NOTE: We recommend that you maintain N +1 or N+N power supplies in yourswitch at all times. Replace failed power supplies immediately to preventunexpected failures.Power management raises a minor alarm if the number of online powersupplies in your switch is less than the number required to maintain theconfigured N+1 or N+N power redundancy. If the problem is not corrected in5 minutes, a major alarm is issued.Power management raises a major alarm if the number of online powersupplies in your switch is less than N power supplies. Power managementprovides power to line cards in priority order until power is exhausted. Theremaining line cards are powered off.If a new line card is installed in an operational switch, power managementdoes not power on the line card if the increased power demand exceeds thetotal available power, including redundant power. If redundant power is usedto power on the line card, a minor alarm is raised, which becomes a majoralarm in 5 minutes if the condition is not corrected.RelatedDocumentationAC Power Supply in a J-EX8200 Switch on page 34•• For more information about power management on the switch, see the DellPowerConnect J-Series Ethernet Switch Complete Software Guide for Junos OS athttp://www.support.dell.com/manuals.Calculating the J-EX8200 Switch Fiber-Optic Cable Power BudgetCalculate the link's power budget when planning fiber-optic cable layout and distancesto ensure that fiber-optic connections have sufficient power for correct operation. Thepower budget is the maximum amount of power the link can transmit. When you calculatethe power budget, you use a worst-case analysis to provide a margin of error, even thoughall the parts of an actual system do not operate at the worst-case levels.To calculate the worst-case estimate for fiber-optic cable power budget (PB ) for thelink:1. Determine values for the link's minimum transmitter power (PT ) and minimum receiversensitivity (PR ). For example, here, (PT ) and (PR ) are measured in decibels, anddecibels are referred to one milliwatt (dBm).PT = –15 dBmPR = –28 dBmNOTE: See the specifications for your transmitter and receiver to find theminimum transmitter power and minimum receiver sensitivity.84Dell PowerConnect J-Series J-EX8208 Ethernet Switch Hardware Guide
