On Tue, Aug 21, 2012 at 06:05:32PM +0200, Gert Doering wrote: > Hi, > > On Tue, Aug 21, 2012 at 12:26:50PM +0000, John Brown wrote: > > Put a real optical power meter on the fibers and adjust with pads as > > needed to get your levels within specs. > > That's *RX* power. Not TX power. TX power is something that is measured > inside the SFP - an the question "how can TX power go high" is a valid > one.
>From an X2-Datasheet: VII. DOM Parameters Values Parameter min. max. Unit Transponder Temperature Monitor Accuracy 1) -5 +5 °C Laser Bias Current Monitor Accuracy 2) -10 +10 % Transmit Power Monitor Accuracy 3) -3 +3 dB Receive Power Monitor Accuracy 3) -3 +3 dB 1) 0 to 70°C case temperature. 2) 0 to 12.5 mA. 3) -8.2 dBm to +0.5 dBm ... so that may be just a measurement error. An other SFP+ shows +-2dB TX or RX Power Monitor Accurancy, and +-10% TX BIAS Accurancy. Did not find an explanation of how optical modules determine optical output power, some kind of handshake with the remote side , increasing output power so that the remote side _sees_ sufficient light? But *cleaning* the fibers and plugs is a very good idea(TM), with (too much) power the reciever gets blind; somtimes the dirt beetween fiber-fiber ore fiber-optics get grilled/emailed onto the glas. -- Juergen _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
