Browse Prior Art Database

Acousto-Optic-Holographic Switch for Fiber-Optic Networks

IP.com Disclosure Number: IPCOM000120517D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 81K

Publishing Venue

IBM

Related People

Huang, KS: AUTHOR [+2]

Abstract

Disclosed is an acousto-optic-holographic (AOH) switch for optical fiber networks (Fig. 1). This switch allows the network to establish N pairs of connections between input and output nodes at any time. There is no splitting loss, and it is non-blocking.

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Acousto-Optic-Holographic Switch for Fiber-Optic Networks

      Disclosed is an acousto-optic-holographic (AOH) switch
for optical fiber networks (Fig. 1).  This switch allows the network
to establish N  pairs of connections between input and  output nodes
at any time.  There is no splitting loss, and it is non-blocking.

      The basic idea is to use an N-channel acousto-optic (AO) device
where N AO bragg cells deflect optical signals (vertically) from
outputs of N nodes into an N-facet hologram, and each facet of
hologram directs its input optical energy into an input fiber of a
node.  Fig.  1(a) shows the physical view of the AOH switch.  The key
technique of the invention is to tilt the input beams (horizontally)
so that they can always be directed to one-dimensional hologram
array.  In this way we avoid conventional O(N2) hardware complexity.
In implementation it is often beneficial to arrange the AO devices
into cylindrical or spherical surface.

      A hologram recorded on a photographic plate can produce a
grating with a spatially varying phase shift as well as a spatially
varying transmittance.  The N-facet hologram used here consists of a
column of N subholograms. Each face (i.e., each subhologram) is
fabricated for directing the input optical signal, which can be the
output from any AO bragg cells, into an input optical fiber of a
node.  Without the N-facet hologram, if we directly couple the
outputs of AO cells into fibers, the coupling efficiencies of AO
cells and fibers are very different and depend on the incident angle.
The hologram is used to achieve constant efficiencies and also to
focus optical energy into the fibers more efficiently.  The
diffraction efficiency of a hologra...