Fiber optic cables are used to connect computers and networking equipment for high-speed communications from 1 to 100 gigabits per second. A fiber tap can be inserted in the cable to split off some of the light and send it down another cable to a network monitoring tool such as an intrusion detection system or a protocol analyzer. The tap's split ratio identifies what percent of the light is split off for the tool. For example, a 50/50 split ratio means that an equal amount of light is sent to the tool and on down the main cable. A 70/30 split ratio tap keeps 70% of the light in the main cable and sends 30% the tool. The optimum split ratio for a given deployment is found by calculating the light budget, based on factors such as the lengths of the various cables and the launch power and receive sensitivity of the optical transceivers at each end of the cables. ixSplitZ takes the drudgery out of these calculations by letting you simply enter the various parameters and immediately see the design margins at each endpoint for various split ratios.
App operation: The footer of the app shows a tap installed in the middle of an east-west network link (the blue and green cables), with tapped data going south to a tool (the gold cable, which carries two data streams down to the tool and no return traffic). Above the graphic, four bars display the light budget margins at each of the four endpoints as you vary the configuration data. If the margin is less than 0 on any endpoint, the bar turns red, alerting you that that split ratio will not work in this deployment.
Select your link speed and cable type, and use the top three sliders to enter your cable lengths. The badges on the left pop up a dialog that you can use to enter the number of additional splices (i.e., patch panels, add +1 for each mated connector pair) in each cable. Each splice adds -0.5dBm for multimode, -0.2dBm for single mode. (The endpoint connections are already factored in, so the badge should read 0 if the cable connects the endpoints directly.) Use the fourth slider to change the tap’s split ratio and watch how it affects the light budget margins at the four endpoints.
Use the SFP Parameters section to specify the launch power and receive sensitivity of the transceivers you are using. If you select “Same SFPs,” the Ixia SFP for the selected speed and cable type is automatically used for all four endpoints. If you select “Different SFPs,” you can select by SFP part number from the pulldown list on the right side, or you can look up the information in the data sheets of your transceivers enter it using the sliders. The pulldown list offers only transceivers that are matched to the link speed and cable type set in the top section.
If you would like to understand the underlying calculations ixSplitZ performs, click the About button in the lower right corner, then click the link "App calculations explained (pdf)".
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