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Optical Network Configurations


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10 minutes ago, jabbr said:

This article is great: https://blog.mellanox.com/2017/03/100g-psm4-the-most-configurable-lowest-cost-single-mode-transceiver-available/

 

I am picking up optical cables including QSFP28 transceivers at each end for <$100 ... again gulp ... so I've been curious in what this technology is... PSM4 (parallel single mode x4) which is a laser split into 4 paths, and then modulated on the silicon chip into 4 x 25 Gbs signals. These cables have 8 single mode fibers (4 duplex).

 

In contrast, the 100GBase-lr4 modules that I am using from my basement to my office multiplex the lasers into 4 different frequencies and then send all 4 down a single single mode fiber! ... and trust me, I'm not spending $8k / module ;) 

 

These integrated silicon photonics chips are bringing the cost of fiberoptic networking down: with careful "shopping" I can afford to do this in my house today, but this technology is being mass deployed and we will all be seeing this (QSFP28 and QSFP-DD connections) in the future. 

 

For "extreme" users this means that NVME storage over the network will be as fast as on a local machine ... we can think of the network as an extension of the PCIe bus.

Love this!

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  • 1 month later...
1 minute ago, plissken said:

 

I like to look at it from a critical thinking perspective. 

 

Fully realized 10G can ship 2 CD's worth of audio every second. My system can cue up a 16/44.1 track in about 300ms and then not use the connection any longer.

 

You are playing out of buffer, not off the wire. As a matter of fact, on well engineered systems, you can start playback and pull the plug. 

If I had to guess, I'd say their comments have nothing to do with the speed of the interface. Just a guess. 

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1 minute ago, plissken said:

 

In a well engineered system, the faster the wire speed, the less the wire is used the less the transceiver is used. Hence talking about MM OM3/OM4/OM4/MPO 12 strand/LC BiDi or SM fiber or transceivers. 10/QFSP+/QFSP28/40/80/100G. 

 

One HAS to accept that we aren't playing off the wire. We are playing out of buffer. The quicker you can fill the buffer (regardless of size) the less the wire is of any issue. If I can get 5000MB/s wire rate (QFSP+) my wire time for a 75MB track is .015 of a second. It's also my tranceiver time. 

 

The only other argument that can be made is that somehow having a SM vs MM tranceiver installed, but playing back from local disk would still be affected, is one that could be effectively made. I'm all ears on that one. 

I hear you 100%. But, the faster the interface the less TIME it is used. I don’t know if faster interfaces have more noise due to higher speeds. No clue. 

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1 hour ago, plissken said:

The bottom line is that network connections are only using power when there is traffic flowing. These are all greened up from a power conservation standpoint. 

I’d say they are only using more power when traffic is flowing. If there was no power use the switch would warn me that the device has dropped off the network. It may be a trickle compared to full blast at all times, but it has to be something. 

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5 minutes ago, jabbr said:

 

The 10gbe and faster serdes/asics maintain the very tight noise requirements *end-to-end* not just on the line. The specs are very demanding. Aside from networks, the eye pattern requirements for PCIe-4 are such that, for example, Intel is not yet able to meet despite the CPU being "enabled" ... its the low noise system requirements that have been giving the Intel platform trouble... I mention 10Gbe and up because that spec was the first to impose the end-to-end testing requirement, so-called "stressed eye pattern" testing.

 

65W_26049_0_Letter_0.pdf 5.5 MB · 1 download

Very cool. 

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22 minutes ago, plissken said:

Wonderful. Nobody on the Ubiquiti forum has responded to my question abut this yet. 

 

Edit: Ouch these are a little pricy. $19.95 +s&h :~)

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  • 3 months later...
2 hours ago, plissken said:

With 10GBe and a theoretical 1250MB/s a 50MB 16/44.1 track will transfer in 4/100ths of a second.

Perhaps a good topic for another thread. I don’t think we are anywhere near this in practice. It would be good to know how each app transfers data. Some say it’s transferred at wire speed then communication stops, but I’ve had many tracks stop shortly after pulling the plug. 
 

anyway, I don’t want to details this thread. 

