INTELLIGENT CABLING
Comparing the variables of optical signal
transmission including more fibres, more
wavelength, higher modulation, results in a mix
of technologies that represents the most suitable
cabling solution for transmitting more data.
It is recommended to follow a
farsighted approach, instead
of looking for the very latest
products on the market, we
recommend an approach based
on the physical variables seen in
optical signal transmission.
Migrations to 100 or 400 GbE could be implemented gradually
and systematically.
However, more fibres also results in more space, more manual
work and more cable management is necessary. This means that
user-friendly solutions must be found, with maximum packing
density, variable and migration-capable equipment possibilities,
and the possibility of automation. Moreover, multi-fibre
connections must also be manufactured with great precision and
operated with care. Cleaning the fibres is a complex process. This
also needs to be considered during planning.
Finally, we also must consider whether the preferred option
is fit for the future. Multi-fibre Push On technology definitely
has potential for innovation. The performance, handling
and maintenance can be optimised. For example, R&M is
developing an expanded beam technology based on micro
lenses for multi-fibre connectors. The transmitting area of the
connector is increased thus making it less sensitive to dirt and
misalignment. Additionally, the fibres no longer have to be
pressed for physical contact.
2. Higher modulation
The latest transceiver generations follow the path of higher
modulation. Among these are QSFP-DD, Quad Small Form
Factor Pluggable Double Density and OSFP, Octal Small Form
Factor Pluggable. QSFP-DD modules should deliver 50 Gbit/s per
channel with four-level pulse amplitude modulation, PAM-4. With
eight channels, they can then transmit up to 400 Gbit/s on each
port. The competing solution OSFP should transmit 50 or 100
Gbit/s per channel to support 400 and 800 GbE.
This is a major step forward, and one which is accompanied
by high energy and cooling demands. Similarly, the demands
also increase when it comes to the precision and quality of the
connectors. The higher the data rate the more reliable the optical
interface needs to be.
3. More wavelengths
Standardised in 2016, the wideband multimode cable category
OM5 raised many expectations. When combined with the latest
Demand is currently growing for pluggable fibre-optic modules for
100 Gigabit Ethernet. Modules for 200 and 400 GbE will soon dominate
the market.
lasers and shortwave division multiplexing on four wavelengths
(SWDM4), OM5 should open the door to increased capacity on
longer fibre links. Up to 40 Gbit/s on a fibre pair, 400 Gbit/s on
four fibres pairs, 1.2 Tbit/s via a 24-fibre Multi-fibre Push On plug
and a range of up to 500 meters are feasible.
This would offer an alternative to single mode infrastructures.
The number of cables could be reduced by a factor of four.
However, on links of up to 100 meters, existing OM4 cabling could
offer similar performance as an OM5/WDM infrastructure under
certain circumstances. The same principle also applies to OM5 –
higher data rates can only be achieved when the connectivity is of
suitable quality and performance.
Whether more fibres, higher modulation or wavelength
multiplexing, the quality and performance requirements increase
on all active and passive components. In certain circumstances,
the evaluation will show that new equipment is required so that
the cabling and transceiver work in harmony. Some of the systems
may be able to be modernised using the pay as you grow principle.
In others, the existing cabling can continue to be used.
Whichever way you look at it, there is no long-term solution
that can cover all requirements and applications at the same time.
More likely is an economically viable mix of technologies that
corresponds to the status, area of application and business case.
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