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RE: [EFM-P2P][EFM] PMD considerations

I find this a very interesting question and worthy of a presentation. While it seems that this can be done, I do not see anything in the objectives that would ensure that it will be done. Similarly, I see no presentation (proposal) to recommend that previous, legacy, technologies be supported. The exception to this is Kevin Daines presentation on OAM ( which recommends legacy support for OAM.

If this direction is adopted (I hope it is), that does not mean that the potential for legacy support is fully realized.

Similarly, support of EFM temperature conditions would also be required.

In short, specific, unambiguous proposals go a long way.


| -----Original Message-----
| From: George, John Emanuel (John)** JV ** 
| [mailto:johngeorge@xxxxxxxxxx]
| Sent: Wednesday, January 09, 2002 3:06 PM
| To: 'bob.barrett@xxxxxxxxxxxxxxx'; Ulf Jönsson F (ERA);
| stds-802-3-efm@xxxxxxxxxxxxxxxxxx
| Subject: RE: [EFM-P2P][EFM] PMD considerations
| All,
| I appreciate the discussion generated by this thread, but 
| please respond to
| my primary question, restated more concisely as:
| Will an existing 802.3 PMD (100BASE-FX for example) that 
| incorporates the
| OAM&P functionality specified in 802.3ah be 802.3ah "compliant"? My
| understanding (from a discussion with Howard) is that according to the
| document structure of 802.3 the answer is yes, but I would 
| like confirmation
| of this. 
| Regards,
| John George
| OFS - Fitel
| Fiber Offer Development Mgr
| 770-798-2432 (v)
| 770-798-3872 (fax)
| -----Original Message-----
| From: Bob Barrett [mailto:bob.barrett@xxxxxxxxxxxxxxx]
| Sent: Saturday, December 22, 2001 12:01 PM
| To: George, John Emanuel (John)** JV **; Ulf Jönsson F (ERA);
| stds-802-3-efm@xxxxxxxxxxxxxxxxxx
| Subject: RE: [EFM-P2P][EFM] PMD considerations
| Quick comment:
| All three of the OAM transport proposals (ipg, preamble, 
| in-frames) will
| cost about the same to implement in 1GE p2p (in our experience /
| expectation). In-frames may cost a little more if one has to 
| add a MAC, even
| then it's peanuts. I would think that we will all be using similar
| 'available today' ICs for this.
| I would imagine that the same is true for p2mp. I can't guess 
| at copper. May
| be Hugh can have a stab at that one.
| Thanks
| Bob
| -----Original Message-----
| From: George, John Emanuel (John)** JV ** 
| [mailto:johngeorge@xxxxxxxxxx]
| Sent: 21 December 2001 18:56
| To: 'Bob Barrett'; Ulf Jönsson F (ERA);
| stds-802-3-efm-p2p@xxxxxxxxxxxxxxxxxx; 
| stds-802-3-efm@xxxxxxxxxxxxxxxxxx
| Subject: RE: [EFM-P2P][EFM] PMD considerations
| All,
| One question that might assist the decision regarding PMDs is 
| to what degree
| may existing Ethernet PMDs be used within an 802.3ah network.
| 1) Some in the group state that the 802.3 document structure 
| would allow the
| use of existing 802.3 PMDs in an EFM network. This would 
| permit service
| providers to benefit from the low cost of existing high volume PMDs.
| 2) Others have stated that if OAM&P functions are integrated 
| within the PCS,
| such legacy Ethernet PMDs would require changes to be used in 
| an 802.3ah
| network. Even with these changes to silicon, however, the PMD 
| would still
| benefit from the use of existing high volume low cost optics 
| (or copper).
| But would it still be 802.3ah compliant?
| 3) If an existing 802.3 PMD must be changed to accommodate 
| OAM&P to be EFM
| compliant, maybe a simple statement in the standard that 
| "existing 802.3
| PMDs employing the OAM&P functions defined in 802.3ah are 
| 802.3ah compliant"
| would be appropriate.
| Is 1 or 2 or both correct? If one had to incorporate EFM OAM&P into an
| existing 802.3 PMD, what would be the cost impact?
| Regards,
| John George
| OFS - Fitel
| Fiber Offer Development Mgr
| 770-798-2432 (v)
| 770-798-3872 (fax)
| -----Original Message-----
| From: Bob Barrett [mailto:bob.barrett@xxxxxxxxxxxxxxx]
| Sent: Tuesday, December 18, 2001 5:00 PM
| To: Ulf Jönsson F (ERA); stds-802-3-efm-p2p@xxxxxxxxxxxxxxxxxx;
| stds-802-3-efm@xxxxxxxxxxxxxxxxxx
| Subject: RE: [EFM-P2P][EFM] PMD considerations
| Dear all
| I went to a customer meeting today and had them tell me that 
| 100M SMF was an
| EFM work in progress. News to me :-). He may not have been 
| correct, but he
| is the customer.
