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

[0060]A counterintuitive result of introducing such gaps is that although the gap has a port density reducing effect in the 1×N array, it actually allows for an increase in the port density in a 2×N array (or M×N). This is because the hitless cross-talk can be accommodated by the vertical gap between ports within a column. As the result, although the area of the optics is increased to 2A, the gaps within the columns in the port configuration shown in FIG. 8B eliminates the need for an access path between the columns as shown in FIG. 7B, thereby increasing the allowable packing density. The elimination of the need of the 2nd access path shown in FIG. 7B reduces the required range of θy from 3θy to 1.33θy. The configuration shown in FIG. 8B thus, reduces the required improvement in the angular range for MEMS mirror from a 200% improvement to a 33% improvement.

[0061]It is noted that in the examples illustrated herein, the gaps are shown separating the last two ports at the ends of each column from the rest of the ports. However, this should not be interpreted as a limitation upon any embodiment of the invention. In principle, the gaps can be located any where in the array. However, since a gap can be shared with adjacent ports (one move down, the other up), more space can be saved by having a gap for two rows. This way, the extreme row at either end of a column does not need a dedicated gap.

[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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