Page 50 - Market Analysis Report of Optical Communications Field in China & Global market 2021

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the shores through a conductor in a submarine cable, attenuation to0.150 dB/km or lower), while beyond ~115 µm
power supply is constrained and limits the number of fibers A there is little improvement in attenuation but withhigher
eff
that could be packed in the cable. Pursuing fiber pair capacity manufacture cost. Second, value of fiber A is somewhat
eff
maximization using a traditional non-linear transmission diminished in SDM systems as showedin Figure 3, while value
system is no longer the most power efficient to transmit large of bend performance is more important in higher density cable
quantities of data. In the 2020’s, SDM with ≥12 fiber pairs per and fiber bendperformance tends to deteriorate with larger
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cable is rapidly becoming a de-facto technology to achieve Aeff. All things considered, 80 – 115 µm seems to be asweet
larger cable capacity and lower cost/bit. In SDM cables, spot for current submarine SDM systems.
generalized signal-to-noise ratio (GSNR) is now an industry Further improvements of SDM will be a move to higher
metric employed to determine the performance of the wet plant fiber counts and minimization of cable manufacturing cost
for open submarine cables. In a power-constrained system, to achieve cost-per-bit with smaller form factors submarine
as is shown in Figure 3, the reduction in launch power leads fiber. For example, asmaller, 200µm outer diameter fiber
to lower capacity per fiber pair. However, this is offset by the can enable up to 50% higher fiber density, without making
ability to design cables with higher fiber counts (with same changes
amount of electric power supply), ultimately achieving higher to cable structure. A smaller, 200 µm outer diameter
overall cable capacity despite reduced capacity per fiber pair. fiber can be achieved via reduction in both primary and
secondary coating, while maintaining cladding diameter
4. Today’s Fiber for SDM Submarine Linear Systems at 125 µm to ensure that the existing fiber processing eco-
In submarine systems, where repeatersare powered from the system can be used (Figure 4). One key consideration for
shores through a conductor in a submarine cable, power supply migrating to smaller diameter fiber is to ensure adequate
is constrained and limits the number of fibers that could be cabled product performance and mechanical reliability.
packed in the cable. Pursuing fiber pair capacity maximization
using a traditional non-linear transmission system is no longer Fig. 4 Visual comparison of 250 vs. 200 µm fibers
the most power efficient to transmit large quantities of data.
In the 2020’s, SDM with ≥12 fiber pairs per cable is rapidly
becoming a de-facto technology to achieve larger cable
capacity and lower cost/bit. In SDM cables, generalized signal-
to-noise ratio (GSNR) is now an industry metric employed to
determine the performance of the wet plant for open submarine
cables. In a power-constrained system, as is shown in Figure
3, the reduction in launch power leads to lower capacity per
fiber pair. However, this is offset by the ability to design cables
with higher fiber counts (with same amount of electric power With higher fiber density, fiber identification will be essential
supply), ultimately achieving higher overall cable capacity to enable correct splicing during installation and future
despite reduced capacity per fiber pair. maintenance activities. Several options of fiber identification
Fig. 3 Different submarine system designs: SDM (Linear) vs. non- have been proposed, mainly involving combinations of solid
SDM (non-Linear). colors and uniquely spaced ring-marks. Careful manufacturing
processes are required to ensure that ultra-low attenuation is
maintained after a particular fiber identification solution is
applied.
Compared with reducing fiber coating for higher cable density,
another option for cable density improvement is reducing fiber
cladding. Reduced coating fiber preserves 125 µm cladding
diameter for backwards compatibility with existing fiber
handling procedures and reduced coating thickness to below
200 µm. Reduced cladding fiber decreases its glass diameter
to<125um, while keeping coating thickness the same or
thinner. Both pathways can achieve higher packing density
but will create some additional challenges. For example, the
primary trade-off when reducing the fiber cladding diameter
In today’s SDM submarine system designs, fiber attenuation is the increase of fiber microbend sensitivity. If not mitigated,
and effective area are two key optical fiberattributes one needs this could lead to an increase of overall attenuation. Hence
to consider. In particular, ultra-low attenuation continues to suitability of these fibers for submarine transmission will be
play an important roleas every 0.001 dB/km fiber attenuation driven by cable design considerations and suitability in terms
improvement will further reduce the overall cost-per-bit. of mechanical reliability.
Insteadof traditional non-linear systems are designed with
largest fiber effective area to 150µm . Today SDM systems 5. Future-Pro of Submarine Fiber Options for
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prefer 80 – 115µm A for two reasons. First, this transition Higher Capacity SDM Systems
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eff
provides a meaningful decrease in attenuation of approximately Single-core fiber designs small outer diameter fiber (e.g. reduced-
0.01 dB/km (e.g. Corning Vascade EX2000 fiber achieves coating and reduced-cladding fiber) can significantly increase
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