[time-nuts] USB over optical fiber

[Scott McGrath]

Wow,  cost cutting at work I have the corning one but its 3 years old Remember when FCC certification meant something for EMC 





> On Dec 6, 2019, at 3:21 PM, David Van Horn <david.vanhorn at backcountryaccess.com> wrote:
> 

Well, it arrived, and it is NOISY.  ☹
It's pushing out longitudinal noise along the cable, and it's deafening my receiver.

After doing some research this morning, it appears that they do the DATA optically but power is taken on copper wires, and I'm betting a boost switcher to compensate for the voltage drop in the 28 ga wire.

https://www.corning.com/microsites/coc/ocbc/Documents/CNT-075-AEN.pdf



I have another candidate arriving today which will require a 5V supply inside the cage, but I can do that with batteries and a linear regulator, much quieter.


--
David VanHorn
Lead Hardware Engineer

Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO  80301 USA
phone: 303-417-1345  x110
email: david.vanhorn at backcountryaccess.com 

-----Original Message-----
From: time-nuts <time-nuts-bounces at lists.febo.com> On Behalf Of David Van Horn via time-nuts
Sent: Thursday, December 5, 2019 6:15 AM
To: Scott McGrath <scmcgrath at gmail.com>; Discussion of precise time and frequency measurement <time-nuts at lists.febo.com>
Cc: David Van Horn <david.vanhorn at backcountryaccess.com>
Subject: Re: [time-nuts] USB over optical fiber

Ok, thanks for the info.  My unit should be arriving today or tomorrow.

--
David VanHorn
Lead Hardware Engineer

Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO  80301 USA
phone: 303-417-1345  x110
email: david.vanhorn at backcountryaccess.com 

-----Original Message-----
From: Scott McGrath <scmcgrath at gmail.com>
Sent: Wednesday, December 4, 2019 9:16 PM
To: Discussion of precise time and frequency measurement <time-nuts at lists.febo.com>
Cc: David Van Horn <david.vanhorn at backcountryaccess.com>
Subject: Re: [time-nuts] USB over optical fiber

You may still have a problem,  That said most of your noise power is going to come from your USB device itself and perhaps the power supply 

That said ive never really had a problem doing similar testing using small chambers from ETS-Lindgren and similar vendors using the Corning interface.     

That said i’d recommend you go a step up to the Newnex and similar devices they are 3x the price but the fiber interlink is just a standard fiber LC-LC patch cord.    

With the low cost interface crimp its cable once accidentally you are buying a new one.    

With the newnex you are buying a 20-30 dollar patch cord.

All that said performance is the same in the end but the newnex and similar have an advantage in an open lab.   For permanent installation in raceway the cost advantage is with the one piece units.

Content by Scott
Typos by Siri

> On Dec 4, 2019, at 10:07 PM, Davida  Van Horn via time-nuts <time-nuts at lists.febo.com> wrote:
> 

I'm not too worried up there, my receivers are working at 457 kHz. 

-----Original Message-----
From: Scott McGrath <scmcgrath at gmail.com>
Sent: Wednesday, December 4, 2019 12:14 AM
To: Discussion of precise time and frequency measurement <time-nuts at lists.febo.com>
Cc: David Van Horn <david.vanhorn at backcountryaccess.com>
Subject: Re: [time-nuts] USB over optical fiber

Its not so much the noise from the interface its the USB device itself i’d worry about as USB 3.0 generates RF signals up to 3 GHz.   And also has fairly strong signals in the 2.4 GHz ISM band.

Content by Scott
Typos by Siri

> On Dec 4, 2019, at 12:07 AM, David Van Horn via time-nuts <time-nuts at lists.febo.com> wrote:
> 

I suppose this is vaguely time-nutty. 😊

I have an application where I need to take USB into an EMC faraday cage.
I see a number of optical fiber implementations available, and the prices ($200-300) are acceptable, but I’m worried about noise that the downstream end may cause, since it will need to be inside the cage.

Does anyone have experience with these?  Ones to stay away from?



--
David VanHorn
Lead Hardware Engineer

Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO  80301 USA
phone: 303-417-1345  x110
email: david.vanhorn at backcountryaccess.com<mailto:david.vanhorn at backcountryaccess.com>

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