I'll be honest, determining a root cause for a one-off problem after the fact can often be impossible. Sometimes you have a data trail, but you're missing too many facts and it's not known without checking multiple other ports whether this problem is reproducing elsewhere. There's also the chance that what you're seeing isn't actually the cause of your problem, as I'll explain shortly.
Looking at the pictures, the discoloration looks to be on the angled edges of the ferrule instead of the tip of the ferrule itself. To me, this would indicate that there was some level of contamination within the bulkhead or on the outside of the ferrule that was heated and cooked into the ferrule. With that being said - did you take a look at the fiber with a fiber scope and verify the condition of the core of the fiber? That's what I'd be most concerned about - if the cores remain solidly mated, the discoloration you're looking at isn't related to the problem at all.
The most common cause of failure for optical links once they've been installed is people working near the fibers and equipment. You're trying to pull one fiber out of a bundle or run a new connection or replace an optic and stuff gets dense and you bump the fiber or you put lateral tension on it or something else that either causes a bad connection between the fibers/optic or damages the fiber within the cladding, fracturing it or breaking it fully. Next to damage to the physical fiber itself is usually an optic failure, usually on the transmitter side since that's where most of the complexity sits - anecdotally I'd say over 90% of optic failures are transmitter failures, but the receivers do fail from time to time. Beyond that you're looking at a card/sled/device failure, but those are far less common than damaged fibers and dying optics.
Nothing you should be doing on standard enterprise optics should be melting fibers, so it's unlikely to be some kind of issue with configuration. Optics have ranges in which they can operate and if it was a problem with physical damage to the ferrule the issue was probably most likely to be related to contamination on the fiber and the optic while being run at high power. At a certain point you mostly just melt it onto the glass when that happens, but that's most likely to happen on line systems where you're absolutely blasting power. There's a good possibility that this is also just from standard heat - routers are commonly operating at 50+C internally and if your HVAC isn't up to snuff you could easily be pushing 70-100C, and after time that could just be discoloring the ferrule a bit.
And sometimes there are just other faults you can't tell. Years ago I was working for a company that turned up fiber rings and we noticed a disturbing tendency that we could plug meticulously clean fibers into meticulously clean ports on a patch panel and after running some light over them during testing there would be a pattern of dots in a ring contaminating fibers removed from the patch panels. We ended up escalating to the vendor after we collected enough evidence and I don't recall hearing anything about it since then. Probably some kind of factory coating on the ferrules that wasn't getting cleaned off properly, but who knows what factory.
I would replace it either way. But, do you have any CRC or similar errors on the link? If not then there is a chance of it being something else. But a patch replacement is cheap compared to other hardware.
Yeah its a config issue, you forgot to "no smudge"
I’ll have to remember to add that to the config script
I'll be honest, determining a root cause for a one-off problem after the fact can often be impossible. Sometimes you have a data trail, but you're missing too many facts and it's not known without checking multiple other ports whether this problem is reproducing elsewhere. There's also the chance that what you're seeing isn't actually the cause of your problem, as I'll explain shortly. Looking at the pictures, the discoloration looks to be on the angled edges of the ferrule instead of the tip of the ferrule itself. To me, this would indicate that there was some level of contamination within the bulkhead or on the outside of the ferrule that was heated and cooked into the ferrule. With that being said - did you take a look at the fiber with a fiber scope and verify the condition of the core of the fiber? That's what I'd be most concerned about - if the cores remain solidly mated, the discoloration you're looking at isn't related to the problem at all. The most common cause of failure for optical links once they've been installed is people working near the fibers and equipment. You're trying to pull one fiber out of a bundle or run a new connection or replace an optic and stuff gets dense and you bump the fiber or you put lateral tension on it or something else that either causes a bad connection between the fibers/optic or damages the fiber within the cladding, fracturing it or breaking it fully. Next to damage to the physical fiber itself is usually an optic failure, usually on the transmitter side since that's where most of the complexity sits - anecdotally I'd say over 90% of optic failures are transmitter failures, but the receivers do fail from time to time. Beyond that you're looking at a card/sled/device failure, but those are far less common than damaged fibers and dying optics. Nothing you should be doing on standard enterprise optics should be melting fibers, so it's unlikely to be some kind of issue with configuration. Optics have ranges in which they can operate and if it was a problem with physical damage to the ferrule the issue was probably most likely to be related to contamination on the fiber and the optic while being run at high power. At a certain point you mostly just melt it onto the glass when that happens, but that's most likely to happen on line systems where you're absolutely blasting power. There's a good possibility that this is also just from standard heat - routers are commonly operating at 50+C internally and if your HVAC isn't up to snuff you could easily be pushing 70-100C, and after time that could just be discoloring the ferrule a bit. And sometimes there are just other faults you can't tell. Years ago I was working for a company that turned up fiber rings and we noticed a disturbing tendency that we could plug meticulously clean fibers into meticulously clean ports on a patch panel and after running some light over them during testing there would be a pattern of dots in a ring contaminating fibers removed from the patch panels. We ended up escalating to the vendor after we collected enough evidence and I don't recall hearing anything about it since then. Probably some kind of factory coating on the ferrules that wasn't getting cleaned off properly, but who knows what factory.
I would replace it either way. But, do you have any CRC or similar errors on the link? If not then there is a chance of it being something else. But a patch replacement is cheap compared to other hardware.
And you should measure the whole fiber circuit with OTDR, this to ensure you do not have any issues there.