Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1997-12-08
2001-03-27
Chan, Jason (Department: 2733)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C385S027000
Reexamination Certificate
active
06208440
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 for OPTICAL WAVELENGTH FILTER AND OPTICAL DEMULTIPLEXER earlier filed in the Korean Industrial Property Office on Dec. 6, 1996 and there duly assigned Ser. No. 624771996.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical wavelength filter and an optical demultiplexer for a receiver of a wavelength division multiplexing (WDM) transmission system, and more particularly, to an optical demultiplexer for a low-loss, high-density WDM transmission system.
2. Description of the Related Art
A WDM transmission system multiplexes the wavelength area of an optical fiber into several channels by simultaneously transmitting signals of several wavelength bands, relying on the wavelength characteristics of an optical signal. In the WDM transmission system, an input optical signal, having been multiplexed to have several wavelength components, is demultiplexed at the receiver and recognized in the respective channels.
In earlier WDM transmission systems a 1×n coupler and first through nth bandpass filters are connected where n represents the number of channels of a transmitted optical signal.
A coupler is a passive device for branching or coupling optical signals and the output power of each branch optical signal is 1
that of the input optical signal to the 1×n coupler. Hence, the power output of each of the n optical signals from the n bandpass filters is 1
that of the input optical signal.
In order to compensate for this loss of power, it is necessary to include an optical amplifier for amplifying the optical signal to increase the power by n times before it is input to the 1×n coupler.
This causes an inconvenience in that the optical demultiplexer for a receiver must have an optical amplifier in order to make for the power loss of the 1×n coupler.
SUMMARY OF THE INVENTION
To solve the above problem, it is an object of the present invention to provide an optical wavelength filter for reflecting only an optical signal of a particular wavelength component with little power loss of the optical signal.
It is another object of the present invention to provide an optical demultiplexer which allows little power loss, for a receiver in an optical wavelength division multiplexing (WDM) transmission system.
Accordingly, to achieve the above first object, there is provided an optical filter comprising first and second couplers and first and second optical wavelength reflectors.
The first coupler has first through fourth ports. The first port receives an input optical signal which has a plurality of wavelength components, divides the output of the optical signal input from the first port and outputs the divided output to third and fourth ports, respectively. The second port combines and outputs the optical signals output from the third and fourth ports, reflected at the first and second optical wavelength reflectors and input back into the first coupler.
The first optical wavelength reflector has an input port and an output port. The input port receives the optical signal from the first coupler via the third port. The output port reflects an optical signal having a predetermined wavelength component among the optical signals received via the input port backward from a light traveling direction, outputs the reflected optical signal to the first coupler via the third port, and outputs an output signal having the other wavelength components.
The second optical wavelength reflector has an input port and an output port. The input port receives the optical signal received from the first coupler via the fourth port. The output port reflects the optical signal having the predetermined wavelength component among the optical signals received from the input port backward from the light traveling direction, outputs the reflected optical signal to the first coupler via the fourth port, and outputs the optical signal having the other wavelength components.
The second coupler has first through fourth ports. The first and second ports receive the optical signals from the first and second optical wavelength reflectors via the outports thereof, respectively. The third port outputs both optical signals received from the first and second ports.
The optical wavelength filter according to the present invention outputs the optical signal received from the second port of the first coupler, having a predetermined wavelength component among the wavelength components of the input optical signal received from the first port of the first coupler, and outputs the optical signal having the other wavelength components except for the predetermined wavelength component among the wavelength components of the input optical signal, to the fourth port of the second coupler.
To achieve the second object, there is provided an optical demultiplexer having a plurality of optical wavelength filters serially connected.
Each optical wavelength filter has a first input port, first and second output ports, first through third couplers and first through fourth optical wavelength reflectors.
The first input port receives an input optical signal which have a plurality of wavelength components. The first output port outputs only an optical signal having a predetermined wavelength component in the input optical signal. The second output port outputs an optical signal having the other wavelength components free of the predetermined wavelength component, and is connected to another first input port corresponding to the second output port. Thus, the optical signal having the other wavelength component except the predetermined wavelength component, output from the second output port, is input to the first input port of another corresponding optical wavelength filter serially connected thereto. Therefore, the optical wavelength filters divide optical signals having different wavelength components and output the same to the respective output ports.
The first coupler has first through fourth ports. The first port connected to the first input port of the corresponding optical wavelength filter receives the input optical signal. The third and fourth ports divide the input optical signal received from the first port into two halves and output the divided outputs, respectively. The second port connected to the first output port outputs optical signals which are reflected from the optical signal output from the third and fourth ports and which are input again to the first coupler.
The first optical wavelength reflector has an input port and an output port. The input port receives the optical signal from the first coupler via the third port thereof. The output port reflects only an optical signal having the predetermined wavelength component in the optical signal received from the input port, outputs the reflected optical signal to the first coupler via the third port thereof, and outputs an optical signal having the other wavelength components free of the predetermined wavelength component.
The second optical wavelength reflector has an input port and an output port. The input port receives the optical signal from the first coupler via the fourth port thereof. The output port for reflecting only an optical signal having the predetermined wavelength component in the optical signal received from the input port, outputs the reflected optical signal to the first coupler via the fourth port thereof, and outputs an optical signal having the other wavelength components free of the predetermined wavelength component.
The second coupler has first through third ports. The first and second ports receive the optical signals from the first and second optical wavelength reflectors via the output ports thereof, respectively. The third port adds both the optical signals received from the first and second ports and outputs the result.
The third coupler has first through fourth port. The first port connected to the second port of the first coupler, rec
Bello Agustin
Bushnell , Esq. Robert E.
Chan Jason
Samsung Electronics Co,. Ltd.
LandOfFree
Optical wavelength filter and optical demultiplexer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical wavelength filter and optical demultiplexer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical wavelength filter and optical demultiplexer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2510302