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Problem with signal after RJ45 to SMA converter (SMA2RJ45EVK/NOPB) for optical transmission

Th Ka
Prodigy 30 points
Other Parts Discussed in Thread: SMA2RJ45EVK

Hi, 

I would like to demonstrate an Ethernet connectivity through a short optical link. Therefore, I purchased SMA2RJ45EVK/NOPB from TI as the interface between RJ45 and SMA, the item can be found here:

http://www.ti.com/tool/sma2rj45evk

And obviously the SMA goes to an SFP module and to an evaluation board from Finisar. I give more details on this if required. 

So initially, I connected two laptops, through two SMA2RJ45EVK/NOPB without any optical link, which means I directly connected both SMA2RJ45EVK/NOPB. I pinged each devices and it worked all well. 

then I introduced the optical link, which is nothing but a SFP (small form pluggable) type laser:

4212.Luminent SPC-MR-LR-49CDA.pdf

and an evaluation board:

5315.FDB-1027.pdf

So the SFP operates only between 100 Mb/s and 2700 Mb/s. But Im not sure of bandwidth characteristics, so I assume since it states 100 Mb/s, it should have good low frequency characteristics. 

However, after connecting the PC to PC link via this optical link, which is based on optical loop back, nothing works. 

I am not sure what is wrong, cause I believe PC Ethernet connection should be less than 100 MHz bandwidth, and this SFP ideally should support that bandwidth range.

Could anyone please advice where I am going wrong.

Thank you.  

  • 0
    TI__Mastermind 31600 points

    I see that this thread was posted to both the Ethernet and Fiber Communication E2E Forums.  While it is difficult to determine where the thread should be to get the necessary support, I do not believe it fits with the focus of the Ethernet forum (primarily support for TLK1xx and DP83xxx Ethernet MAC and PHY products).  Therefore, I will remove the post from the Ethernet forum and direct support to this post. 

    Patrick

  • 0 in reply to Patrick OFarrell
    Prodigy 30 points

    Thank you Patrick. Since my post is related to both, so posted in both segments to get more attention. But this will do, thank you very much. 

  • 0
    TI__Mastermind 43795 points

    When an optical link is inserted into a working electrical interface, several things could be going wrong. The module and optical fiber are not compatible (single mode vs. multi-mode fiber) The ethernet devices may need to be told to work only at 100 Mbps. Negotiating the link or going into 10M mode would likely drop the link due to low frequency optical limitations.

    I'm not an optical or ethernet expert, but these are a few things I've run into with optics

    Lee

  • 0 in reply to Lee Sledjeski
    Prodigy 30 points

    Hi Lee, 

    I think its due to the low frequency optical limitations, because I have personally integrated SMF and MMF before and it works. 

    Thank you for your advice. Anymore inputs on the RJ45 to SMA converter (SMA2RJ45EVK/NOPB) are welcome. 

    Furthermore, how can I tweak for continuous response of 100 Mb/s or even 1 Gb/s?? 

    Thanks

  • 0 in reply to Th Ka
    TI__Mastermind 43795 points

    Sorry, I do not know how to control the port to enable only higher datarates and continuous transmisssion.

    - Lee