Hybrid optical amplifier with optimized noise figure
View Patent ↗Methods for optimizing a noise figure of a variable gain hybrid amplifier (HA) which includes a variable gain Raman amplifier with adjustable average gain G R and gain tilt T R and a variable gain lumped amplifier with adjustable average gain G L and gain tilt T L . In various embodiments, the methods include receiving as input a required hybrid amplifier average gain G H value and a required gain tilt T H value and deriving a set of G R , T R , G L and T L values which yield an optimal optimized hybrid amplifier NF and satisfy the conditions G R +G L =G H and that T R +T L is within a specified hybrid amplifier operating tilt range. In some embodiments, the derived T R and T L values satisfy the condition T R +T L =T H .
1. A method for operating a variable gain hybrid amplifier to optimize a noise figure, the hybrid amplifier having an adjustable average gain G H and including a variable gain Raman amplifier with adjustable average gain G R and gain tilt T R and a variable gain lumped amplifier with adjustable average gain G L and gain tilt T L , the method comprising the steps of:
a) receiving as input a required hybrid amplifier average gain G H value; and
b) deriving a set of G R , T R , G L , and T L values such that the hybrid amplifier noise figure is optimized, wherein the derived G R and G L values satisfy the condition G R +G L =G H and wherein the derived T R and T L values satisfy the condition that T R +T L is within a specified hybrid amplifier operating gain tilt range.
2. The method of claim 1 , wherein the hybrid amplifier further has an adjustable gain tilt T H and wherein the step of receiving as input further includes receiving a required T H value and wherein the derived T R and T L values satisfy the condition T R +T L =T H .
3. The method of claim 1 , further comprising the step of:
c) setting the Raman amplifier G R and T R to respectively the derived G R and T R values and setting G L and T L to respectively the derived G L and T L values.
4. The method of claim 1 , wherein the step of deriving includes retrieving the set of G R , T R , G L and T L values from a lookup table.
5. The method of claim 1 , wherein the step of deriving includes retrieving the set of G R , T R , G L and T L values from a formula.
6. The method of claim 1 , wherein the lumped amplifier gain tilt has a nominal value T L0 and wherein the derived T L value is different from the T L0 value for at least some G H values.
7. The method of claim 6 , wherein the lumped amplifier is an Erbium doped fiber amplifier and wherein the derived T L value is larger than the T L0 value.
8. The method of claim 3 , wherein the lumped amplifier is specified to operate at a maximum average gain G L0 value and wherein the lumped amplifier includes a variable optical attenuator (VOA) with attenuation V and wherein, as a result of the setting of the G R , T R , G L and T L values, V is set to a value that satisfies the condition V<G L0 −G L for at least some G H values.
9. A variable gain hybrid amplifier with an adjustable average gain G H , the hybrid amplifier including a variable gain Raman amplifier with adjustable average gain G R adjustable average gain tilt T R and a variable gain lumped amplifier with adjustable average gain G L and adjustable average gain tilt T L , the hybrid amplifier comprising a control unit adapted to set G R , T R , G L and T L to respective G R , T R , G L , and T L values, the control unit including means to receive as input a required G H value and a logic module configured to derive the respective G R , T R , G L , and T L values such as to optimize a hybrid amplifier noise figure and such that G H is set to the required G H value, wherein the derived T R and T L values satisfy the condition that T R +T L is within a specified hybrid amplifier operating tilt range.
10. The hybrid amplifier of claim 9 , wherein the logic module includes a lookup table.
11. The hybrid amplifier of claim 9 , wherein the logic module uses a formula to derive the respective G R , T R , G L and T L values.
12. The hybrid amplifier of claim 9 , wherein the hybrid amplifier further has an adjustable gain tilt T H , wherein the control unit further includes means to receive as input a required T H value, and wherein the logic module is configured to derive, based on the G H and T H values, the respective G R , T R , G L and T L values such as to optimize the hybrid amplifier noise figure and such that both G H and T H are set respectively to the required G H and T H values.
13. The hybrid amplifier of claim 9 , wherein the lumped amplifier is specified to operate at a maximum average gain G L0 value, wherein the lumped amplifier includes a variable optical attenuator (VOA) with attenuation V which receives a value that satisfies the condition V<G L0 −G L for at least some G H values.
14. The hybrid amplifier of claim 9 , wherein the lumped amplifier has a nominal gain tilt value T L0 , and wherein the derived T L value is different than the T L0 value for at least some G H values.
15. The hybrid amplifier of claim 14 , wherein the lumped amplifier is an Erbium doped fiber amplifier (EDFA), and wherein the derived EDFA T L value is larger than the T L0 value for at least some G H values.
16. A variable gain hybrid amplifier having an adjustable average gain G H and comprising:
a) a variable gain Raman amplifier with independently adjustable average gain G R and gain tilt T R ;
b) a variable gain lumped amplifier with independently adjustable average gain G L and gain tilt T L ; and
c) a control unit adapted to independently set each of G R , T R , G L and T L to respective G R , T R , G L and T L values such as to optimize a hybrid amplifier noise figure.
17. The hybrid amplifier of claim 16 , wherein the hybrid amplifier further has an adjustable gain tilt T H , wherein the control unit includes means to receive as input a required G H value and a required T H value and a logic module configured to derive, based on the G H and T H values, the respective G R , T R , G L and T L values such as to optimize the hybrid amplifier noise figure and such that G H and T H are set respectively to the required G H and T H values.
18. The hybrid amplifier of claim 16 , wherein the lumped amplifier is specified to operate at a maximum average gain G L0 value, wherein the lumped amplifier includes a variable optical attenuator (VOA) with attenuation V which receives a value that satisfies the condition V<G L0 −G L for at least some G H values.
19. The hybrid amplifier of claim 16 , wherein the lumped amplifier has a nominal gain tilt value T L0 , and wherein the derived T L value is different than the T L0 value for at least some G H values.
20. The hybrid amplifier of claim 16 , wherein the lumped amplifier is an Erbium doped fiber amplifier (EDFA), and wherein the derived EDFA T L value is larger than the T L0 value for at least some G H values.