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Re: Parallel fiber PMD

Hi Tom

Parallel Optics is very cost effective for short reach applications,  that's
why we chose it in IB. As the link distance increases beyond 50 m, the cable 
cost overwhelms the total cost.  

Parallel optics fits very well in the central office or computer room 
applications with max link distance of 100 m.  The 802.3ae is choosing 
3 PMD, but they are not preventing anyone from using parallel optics.  
With Hari "XAUI" compatibility you will find parallel optics in central 
office / Computer room regardless of 3PMD selection as long as it is 
cost effective.

So my reading is the 3PMD is for outside the computer room.


Ali Ghiasi
Sun Microsystems

> Date: Mon, 26 Jun 2000 16:58:23 -0500
> From: "Tom Palkert" <tomp@xxxxxxxx>
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> Subject: Parallel fiber PMD
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> Even after reading all the 3 PMD emails I am still a believer in the
> parallel fiber PMD. I would like to throw out my rationale and look for
> feedback please. 
> Note: I am not proposing that we replace any of the exising PMDs with
> the parallel fiber. They all have distinct application spaces. i.e. CWDM
> is required for 300m over existing fiber, serial for long distances etc.
> I just believe the very short reach application space justifies the cost
> savings and time to market provided by the parallel fiber.
> Technical feasibility:
> The technology to make a short wavelength 2.5 Gbps VCSEL is very
> similiar to the 1.25 Gbps VCSELs giving them, I believe, the lowest cost
> basis of any of the PMDs proposed.
> There are no issues with Open Fiber control. (The power is on each
> individual fiber not combined on a single fiber) i.e. Lower complexity.
> 2.5 Gbps SERDES can be designed in std cmos technology. This makes the
> SERDES low cost or integrated with the framer.
> The SERDES parts can be identical for either the WAN Phy or the LAN Phy
> assuming the OIF 622 LVDS interface is used.
> Other standards compatibility:
> OIF: They are generating interoperability agreements for Very Short
> Reach OC192 connections based on parallel fiber. The WAN Phy application
> will need to connect to the OC192 equipment. I think it would be highly
> desirable to have the OIF 4 wide parallel fiber solution specified in
> Infiniband: They are sending 10 Gbps data across very short links using
> parallel 2.5 Gbps VCSEL based fiber links. The optical modules should be
> interchangeable. 
> General Market trends:
> Terabit routers and high density digital crossconnect applications are
> using large volumes of parallel fiber between equipment racks in their
> systems.  I would assume that they have done extensive cost analysis
> before committing to these programs. Most of the link analysis done for
> these applications assumes distances between 100 and 300m. Therefore, if
> a number of large volume users have analyzed a link that is virtually
> identical to the 10 GBE application and decided that 2.5 Gbps parallel
> fiber is the best solution, why shouldn't the 802.3ae group follow?
> It appears that 2.5 Gbps VCSELs will be readily available from multiple
> vendors either now or in the next couple of months.
> 2.5 Gbps cmos SERDES and integrated core macros will be readily
> available from multiple vendors either now or in the next couple of
> months.
> Comments: