This is the information to share with you. I read it in some other documents and also applied in our Transmisson Network.

• 50 GHz DWDM with 0.2 (bit/s)/Hz spectral efficiency
• Up to 3000 km reach on compensated fiber (unless pre - distorted)
• FEC w/ coding gain ~9 dB, leading to EOL OSNR <14 dB
• PMD tolerance 30 ps DGD, CD tolerance 1000 ps/nm

I can add one more constraint according to my experience in our network: the age of fiber, when the fiber become old and old the mechanical characteristic of the fiber change and impact the optical budget

It may be safer to test first fiber with OTDR tool before any network design and do not rely on some OTDR test done years ago when the fiber was new

Good post.

Very Agree with your comment! Even more I think it?s mandatory to certify with OTDR tool the fiber again before the put on service of a DWDM link.

nice sharing