The basic mechanical failure mechanism for optical fibres is the slow
to rapid growth of any glass imperfections in the fibre caused by the
fibre being under stress. This 'fatigue' phenomenon can be accelerated
with the presence of moisture (H2O) molecules at the glass surface of
the fibre. So the waterproof for fiber optic cable is very important .
Now let us know more info about
waterproof cable.
All
manufacturers of fibre optic cables intended for use outdoors must
address the issue of protecting the fibre's glass surface from the
presence of moisture. Many manufacturers provide the waterproof
characteristic to solve the problem. This is because the 250μm primary
fibre coating provides only a 62.5μm-thick layer of UV-cured acrylate
material as basic protection over the fibre's glass surface. This
UV-cured acrylate material is not chosen by the fibre manufacturers for
its optimal resistance to water or its minimal porosity. It is in fact
chosen primarily because of its fast processing speed,since a primary
cost driver for fibre manufacturers is the draw speed, which is steadily
increasing. The very thin UV-cured acrylate layer is porous to water
molecules and will permit concentration of OH-ions at the fibre surface,
if the fibre is immersed in water.
All plastic materials are
porous to varying degrees. The general category of thermoplastic
materials commonly used in cable constructions will to some extent
absorb water; however, thermoplastic materials certainly do not act as a
complete water block. Only materials like metals or glass can provide a
true 'hermetic' seal. Plastic materials are generally characterised
with parameters such as water absorption and absorption of other common
solvents such as oils, gasoline, kerosene, etc. This being the case,
water molecules cannot be eliminated from the glass surface of any
fibres incorporated in a cable having plastic jackets. The issue is to
minimise the concentration of water molecules at the glass surface so
that stress crack growth effects are minimised.
There are two different designs approaches to water and moisture protection in fibre optic cables.
The
loose tube gel-filled cables must prevent water from reaching the 250μm
coated fibres. This approach is to 'waterproof' the cable by 'filling'
the empty spaces in the cable with gel, theoretically preventing water
from reaching the 250μm coated fibres. To insure that this is
accomplished, the 'filled' cables are generally subjected to a hosing
test to show that water will not flow through a short section (one
meter) of cables. The fact that gels can move, flow, and settle, leaves
an uncertainty of the filled level of any particular point of a
loose-tube gel-filled cable. This uncertainty of the filling is
highlighted by the routine practice of water-blocking the loose-tube
gel-filled cables at the entrance to splice housings to keep water from
migrating from the cable into the splice housing.
The
tight-buffered, tight bound indoor/outdoor cables utilise an entirely
different design approach to deal with the moisture issue. Rather than
attempting to be 'waterproof', they are designed to be water tolerant.
Recognising
the porosity of plastic materials and the inherent problems of
waterproofing a cable, the moisture protection is concentrated at the
fibre surface where it is most needed.
Correctly designed harsh
environment tight-buffer systems consist of extremely low moisture
absorption coefficient materials at the fibre coating. This provides a
buffer system thickness of 387μm over the glass which is more than six
times as thick as the 62.5μm coating found in the loose-tube cables.
Buffer
materials are low-porosity plastics with excellent moisture resistance.
This construction very effectively minimises the water molecule and
OH-ion concentration level at the glass surface and virtually eliminates
the stress corrosion phenomenon. The tight-buffered design also has the
great advantage of being a solid, non-flowing, non-moving structure.
The same level of protection remains in place all along the fibre, regardless of installation conditions, environment, or time.
The balance of the tight-buffered, tight bound cable designs is such
that it minimises the open spaces available in the cable structure in
which water can reside. Even if an outer cable jacket is cut, or water
otherwise enters the cable structure, only a very small percentage of
the cross-sectional area is open to water.
1,Water penetration
refers to the effectiveness of cable in restricting the longitudinal
movement of water or moisture along the core. This requirement is
primarily intended to localise any water penetration to minimise the
adverse effect on cable performance and to prevent water or moisture
leaking into joints and terminations that may cause corrosion problems.
2,Additionally, cable installed underground should have a high density
compound sheath material (such as poly ethylene) that provides an
adequate barrier to moisture entry to the cable core. The addition of a
lapped metal tape ('moisture barrier') and/or grease or gel within the
core ('filled' or 'flooded' cable) provides even higher protection
against moisture entry.
The above considerations is very important
and should always be considered. Always refer to the manufacturers
specification sheet and follow their installation instructions.
For
the diverse requirements of our customer, we are involved in offering a
wide assortment of waterproof cables. FiberStore offer these cables at
very economical rates in the market. These cables are widely used and
are highly demanded in the market due to their water proof nature. In
addition to this, we offer these cables in various
fiber optic cable specifications as per the requirements of our clients. We provide fiber optic cable products(such as
duplex fiber cable,simplex fiber optic cable) are absolutely high quality and low price.
