What is typical Transmit Power (dBm) for 1000BASE-SX

dabrooks · ‎03-12-2007

I have a particular situtaion that will result in a 9 db loss on a fibre cable between two devices. The data sheet for the 1000BASE-SX SFP states a Transmit Power (dBm) range of -4 to -9.5 . The receiving 1000BASE-SX SFP has a Receive Power Range (dBm)0 to -17. I want to understand the reasons for the -4 to -9.5 range. I am not able to guarantee to my customer that this solution will work, that is if the SFP transmits at -9.5 db.

The solution may work when installed but are there factors that could stop the solution working in the future, e.g. reasonable variations in temperature , deteriation of the device over a few years etc leading to lower Transmit Power (dBm).

Some manufacturers specific typical db levels as well as min and max but I've not found this for the Cisco SFPs.

carenas123 · ‎03-16-2007

1. The 1000BASE-SX launch power shall be the lesser of the class 1 safety limit as defined by 802.3 38.7.2 or

the average receive power (max) defined by 802.3.

2. Examples of an OFF transmitter are: no power supplied to the PMD, laser shutdown for safety conditions, activation of a

"transmit disable" or other optional module laser shut down conditions. During all conditions when the PMA is powered,

the ac signal (data) into the transmit port will be valid encoded 8B/10B patterns (this is a requirement of the PCS layers)

except for short durations during system power-on-reset or diagnostics when the PMA is placed in a loopback mode.

3. Radial overfilled launches as described in 802.3 38A.2, while they may meet CPR ranges, should be avoided.

http://www.cisco.com/univercd/cc/td/doc/product/ong/15305/305docs/305r20io/520iog20.pdf