| The point being that this customer was deploying 100M SMF and 
| would like it
| to be standardised. I advised them to at least visit the 
| email archive on
| the reflector, if not join the mailing list.
| Thanks
| Bob
| -----Original Message-----
| From:
| []On Behalf Of Ulf
| Jönsson F (ERA)
| Sent: 17 December 2001 19:49
| To: stds-802-3-efm-p2p@xxxxxxxxxxxxxxxxxx;
| stds-802-3-efm@xxxxxxxxxxxxxxxxxx
| Subject: [EFM-P2P][EFM] PMD considerations
| Hi all,
| The following text brings up some considerations regarding 
| the EFM optical
| PMD from a component perspective. It has been written with 
| great help from
| our Ericsson internal experts on the optoelectrical component side.
| For the physical medium, i.e. the O/E-converters and the 
| fiber connecting
| them, a few aspects may be high-lighted:
| 1. Data rate
| 2. Single or multimode fiber
| 3. Single or dual fiber
| We will discuss these aspects in more detail and will also 
| try to draw a
| conclusion. Hopefully this will start a discussion on the 
| reflector that may
| make it easier for us to agree on a (few) baseline 
| proposal(s) in March.
| 1. Data rate
| ------------
| The choice is between 100Mbps and 1000Mbps. Of course one 
| must pay a premium
| for a tenfold speed increase, throughout the entire system (A 
| more detailed
| cost analysis will be presented at the January interim). 
| Optimizing an O/E
| converter design for 100Mbps instead of 1000Mbps means
| * inherent improvement of receiver sensitivity.
| * lowered demands on output optical power (consequence of above).
| * lowered demands on thermal management (both inherent, due 
| to lower speed,
| and consequence of above)
| * lower crosstalk
| All these factors will facilitate the module design, simplify 
| the assembly
| and increase the yield, thus substantially lower the costs. 
| The argument for
| 1000Mbps, that the higher volumes for this product will yield 
| lower cost,
| neglect the impact of EFM as a cost driving application itself. This
| application should in itself be enough to create sufficient production
| volumes. Thus, it does not seem optimal to let the vast majority of
| connections where 100Mbps is sufficient pay that cost 
| premium, especially as
| a P2P topology allows for relatively easy individual line 
| upgrades. On the
| other hand, 1000BASE-X will in a P2P topology be appropriate 
| for premium
| subscribers and for aggregate traffic higher up in the access 
| network and it
| will of course be appropriate to use in a P2MP network. 
| Hence, we see a need
| to include both a 100Mbps PMD and a 1000Mbps PMD in EFM.
| 2. Singlemode or multimode fiber
| --------------------------------
| As of now, multimode systems are significatly more low-cost 
| than singlemode
| systems. Though this difference will decrease as the 
| singlemode component
| volumes increase, a certain difference will always remain, 
| due to the less
| stringent geometrical tolerances in a multimode system. For those
| applications where multimode systems are appropriate, there 
| is no need to
| pay the singlemode premium. What is important is that a large 
| number of
| connections require singlemode systems, both due to present distance
| limitations and to future upgradeability.
| 3. Single or dual fiber
| -----------------------
| O/E converters for a single fiber system are inevitably more 
| expensive than
| those for a dual fiber system, due to the higher complexity. Just as
| inevitable is the fact that this difference will be more than 
| compensated at
| very long link lengths. The question is the cross-over 
| distance, and the
| distribution of potential installations below and beyond this 
| cross-over,
| respectively. If it is regarded necessary to include both 
| options in the
| standard, how can that be made with a minimum of effort? Let 
| us examine the
| implications on the basic parameters.
| 3.1. Power budget
| A dual fiber system can, and should, allow for a wide output 
| power range, in
| order to achieve high production yields in a low-cost 
| assembly process.
| If wavelength separation is used in the single fiber case, the power
| specification should be equal for dual and single fiber. The extra
| attentuation caused by the splitters are hidden inside the 
| converters, and
| just has to be compensated for by extra laser power and 
| increased internal
| receiver sensitivity, respectively.
