No connection of S3300-28X Smart Switch with Juniper Router using fiber optics

Hello,

we have a S3300-28X ProSAFE 24-Port Gigabit Stackable Smart Switch from Netgear that we want to connect to another network via a Juniper router using a multimode fiber optics connection.

Our first issue has been that we couldn't get a physical connection (no link light at Netgear Switch). Trying other not smart switches from Netgear and Aruba we immediately get a physical link without any issues regardless of the used SFP modules and we are also able to ping and communicate with the Juniper router using the other switches. After a lot of troubleshooting we managed to get a physical link also at S3300-28X Netgear switch by using a media converter and an ethernet port of Netgear-Switch instead of using SFP port & module directly. We are not able to get a physical link if we plug the fiber optics cable directly into Netgear-Switch with our SFP Module.

But still we are not able to ping or communicate with the Juniper router even the physical connection seems to be alright now with media converter (light is blinking). We have been troubleshooting for a long time and tested different things:

1) Doublechecked direction of fiber optics cables and made sure that fiber optic link’s transmit signal (Tx) at end of the cable matches the corresponding receiver (Rx) at the other end

2) Ping router from switch Web-UI using VLAN interface / ip address directly (instead of using connected pc)

3) Change the MTU from 1500 to 1522 as Juniper router uses 1522

4) Do a software update of the switch from 6.6.4.26 to newest version 6.6.4.28 

5) Study the logs, but from our view there are only informative information and no issues. The only things which might be interesting is that: (broad_tx.c(228) 534 %% hapiBroadTxLplist: No TX ports given)

6) Made sure port mirroring is disabled (already had been disabled)

We are not sure why...

a) ...we don't get a physical link if we use SFP module directly even it works perfectly with other (not smart) switches.

b) ...we can't communicate with Juniper router if we have a physical link using the workaround with the media converter.

Please assist and thank you in advance!