Troubleshooting Media Converter vs. SFP - LH

[burgessf]

I am having an issue connecting two buildings. I have thoroughly tested the two switches and the SFP's to know that they work properly. My cabling vendor insists that his fiber pull, couplers, jumpers and tips are all perfect. We are at a stand still. To give evidence that the fiber run and connection is good, he connected a 10-BaseFL - 10-Base-T converter at both ends. Both ends show a link.

Is this a good test? Here is a little more information that might help with ideas.

• The fiber run is SM.
  
• SFP modules are GLC-LH-SM
  
• Switches are Catalyst 3750 to 3560X.
  
• This is a connection that worked until 2 weeks ago. The fiber was broken and then fusion spliced.
  

I would greatly appreciate any/all insight.

[Reza Sharifi · Accepted solution]

Since both sides of the connections use SC type connector, try switching the strands (TX & RX) around on one side and see if you get link light.

HTH

[burgessf]

Thank, I have tried switching TX & RX.  Is there a reason the link would work for a media converter instead of the SFP's?

Frequency/wavelength/power? 

I'm not a fiber guy, so my exposure to media converters and tranceivers is minimal.  Should both the TX and RX light  be green?         

[Alessio Andreoli]

Hi,

i do not believe that a 10-based media converter is a good test because apart the media converters being a sort of active hub on two single-port implementing different media, you want to know more baout your fiber. Your switches could for example analyse speed and duplex mode while the Media Converter just check if the signal is there. They are a kind of layer 1 and half devices and do not provide massive information. As long as the signal arrives, most of the MC are happy. your cabling company for sure will have some testers (like Fluke) that can size the frequencies, the interferences and to generate traffic from one side to another. These would be more reliable tests. By the way Reza gave you already a beter test than a MC. To loop a fiber is always a quite indicative test

Good Luck

[Reza Sharifi]

I'm not a fiber guy, so my exposure to media converters and tranceivers  is minimal.  Should both the TX and RX light  be green?       

There is only one green light.  When everyting is working you will see one green light. if not than there is no light at all.

Can you clarify a couple of things?

3560x comes with 4 port 1 gig module or 2 port 10Gig. Are you using the one gig module?

3750, whay type of 3750 is this? is the fiber uplink 1 gig SFP also?

Are your fiber patch cords SM also?

one more question:

are you using patch panels or home run connections?

[burgessf]

Can you clarify a couple of things?

3560x comes with 4 port 1 gig module or 2 port 10Gig. Are you using the one gig module?

4 port, 1G

3750, whay type of 3750 is this? is the fiber uplink 1 gig SFP also?

3750 (not 3750X). 1G uplink

Are your fiber patch cords SM also? Yes

one more question:

are you using patch panels or home run connections? Each closet has a fiber box where the fiber is terminated into couplers.

I'm suspicious about his couplers.  I cannot tell the difference between SM/MM couplers.

[jimmysands73_2]

>>Thank, I have tried switching TX & RX.  Is there a reason the link would work for a media converter instead of the SFP's?

No (not that I am aware of unless of speed/duplex mismatch).

You tried switching tx/rx....its working now but you said before it was not (even when you switched them)?

Odds are it was switched somewhere along the way when the fiber guys were testing. 

BTW, the term is called  'rolling fiber'.

Glad you were able to get the link up!!

[burgessf]

Thanks to everyone who replied with suggestions and ideas.  Reza was correct!

[sansarav720e]

Dear Burgessf ,

                   You statement says after fiber broken , fiber has been spliced .Then after u lost connectvity between two building earlier it was working fine .

     My insight over here when your fiber splicing is done , have the spliced it properly with mimum loss , if they have not spliced properly ,all light source will be dropped at splicing area .

          when u did media converter test , what is light power gain u have got at another side . Have your splicing vendor verified this properly

        If your fiber loss is very high your connection wont come up . how many fiber core u have 1 pair or 2 pair or 4 pair . try to use another pair of core if this core does not work properly .

           what is distance between building ??

HTH

Thks

santhosh sarav

[burgessf]

Concerning your first question - are db loss and light power gain two different things?  db loss is .05.

Only one pair of fiber is terminated.  There should be two more pairs terminated.  I am suspicious about the couplers.  I don't feel the vendor is being 100% honest right now.  I think he's trying to buy time.

[sansarav720e]

Dear Burgessf ,

                   db loss is called atteunation how much percentage can be lost during transmisson , same db value can be used to calculate how much can be your power output

you can define the formulas for attenuation and gain:

Attenuation (dB) = 10 x Log₁₀(P in/P out) = 20xLog₁₀(V in/V out)

Gain (dB) = 10 x Log₁₀(P out/P in) = 20 x Log₁₀(V out/V in)

For your db .05

dB      Power Out as a % of Power In     % of Power Lost

.05               99%                                          1%

http://www.timbercon.com/db-power-loss/

http://www.cisco.com/en/US/tech/tk482/tk876/technologies_tech_note09186a008011b406.shtml#topic5

Ask your vendor whether its single core or multicore fiber . It can be identfied by seeing fiber patch panel LIU

HTH

Thks

Santhosh Sarav