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Ethernet cables for audio - Part C: use of fibre optical cables, SFPs, media convertors, etc


dbastin

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Let's use this thread to share and discuss ideas, experiments and experiences with fibre.

 

Yes, fibre is not really intended for short distance transmission, but it does provide isolation.  However, that benefit may come at the cost of other nasties due to conversion and power supply noise and regulation.

 

It is worth noting some Audio grade ethernet switches have fibre ports, and Sonore also advocates fibre with Opti rendu and Optical Module (media convertor).

http://sonore.us/opticalModule.html

 

For newbies to this subject, this is one type of fibre cable.

Screenshot_20201023-214933_Chrome.jpg

The cable plugs into a transceiver ...

sfpglcsxmmst.main.jpg

 

And the transceiver plugs into a Small Form-factor Pluggable (SFP) ... 

https://en.m.wikipedia.org/wiki/Small_form-factor_pluggable_transceiver.

Screenshot_20201027-212558_Chrome.jpg

 

The tranceiver needs to match the type of fibre cable and needs to be compatible with the device it is plugging into.

 

Domestic network hardwate typically doesnt have fibre capability.  Enterprise class hardware often does.

 

A Media Convertor is a device that converts between optical and wired ethernet.  Sonore Optical Module is an example of a Media Convertor, but there are many such as this generic one ...

 

Screenshot_20201027-215017_Chrome.jpg

 

Edited by dbastin
added link to Sonore, improved info
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8 hours ago, dbastin said:

Yes, fibre is not really intended for short distance transmission, but it does provide isolation.  However, that benefit may come at the cost of other nasties due to conversion and power supply noise and regulation.

 

Not true - plenty of technical applications using fibre for 1-5m runs. 

 

Conversion has no nasties. PSU maybe. 

 

Again if assuming the data gets there just fine, the only thing affected is timing, whether via PSU or non. Noise along cable a non-issue though. 

 

Most issues with fibre IMHO are at the receive end - timing's as good as what you use to convert back to Ethernet if that's what you've got. Most have an RJ45.

 

Best way is a fibre NIC in a PC/whatever with a well-clocked source at the other end. I'm a few months away from this experiment though will report back when complete.

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7 hours ago, rmpfyf said:

Most issues with fibre IMHO are at the receive end - timing's as good as what you use to convert back to Ethernet if that's what you've got. Most have an RJ45.

And that's probably where most of the PSU noise and jitter nasties emerge.

However I am curious if changes on the upstream end of the optical link make any differences. 

 

In ethernet audio, the strangest things matter.  So my assumption is there is potentially nasties at every link in the chain and the aim is to establish if that is the case and link by link from source moving upstream to reduce the impact of those problems to a tolerable level. 

Edited by dbastin
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Just now, dbastin said:

And that's probably where most of the PSU noise and jitter nasties emerge.

 

Not sure about that but would make for an interesting experiment.

 

If it's reclocking (suspect they are) then slot in a nicer oscillator, make the PSU as genuinely independent as can be, get oscillator power on a nice LDO and Robert is your mother's brother. From a 'clean the stuff upstream' perspective fibre certainly takes care of EMI along the upstream line; you're really just left with timing out. 

 

'Most' of the 'nasties' might emerge there though that's relative to 'how many are left'. 

 

You've got to have a problem/opportunity to be able to fix it.

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9 hours ago, rmpfyf said:

Conversion has no nasties

That may depend upon what you define as “nasties”.  I have two optical converters and an optical cable.  To me there is no question as to whether there is a change with the converters in vs not in.  The important question is whether the noticeable to me change is beneficial or not.  My personnel preference is the converters in.  However, it may be that with the conversions that happen something very small that should be there, is removed from the signal during the conversion processes.  Another person who has heard my converters says that to him the dynamics of the sound is reduced very slightly.  It is not a big deal but interesting to consider. 

John

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1 hour ago, Assisi said:

That may depend upon what you define as “nasties”.  I have two optical converters and an optical cable.  To me there is no question as to whether there is a change with the converters in vs not in.  The important question is whether the noticeable to me change is beneficial or not.  My personnel preference is the converters in.  However, it may be that with the conversions that happen something very small that should be there, is removed from the signal during the conversion processes.  Another person who has heard my converters says that to him the dynamics of the sound is reduced very slightly.  It is not a big deal but interesting to consider. 

 

John

 

There are a few schools of approach here. 

 

We can keep adding/trying towards better results, and note where steps are directionally correct. This isn't bad at all, it's just not accessible for everyone to trailblaze. We're fortunate that you and others continue to share your journeys to these ends accordingly. 

