Fiber optic cross connect with transparent substrate

Details Fiber optic cross connect with transparent substrate Fiber optic cross connect with transparent substrate

2000-04-14

2002-05-28

Schuberg, Darren (Department: 2872)

Optical waveguides

With optical coupler

Switch

C385S019000, C385S016000, C359S223100, C359S224200, C359S872000

Reexamination Certificate

active

06396973

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to fiber optic cross connects, and more particularly to the substrate used in fiber optic cross connects.
BACKGROUND OF THE INVENTION
The use of optical cross connect (OXC) switching systems are well known in the art for directing a light beam from one optical port in an optical transmission system to another optical port. In a typical OXC, a plurality of input optical fibers, or ports, carry light beams into the OXC. The OXC then directs, or switches, the light beams to their respective plurality of output ports. Many conventional OXCs perform the switching utilizing micromirrors, which are micro-machined onto a chip. The micromirrors are used to reflect a light beam from an input port to a particular output port. In this specification, the words “input” and “output” are used to indicate a direction of travel for a light beam into and out of, respectively, a switch. In reality, the input and output ports can be used simultaneously for input and output, as is the case in bi-directional data transfer.
High port count switches utilizing micromirrors are of high demand in the industry. Such switches require a tight packing density of the micromirrors onto the substrate. Some conventional switches use a digital switching matrix for N input and N output ports with an N×N array of micromirrors. This requires a total of N
2
number of micromirrors. However, this architecture becomes impractical for switch port counts greater than a few hundred.
Some conventional switches use an analog switching matrix for N input and N output ports. This requires 2*N micromirrors. In this configuration, two separate substrates, or one very large substrate, are necessary to accommodate port counts greater than a few hundred. However, the use of more than one substrate is cumbersome as they need to be aligned to each other within the package of the switch. This adds complexity to the assembly of the package and increases package size. Also, with a hundred or more micromirrors on a single substrate, or one half of a two-substrate OXC, device yield is compromised due to the large number of possible failure points. Additionally, the optical components of the OXC are typically hermetically sealed. Such hermetic sealing of the optical components requires additional complex steps in the manufacturing process, such as metallization of the fibers or optical component attached to the fibers.
Accordingly, there exists a need for an improved OXC package which reduces the size of the package while still allowing a high port count. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The present invention provides an improved fiber optic cross connect (OXC) package. The OXC includes a substrate, where light beams may travel through the substrate; a plurality of optical fibers optically coupled to a first surface of the substrate; and a micromirror array coupled to a second surface of the substrate. In the preferred embodiment, this substrate is optically transparent to the wavelengths of interest. The light beams enter the substrate from one surface, traverses the substrate, and exits from an opposite surface of the substrate. The opposite surface is populated with micromirrors. By utilizing the substrate in a switch architecture, the size of the switch package is reduced while maintaining a high port count. Using the substrate in combination with a modular approach to substrate population allows for a single die switch with a higher die yield and scalability. Integrated circuits may be placed on the same substrate as the micromirrors, and the complexity of the assembly process is reduced. With the addition of the second cap, the light beam is folded during the switching operation, resulting in a smaller switch package. By utilizing the same redirection length for each micromirror, the number of ports may be optimized.


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“Optical-layer Networking: Opportunities for and Progress in Lightwave Micromachines,” OFC 2000 Tutorials, Lih Y. Lin and Evan Goldstein, ATT Research, Mar. 10, 2000.

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