Parallel fiber PMD
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
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.
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
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