Re: [8023-10GEPON] Upstream Wavelength
Dear Mr. Jim Farmer
This is Akihiro Otaka from NTT.
I don't understand your concern about 1260 nm
wavelength.
Fiber type of 10G-EPON is IEC 60793-2 B1.1 and B1.3.
The maximum cable cut-off wavelength is 1260 nm.
I think 1260-1280 nm is not dangerous.
And I understand it is not necessary to allocate
100 nm band for 10G-EPON upstream.
So I think narrow and enough bandwidth is prefer for
future use of wavelength. (i.e. co-ex with enhanced band
G-PON)
Best regards,
Akihiro Otaka
Jim Farmer:
> I'm campaigning for a comment submitted barely in time for the May
> meeting. The 10 Gb/s upstream wavelength is currently defined as 1260
> to 1280 nm. See for example, Table 91-6 and many following references.
> This wavelength is also specified for the for 10/1GBASE–PRX–D3 (Table
> 91-7)*. * According to my expert, this wavelength is dangerous because
> single mode fiber becomes overmoded at about 1260 nm, resulting in a
> second propagation mode at a different velocity. In addition, this
> wavelength will be overlapped by the normal 1310 nm 1 Gb/s upstream
> optical signal. This is acknowledged in the proposed document:
>
> *91A.3.2 Upstream wavelength allocation*
> The 1.25 GBd upstream transmission uses the 1270 – 1360 nm wavelength
> band, as specified in Clause 60. The 10.3125 GBd upstream transmission
> uses the 1260 – 1280 nm wavelength band, as specified in Clause 92. The
> two wavelength bands overlap, thus WDM channel multiplexign {sic} cannot
> be used to separate the two data channels.
>
> An OLT supporting both upstream channels must use TDMA techniques to
> avoid collisions between transmissions originating from different ONUs.
>
>
> We presume that the reason for specifying a separate wavelength band is
> to afford the opportunity to build a mixed-mode OLT receiver (capable of
> receiving both 1 Gb/s and 10 Gb/s) that is optimized for 10 Gb/s.
> However, this would imply a WDM at the OLT receiver, whose loss could
> rob a good bit of the improvement to be gained. This is acknowledged in
> Section 91A.5. Furthermore, this implies tight standards for the ONT 10
> Gb/s laser, which could add cost. Since we have already acknowledged
> that the OLT will need to use TDMA to separate the 1 Gb/s from the 10
> Gb/s upstream, we propose that the 1260-1280 nm upstream requirement be
> dropped, and that upstream transmitters for both speeds use the same
> wavelength band.
>
> Figure 91A-5 shows some dual-rate receiver architectures that seem
> practical and which can provide optimization for each speed without
> having to use dual receivers. Implicit in these receivers is the
> ability to not only switch bias, but to also switch low pass filtering -
> since you have electrical amplification ahead of the filters, you can
> even leave both filters connected to the source and their respective
> loads all the time, so that the transient response of the filter is
> minimized.
>
> This seems a better solution than using dual wavelengths, with the
> potential issues of the 1260 - 1280 nm band.
>
> Thanks,
> jim
>
> Jim Farmer, K4BSE
> Chief Technical Officer,
> Wave7 Optics, Inc.
> An Enablence Technologies Company
> 1075 Windward Ridge Parkway
> Alpharetta, GA 30005 USA
> 678-339-1045
> 678-640-0860 (cell)
> jim.farmer@w7optics.com
> _www.wave7optics.com_ <file://www.wave7optics.com>
>