Port array topology for high port count wavelength selective switch

Abstract

An optical apparatus can include an optical port array having an M×N array of fiber collimator ports. The array of ports is configured such that there is a gap within each column of ports located between two rows of ports. The gap is wide enough to permit a hitless beam switching trajectory to pass between the two rows of ports from one side of the array of ports to an opposite side.

Description

FIELD OF THE INVENTION[0001]This invention generally relates of optical switch systems and more particularly to fiber collimator array or ports of the wavelength selective switch (WSS) to achieve the maximum port count with limited angle ranges of the beam deflecting elements.BACKGROUND OF THE INVENTION[0002]Multi-channel optical signals typically comprise a plurality of spectral channels, each having a distinct center wavelength and an associated bandwidth. The center wavelengths of adjacent channels are spaced at a predetermined wavelength or frequency interval, and the plurality of spectral channels may be wavelength division multiplexed to form a composite multi-channel signal of the optical network. Each spectral channel is capable of carrying separate and independent information. At various locations, or nodes, in the optical network, one or more spectral channels may be dropped from or added to the composite multi-channel optical signal, as by using, for example, a reconfigur...

AI Technical Summary

Benefits of technology

[0040]Allowing for manufacturing tolerances one can use, e.g., 4θo (=θmin) for port-to-port cross talk and 3θo for hitless reconfiguration as examples of design rules. Those skilled in the art can design the system according to their actual requirements. The number of the resolvable spots (in this case constrained by the port cross-talk) is simply the ratio of the angle range of the BDE (2θmax) and the minimal allowed angle (Δθ=θmin):Nrs=22θmax4θo=θmaxθo=πωoθmaxλ(6)where θmax is the maximum angle the mirror can turn in each direction. Note that an additional factor of 2 accounts for the angle of the steered beam, which is twice the rotation angle of the mirror. Eq. (6) illustrates the additional restriction of the resolvable spot imposed by the port to port cross talk. When the light beam is moving across the port array, it needs to satisfy the port-to-port cross talk and the hitless requirement simultaneously. This reduces the density of the port array

[0062]If the limitation of the MEMS angle is more stringent, one can further reduce its requirements by staggering the columns to increase the packing of the collimators as shown in FIG. 8C. The staggering of the columns can keep the center-to-center distance between ports the same as in the configuration shown in FIG. 8B, but the required lateral movement of the beam can be reduced by a factor of cos30° if the staggered port columns are in a port packing configuration sometimes referred to as “hexagonal close packed”. In order to maintain the low cross-talk during the switching, the gap between the clusters of fiber collimators should be increased by about 24%. While this may further reduce the density of ports in the columns, it increases the overall density of ports due to the reduced horizontal distance between the columns. The net port density increases slightly, e.g., by about 7%. This enables the 2×N configuration since less micro-mirror rotation is needed about the y axis and less optics area is required. By way of example, the staggered column 2×N port array shown in FIG. 8C can be configured such that the optics area is increased by only 1.5× and the required angular range for the beam reflecting elements is only 1.16θy.

Problems solved by technology

With the substantial growth of the demand for internet bandwidth, the internet traffic requirements have become quite unpredictable.

The colored WSS is not flexible because fixed or specified wavelengths of the lasers are needed for the ADD module, even though tunable laser is widely available.

However, each tunable laser can only transmit data via one WDM channels.

However, there are many constraints to limit the number of ports in a WSS.

The requirement hitless switching sets a topology challenge to the design of WSS.

Currently, the port count of a free-space optical WSS is limited by the maximum angle that the micro-mirrors or light modulators can tilt.

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