Dear all,
I’ll start the ball rolling with a
discussion of definitions.
I would like to speak in favor of the
system of definitions that are established in G.957.
The text below is cut from the document (I
hope this snippet falls within the bounds of ‘fair use’. In any
case, the document will become open on Jan 1st, 2007, so we needn’t
be too concerned.)
I have highlighted the key text that, in
my humble opinion, have been the biggest source of difference.
The biggest “style statement”
that this approach makes is one of ‘who has the responsibility’. The
manufacturers have the responsibility for the transmitters and receivers. The
operators have the responsibility for the fiber plant. No crossing of the
lines is allowed.
So, the manufacturer’s must provide
a guarantee that their transmitter will be no worse than the specification
(output power, eye-mask, and spectral characteristics, mainly), and that their
receivers will work as specified, even given the worst-case transmitter. No
fiber impairments are included here, and the ultimate link-test is done using
an attenuator.
Similarly, the operators must guarantee
that their fiber falls within the spec. Note that this goes beyond setting the
optical loss. The operators are responsible for any other impairments that are
caused by their fiber, such as dispersion, reflections, polarization, nonlinear
self-impairments, and non-linear crosstalk impairments. If it’s caused
by the fiber, it is the operator’s engineering responsibility.
Now: of course, as we prepare the
standard, we will consider all these impairments, and we will set the benchmark
for how many dB’s should be allocated to them. Also, when the standard
finally boils down to listing a number, it is the ‘attenuation maximum’
that gets the top billing. You will notice that there isn’t even a name
defined for the (minimum launched power) – (receiver sensitivity). That
is not a number that is expected to be used in applications.
Anyway, that’s my two cents.
Sincerely,
Frank Effenberger
8 Optical engineering
approach
The selection of applications and set of
optical parameters covered by this Recommendation are chosen to reflect a
balance between economic and technical considerations to provide the
possibility for transverse compatible systems using the synchronous digital hierarchy.
This clause describes the use of the parameters in Tables 2 to 4 to obtain a
common system design approach for engineering SDH optical links.
8.1 Design assumptions
To meet the greatest number of application
possibilities with the smallest number of optical interface component
specifications, three-interface categories are assumed for each level of the
SDH hierarchy. These are distinguished by different attenuation/dispersion
regimes rather than by explicit distance constraints to provide greater flexibility
in network design while acknowledging technology and cost constraints for the
various applications.
Worst-case, end-of-life
parameter values are specified in this Recommendation to provide simple design
guidelines for network planners and explicit component specifications for
manufacturers. As a result, neither unallocated system margins nor equipment
margins are specified and it is assumed that transmitters, receivers, and cable
plant individually meet the specifications under the standard operating
conditions. It is
recognized that, in some cases, this may lead to more conservative system
designs than could be obtained through joint engineering of the optical link,
the use of statistical design approaches, or in applications and environments
more constrained than those permitted under the standard operating conditions.
8.2 Worst-case design
approach
For a worst-case design approach, the
optical parameters of Tables 2 to 4 are related as shown in Figure 3. In
loss-limited applications, a system integrator may determine the appropriate
application code and corresponding set of optical parameters by first fixing
the total optical path attenuation, which should include all sources of optical
power loss and any cable design margin specified by the system integrator. For
those situations in which the system attenuation falls within the attenuation
overlap region of two applications, then either set of optical parameters would
apply. The most economical designs will generally correspond to the application
code having the narrower attenuation range. For
each installation, it should be verified that the total optical path penalty,
which includes combined dispersion and reflection degradations, does not exceed
the value given in 6.4.4 and Tables 2 to 4 since a higher value may lead
to rapidly deteriorating system performance.
Figure 3/G.957 –
Relationship of the optical parameters
For dispersion-limited systems, the system
integrator may select an appropriate application code and corresponding set of
optical parameters by determining the total dispersion (ps/nm) expected for the
elementary cable section to be designed. The most economical design generally
corresponds to the selection of the application having the smallest maximum
dispersion value exceeding the dispersion value determined for the system
design. Again, the total optical path power
penalty should be verified as described above.
