Communication system using S-band Er-doped fiber amplifiers with depressed cladding
View Patent ↗An optical communication system such as a Wavelength-Division-Multiplexed (WDM) or Dense Wavelength-Division-Multiplexed (DWDM) communication system using Erbium doped fiber amplifiers (EDFAs) for amplifying signals in the S-band. The fiber amplifier has a core doped with Erbium and defined by a core cross-section and a refractive index n 0 . The fiber amplifier has a depressed cladding surrounding the core and a secondary cladding surrounding the depressed cladding. The depressed cladding has a depressed cladding cross-section and a refractive index n 1 , and the secondary cladding has a secondary cladding cross-section and a refractive index n 2 . The fiber amplifier has a pump source for pumping the Erbium to a level of high relative inversion D such that the Erbium exhibits positive gains in the S-band and high gains in a long wavelength band longer than the S-band, i.e., in the C- and L-Bands. The core cross-section, the depressed cladding cross-section and the refractive indices n 0 , n 1 , and n 2 are selected to obtain losses at least comparable to the high gains in the long wavelength band and losses substantially smaller than the positive gains in the S-band. The optical communication system can employ the fiber amplifier as a pre-amplifier, a power-boosting amplifier or an in-line amplifier.
1. An optical communication system comprising:
a) a signal source for providing a signal in an S-band of wavelengths;
b) a fiber amplifier for amplifying said signal, said fiber amplifier having:
1) a core doped with Erbium and having a core cross-section and a refractive index n 0 ;
2) a depressed cladding surrounding said core, said depressed cladding having a depressed cladding cross-section and a refractive index n 1 ;
3) a secondary cladding surrounding said depressed cladding, said secondary cladding having a secondary cladding cross-section and a refractive index n 2 ;
4) a pump source for pumping Erbium contained in said core to a relative inversion D greater than about 0.7, such that said active material exhibits positive first gains in said S-band and second gains in a long wavelength band longer than said S-band, wherein said second gains are higher than said first gains;
wherein said core cross-section, said depressed cladding cross-section, and said refractive indices n 0 , n 1 , and n 2 are selected to produce losses at least comparable to said second gains in said long wavelength band and losses substantially smaller than said first gains in said S-band.
2. The optical communication system of claim 1 , wherein said fiber amplifier is an amplifier selected from the group consisting of pre-amplifier, power-boosting amplifier, and in-line amplifier.
3. The optical communication system of claim 1 , wherein said optical communication system is a Wavelength-Division-Multiplexed communication system.
4. The optical communication system of claim 3 , wherein said fiber amplifier is an amplifier selected from the group consisting of pre-amplifier, power-boosting amplifier, and in-line amplifier.
5. The optical communication system of claim 3 , further comprising:
a) a communication fiber;
b) a Wavelength-Division-Multiplexer for multiplexing said signal over said communication fiber; and
c) a Wavelength-Division-Demultiplexer for demultiplexing said signal.
6. The optical communication system of claim 5 , wherein said fiber amplifier is a pre-amplifier installed after said Wavelength-Division-Demultiplexer.
7. The optical communication system of claim 5 , wherein said fiber amplifier is installed between said Wavelength-Division-Multiplexer and said Wavelength-Division-Demultiplexer.
8. The optical communication system of claim 7 , wherein said fiber amplifier is an amplifier selected from the group consisting of pre-amplifier, power-boosting amplifier, and in-line amplifier.
9. The optical communication system of claim 3 , wherein said signal source comprises a laser belonging to a laser array.
10. The optical communication system of claim 1 , wherein said long wavelength band comprises at least a portion of the C-band or L-band.
11. The optical communication system of claim 1 , wherein said pump source is a laser diode providing pumping radiation at about 980 nm.
12. The optical communication system of claim 1 , wherein said signal is an information-bearing signal.
13. The optical communication system of claim 1 , wherein said fiber amplifier is tuned for amplifying a sub-band of said S-band.