Arrayed waveguide grating

#1. Field of the Invention

#The present invention relates to an arrayed waveguide grating to be used for optical communications.

#2. Description of the Related Art

#These and other objects and advantages of the present invention will be come more apparent and more readily appreciated from the following detailed description of the exemplary embodiments of the invention taken in conjunction with the accompanying drawings, in which:

#FIG. 1 is a constructional view of the main part schematically showing an embodiment, of the arrayed waveguide grating relating to the invention.

#FIG. 2 is a graph showing the relationship between the interval between arrayed waveguide groups and the operation time for insertion of the half-wavelength plates when the arrayed waveguides provided in the arrayed waveguide grating is divided into two arrayed waveguide groups.

#The abovementioned construction may be characterized in that the polarization mode conversion part to convert the TE mode and TM mode of light to be transmitted through the arrayed waveguides is provided so as to cross the middle portion in the length direction of all arrayed waveguides. Therefore, by the invention, polarization dependence loss caused due to a difference in transmission speed between the TE mode and TM mode of light to be transmitted through the arrayed waveguides can be eliminated.

#Furthermore, in the prior-art arrayed waveguide diffraction grating, since the abovementioned polarization mode conversion part is formed of one half-wavelength plate, in the case where the number of alignments of the arrayed waveguides is large and the width of the arrayed waveguide forming range is wide, a long half-wavelength plate having a length corresponding to the width must be provided. The long half-wavelength plate is expensive and it is difficult to insert it into the arrayed waveguide diffraction grating. On the other hand, in the arrayed waveguide diffraction grating of the invention, since a plurality of half-wavelength plates are aligned in series in the vertical direction of the plurality of arrayed waveguides so as to cross them, the length of each of the half-wavelength plates can be made short. Therefore, the invention can reduce the cost of the half-wavelength plates forming the polarization mode conversion part.

#Furthermore, in the invention, a plurality of arrayed waveguides crossed by one half-wavelength plate is defined as one arrayed waveguide group, and based on this, arrayed waveguide groups are formed by a number corresponding to the number of the disposed half-wavelength plates, and the interval between adjacent arrayed waveguide groups at the disposed portion of the half-wavelength plates is set to 50 μm or more. Therefore, in the invention, by properly setting the interval between the adjacent arrayed waveguide groups, the operation to insert the half-wavelength plates can be easily carried out. Accordingly, by the invention, an arrayed waveguide grating is realized which can be easily manufactured, in which the half-wavelength plates can be prevented from bending and taking-in bubbles when being inserted, and an increase in crosswalk can be suppressed.