Two-stage erbium doped fiber amplifier using remnant pumping...

Details Two-stage erbium doped fiber amplifier using remnant pumping... Two-stage erbium doped fiber amplifier using remnant pumping...

1999-07-06

2001-12-25

Hellner, Mark (Department: 3662)

Optical: systems and elements

Optical amplifier

Optical fiber

Reexamination Certificate

active

06333810

ABSTRACT:

CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C §119 from an application entitled Two-Stage Erbium Doped Fiber Amplifier Using Remnant Pumping Light earlier filed in the Korean Industrial Property Office on Jul. 3, 1998, and there duly assigned Ser. No. 98-26833 by that Office.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a two-stage erbium doped fiber amplifier (EDFA) using remnant pumping light, and more particularly, to a two-stage EDFA wherein a front-stage EDFA is excited using remnant pumping light after a rear-stage EDFA is excited, thereby amplifying signal light.
2. Description of the Related Art
In an optical transmission system, an erbium doped fiber amplifier(EDFA) directly amplifies an optical signal that has been weakened during transmission without converting the optical signal into an electrical signal, thus remarkably extending the transmission distance. U.S. Pat. No. 5,768,012 to Raymond Zanoni et al. entitled Apparatus And Method For The High-Power Pumping Of Fiber Optic Amplifiers and U.S. Pat. No. 5,673,129 to Victor Mizrahi entitled WDM Optical Communication Systems With Wavelength Stabilized Optical Selectors are examples of known optical amplifiers.
FIG. 1
shows a structure in which a optical signal is amplified by the above-mentioned two-stage EDFA. The EDFA shown in
FIG. 1
includes an input connector
100
, a first divider
110
, a first photodiode
120
, a controller
130
, a first pumping source
140
, a first erbium doped fiber amplifying unit
150
, a second pumping source
160
, a second erbium doped fiber amplifying unit
170
, a second divider
180
, a second photodiode
190
, and an output connector
195
.
The operation of the EDFA is as follows. When optical signal is input through the input connector
100
, the first divider
110
divides the optical signal according to a predetermined ratio. The first photodiode
120
converts the divided optical signal from the first divider
110
into an electrical signal and outputs the electrical signal to the controller
130
. First pumping light generated by the first pumping source
140
is multiplexed with optical signal in the first erbium doped fiber amplifying unit
150
. In this way, the first erbium doped fiber amplifying unit
150
amplifies the optical signal in response to the first pumping light. Second pumping light generated by the second pumping source
160
is multiplexed with optical signal amplified by the first erbium doped fiber amplifying unit
150
. In this way, the second erbium doped fiber amplifying unit
170
re-amplifies the amplified optical signal in response to the second pumping light. The second divider
180
divides optical signal that has been re-amplified by the second erbium doped fiber amplifying unit
170
according to a predetermined ratio. The second photodiode
190
converts the divided optical signal into an electrical signal and outputs the electrical signal to the controller
130
. The controller
130
controls the amplification factor of the first and second optical fiber amplifiers
150
and
170
by checking the intensity of optical signal from the electrical signal output from the first and second photodiodes
120
and
190
and controlling the intensity of pumping light of the first and second pumping sources
140
and
160
.
Since two pumping sources are used in such a two-stage EDFA, the efficiency of the pumping light is low.
SUMMARY OF THE INVENTION
To solve the above problem, it is an objective of the present invention to provide a two-stage EDFA using remnant pumping, light from the rear stage EDFA for amplifying the optical signal by a front-stage EDFA, and using a pumping light from a pumping sourse to amplify the output optical signal from the front-stage EDFA.
Accordingly, to achieve the above objective, there is provided a two-stage erbium doped fiber amplifier (EDFA) using remnant pumping light, comprising a first erbium doped fiber amplifying unit for multiplexing remnant pumping light received from a rear-stage and a received optical signal, wherein the optical signal is amplified by the remnant pumping light, and a second erbium doped fiber amplifying unit which receives pumping light generated by a pumping source and the amplified optical signal output from the first erbium doped fiber amplifying unit, multiplexes the pumping light and the amplified optical signal, amplifies the amplified optical signal output from the first erbium doped fiber amplifying unit in response to the pumping light via a demultiplexer, and outputs the remnant pumping light to the first erbium doped fiber amplifying unit.


REFERENCES:
patent: 5506723 (1996-04-01), Junginger
patent: 5673129 (1997-09-01), Mizrahi
patent: 5703711 (1997-12-01), Hamada
patent: 5768012 (1998-06-01), Zanoni et al.
patent: 5808786 (1998-09-01), Shibuya
patent: 98-059190 (1998-10-01), None

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