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AssigneeMitsubishi Gas Chemical Company, Inc.
InventorsTerutaka Tokumaru, Toshihiko Takano
Estimating the term…
A small-sized and low-cost wavelength division multiplexer having little insertion loss, little polarization dependence and a broad wavelength bandwidth, the wavelength division multiplexer adopting a grating configuration in which an incident light is retroreflected, exit lights from respective grooves are enhanced by interference effect in the incident direction of the light, wave surfaces of evanescent waves in the grooves are parallel to the normal direction of the grating and phases of the evanescent waves in the respective grooves agree with each other. The wavelength division multiplexer has high diffraction efficiency in each of TM and TE polarized lights at a several-order diffraction order and accordingly has a broad wavelength bandwidth and remarkably low polarization dependence.
A monochrometer comprising a grating, in which an incident angle of light entering said grating agrees with an exit angle of a diffracted light exiting said grating, wherein
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
As bulk element, i.e. free space arrangement external to a light guide: diffractive element operating in reflection
Using diffraction elements, e.g. grating: plane gratings
Characterised by the function or use of the complete device: for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g.…
Optical multiplex systems: wavelength-division multiplex systems
Term ended 21 Mar 2022 (estimated)
The present invention relates to a wavelength division multiplexer for use in a wavelength division multiplexing (WDM) transmission. Particularly, it relates to a small-sized and low-cost wavelength division multiplexer having little insertion loss and little polarization dependence and having a broad wavelength bandwidth.
In a WDM optical transmission, a wavelength division multiplexer combines optical signals of various wavelengths, the signal consisting of the various wavelengths is transmitted to a transmission path, and a wavelength division demultiplexer separates the optical signal received from the transmission path into respective wavelengths. In the WDM, the quantity of signals which can be transmitted by one transmission path is the product of the bandwidth of one wavelength and the divided number of the wavelength. In one wavelength, the bandwidth which can be modulated is approximately several tens of GHz under the current circumstances. For increasing the quantity of transmission, it is preferred that the divided number is large.
U.S. Pat. No. 5,748,350 (May 5, 1998) disclosed by Jing-Jong Pan et al. discloses an example concerning a wavelength division multiplexer. This publication discloses a method in which wavelengths are individually one by one separated or combined with a dielectric multilayer filter. Since the configuration of the above method is simple, it has advantages in size reduction and cost reduction. On the other hand, it is required to use dielectric multilayer filters of the same number as the number of wavelengths to be separated or combined. When a few wavelengths are separated or combined, no problem occurs. However, when several tens of wavelengths are separated or combined, the number of parts increases and a defect is that to reduce a size or reduce a cost is difficult.
FIG. 1 is a diagrammatic illustration explaining the grating configuration of the present invention.
FIG. 2 is a diagrammatic illustration explaining a conventional grating configuration.
FIG. 3 is a diagrammatic illustration explaining evanescent wave in the grating configuration of the present invention.
The present inventors have made diligent studies for developing a small-sized and low-cost wavelength division multiplexer having little insertion loss, little polarization dependence and a broad wavelength bandwidth and as a result have found that a polarization-independence type monochrometer configuration exists also in a method using a grating in free space. On the basis of the above finding, the present inventors have reached the present invention.
The configuration of the present invention will be explained hereinafter.
In order to facilitate understanding, first, actions in a blazed grating used in a conventional monochrometer configuration will be explained. Next, the monochrometer of the present invention will be explained with regard to differences of actions between the monochrometer of the present invention and the blazed grating with reference to figures respectively.