Re: optical circulator as a bidirectional one fiber solution

[Ben Cannon <ben () 6by7 net>]

What about 100Ghz ITU spacing on the tx, are the rx optics broad enough to take the off-band input?

-Ben

> On Aug 13, 2018, at 3:19 PM, Jameson, Daniel <Daniel.Jameson () tdstelecom com> wrote:
>
> You would still need to frequency shift TX and RX.  They are travelling opposite directions on the same piece of 
> glass;  as the traffic rate increases the likelihood of collisions increases and you’ll start to get errors.  The 
> collision would either cancel the ‘bit’ or act like OBI and get erroneous bits and checksum errors or missing chunks 
> from the constellation.  There are BIDI 100G transceivers for Multi-mode available today based on the Foxconn optics, 
> I’d imagine we’ll see BIDI for the O and C bands in the next 18 months.
>  
> From: NANOG [mailto:nanog-bounces () nanog org] On Behalf Of Eric Kuhnke
> Sent: Monday, August 13, 2018 3:56 PM
> To: ben () 6by7 net; nanog () nanog org list
> Subject: Re: optical circulator as a bidirectional one fiber solution
>  
> For 1 and 10Gbps OOK modulation yes, but not for something like a ITU DWDM grid channelized or tunable coherent 
> optic. In which the (QPSK, 8PSK, 16QAM) signal has a specific THz width and frequency not unlike a radio operating in 
> a very, very narrow waveguide.
>  
>  
> On Mon, Aug 13, 2018 at 1:57 PM Ben Cannon <ben () 6by7 net> wrote:
> Good news about almost all optics, their Rx window is pretty wide. Meaning a 1550nm optic will activate the receiver 
> on a 1560nm optic just fine (and probably anything in the 1500nm band).  Careful use of specialized single strand 
> DWDM muxes (FS.com) can yield great bidi-like results with increased channel count. 
>
> -Ben
>
> On Aug 13, 2018, at 10:49 AM, Eric Kuhnke <eric.kuhnke () gmail com> wrote:
>
> Something that is broadly the same as a coherent 100G QPSK single wavelength optical module, but in two different 
> frequencies, and a passive CWDM mux/demux prism at each end might work. The limitation would be availability of 
> optics for a modern 100G MSA that are both coherent and Tx/Rx at two different THz frequencies.
>  
> Or with some box and vendor equipment in between, such as:
>  
> http://cdn.extranet.coriant.com/resources/Application-Notes/AN_Groove_Bidirectional_Fiber_74C0169.pdf?mtime=20180206023321
>  
> On Tue, Aug 7, 2018 at 1:00 PM Daniel Corbe <dcorbe () hammerfiber com> wrote:
> On 8/7/2018 15:46:03, "Baldur Norddahl" <baldur.norddahl () gmail com> 
> wrote:
>
> > Hello
> >
> > There is a lack of bidirectional one fiber (BIDI) options for 40G and 
> > 100G optics. Usually BIDI is implemented using two CWDM wavelengths, 
> > one for tx and one for rx. However there is also a lack of CWDM and 
> > DWDM options for 40G and 100G.
> >
> > Would it be possible to use an optical circulator like this one 
> > (customized to 1310 nm)?
> >
> > https://www.fs.com/de/en/products/33364.html
> >
> > Combined with a traditional two fiber 1310 nm 10 km 40G QSFP module 
> > like this: https://www.fs.com/de/en/products/24422.html
> >
> > The link distance would be 5 km.
> >
> > The optical circulator separates tx and rx by the direction the light 
> > travels in. It would work even though both directions use the same 
> > wavelength. There will likely be some reflection but hopefully 
> > attenuated enough that it is regarded as background noise.
> >
> > Has anyone done this? Any reason it would not work?
> >
> > Regards,
> >
> > Baldur
>
> The main issue you're going to run into (especially trying to plug 
> anything into a DWDM shelf) is 40G and 100G transceivers usually emit 4 
> lanes of traffic instead of a single lane like 10 and 1G optics do.
>
> I'd imagine that's why there are so few solutions that don't involve 
> things like OTN.