WDMX optical multiplexing network models

Overview

A WDM line (OTS) is a bidirectional multicolored composite optical line that connect WDM systems into networks. If only one WDM line is used, the system is referred to as an end terminal and can be used in point to point networks or at the end of chain of ring nodes. Two lines are required for optical add/drop multiplexers (OADMs) used as rings, nodes, and in linear chains: one line faces West (slot 1 of an OMD [LNW785] pack pair, e.g., d1-ots), and the other line faces East (slot 2 of an OMD [LNW785] pack pair, e.g., d2-ots).

The following network examples illustrate various arrangements of end-terminals and add/drop ring nodes that can be used for WDMX. In the following examples, a single line represents two-fiber connections between NEs.

Point-to-point/end-terminal-to-end-terminal

This simple configuration can provide extra wavelengths between two points.

Terminated ring

The terminated ring configuration can provide extra wavelengths between three or more points, terminating back at the single end-terminal.

Linear chain

This is expected to be the most common use of WDMX to get extra wavelengths between three or more points in the network for traffic demands that tend to emanate and terminate at two central points in the network. For this approach the traffic from the OADMs is expected to be dual feed to each end-terminal. Some IPTV applications may use this network approach.

Double-terminated ring

The double terminated ring is also expected to be very a common topology. It is composed of two EAR rings, joined at the end-terminals. The End terminals typically are the hubbing locations that sync and source the traffic. The Ring nodes typically allow relatively small counts of wavelengths to enter the network and send it in diversely routed directions toward independent end-terminals. This allows for the protection of services.

Pure ring

Pure rings contain no end-terminals, and allow any traffic mix between the ring nodes. This arrangement provides greater flexibility. However, care must be taken to assure optical noise loops (lasing) are not created. This is accomplished by creating high attenuation on pass-throughs for all optical channels that are not equipped.

WDMX channel wavelengths

The WDMX channel wavelengths are based on the industry standard ITU-T grid at 100 GHz spacing in the Cband. The lowest frequency is 195200 GHz and the highest is 195900 GHz. The channels are generally described using only the middle four digits. For example, ITU channel 55 is at frequency 195500 GHz. Some device labeling only uses middle 2 digits. For example, 195500 GHz could also be represented on device labeling as frequency “55”. These 8 channels overlap with the 32 channel wavelength plan of the Lucent Wavelength Extension Solutions (WES) product, and 6 of the 32 channel wavelength plan of the EON system. (EON uses ITU-T channel 52 - 57 in common with WDMX.)

The optical components of WDMX are optimized for transport of XFP based 10G transmitter for metro access and metro core applications. This optimization allows for lower cost of WDMX and allows for better interoperability with the alien wavelengths expected in the metro access and metro core.