Optical Network Configurations

[marce]

On 30/05/2015 at 2:36 AM, jabbr said:

I have successfully used a gigabit ethernet connection between a Netgear Switch (1000base-T) to a TP-Link MC220L fiber media converter (FMC) over LC-LC Duplex OM3 fiber to MC220L to DN2800MT motherboard (NAA).

 

SFPs successfully used with MC220L:

Finisar FTLX8571D3BCL (supposed to be 10g but works ...)

GLX-SX-MM-TO (Cisco compatible labeled "iNet")

Cheers I will do some research.

[marce]

!

[marce]

16 hours ago, jabbr said:

 

The power supply used to power the opticalRendu is more important than merely for the SFP module and network clock because it’s also supplying the USB and many DACs are bus powered. In all cases the USB touches the DAC.

 

For the FMC I think any reasonably good PSU would suffice, eg linear if the FMC is near the audio equipment. The fiberoptic cable will not transmit leakage current!

 

Professional equipment uses SMPS — I assume well designed because the jitter specs are very tight. But they don’t use really cheap wall warts!

And the finesse of power supplies is not just the main supply, more critical are local decoupling and isolated supply islands with either LDO's or PI filtering for local circuitry... These have to be done correctly when the board is designed, instrumentation and some control stuff has upwards of 20 separate supplies. A basic design with Ethernet, USB, processors should have a separate controlled supply for each section (one 0V plane,  in most instances) for best noise mitigation.

 

[marce]

17 minutes ago, Em2016 said:

 

Understood. Although a little disappointing that you talk about engineering and measurements but won't let @JohnSwenson eye pattern diagrams...  which I know he would have as part of development, since he has talked about improving USB signal integrity for years...

 

What does an eye pattern tell you though, as long as the required opening is clear the signal will get trough for a specific interface... The tighter the lines are the better the signal, but other information is required, such as supply noise, waveforms etc.

[marce]

Lower power supply noise always helps, but digital is also immune to noise to a certain degree, so the interface could work perfectly, the PSU noise could effect other circuitry.

Signal integrity is the opposite face of a coin, EMC being the other face. Both are critical in the design  of a product, the levels you need to achieve differ for different implementations and uses of circuitry. That said I apply the same diligence and OCD to all PCB layouts and I am a great believer in over engineering to an extent.

The results you seek would be interesting and informative I do agree. My view on the front end supply is as long as it is a decent supply it should not make any difference to the results as the main and critical part of any power delivery system is already on the board as I explained above... One would hope.

[marce]

There is a different requirement for longer distance signal transmission than the few feet we use in our homes...