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https://www.opnt.nl/white-rabbit-switch/

 

White Rabbit Switch
(WRS-3/18)

OPNT is a provider of the 18 Port White Rabbit Switch (WRS-3/18), a key component of many White Rabbit networks. White Rabbit combines optical Gigabit Ethernet connectivity with accurate, reliable, and deterministic time and frequency synchronization, achieving time transfer with sub-nanosecond accuracy over distances of more than 100 km of optical fiber. In combination with OPNT’s unique range of optical amplifiers and optical multiplexers, the range of White Rabbit can be further extended to many hundreds of kilometers, and White Rabbit wavelengths can be made to run in parallel with existing signals in fiber-optic networks.

 

Features

Sub-nanosecond time synchronization accuracy

Optional Low-Jitter Daughterboard factory installed

Truly phase-coherent replicas of 1 PPS and 10 MHz signals at each node

Optical Gigabit Ethernet connectivity and switching capacity

Autonomous and reliable operation

18 SFP interfaces supporting multiple and configurable network time protocols

Housed in a standard 1U 19’’ case

Easy to configure through remote interface

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24 minutes ago, R1200CL said:


Well, they didn’t go for 10GB or above in the White Rabbit project 😀

 

Remember my point was if any of that technology used in their switches, could be adopted in “audio switches”.
Not the time synchronization in long distances, which I think those guys are after.

 

(Well unless we’re starting our DAC to synchronize with Tidal, Qobuz etc. Wow, Roon in cloud with atom clocks syncing to your DAC 🤓).

 

Actually important in 5G network. Look at Cisco solutions if someone like to study more.

 

So far no one did brother to comment on different jitter specs in SFP data sheets. I don’t have the skills to interpret everything those sheets says. But, 0,0007 compared to 23 seems to make a huge difference. So I was hoping you or @plisskencould enlighten us. If you guys don’t know either, maybe you know who to contact. 
 

And why did they (WR) even bother to develop switches in 1GB, if 10 GB and above should be sufficient when it comes to jitter. 
I would expect these guys know what they’re talking about. 
 

Also the standard mentioned is more than 600 pages, meant to cover everything. Those who “hide” behind that or other standard. Come and show me how that standard demands no jitter. When I scanned through those 600 pages, I didn’t see any eye pattern. I find manufacturers with expensive equipment showing off pictures so measurements can be made. 
 

Again why isn’t there eye pattern available for SPF modules and switches. They do go up to almost 5GB. 

 

And if you study the Finsair selection chart, there is only one module (FTLX1471D3BCV which they won’t tell jitter. Only comply with a spec from 2005), that will comply with optical Ethernet. Rest will only work with 10GB as I understand it. 
So unless you’re building 10GB all over, you will probably struggle, unless you’re using a PC as endpoint. (No other device will comply). 

Also, I’m still not sure it the jitter reduction is related to switch vs module or a combination. 
Does the switches display jitter info in data sheets ?

 

 

 

 

I’m talking to a vendor now about WR switches :~)

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23 minutes ago, plissken said:

 

1: I think there is a fundamental misunderstanding of 10G interface jitter vs audio clock jitter. They are wholly unrelated.

   If I transfer 1250MB 16/44.1 PCM track and buffer that on my end point all at once jitter mattered for 1 second.

   If I transfer 1250MB 16/44.1 PCM track and I buffer 1MB at a time, then jitter only mattered for 1/1250th of a second.

 

2: Ethernet, with no manipulation in place or contention, transfers at full wire right. Period. There's no are are partial rates. You will get the the highest speed of the lowest speed link in the chain (generally your ISP excepting some of you lucky bastards).

 

3: 0.0007 vs 23? What huge difference to you? To your audio?

These numbers are all theoretical. With audio devices one can't pick and chose what to buffer or how large/small the buffer is in the endpoint. Most manufacturers won't tell you the size of the buffer either. 

 

The speed at which an audio endpoint can handle data is far less than wire speed, even if rated for say 1G. These are usually low power ARM devices. 

 

It's all very interesting to me and I'd love to dig in further, with you of course because I value your expertise. 

 

P.S. I'm one of those lucky bastards with 1G up/down from my ISP for $65 per month. I've been thinking about bringing in a second strand of fiber or even 1G service from another ISP for failover. Yes, I know, first world problems :~)

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