Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1998-11-05
2002-06-11
Spyrou, Cassandra (Department: 2872)
Optical waveguides
With optical coupler
Particular coupling structure
C385S048000, C385S014000
Reexamination Certificate
active
06404957
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 Optical Power Divider And Fabrication Method Thereof earlier filed in the Korean Industrial Property Office on Nov. 5, 1998, and there duly assigned Serial No. 97-58240 by that Office.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical power divider, and more particularly, to an optical power divider using a beam separator and a beam expander, and a method for fabricating the same.
2. Description of the Related Art
In general, an optical power divider is for distributing incident light among a plurality of regions. The optical power divider can be applied to various fields such as an optical communications system or an optical access network, and is a basic element used for optical communications. The optical power divider may be classified according to the number of output ports, into 1×2, 1×4, 1×8, . . . , 1×N types, where N=2
m
and m is a natural number. The light is usually output to each output port with a uniform ratio. However, a splitting ratio at each port may be different for a special application. As shown in
FIGS. 1A and 1B
, the optical power divider is expanded by connecting Y-type branched optical waveguides each having two output ports in series and parallel to each other, like a tree. That is, the 1×4 type optical power divider of
FIG. 1A
is formed by connecting three 1×2 Y-type branched optical waveguides in series and parallel to each other, and the 1×8 type optical power divider of
FIG. 1B
is obtained by connecting seven 1×2 Y-type branched optical waveguides in series and parallel to each other.
Assuming that the optical power divider is expanded by the above manner, more serial connections are required as the number of output ports increases. Thus, the length of a 1×4 branched optical waveguide or a 1×8 branched optical waveguide is two or three times the length of the 1×2 branched optical waveguide. In addition, as the length of an optical power divider increases, propagation loss of the light also increases. Here, we have determined that the length of the Y-type branched optical waveguide can be reduced by increasing a branch angle within the structure of the optical waveguide. We have also determined, however, that such an increase in the branch angle increases radiation loss at a branch area, so that decreasing the length of the branched optical waveguide has limitations. Thus, in order to increase the branch angle while maintaining the radiation loss at a minimum, a branch area has been designed to have a specific structure [H. P. Chan and P. S. Chung, Electron Lett., vol. 32, pp. 652-654, 1996], and a microprism structure has been inserted in a branch area [H. B. Lin, R. S. Cheng and W. S. Wang, IEEE Photon. Technol. Lett., vol. 6, pp. 825-827, 1994].
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide an optical power divider adopting a beam separator and beam expanders such that additional loss does not occur and such that the length of the optical power divider does not increase when output ports of the optical power divider are expanded.
It is another object of the present invention to provide a method for fabricating the optical power divider.
According to an aspect of the first object, there is provided an optical power divider comprising: an input optical waveguide having an input port for receiving incident light, for guiding the light incident via the input port; a plurality of output optical waveguides having at least two output ports, for outputting the light incident via the input optical waveguide to the output ports, wherein the number of output optical waveguides is equal to one less than the number of the output ports; and a beam separator located at a branch area in which the light incident on the input optical waveguide diverges toward the output optical waveguides, the beam separator being made of a material having a refractive index lower than the core of the input and output optical waveguides, for separating the light to the output optical waveguides with a predetermined ratio.
Preferably, the optical power divider further comprises beam expanders located near the outer sides of the branch area in which the light incident on the input optical waveguide diverges toward the output optical waveguides, the beam expander being made of a material having a refractive index higher than the cladding region of the input and output optical waveguides, for dividing the light to be output uniformly to the output ports.
Preferably, the beam separator has a triangular shape, and the light output to the output ports is separated in a predetermined ratio according to the refractive index, and the height and the length of a side of the triangle.
According to another aspect of the first object, there is provided an optical power divider comprising: an input optical waveguide having an input port for receiving incident light, for guiding the light incident via the input port; a plurality of output optical waveguides having at least two output ports, for outputting the light incident via the input optical waveguide to the output ports, wherein the number of output optical waveguides is equal to that of the output ports, and beam expanders located near the outer sides of the branch area in which the light incident on the input optical waveguide diverges toward the output optical waveguides, the beam expander being made of a material having a refractive index higher than the cladding region of the input and output optical waveguides, for dividing the light to be output uniformly to the output ports.
Preferably, the beam expander has a triangular shape, and the light output to the output ports is separated in a predetermined ratio according to the refractive index, and the height and the length of a side of the triangle.
According to still another aspect of the first object, there is provided an 1×4 optical power divider comprising: an input optical waveguide having an input port for receiving incident light, for guiding the light incident via the input port; four output optical waveguides having four output ports, for outputting the light incident via the input optical waveguide to the output ports; a beam separator located at the point of symmetry between upper and lower regions of the branch area in which the light incident on the input optical waveguide diverges toward the four output optical waveguides, with a triangular shape, the beam separator being made of a material having a refractive index lower than the core of the input and output optical waveguides, for separating the light to the output optical waveguides with a predetermined ratio according to the refractive index, and the height and the length of a side of the triangle; and beam expanders located near the outer sides of the branch area in which the light incident on the input optical waveguide diverges toward the output optical waveguides, the beam expander being made of a material having a refractive index higher than the cladding region of the input and output optical waveguides, for dividing the light to be output uniformly to the output ports according to the refractive index, and the height and the length of a side of the triangle.
Preferably, the refractive index of the beam separator is the same as that of the cladding region of the input and output optical waveguides, and the refractive index of the beam expander is the same as that of the core of the input and output optical waveguides.
Preferably, branch angle between the four output optical waveguides are the same.
Preferably, assuming that the four output optical waveguides are called first, second, third and fourth output optical waveguides from the top, and there are an imaginary line AA′ parallel to the width of the input optical waveguide and pa
Jang Woo-hyuk
Rhee Tae-hyung
Shin Sang-yung
Song Hyun-chae
Yi Sang-yun
Boutsikaris Leo
Bushnell , Esq. Robert E.
Samsung Electronics Co,. Ltd.
Spyrou Cassandra
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