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Optical Networking & SFPs


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I’m wondering if Digital diagnostics monitoring of SFP can help us in any way to ensure jitter free transmissions ? 

http://www.fiber-optic-tutorial.com/do-you-know-digital-diagnostic-monitoring.html
 

I did a search “digital diagnostics monitoring interface for sfp optical transceivers”

 

I also saw this article in understanding SPF+ transceiver testing. I think I stay away from that topic 😀

 

God explanation of eye pattern.

78F93CB4-BB19-49ED-86FB-AFE38D034D0F.jpeg

90BE9B60-62C7-4AB2-800B-56292434ED18.jpeg

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  • 9 months later...
16 minutes ago, plissken said:

LOL.... The modification is the price. Dear lord. I can't wait for all the gushing reviews by morons.

This on I totally agree upon. 
 

It’s also funny to see these people trying SFP+ interconnects cheap cables with everything (cable and SFP+ modules) at a cheap price and think they’ve got fiber isolation. And still claiming good SQ. 
 

People get screwed all the to time, and when some of us trying to give a friendly advice, they just don’t get it. Calling them morons is polite. 

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33 minutes ago, PYP said:

Context is important:  in-wall cat 6 utp feeds the eR, so the oM was connected with 1 meter of fiber.  I would think a long run of fiber from router to your system, using single-mode SFP, might yield a different result.  


The length of fiber shouldn’t matter at all in my opinion. 
 

 

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5 hours ago, PYP said:

So, you are suggesting that options 2 and 3 would sound the same,

Yes, and no. My understanding is you’re now using two EtherRegen’s, so then yes. 
The in wall fiber will of cause have a source. Switch or EtherRegen? Or place the OM upfront?

 

My point was only length of fiber won’t matter. 

 

 

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  • 6 months later...
3 hours ago, MarcelNL said:

you're right, 1475 is 10Gbe, dunno what happened there....bottom line stays the same, check your gear for compatibility first or find suitable equipment to go with it. 

Go 1421. That’s cheaper, and same technology inside. 
 

I predict same results SQ as with the more expensive 1475. 
 

 

Here is my advice on fiber. Copied earlier posts in other threads. 
 

Use single mode fiber and DFB laser ("distributedfeedback" versus FB (Fabry-Perot) Finisar 1421 is good, and should be found cheap on eBay. 
https://audiophilestyle.com/applications/core/interface/file/attachment.php?id=82650

 

You can also use SFP+ mudule. 
https://audiophilestyle.com/applications/core/interface/file/attachment.php?id=82648

 

You may check comparability with your switch/router. EtherRegen works with both.

If you have a 10GB switch, You can’t normally use 10GB SPF both places. I think most users could stay away from 10 GB modules. There is absolutely no reports on better SQ. 

You want yellow cable with blue connectors. 

 

I would say that a DFB laser(1421 & 1475 ) is technologically better than a Fabry-Perot (1321 & 1324) laser. And usually more expensive as well. 
DFB has better (lower) Relative Intensity Noise (RIN). Jitter numbers is better as well. 

 

If this means better SQ, I can’t say, but this is one reason I recommend DFB laser for SFP modules. Just to be sure 😀

 

 

Here is a link to the matrix of all the current Finisar (now owned by a company called "II-VI") transceivers:

https://app.boxcn.net/shared/static/51oh3iddtgitlc9h4cpaap1ijziv575v.pdf


(Thanks for finding that table Superdad. It lost it before). 

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On 2/8/2022 at 12:02 AM, tategoi said:

Would 1471 also a good substitute?

I would think so, but you may run into trouble, but i really don't know.

 

"The FTLX1471D3BTL is a “limiting module”, i.e., it employs a limiting receiver. Host board designers using an EDC PHY IC should follow the IC manufacturer’s recommended settings for interoperating the host-board EDC PHY with a limiting receiver SFP+ module"

 

https://www.lightwaveonline.com/optical-tech/article/16649832/technology-advances-for-sfp-limiting-module-designs

 

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  • 2 months later...

Hi  @JohnSwenson

How is your measurement’s going ?

 

If I remember correctly, you said you may have a way to measure “noise” being showed on DAC output depended on the digital quality input. But you needed to build the equipment for measuring your self. 
 

Is there any progress in this project you can share ?
 

So fare I think it’s beyond no doubt that phase noise matters. Even @barrows surprisingly had to agree a better clock could improve the already superb opticalRendu. 
 

@Archimago

I’ve been told it’s possible to measure the noise in the streaming algorithm in use from the various streaming services. And there is a difference. (And I also know what service won). I think the experiment was done in Netherlands.

But this noise has nothing to do with sound quality at all. But it’s an interesting observation. 
 

As I’m also a bit fascinated about the possibility to have external clocks remotely located.
Below is a reply I got those guys that probably have best knowledge about these things. 

 

I was also thinking as the ultimate solution, the streaming services or Roon could implement a remote clock. 
However, it seems to me this isn’t a way to go. The phase noise numbers isn’t good enough. (Maybe someone will disagree). 

Still all digital signals locally over fiber is what I believe to be the future.

———————————————-

Dear Andreas, 

Apologies for the delay in responding, I was busy with conferences in the last couple of weeks. 

First let me clarify: 
- in TiFOON, we look at clock signals delivered over fibre, but not usually using ethernet protocols. The technologies we consider interact with the physical layer directly. In many cases this means we use dark fibre, or at least a piece of spectrum like one ITU DWDM channel. For ethernet-based time and frequency transfer, see White Rabbit. 
- also, in TiFOON, we look at techniques combining optical frequency transfer with "normal" time and frequency transfer, like 10 MHz and 1 PPS signals. Optical frequency transfer means that the light wave transmitted in the fibre is itself the clock signal. This method achieves the best relative instability. One approach we have persued is to simply send both an ultra-stable laser signal and the signals of a commercially avaialble RF-over-fibre system through the same fibre, separated in wavelength. 

A state-of-the-art RF-over-fibre system like ELSTAB (commercially available unter name OSTT) achieves an Allan Deviation of 3e-13 at 1 second averaging  for the 10 MHz signal, and a time deviation of a few ps for the PPS signal.  Ref: https://doi.org/10.1109/TUFFC.2015.2502547 (available for free here). The phase noise of the 10 MHz is about -105 dB @ 1 Hz and - 120 dB @ 10 Hz. Ref: https://doi.org/10.1051/0004-6361/201730615 
 

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