With
the pre-terminated plug & play benefits and ease of scalability
from 10-40-100G, MPO/MTP connectors are rapidly becoming the norm of
switch-switch connections. In the previous post “Introduction to MPO Connector”,
I have talked about two types of MPO connectors—12 fiber MPO connector
and 24 fiber MPO connector. And both the two MPO/MTP cable types can be
used for 100G data transmission. So someone may ask “for MTP link
performance, is there any difference between higher fiber count and
lower fiber count, or, which produces better performance, higher fiber
count or lower fiber count?”. This post simply tells the answer.
MTP Link: Higher Fiber Count ≠ Higher Insertion Loss
Generally,
lower overall optical loss allows more margin for the network to
operate, or in the case for some users, offers the option of more
connections for patching locations. Then some network designers claim
that higher fiber count will lead to higher insertion loss. Actually,
this point of view is wrong. For both 12-fiber and 24-fiber MPO
connector performance, the industry standard product rating is 0.5 dB
maximum. When using proper polishing techniques, 24-fiber MPO/MTP
terminations can meet the same performance levels as 12-fiber MTP
assemblies. Furthermore, using low-loss ferrules, both 12 fiber and 24
fiber MPO connectors can be rated at 0.35 dB maximum.
MTP Link: Higher Fiber Count = Higher Performance
As you know, both MPO 24 fiber cable
and MPO 12 cable can be used in 100G applications. MPO 12 cable can be
used in 4x25G solutions, remaining 4 fibers unused. By using MPO 24
fiber cable, it can be converted into three 8-fiber 100G channels that
run over one cable, with all 24 fibers used to support traffic. Let’s
show an example to further prove which is better. If you need to support
twelve 100G channels with the 4x25G standard, using 12 fiber MPO cable,
you need to install 12 connectors, or 144 fibers total, with 33% of the
fiber wasted. Using MPO 24 fiber cable supporting the same 12 channels,
only 4 cables would be required, using 96 fibers total, at 100% fiber
utilization.
Summary
From
what have described above, we can summarize that MPO 24 fiber cable
does not translate into higher insertion loss and can work as well as
MPO 12 cable. Moreover, the 24 fiber MPO cable, while allowing the use
of the ratified 100GBASE-SR10 20-fiber technology, can at the same time
maximize the installed infrastructure investment in the event of 4x25G
ratification and ultimate implementation. Choosing MPO 12 cable simply
cannot accomplish this because it drives down return on investment and
subsequently increases the total cost of ownership. And this is the
exact opposite of the design intent of a data center infrastructure
system.
