Cisco 7206VXR Configuration Guide - Page 124

Connecting I/O Controller, NPE-G1, or NPE-G2 Cables Chapter 3 Installing a Cisco 7200 VXR Router Note The 1000BASE-ZX GBIC provides an optical power budget of 21.5 dB. You should measure your cable plant with an optical loss test set to verify that the optical loss of the cable plant (including connectors and splices) is less than or equal to 21.5 dB. The optical loss measurement must be performed with a 1550-nm light source. Mode-Conditioning Patch Cord Description A mode-conditioning patch cord can be used with the WS-G5486= or GBIC-LX/LH= to allow reliable laser transmission between the single-mode laser source on the GBIC and a multimode optical fiber cable. When an unconditioned laser source designed for operation on single-mode optical fiber is directly coupled to a multimode optical fiber cable, an effect known as differential mode delay (DMD) might result in a degradation of the modal bandwidth of the optical fiber cable. This degradation results in a decrease in the link span (the distance between a transmitter and a receiver) that can be supported reliably. The effect of DMD can be overcome by conditioning the launch characteristics of a laser source. A practical means of performing this conditioning is to use a device called a mode-conditioning patch cord. A mode-conditioning patch cord is an optical fiber cable assembly that consists of a pair of optical fibers terminated with connector hardware. Specifically, the mode-conditioning patch cord is composed of a single-mode optical fiber permanently coupled off-center (see Offset in Figure 3-19) to a graded-index multimode optical fiber. Figure 3-19 shows a diagram of the mode-conditioning patch cord assembly. Figure 3-19 GBIC Mode-Conditioning Patch Cord Assembly 6 1 2 / / / / Offset / / 1 9 57011 RX 3 TX 4 5 1 Beige color identifier 2 To GE interface 3 RX 4 TX 5 Blue color identifier 7 8 6 1 6 Multimode fiber 7 Single-mode fiber 8 Offset 9 To cable plant A mode-conditioning patch cord assembly is composed of duplex optical fibers, including a single-mode-to-multimode offset launch fiber connected to the transmitter, and a second conventional graded-index multimode optical fiber connected to the receiver. The use of a plug-to-plug patch cord maximizes the power budget of multimode 1000BASELX and 1000BASELH links. 3-28 Cisco 7200 VXR Installation and Configuration Guide OL-5013-09