Also confirm that ALL input levels are FLAT to the optical transmitters. If 1 carrier is excessively high anywhere across the RF spectrum, it is possible to overdrive and "clip" the laser. This will result random distortions that will be seen in the node and further degraded as the cascade gets deeper.
Another possible senerio is that your optical light power level is excessive to the recievers in the field and causing distortions in the reciever and transfered to the launch amp. Most recievers work well at 0dBm +/- a specified manufacturer specification window.
Depending on your node/launch amplifier configuration and manufacturer, you may be overdriving the launch amplifier and it may need some type of interstage attenuation or equalization for optimum performance and minimal distortions.
Good luck and feel free to e-mail me or call me on my cellular if you have any questions.
Greg Tobin
(-REDACTED-)
(314) 422-4423