 

Some of the rest of us need to try to pick apart the science/engineering involved to guide choices. 

 

To the latter I'd offer that along the optical cable there's bugger all EMI along the line. 

 

Assuming the conversion works as a gateway with usual NICs then there's a clock in the converter too, and related hardware that affects, ultimately, packet jitter. That's it IMHO. You're not hearing 'optical', you're hearing packet timing. Optical = directionally correct. Compromised timing = directionally incorrect. 

 

Mod your Weiss with an optical NIC and feed it from a 2960's SFP and you'd be closer to seeing what optical can do IMHO :) 

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For those who dont know what a NIC is ...

 

https://en.m.wikipedia.org/wiki/Network_interface_controller

 

I dont know if there is a NIC that can be used outside a computer.

 

I have wondered how to somehow install one of these into an endpoint.

 

https://sonore.us/opticalModule.html

 

Or maybe Sonore or Uptone could make the equivalent of this link but ethernet rather than USB ...

 

https://uptoneaudio.com/products/uspcb-a-b-adapter

 

Edited by dbastin
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13 hours ago, rmpfyf said:

Mod your Weiss with an optical NIC and feed it from a 2960's SFP and you'd be closer to seeing what optical can do IMHO :) 

I will forgo the  pleasure of finding out whether what you suggest in respect of a NIC mod would have a benefit.  There may be a benefits with modifications.  The result that I get from the three 3 Weiss components that are in my system provide for me, a quality outcome without utilising any modifications.

John

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1 hour ago, Assisi said:

I will forgo the  pleasure of finding out whether what you suggest in respect of a NIC mod would have a benefit.  There may be a benefits with modifications.  The result that I get from the three 3 Weiss components that are in my system provide for me, a quality outcome without utilising any modifications.

John

 

John, be imaginative - rather than a call to crack out the soldering iron, I'd tell Weiss they need to up their game with a prototype optical in version of what you have, and that in being a valued customer you'll trial it for them against that which you already have :P 

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1 minute ago, rmpfyf said:

 

John, be imaginative - rather than a call to crack out the soldering iron, I'd tell Weiss they need to up their game with a prototype optical in version of what you have, and that in being a valued customer you'll trial it for them against that which you already have :P 

I like the idea Ric.  I will have a conversation with the Weiss Australian representative who talks with Daniel Weiss regularly.  Weiss for a long time has preferred Firewire to USB ostensibly because of the additional quality.  I do not do Firewire.  I wasn't happy when I first got the Network player and had to use an "I" tablet.  I saw that as crossing to the dark side.

 

John

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  • 2 weeks later...

I was reminded of this thread, which got closed, but some good info there ...

 

Oh, and it reminds me of reading about people who sent their Media Convertors to the likes of SOtM to be modified and upgraded, and the variuos imoacts of power supllies and regukators, and DIYers doing the same ... which led me to discover the Sonore Optical Module.

Edited by dbastin
um, tweaks..
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If you are running fibre under 300mt and buying from scratch, then use multimode/850nm, it's cheaper and you won't burn out your optical receiver with high light levels 

 

Single Mode, which is mainly 1310nm which is designed to run Kms is far more expensive and if you don't attenuate it over short distances it will burn out the receiver over time. 

 

Now the question.. Which one sounds better? 

 

you are converting electrical to light then back to electrical, more things to introduce problems if not done correctly. 

 

Fibre is good for speed and noise rejection, in controlled environments as in data centres, most short distance connections 1G and under are still just Cat6 copper 

 

But if you to experiment Fiberstore is a good place to start, some good reading on there too. 

https://www.fs.com/au/

 

Hifi is a funny beast, what shouldn't matter does and you might just stumble across something good

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BTW.. 

 

Don't look into the ends of any fibre gear, it will take out your eye sight over time..

 

Also, cap all ends when not in use. Clean ends with either properly designed cleaners or lint free wipes and some isopropyl alcohol. 

 

Dust will cause packets loss, multimode is less susceptible to dust than single mode but both will be affected 

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Some interesting chat about fibre from page 3 of the Switches Part A thread.

 

One member noted better results with fibre even tho the last libk to streamer isxa filtered SOtM Cat 7.

 

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Some interesting info about use of fibre here

 

 

On 03/03/2020 at 7:09 PM, Hytram said:

Single Mode, which is mainly 1310nm which is designed to run Kms is far more expensive and if you don't attenuate it over short distances it will burn out the receiver over time. 

