Optical: systems and elements – Optical amplifier – Correction of deleterious effects
Reexamination Certificate
1999-07-02
2001-06-26
Tarcza, Thomas H. (Department: 3662)
Optical: systems and elements
Optical amplifier
Correction of deleterious effects
C359S341430
Reexamination Certificate
active
06252700
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
Erbium Doped Fiber Amplifier Suitable For Long Wavelength Light Signal
earlier filed in the Korean Industrial Property Office on Jul. 2, 1998, and there duly assigned Serial No. 98-26651 by that Office.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber suitable for amplifying a long wavelength light signal, and more particularly, to a long wavelength optical amplifier whose gain and noise figure characteristics are improved by inserting an isolator between two erbium doped fibers.
2. Description of the Related Art
In an optical fiber communications system, transmission loss can be easily compensated for by using an erbium doped fiber amplifier (EDFA). The EDFA directly amplifies a light signal without converting the light signal into an electrical signal. 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.
EDFAs are used to amplify weak light signals which have been transmitted over a long distance and carry a large amount of data, in order to compensate for the attenuation of the light signals when they are transmitted over a long length of optical fiber. In contrast with a transmission method in which light is converted into an electrical signal to be amplified and then converted back into light, since the EDFA can directly amplify light, it exhibits a good amplification efficiency without the need for optical-to-electrical conversion.
In general, EDFAs have a high gain in the range of 1525 to 1565 nm. If the length of an EDFA is sufficiently increased, a high gain can be obtained even in the range of 1570 to 1610 nm. Therefore, in order to increase the amplification band of an EDFA, two amplifiers having different amplifying bands may be employed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a long wavelength optical amplifier using pumped light having a wavelength in the 980 nm band, whose gain and noise figure characteristics are improved by inserting an isolator in the middle of an erbium doped fiber.
It is another object of the present invention to provide a long wavelength optical amplifier using pumped light having a wavelength in the 1480 nm band, whose gain and noise figure characteristics are improved by inserting an isolator in the middle of an erbium doped fiber.
Accordingly, to achieve the above objects, there is provided an erbium doped fiber amplifier (EDFA) for amplifying a received light signal including a pump light source for generating pump light in the 980 nm band, a light coupler for receiving the pump light from the pump light source and coupling the same to the received light signal, first and second optical fibers doped with erbium ions, for amplifying the received light signal by the pump light, and an isolator positioned at a point between the first and second optical fibers, the point, from the input terminal of the first optical fiber, corresponding to 9 to 15% of the combined length of the first and second optical fibers.
According to another aspect of the present invention, there is provided an erbium doped fiber amplifier (EDFA) for amplifying a received light signal including a pump light source for generating pump light in the 980 nm band, a light coupler for receiving the pump light from the pump light source and coupling the same to the received light signal, first and second optical fibers doped with erbium ions, for amplifying the received light signal by the pump light, and an isolator positioned between the first and second optical fibers, wherein the combined length of the first and second optical fibers is 48 to 66 m and the isolator is positioned at a point from the input terminal of the first optical fiber corresponding to 3 to 7% of the combined length of the first and second optical fibers.
According to still another aspect of the present invention, there is provided an erbium doped is fiber amplifier (EDFA) for amplifying a received light signal including a pump light source for generating pump light in the 1480 nm band, a light coupler for receiving the pump light from the pump light source and coupling the same to the received light signal, first and second optical fibers doped with erbium ions, for amplifying the received light signal by the pump light, and an isolator positioned at a point between the first and second optical fibers, the point, from the input terminal of the first optical fiber, corresponding to 11 to 25% of the combined length of the first and second optical fibers.
Alternatively, there is provided an erbium doped fiber amplifier (EDFA) for amplifying a received light signal including a pump light source for generating pump light in the 1480 nm band, a light coupler for receiving the pump light from the pump light source and coupling the same to the received light signal, first and second optical fibers doped with erbium ions, for amplifying the received light signal by the pump light, and an isolator positioned between the first and second optical fibers, wherein the combined length of the first and second optical fibers is 60 to 68 m and the isolator is positioned at a point, from the input terminal of the first optical fiber, corresponding to 7 to 11% of the combined length of the first and second optical fibers.
REFERENCES:
patent: 5808786 (1998-09-01), Shibuya
patent: 5914808 (1999-06-01), Mitsuda et al.
patent: 6104527 (2000-08-01), Yang
Ole Lumholt et al., “Optimum Position of Isolators within Erbium-Doped Fibers”, Jun. 1992, IEEE Photonics Technology Letters, vol. 4, No. 6, pp. 568-570.*
M.N. Zervas et al. “Efficient Erbium-Doped Fiber Amplifiers Incorporating an Optical Isolator”, IEEE Journal of Quantum Electronics, vol. 31, No. 3, pp. 472-480, 1995.
Hwang Seong-taek
Nilsson Lars Johan Albinsson
Yoon Soo-young
Bushnell , Esq. Robert E.
Hughes Deandra M.
Samsung Electronics Co,. Ltd.
Tarcza Thomas H.
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