1. Field of the Invention
The present invention relates to an optical waveguide device for wave-dividing and outputting each input light signal having each wavelength that is wavelength-multiplexed and wave-multiplexing each light signal having each wavelength. In particular, the present invention relates to a multiplexing wave division device having the waveguide formed in a planar waveguide.
2. Description of Related Art
In the field of optical communication, a wavelength division multiplexing (WDM: Wavelength Division Multiplexing) system, which encodes a plurality of signals as respective separate division lights and transmits by way of an optical fiber, has been developed. In this system, it is required to divide or multiplex lights having different respective wavelengths so as to input and output. Conventionally , various types of devices such as array waveguide grating devices, devices utilizing gratings, and so forth have been acknowledged as such optical wave division devices. Examples of optical wave division devices utilizing the gratings are shown in FIGS. 1 and 2.
In the device shown in FIG. 1, a linear waveguide 2 is provided on a substrate 1, and a linear chirp grating 3 is formed thereon. A planar waveguide 4 is formed parallel with the linear waveguide 2, and one or more output waveguides 5 are formed and connected to the boundary face thereof. The light input from a part of the linear waveguide 2 is reflected onto the grating 3, and input to a planar waveguide 4 through the linear waveguide 2.
The closer to the top position the grating 3 is, the smaller the period thereof becomes. Accordingly, the light transmits so as to be focused onto the boundary portion of the planar waveguide 4 as shown in the figure*1. Each focusing point having each wavelength is different from the other corresponding to the interference condition of the light depending on the wavelength on this boundary, and it becomes possible to select each light having each wavelength if the output waveguide 5 is provided in the boundary. Furthermore, as shown in FIG. 2, another method, in which such a special grating as used in the structure of FIG. 1, has been proposed.
In the structure of FIG. 2, the grating, formed at even intervals, is provided in a curved waveguide 13 arranged in the shape of an arc, and not in a linear waveguide. Furthermore, a planar waveguide 14 is provided along the curved waveguide 13, and one or more output waveguides 15 are provided in a central position of the arc of the curved waveguide 13*2. The grating is tilted to the center of the waveguide in order for the light reflected onto the grating to gather at the center of the arc thereof According to the structure of FIG. 2, it is possible to condense the light to a point even if the grating is formed at even intervals.
It is a primary object of the present invention to replace a conventional grating with a reflecting surface capable of being manufactured through a waveguide manufacturing process. The present invention includes an output waveguide and a curved waveguide for an input in a planar waveguide, whereby the curved waveguide for the input forms a discontinuous structure. In addition, optical signals are wavelength-divided by way of reflection by the discontinuous surface thereof and each optical signal having each wavelength is focused in an output waveguide. Accordingly, it is possible to form the structure having the best suitable waveguide shape and the reflecting surface, and thus a qualified controllable device is capable of being formed.