It would be great if you could explain a little about attenuators.

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For interest, After Dark Constellation SFP modules and fibre cable ... 

https://www.adark.co/collections/online-shop-special-on-grand-opening/products/copy-of-uptone-etherregen-femto-switch-pre-order-enjoy-worldwide-free-shipping-tax-free

BTW, the link does not go to a special deal on ER.

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22 hours ago, dbastin said:

 

It would be great if you could explain a little about attenuators.

https://community.fs.com/blog/guideline-for-fixed-fiber-optic-attenuator.html

 

https://community.fs.com/blog/basics-of-fiber-optic-attenuator.html

 

some good basic reading there

 

to put it basically

 

singlemode, which 'usually' can be defined by the SFPs being 1310 or 1550nm and the patch leads being yellow its designed for long distances, usually 1km to 100km+

 

to achieved this that have to pump up the laser power and make the receiver more sensitive

over longer distances, the fibre, joints and patches will add attenuation.

 

if the the received level is too low you will get packet loss and errors, to fix that its either a higher power/longer range SFP or fix the fault in the fibre run if thats the cause

 

if the received level is too high, you can shorten the lifespan of the SFP by burnout of the receiver, the articles above say you can also introduce errors into the link, but I have questioned some of our Senior IP Engineers about that and they have never seen it, but we dont do silly things like put in 120km SFP on a 2 mt run
anywho, to fix high recieve levels, you need to attenuate the laser, hence attenuators

how do you work out what attenuator you need?

 

you need 

the receiver sensitivity 

and a power measurement of light received

 

the receiver sensitivity 

this is stated in the datasheet of the SPF

 

and a power measurement of light received

so logging onto the equipment and querying the SFP to  state its receive power

or using a power meter https://www.fs.com/au/c/optical-power-meter-35 to measure the light coming out of the end of the fibre patch lead before it hits the Rx of the SPF

 

using https://www.fs.com/au/products/12622.html which is the FS equivalent of the After Dark Constellation SFP, its transmit power is -9.5dBm and its Receiver Sensitivity is< -23dBm

I would be planning on around 16dBm, so a 7dB attenuator would be needed, one in both directions on a couple meter patch lead

 

 

this is why you use Multimode on short runs, its a LED based light and you don't have these problems 

we use 1000s of SPF in our network and now use only Singlemode and attenuate, because we have the know how to do it and means we can just stock less spares

 

 

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On 11/03/2020 at 10:11 PM, dbastin said:

For interest, After Dark Constellation SFP modules and fibre cable ... 

https://www.adark.co/collections/online-shop-special-on-grand-opening/products/copy-of-uptone-etherregen-femto-switch-pre-order-enjoy-worldwide-free-shipping-tax-free

BTW, the link does not go to a special deal on ER.

 

the SFPs are Cisco CN8ID42AAA GLC-LH-SM 1Gbps 1000Base-LX/LH Single-Mode Fiber 10km 1310nm Duplex LC Connector SFP Transceiver Module

 

the patch lead is a commscope

 

both good industry leading gear... not sure where they got the "audiophile' tag from though

 

2 SFP and a 5mt lead $280 AUD

 

 

here is the Fiberstore equivalent SFP (x2)

https://www.fs.com/au/products/12622.html

and 5mt lead

https://www.fs.com/au/products/68297.html

throw in a couple of attenuators 

https://www.fs.com/au/products/48525.html

 

$53

 

or go the multimode route

2 x https://www.fs.com/au/c/sfp-transceivers-57 

5mt lead https://www.fs.com/au/products/43135.html

 

$38

 

 

just be aware

 

looking at what is on that link, the uptone etherregen switch uses cisco compatible SPFs

 

the other end that your are plugging into (a brand "X" switch) will need a brand "x" compatible SFP

 

 

 

will any of this make things sound better
 

I don't F-ing know

Edited by Hytram
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1 hour ago, Hytram said:

will any of this make things sound better

 

I don't F-ing know

Thank you for your posts on SFPs. I do not know enough and likely will not go down that rabbit hole with my EtherREGEN (which I am happy with). Some people say SFPs sound different; I'll pass on that.

Edited by Snoopy8
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Yeah, I am a fence sitter and would love to explore this part of the Audio world, but simply don't have the time ATM (maybe 14 days isolation might change that... Not me, yet)  

 

But in the mean time, if can help out anyone who wants to experiment and share my knowledge, I am happy to help when I can. 

