Cisco Systems 15501 manual Ring Topologies, Power Equalization in an Amplified Ring Network

Chapter 1 Product Overview

Cisco ONS 15501 Applications

Ring Topologies

An amplified ring topology requires more fine-tuning of power for each channel or band. Figure 1-1illustrates a hubbed ring network utilizing counter-clockwise signal transmission. All bands (A, B, C and

D)are transmitted from node 1. Node 2 terminates and transmits bands A and B; node 3 terminates and transmits band C; and node 4 terminates and transmits band D.

Figure 1-1 Power Equalization in an Amplified Ring Network

In general, EDFAs in a ring topology should be placed so they maintain the power level at the receiver, as well as the OSNR, of each channel. In this case, EDFAs serving as postamplifiers are located at nodes 2 and 4.

At node 2, the input power level of the EDFA is much higher than the input power level of the pass-through band (bands C and D), due to the added power from bands A and B. If trunk attenuation is employed directly before the EDFA at node 2 to keep the unit’s total input power within the required range, the power levels of both the add bands (bands A and B) and the pass-through bands (bands C and D) are attenuated equally. As a result, the power level of the pass-through bands is much lower than that

	Cisco ONS 15501 User Guide
1-6	78-14134-02, Release 2.0