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Re: Equalization and benefits of Parallel Optics.


If you have 75% support for 6-PMDs to include parallel-interconnect, I will 
vote for parallel, since I support all VCSEL technologies.  Otherwise, 5-PMDs 
is sufficient already.

The Parallel approach is mainly for up to 20 meter connections.  It is not 
designed for 100 meter to go through ducked, or underfloor pipe 
installations, because a ribbon fiber is not jacketed enough for those rough, 
punishing pulling environment.  Furthermore, at the patch panel connections, 
the fibers are all single (duplex fibers) fibers, but not 4-parallel (duplex) 
fibers.  For a parallel fiber to connect to an existing single (duplex) fiber 
at the patch panel, one has to perform field termination, to which a parallel 
fiber is not designed for due to the tight tolerance of spacing between 
adjacent channels.  Normally, the parallel ribbon fiber cable is factory 
terminated only.  

However, if the parallel fibers are used just as a jumper cable to 
interconnect closely located nodes -- 5 meter, 10 meter,-- the ribbon cable 
can do the job.  Then, how about the serial 850 nm approach, which is 
cheaper, and easier eventually to reach more than 20 meters?

I was a member of OETC consortium in early 1991, which promoted the parallel 
interconnect in industry with the blessing from ARPA.  The project failed 
several years later due to the lack of interest from industry.  The reason 
was too expensive, difficult in termination and alignment, and expensive 
ribbon cables.

I was a big fun for, the industry first commercial parallel interconnect, 
OCTOBUS.  I tried very hard to implement to my company's equipment.  After 
several years, the product never reach production stage, and was canceled, 
due to the lack of interest from industry.  The reason was the same as OETC.

There was only two ribbon cable suppliers and was expensive that time.  The 
factory only termination was very inconvenient for users.  It implies there 
is no flexibility in modifying the cable lengths, when an equipment, or 
terminals are rearranged to a different location.  One has to go back to 
order new set of cables?

For last 10 years, parallel interconnect was highly valued; however, it was 
never motorized as a contender for the top interconnect solutions.  I hope it 
will this time?

Ed Chang

NetWorth Technologies, inc.


 > I have one question:
 > Which of our distance objectives is satisfied with parallel fiber and
 > parallel optics?
 The 100 m data center applications.
 > It has been my interpretation that when we talked about f installed
 > base of MMF, that we were referring to the MMF fiber currently available 
 > use by 802.3z.  Parallel optics does not operate over this installed base.
 You are correct parallel optics would not operate over an installed two fiber
 plant.  Parallel optics would loose if you go in to an installed fiber base.
 What I suggested was 100m data center applications, where the fiber are not
 installed in the building wiring.
 Data center application are very significant as stated in the last meeting
 about half the total market.  Solutions significantly lower cost targeted
 for sub 100 m is needed, otherwise there will several proprietary solutions.
 Parallel optics is the lowest cost, almost mature after 3 years, lowest 
 and smallest foot print.  Parallel optics is ideal to get bandwidth off the 
 edge of your board. 
 Serial 850 or CWDM 850 can be another candidate for low cost data center
 applications by having cable advantage over parallell fiber.  But you need 
 to offset fiber advantage against power, size, cost, testing, and maturity.  
 > Or am I missing the point here?
 > Cheers,
 > Brad
 Ali Ghiasi
 Sun Microsystems
 >  -
 >  Sharam 
 >  > 
 >  > 
 >  > Although parallel fiber is technically an easier solution, the
 > major reason
 >  > for support of 850nm has been to consider the installed base, and
 > cost. If
 >  > users have to pull new fiber, IMHO, parallel fiber would not be on
 > top of
 >  > the list and most of installed base is single fiber.
 >  I did not suggest to pull any new fiber.  Limit the shortwave
 > variant
 >  including parallel optics to the data center with 100 m radius.
 >  Thanks,
 >  Ali Ghiasi
 >  Sun Microsytems
 >  > 
 >  > Sharam Hakimi
 >  > Lucent Technologies
 >  >