Optical: systems and elements – Optical amplifier – Optical fiber
Reexamination Certificate
1999-11-24
2001-11-13
Tarcza, Thomas H. (Department: 3662)
Optical: systems and elements
Optical amplifier
Optical fiber
Reexamination Certificate
active
06317254
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. § 119 arising from an application entitled, PARALLEL OPTICAL FIBER AMPLIFIER WITH HIGH POWER CONVERSION, filed earlier in the Korean Industrial Property Office on Nov. 24, 1998, and there duly assigned Ser. No. 1998-50407.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical device for optical communications, and more particularly to a parallel optical fiber amplifier having a configuration capable of reusing an amplified spontaneous emission (ASE) light as a secondary pumping source.
2. Description of the Related Art
Currently, Er
3+
-doped fiber amplifiers (EDFAs) having a wide gain band have been proposed to increase the capability of wavelength division multiplexed (WDM) systems to meet the continued demand for higher capacity. For the practical systems using such EDFAs, it has been regarded as inevitably necessary to use silica-based EDFAs of a typical C-band (a wavelength band of 1,530 to 1,560 nm) and/or an L-band of long wavelengths (a wavelength of 1,570 to 1610 nm) coupled together in parallel, in spite of the fact that optical fiber amplifiers made of new materials such as tellurite-based EDFAs have been developed.
In association with L-band EDFAs, there are many pending problems to be solved due to a short history in the development of L-band EDFAs. For example, L-band EDFAs have low power conversion efficiency and thus require high-power pumps. Due to such low pumping efficiency of L-band EDFAs, the silica-based optical fiber amplifiers with an L-band EDFA in a parallel configuration have a limitation in its application in the wide bands. In order to improve the power conversion efficiency of L-band EDFAs, the present inventors have developed a technique for reusing the useless amplified spontaneous emission (ASE) light as a secondary pumping source in an EDF region, which is not being pumped by a light source. In accordance with this technique, a considerable improvement in performance is exhibited. This technique is disclosed in Korean Patent Application No. 98-34370.
In association with the reuse of obsolete reverse ASE light, the present inventors have devised a technique for reusing the reverse ASE light, generated in a C-band EDFA, for amplification at L-band EDFA stage, which is applicable to wide-band silica-based optical fiber amplifiers having a parallel connection configuration.
SUMMARY OF THE INVENTION
Therefore, an object of the invention is to provide an optical fiber amplifier that exhibits high power conversion efficiency in wide wavelength bands.
In accordance with the present invention, this object can be accomplished by providing a parallel optical fiber amplifier comprising a first EDFA stage and a second EDFA stage connected to the first EDFA stage in parallel, the second EDFA stage having a gain wavelength band different from that of the first EDFA stage, and the means for reusing spontaneous emission light emitted from the first EDFA stage as a secondary pumping source for the second EDFA stage.
The first EDFA stage includes a C-band EDFA, and the second EDFA stage includes an L-band EDFA. Accordingly, it is possible to embody a parallel optical fiber amplifier capable of exhibiting a high power conversion efficiency at relatively wide wavelength bands.
The reusing means includes a circulator for receiving the spontaneous emission light from the first EDFA stage, a connecting optical fiber for transmitting the received spontaneous emission light to the second EDFA stage, and a wavelength selective coupler connected between the connecting optical fiber and the second EDFA stage in such a fashion that the spontaneous emission light from the connecting optical fiber is transmitted to the second EDFA stage.
The second EDFA stage includes optical pumping means, a first optical fiber portion adapted to be optically pumped by the optical pumping means, and a second optical fiber portion not being pumped by the optical pumping means. The optical pumping means of the second EDFA stage is disposed between the first and second optical fiber portions and performs a forward pumping operation to the first optical fiber portion. Accordingly, a more efficient optical amplification for the second EDFA stage can be achieved because the second EDFA stage is supplied with the useless reverse ASE light from its first optical fiber portion as well as the useless reverse ASE light from the first EDFA stage, which are then used as a secondary pumping source.
In each of the above mentioned cases, the first and second EDFA stages are preferably comprised of a silica-based optical fiber.
REFERENCES:
patent: 5859725 (1999-01-01), Sugiya et al.
patent: 5978130 (1999-11-01), Fee et al.
patent: 6049417 (2000-04-01), Srivastava et al.
patent: 6049418 (2000-04-01), Srivastava et al.
patent: 6091743 (2000-07-01), Yang
patent: 6104527 (2000-08-01), Yang
Park et al., ‘Efficient and low-noise operation in a gain-flattened 1580nm band /EDFA’, OFC/IOOC '99 Technical Digest, Feb. 21-26, 1999, pp. 123-125.*
Lee et al., ‘Improvement of 1.57—1.61 micrometer Band Amplification Efficiency by Recycling Wasted backward ASE through the Unpumped EDF Section’.
Lee Ju-Han
Park Nam-Kyoo
Ryu Uh-Chan
Cha Steve
Hughes Deandra M.
Klauber & Jackson
Samsung Electronics Co,. Ltd.
Tarcza Thomas H.
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