| The single wavelength case is more difficult, due to 
| constraints imposed by
| the reflection crosstalk. In order not to have completely unrealistic
| back-reflection demands, the span of the allowed output power must be
| minimized. Otherwise, the transmitted power from a "low-end" 
| module would
| drown in the reflected power from a relatively high power 
| module. Assume
| e.g. a power span of 10dB, a link budget of 10dB and a 
| required SNR of 10dB.
| This implies a total allowed near-end reflection of below 
| -30dB, which is
| not easily achieved.
| Thus, if the output power range for dual fiber is e.g. -5dBm 
| to -15dBm, the
| single fiber version should probably be a part of that, something
| like -12dBm to -15dBm.
| 3.2. Wavelength
| For dual fiber systems, the operating wavelegth window can, 
| from a component
| perspective, be selected freely within the SM fiber window 
| 1300-1600mn. A
| wavelength separated single fiber system of course have 
| strict requirements
| regarding this matter. For such a system it is also required 
| to have two
| types of transceivers, for each end of the connection. 
| Depending on the
| actual implementation of the components for a single 
| wavelength single fiber
| system, some wavelength restrictions could be needed, as the 
| splitters might
| have a wavelength dependence.
| 3.3. Connectors
| For dual fiber, several types of standard connectors should 
| be allowed, e.g.
| MT-RJ, LC, MU, etc. The requirements on connector performance 
| can be kept
| low, to reduce costs, since the desired power budget is 
| easily achieved, and
| there is no back-reflection problem.
| The same should be valid for single fiber WDM systems, even 
| though the power
| budget is a bit harder to meet in this case. Possibly the connector
| attenuation must be a bit tighter specified.
| For non-WDM single fiber, the crosstalk problem make low reflection
| connectors necessary throughout the entire system.
| Conclusion
| ----------
| Eight different P2P relevant configurations, each with its 
| own merits and
| drawbacks, can be distinguished. These are:
| 100 Mbps MMF dual fiber
| 100 Mbps SMF dual fiber
| 100 Mbps SMF single fiber
| 100 Mbps SMF single fiber WDM
| 1000 Mbps MMF dual fiber
| 1000 Mbps SMF dual fiber
| 1000 Mbps SMF single fiber
| 1000 Mbps SMF single fiber WDM
| of these three already exist as standards within IEEE 802.3, namely
| 100 Mbps MMF dual fiber
| 1000 Mbps MMF dual fiber
| 1000 Mbps SMF dual fiber
| 100 Mbps SMF dual fiber is at present not an Ethernet standard. Still,
| components exist and are used when needed. ANSI has 
| standardized a PMD for
| 100Mbps FDDI over SMF (ANSI X3.184-1993). The corresponding 
| FDDI standard
| for MMF is used as a reference for Ethernet 100BASE-FX.
| The need to incorporate 100 Mbps SMF dual fiber within the 
| Ethernet family
| is obvious. Since it also seems to be the most appropriate 
| choice for a
| large number of EFM connections, it should be the first 
| choice for an EFM
| PMD. This PMD should of course to a large extent be based on 
| the 100BASE-FX,
| with the physical media specifications optimized for low-cost 
| components
| with sufficient performance.
| To give a variety of options, it seems reasonable to also incorporate
| 100Mbps MMF dual fiber as well as 1000Mbps dual fiber in EFM. 
| As already
| being Ethernet standards, this should be possible without 
| much extra work.
| Single fiber systems are a bit more complicated, since the 
| requirements are
| more closely connected to the actual implementation, and a 
| PMD are more
| different from existing standards. One way to go, since the 
| requirements
| (with wavelength for the WDM solutions as a possible 
| exception) is within
| the dual fiber specification, only tighter specified, would 
| be to use the
| dual fiber PMD as a base and have different categories within 
| that. These
| could be one or two single fiber options, but also extended 
| temperature and
| extended range dual fiber options. Depending on the progress 
| of the work,
| the single fiber options can either be tightly defined within 
| the base PMD,
| or kept rather open for different manufacturer 
| implemenations. The important
| issue is to let the time-schedule be set by the most 
| straightforward, dual
| fiber, solution.
| Best regards,
| Ulf Jönsson & Hans Mickelsson
| Ericsson