xWDM Optical Rings

Universities, Local Institutions, and Regional Governments have numerous delegations and work centers in a metropolitan area. Generally, this type of organization has its own fiber-optic network or leases one to connect its centers. In most cases, this optical fiber is underused, carrying a single service, and the topology of the interconnections between centers doesn’t guarantee availability of redundant routes. This document provides a simplified description of a solution that illustrates the development of an xWDM optical ring to interconnect 8 centers or delegations with two central offices.

The first step, based on the topology of the LAN Network is to establish a lambda plan. The figure below, to the left, shows a network topology in which each delegation is connected over Gigabit Ethernet to both central offices. These main centers are in turn connected to each other by two 10GbE links.

In the previous image (right) we set up a ring that is made up of two independent segments, one North-West, and a second South-East. The delegations in each segment are assigned an exclusive wavelength, that will be used to maintain the connection with Central Office 1 and 2 at the same time.

The equipment in each delegation consists of a TriSAE chassis with an AO GbE 1+1 optical adapter and a 1-lambda OADM (Optical Add&Drop Multiplexer).

As shown in the image, the Gigabit Ethernet switch in each center is connected to the AO GbE 1+1 module, which has two outputs.  The SFP lasers with the wavelength assigned to the delegation will be inserted into these. The use of the AO GbE 1+1 makes it possible to immediately detect the failure of a segment and activate an alternate route. The AO GbE 1+1 module will then be connected to the Optical ADM. The purpose of the OADM, or Optical ADM, is to extract and insert one or more wavelengths, allowing the rest to pass.

The final design of TELNET’s proposed solution consists of one node per delegation – adjusted to a specific lambda – and two MetroSAE 5U head end units, one in each Central Office.

Each MetroSAE 5U chassis is equipped with two CWDM multiplexers; each one of these multiplexers will be used for a segment of the ring.