A fibre cable laid between buildings or through a duct has a hard life compared with one inside a clean server room. It may face water, rodents, sunlight, soil pressure and sometimes a careless spade. Standard indoor cable would not last long in those conditions. That is why outdoor routes often use an armoured fibre optic cable. This article explains what armour does and what to check before buying, based on the product information published by OMC Cable.
What armour means
Armour is a protective layer, usually metal, placed around the fibre core inside the outer jacket. It adds strength and resists crushing, cutting and pulling. OMC says its armoured outdoor cables use steel or aluminium tape armour, with a general tensile strength rating of up to 1500 N. Some specific models use corrugated steel tape, and one of them, the GYTC8S, has a central steel wire as a strength member. Another, the GYXTP, is described as having steel wires and steel tape wrapping, with tensile strength up to 1200 N.
Tensile strength tells you how much pulling force a cable can withstand. It matters during installation, when the cable is drawn through ducts or strung over a span, and later when it is exposed to movement or load.
The materials around the fibre
Armour is only one part of the design. OMC says its cables use gel filled PBT loose tubes, water blocking tape and glass yarn to keep moisture out. Water is a serious threat to outdoor fibre, because it can enter through damage and spread along the cable, so water blocking materials are important. The outer jacket is HDPE, and the company says the cables resist UV light and rodents, as well as abrasion, pulling and external interference.
Types of cable on the page
The OMC category page lists a variety of designs.
There are aerial self supporting figure 8 cables, for example the 12 to 48 fibre GYTC8S stranded loose tube and the 2 to 12 fibre GYXTC8S unitube. A figure 8 design combines the cable and a supporting wire in one piece, so it can be hung between poles.
There are stranded loose tube designs with different fibre counts, such as the 12 fibre GYFHTS, the 144 fibre double sheath GYFHTY53 and the 144 or 288 fibre double sheath GYFTY53. Double sheath options are described as suitable for heavy duty underground and duct use.
There are smaller unitube designs of 2 to 12 fibres, such as the double sheath GJFXTKV53 and the GYXTP and GYXTS types. There is also the 2 to 144 fibre range of GYTS, GYTA and GYTZS stranded loose tube cables.
Technical details published by the company
OMC lists an operating temperature range of minus 40 to plus 70 degrees Celsius, a service life of more than 25 years under normal conditions, and attenuation below 0.36 dB per km for the GYFHTY53. It states that single mode fibre types G.652D and G.657A2 and multimode types OM2, OM3 and OM4 are available, and that its products are ISO and IEC compliant.
Attenuation is the signal loss per kilometre of fibre. Lower is better, but you should always compare values for the same wavelength and fibre type. Ask for the full datasheet for the exact cable you plan to buy, because these figures differ between models.
Where it is used
The company names enterprise campuses and industrial parks, where cables run outdoors between buildings, along with telecom backbone and access networks, data centre interconnections and FTTH last mile connections. The FAQ on the page says the cables are suitable for direct burial, but a project should always follow the specific installation guidance for the chosen model.
Quality checks and delivery
The company says it tests cables with OTDR and tension tests, along with checks of attenuation, tensile strength and water resistance before shipping. An OTDR is an instrument that sends light pulses into a fibre to find loss and faults along its length. It also states that batch orders can be up to 10,000 metres and that standard delivery is 7 to 15 working days depending on quantity and customization. Length, jacket material and fibre type can be customized.
How to choose
Describe your route first. Will the cable be hung on poles, pulled through ducts or buried? Aerial routes suit figure 8 designs, while buried or duct routes may need double sheath armoured cable. Think about the environment, including temperature range, risk of rodents and likelihood of water. Decide on fibre type and count, allowing room for future growth.
Handling and installation
Armoured cable is strong but not indestructible. Respect the minimum bend radius, avoid exceeding the tensile limit while pulling, and seal cable ends against moisture. Metal armour should be properly grounded or bonded according to local rules and the manufacturer’s instructions, so use qualified installers.
About the supplier
OMC says it is Guangdong OMC Cable Communication Co., Limited, with over 15 years of experience in fibre optic production and customers that include telecom carriers, internet service providers and data centres worldwide. Its address is in Huizhou, Guangdong, China, with a Shenzhen office.
Summary
Armoured cable protects outdoor fibre links from the stresses that would damage ordinary cable. Match the design to your route, ask for datasheets and test results, and work with experienced installers. A well chosen cable can keep a network running for many years.