Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-09-14
2002-09-03
Chan, Jason (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200
Reexamination Certificate
active
06445472
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to an optical fiber subscriber network, and in particular, to a wavelength division multiplexed (WDM) optical fiber subscriber network for serving an expanded number of subscribers.
2. Related Art
As high speed, high-capacity user communication services progress along with the development of the information-oriented society, there have been demands for a wideband communication network capable of accommodating different types of data including voice, data, still-image, and live-video/voice multicast transmissions to a large number of users. One of the fast-growing constituents of wideband communication networks is an optical fiber subscriber network which uses optical signals to convey information across an optical waveguide. Frequently, time-division multiplexing (TDM) is employed to convey information from plural information sources on a single channel. However, the transmission capacity is limited by fiber dispersion and the need to generate high peak power pulse.
Wavelength division multiplexing (WDM) has been recently developed as a cost-effective way to increase the information-carrying capacity of existing fiber optic network. A wavelength division multiplexed (WDM) optical fiber subscriber network employs plural optical signal channels, each channel being assigned a particular channel wavelength. In a WDM system, signal channels are generated, multiplexed, transmitted over a single waveguide, and demultiplexed to individually route each channel wavelength to a designated receiver. Through the use of optical amplifiers, such as doped fiber amplifiers, plural optical channels are directly amplified simultaneously, facilitating the use of WDM systems in long distance optical systems. Exemplars of wavelength division multiplexed optical fiber subscriber networks are disclosed in U.S. Pat. No. 4,901,306 for Wavelength-Division Multiplexed Optical Fiber Network issued to Gardner, U.S. Pat. No. 5,119,223 for Bidirectional Light Wavelength (LWG) Telecommunication System And Method For Wavelength Separation Mode (Bidirectional Wavelength Separation Mode) Between A Central Telecommunication Location And Plurality Of decentralized Telecommunication Locations issued to Panzer et al., U.S. Pat. No. 5,351,146 for All-Optical Network Architecture issued to Chan et al., U.S. Pat. No. 5,457,760 for Wavelength Division Optical Multiplexing Elements issued to Mizrahi, U.S. Pat. No. 5,510,921 for Optical Frequency Division Multiplexing Network issued to Takai et al., U.S. Pat. No. 5,550,818 for System For Wavelength Division Multiplexing/Asynchronous Transfer Mode Switching For Network Communication issued to Brackett et al., U.S. Pat. No. 5,557,439 for Expandable Wavelength Division Multiplexed Optical Communication Systems issued to Alexander et al., U.S. Pat. No. 5,587,830 for high Capacity Optical Fiber Network issued to Chraplyvy et al., and U.S. Pat. No. 5,717,795 for Optical Wavelength Division Multiplexed Network System issued to Sharma et al.
Many conventional optical fiber subscriber networks require high density wavelength division multiplexing which uses more than three wavelengths to increase the information-carrying capacity of existing fiber optic network. A wavelength variable filter or WDM multiplexer/demultiplexer must be used which requires precise manufacturing technology. Therefore, in building subscriber networks, there arise safety and cost problems. In particular, there is a limitation in expanding the new subscribers or increasing the communication speed.
SUMMARY OF THE INVENTION
Accordingly, it is therefore an object of the present invention to provide an improved wavelength division multiplexed optical fiber subscriber network.
It is also an object to provide a cost-effective wavelength division multiplexed optical fiber subscriber network.
It is another object to provide a wavelength division multiplexed optical fiber subscriber network for supporting expanded number of subscribers with high reliability and flexibility.
It is yet another object to provide a wavelength division multiplexed optical fiber subscriber network for carrying increased number of subscribers with greater margin of safety and cost efficiency.
These and other objects of the present invention can be achieved by an optical fiber subscriber network including a central office for allocating a unique combination of optical for wavelengths to a subscriber upon receipt of a service request signal from the subscriber, wavelength division multiplexing (WDM) service requested information together with the combined optical wavelength, and for transmitting the WDM optical wavelength through an optical fiber; and a plurality of optical subscriber devices for optically distributing, filtering and combining the WDM optical signals received through the optical fiber to select optical wavelengths allocated thereto and outputting the selected optical wavelengths to corresponding subscriber terminals.
Preferably, the central office includes: an exchange for allocating a combination of the wavelengths to a subscriber upon receipt of the service request signal from the subscriber; a plurality of optical transmitters for converting electric signals output from the exchange to optical signals of unique wavelengths; a WDM multiplexer for multiplexing the optical signals output from the optical transmitters and transmitting the multiplexed optical signals to the optical fiber; and an optical amplifier for amplifying the output of the WDM multiplexer to compensate for transmission loss of the multiplexed optical signals being transmitted to the subscriber through the optical fiber.
Preferably, the optical subscriber device includes: an optical distributor for distributing the WDM multiplexed optical signals received through an incoming optical fiber to Q internal optical fibers; a fixed optical filter for filtering a wavelength group allocated thereto out of the WDM multiplexed optical signals to receive an optical wavelength group pre-allocated in the central office; an optical receiver module connected to an output of the fixed optical filter for converting the optical signals output from the fixed optical filter to electric signals; a concentrator for switching and concentrating an output of the optical receiver module to multimedia terminals connected to output ports of the optical subscriber device; and an electronic signal converter for converting an output of the concentrator so as to connect the multimedia terminals to the concentrator.
In addition, the optical fiber subscriber network includes a plurality of optical distributors placed on the optical fiber intervening between the central office and the optical subscriber devices for distributing the optical signals output from the central office according to construction of a service requested network. The optical fiber subscriber device may include an optical amplifier placed on the optical fiber intervening between the central office and the optical subscriber devices for compensating for distribution loss of the optical signals due to the optical distributors.
The present invention is more specifically described in the following paragraphs by reference to the drawings attached only by way of example.
REFERENCES:
patent: 4441180 (1984-04-01), Schussler
patent: 4901306 (1990-02-01), Gardner
patent: 5119223 (1992-06-01), Panzer et al.
patent: 5202780 (1993-04-01), Fussganger
patent: 5337175 (1994-08-01), Ohnsorge et al.
patent: 5351146 (1994-09-01), Chan et al.
patent: 5452115 (1995-09-01), Tomioka
patent: 5457760 (1995-10-01), Mizrahi
patent: 5469283 (1995-11-01), Vinel et al.
patent: 5510921 (1996-04-01), Takai et al.
patent: 5550818 (1996-08-01), Brackett et al.
patent: 5557439 (1996-09-01), Alexander et al.
patent: 5587830 (1996-12-01), Chraplyvy et al.
patent: 5706111 (1998-01-01), Morales et al.
patent: 5717795 (1998-02-01), Sharma et al.
patent: 5748348 (1998-05-01), Heidemann et al.
patent: 5808767 (1998-09-01), Williams et al.
patent: 5946117 (1999-08-01), Meli et al.
p
Choe Won-Ha
Kim Jin-Han
Lee Soong-Hee
Bushnell , Esq. Robert E.
Chan Jason
Leung Christina Y
Samsung Electronics Co,. Ltd.
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