From: Hajduczenia,
Marek [mailto:marek.hajduczenia@SIEMENS.COM]
Sent: Tuesday, November 21, 2006
6:02 AM
To:
STDS-802-3-10GEPON@listserv.ieee.org
Subject: [8023-10GEPON] Ad hoc on
10GEPON channel model
Importance: High
Dear all,
so far, 10 people registered for participation in the 10GEPON
channel model ad-hoc. Here is the complete list:
1. Marek Hajduczenia (chair), Siemens Networks S.A. (marek.hajduczenia
AT siemens.com)
2. Glen Kramer, Teknovus Inc. (glen.kramer AT teknovus.com)
3. Frank Effenberger, Hauwei (feffenberger AT huawei.com)
4. Sergey Y. Ten,
5. Keiji Tanaka, KDDI Labs, (kj-tanaka AT kddilabs.jp)
6. Eric Lynskey, Teknovus Inc., (eric.lynskey AT teknovus.com)
7. Paul Kolesar, CommScope Enterprise® Solutions, (PKOLESAR AT systimax.com)
8. Tsutomu Tatsuta, NTT, (tatsuta AT ansl.ntt.co.jp)
9. Robert Lingle, OFS Optics, (rlingle AT ofsoptics.com)
10. Dawe Piers, AvagoTech, (piers.dawe AT avagotech.com)
I would like to first thank everybody for their will to
participate. Let's hope that this ad-hoc is as successful as the last one.
Regarding the tasks related with this particular ad-hoc, I would
like to suggest some of them. Please feel free to provide any comments /
feedback / suggestions.
Task 1: Channel model definitions:
- conformance between 802.3 definitions and
channel model spreadsheet
- establish definitions for loss budget,
channel insertion loss, power budget margin and its individual components
Task 2: Identification of necessary channel model extensions to be
included in the new spreadsheet
- non-linear transmission channel impairments
(e.g. SBS?)
- RF video overlay (?)
- realistic PSC loss modelling
- any other ?
Task 3: Overhaul of the Excel spreadsheet and update to meet
requirements of the 10GEPON
- separation of the parameter sheet and results
sheet to increase readability ...
- add missing channel impairment parameters
(e.g. SBS threshold)
- add RF channel modelling and include all
related transmission impairments (+ penalties)
- add PSC component modelling as well as
include PSC loss in the channel model
- any other which are identified by
the ad-hoc
Task 4: Model compatibility issues
- is Excel spreadsheet sufficient to model all
the effects in 10GEPON system?
- what are other options for publicly available
software which could do the job better?
- do we need to improve the modelling precision
to remove 1-2 dB overshoot which was signalled in the case of 10GE links ?
- any other compatibility issues ?
I would appreciate if the participants could identify the tasks
which are of their primary interest. Feel free to email me with any suggestions
regarding changes, wording, addition of tasks etc.
If possible, I would also like to start the discussion on the
defintions of individual channel parameters, since it was suggested that we
ought to clarify finally concepts like channel insertion loss and whether power
budget margins should be internally divided into channel insertion loss margins
and other components related with Rx/Tx equipment. I would like to suggest
discussion based on the presentation from Tanaka-san, available at: http://grouper.ieee.org/groups/802/3/av/public/2006_11/3av_0611_tanaka_1.pdf
I am looking forward to hear Your opinions on this topic.
Best wishes
Marek Hajduczenia (141238)
SIEMENS
Networks S.A. - IC COM D1 R
Rua Irmãos
Siemens, 1
Ed. 1, Piso 1
Alfragide
2720-093 Amadora
Portugal
* Marek.Hajduczenia@siemens.com
http://marekhaj.easyisp.pl/index.php
(+351.21.416.7472 4+351.21.424.2082