal received.
26. The optical amplifier of claim 25 , further including a control module configured to monitor the performance of the optical amplifier by analyzing the electrical signal sent by the photodetector.
27. The optical amplifier of claim 20 , wherein the filter member comprises a core and a cladding surrounding the core, wherein the light-absorbing coating is disposed upon a portion of the cladding such that the light absorbing coating attenuates a light propagating through the cladding.
28. The optical amplifier of claim 20 , wherein the filter member comprises a core and a cladding with a protective coating, wherein the light-absorbing coating is disposed upon a portion of the protective coating such that the light absorbing coating attenuates a light propagating through the protective coating.
29. The optical amplifier of claim 20 , wherein the filter member comprises a core and a cladding surrounding the core, wherein the light-absorbing coating is disposed upon a portion of the cladding such that the light absorbing coating reduces light leaking from an adjacent fiber from entering the first filter member.
30. The optical amplifier of claim 20 , wherein the light-absorbing coating is marking ink.