Switchable optical components

Abstract

This invention relates to a number of components, devices and networks involving integrated optics and / or half coupler technology, all of which involve the use of electronically switchable Bragg grating devices and device geometries realized using holographic polymer / dispersed liquid crystal materials. Most of the components and devices are particularly adapted for use in wavelength division multiplexing (WDM) systems and in particular for use in switchable add / drop filtering (SADF) and wavelength selective crossconnect. Attenuators, outcouplers and a variety of other devices are also provided.

Description

PRIOR APPLICATIONS [0001] This application is a continuation in part of application Ser. No. 08 / 797,950 filed Feb. 12, 1997 (the '950 application) and claims priority from provisional specification 60 / 055,571 filed Aug. 13, 1997, the subject matter of both the parent application and the provisional being incorporated herein by reference.FIELD OF THE INVENTION [0002] This invention relates to switchable optical components, particularly ones utilizing guided wave optics and to ones particularly adapted for use in wavelength division mutliplexing (WDM) systems, including switchable waveguide gratings, particularly ones used for switchable add / drop filtering (SADF) and wavelength selective cross-connect (WSXC), to designs utilizing coupler-halves or side-polished fibers, to attenuators and other optical grating components utilizing very small period optical grating elements, to other wavelength selective or wavelength independent components, to devices using such components, to methods ...

AI Technical Summary

Problems solved by technology

While a number of techniques have been proposed over the years for performing N×M switching optically, none of these techniques have proved to meet all requirements simultaneously.

The data capacity demands on fiber optic networks are also becoming more complex, imposing a requirement that switching technologies be scalable so as to be extendable in a straight forward manner from small switches (for example 2×2 or 4×4 to larger switches such as 64×64, 1024×1024, and beyond).

However, designing such structures, particularly for larger switches, is very complex even for single channel operation, and the complexity increases dramatically for multichannel WDM operation (i.e., wavelength selective switching with an N×M×m switch, where m is the number of WDM channels).

Further, in the present state of the art, neither space switching, nor wavelength selective switching techniques, are entirely satisfactory.

This technique can be expensive, time consuming, impose bandwidth limitations on the system and introduce several sources of potential error.

It can also limit the flexibility of the system and is generally not an efficient way to operate.

Until recently, few mechanism were available for switchable Bragg gratings.

Liquid crystal gratings, usually formed by physically structured electrodes, may be switchable, but are primarily relevant to free space non-volumetric gratings, are excessively scattering for use with fiber optic signals and are relatively slow, switching being in the millisecond range.

All manner of switchable gratings that involve the use of structured electrodes to produce the spatial periodicity, such as magneto-optic materials and lithium niobate materials, are limited in their application in that the spatial period and depth of grating are dependent on the lithographic processes of fabricating electrode patterns.

Such structured electrode gratings are not practical at spatial periodicities much less than one micrometer, which smaller periods are essential in various fiber optic applications, and also do not tend to produce volumetric (Bragg) gratings since the electrode periods cannot penetrate unlimited volumes.

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