 

My job in the real world is to build the solid foundations so the experts and weave their magic 

Edited by Hytram
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3 hours ago, Hytram said:

will any of this make things sound better
 

I don't F-ing know

Well, I hope to find out I've not blown $200+ too much.  After Dark use the term audiophile a bit too much however in this case they EMI treat the SFP which I assume gains an improvement. Is that worth $200?  I'll get 2 stock versions of the same SFPs to compare let you know.

 

I may also compare with the Sonore certified SFPs and fibre too.

3 hours ago, Hytram said:

the other end that your are plugging into (a brand "X" switch) will need a brand "x" compatible SFP

Aw dang!  The rabbit hole has yet another tunnel.  I am considering Sonore Optical Module.  Sonore has System Optique certified stuff, the fibre cable and SFPs are multi mode though, and they dont have a Contact Us to ask them for compatibilty info ...

 

4 hours ago, Hytram said:

so a 7dB attenuator would be needed, one in both directions on a couple meter patch lead

If there is one at the end of each direction, the other half of each connector wont reach into the SFP.  So do we assume both attenuators go in the 2 sides of just 1 connector?

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I note the ER review on Audiophile Style (referred to above) states ...

 

I settled on the Startech SFP1000ZXST 1550nm/80km transceivers, with a 2m cable. Since these transceivers are designed for long  distances (note the 80km rating), I used 10dB attenuators, which also improved SQ. This combination was notably better sounding than the (Sonore SyatemOptique) TP-Link transceivers. With this configuration, the oM leapfrogged the The Linear Solution OCXO switch. (upsteeam of ER). The oM added even more dimensionality, more meat on the bone, while also opening up the soundstage.

 

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7 hours ago, dbastin said:

 

I may also compare with the Sonore certified SFPs and fibre too.

Aw dang!  The rabbit hole has yet another tunnel.  I am considering Sonore Optical Module.  Sonore has System Optique certified stuff, the fibre cable and SFPs are multi mode though, and they dont have a Contact Us to ask them for compatibilty info ...

 

Sonore look like they use TP lINk SFPs, nothing special

"systemOptique Certified SFP module" sounds exotic, its marketing speak for  "we plugged it in and it worked"

 

and from https://static.tp-link.com/JetStream - FAQ_Hardware.pdf?configurationId=22931

 

7 Does the Switch Support the Optical Modules of Other Vendors?

Generally, the switch supports the optical modules of other vendors as the TP-Link switches are in accordance with the industrial standard. However, some vendors customize their products for specific purposes and their products may not be compatible with the TP-Link switches. Here you are recommended to choose SFP modules produced by TP-Link, which deliver high speeds while extending your network.

 

 

so I would say any Generic SFP will work in both

https://www.fs.com/au/products/75326.html

 

only the big boys lock their gear down to their own SFPs and there are ways around that

 

7 hours ago, dbastin said:

 

If there is one at the end of each direction, the other half of each connector wont reach into the SFP.  So do we assume both attenuators go in the 2 sides of just 1 connector?

 

 

from

https://community.fs.com/blog/guideline-for-fixed-fiber-optic-attenuator.html

 

How to Use Fixed Fiber Attenuator?

As shown in the figure below, fixed fiber optic attenuators should be always installed at the receiver end of the link (X in the drawing). This is because it's more convenient to test the receiver power before and after attenuation or while adjusting it with your power meter at the receiver, plus any reflectance will be attenuated on its path back to the source.

4.png.e5c6e910e6d16ade88633d6f554b98b8.png

 

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Hmm, it looks like an attenuator will make the connector it is inserted onto a little longer.  And if that is correct, then one of the two  parts of the connector will be longer than the other, and thus will not fit properly into SFP.  Am I missing something?

 

Or maybe installation is not diy?

20200313_125715.jpg

Screenshot_20200313-124752_Chrome.jpg

Screenshot_20200313-125317_Chrome.jpg

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You have to pop the clip off and yes it makes them offside

 

We pop the clip off all the time, you have to when you 'roll the fibres' which means swapping Tx/Rx on the link, usually when multiple leads are in the link. Some people put the clip back on, I leave it off indicating that the patch lead has been rolled.  

 

20200313_201525.thumb.jpg.5bbc0a62f04f7cbafe802e6cf6fc0932.jpg

 

Or if you are just running one patch lead between the 2 SFPs you could just put both at one end.. If will work fine, you just wouldn't do that over Kms, the attenuators are not directional 

 

20200313_201857.thumb.jpg.6c78e6466d94e94255b70f370f9cdea5.jpg

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