Extending the Life of Fiber Optic Cables

How to ensure the service life of Fiber optic cable more than 20 years
In the long-distance optical communication systems, Fiber Optic Transmission characteristics should be the long-term stability, especially long distance buried Fiber Optic Cable and submarine cable systems, long life put forward higher requirements for fiber optic cable. Generally land cable service life and hope to have more than 20 years of safe use, while the submarine cable is required to improve its service life to 25 years, and its mean time between failure of 10 years required. Therefore, how to enxtend the life of the cable, how to properly use the fiber optic cable, is an important technical issues people care about, from the aspects of the structure of the cable under the talk about how to extend the service life of the cable.
There are three factors affect the life of Optic Fiber Cable
Optical fiber is one of the most important composition of the material in the fiber optic cable, to improve the service life of the cable, the most fundamental is to improve the service life of optical fiber.
The main factors for influencing service life of optical fiber are:
1. Fiber surface microcracks existence and expansion;
2. Atmosphere of water vapor molecules on the surface of the fiber and etching;
3. Unreasonable cable laying stress left over from long-term effects, etc.
For these reasons, making quartz glass-based optical fiber mechanical strength decreased, attenuation gradually increased, finally to a fiber break, the life of the cable termination. Because of the fiber surface there will always be a micro-cracks, occurring in the atmosphere slowcrack growth, the crack continues to expand, the gradual degration of the mechanical strength of the fiber. For example, a 125μm diameter quartz fiber, after three years of slow change in the future, the tensile strength of the fiber from 180kpsi (equivalent to 1530g tensile strength), dropped 60kpsi (equivalent to 510g tensile strength). Such slow changes caused by the fiber mechanical strength reduction principle is: When the fiber surface micro-cracks (or defects), under the external stress, the fracture does not immediately, only when the stress reaches the critical value of crack, the fiber will break. the silica fibers exposed to a constant stress less than the critical value, the surface cracks will occur slowly expanded, the depth of the crack fracture critical value, which is the process of degradation of the mechanical strength of the fiber. Quartz optical fiber mechanical strength degradation is due to the stress of water and atmospheric environment under the joint action of erosion and water vapor molecules.
The method for prolonging the service life of the optical fiber
When the fiber in a vacuum environment, since there is no water molecules, so that the stress does not occur erosion, the fatigue parameters of N is the maximum value, the fiber also has the highest strength, when the strength is the strength of the inert fibers, called Si. Fibers in the environment of use and it has a service life of ts and the stress σ inert fibers have the following relationship between the intensity of Si:lgts=-nlgσ+lgB+(n-2)lgSi the latter two are the above formula constant, when subjected to constant stress σ, the service life of the fiber and fiber fatigue ts only value the parameter N. The larger the value of N, the optical fiber is the longer life of ts.
Therefore, improving the service life of the optical fiber in two ways:
First, when the fatigue parameter n is fixed, the service life of the optical fiber is exposed only to ts stress σ, and therefore, reduce the stress exerted onto the optical fiber is to improve the service life of a method of optical fiber. When people make optical fiber on fiber surface to form a compressive stress to fight on the tensile stress, decrease the tensile stress at a level that is as small as possible, thereby generating a compressive stress on the cladding layer technology to manufacture optical fibers.
If set to withstand stress fiber σa, life t1, when the fiber cladding has a compressive stress σR, the fiber’s life t2: t2 = t1 [(σa-σR) / σa]-n
Of which, (σa-σR) for the fiber to withstand real net stress. It is suggested that: a compressive stress cladding optical fiber than the life longer. In recent years, some people do quartz GeO2-doped fiber surface compression layer, it was done with a quartz optical fiber doped TiO2 cladding tensile strength of the fiber itself from 50kpsi increased to 130kpsi (considerable tensile strength increased from 430g to 1100g), also the optical fiber static Fatigue from n= 20~25 raised to n = 130.
The second, to improve the static fatigue parameter n optical fibers to improve the service life of the fiber. Therefore, people in the manufacture of optical fibers, quartz fibers themselves try to cut off the atmosphere, so that from atmospheric environment, the possible value of n material parameters from the environment into the parameters of fiber material itself, can make the value of n becomes large, resulting in the surface of the fiber of the “seal coating technology”.
Over the past decade, the use of “seal coating technology” to produce optical fiber made tremendous progress. Extended by a metal coating material to the metal oxides, inorganic carbides, inorganic nitrides, carbides, oxides of nitrogen and CVD-deposited amorphous carbon. Coating layer structure of the metal coating layer by a single seal coating layer to the development of the organic coating layer is combined with a composite coating layer structure, the fiber value of more practical application, the fiber optical properties, mechanical properties and fatigue resistance are improved.
For example:
1. metal coated optical fiber: aluminum coated optical fiber can withstand 1Gpa (150kpsi) stress test submerged in water, at a temperature of 350℃ to use, life expectancy at 10 years.
2. Metal oxides and other inorganic fibers coated: with C4H10 and deposited on the fiber surface SiH4 Si0.21O0.22C0.77 sealing coating layer was coated with the organic layer, the n-value of the fiber to 256.
3. As sealed with a coating layer of boron nitride fibers: 200kpsi can withstand the tension, n value can be increased to 100 or more. Another example is coated with a sealing TIC 400 ~ 500kpsi fiber has a strength of 100 ℃ water resistant.
4. Seal amorphous carbon coated optical fiber: the inorganic coating material, the amorphous carbon coating layer is not only the fiber optical properties and mechanical strength of the effect is little damage, and showed excellent water resistance properties and resistance to hydrogen. This technology has come of industrial production. The typical tensile strength of the fibers has reached 500-600kpsi, dynamic n-value of 350 to 1000. After 25 years at room temperature, the carbon fiber penetration seal coating hydrogen is only an ordinary fiber 1/10000; in fiber optic cable, these fibers may allow hydrogen pressure is 100 times higher than normal fiber. With this optical fiber cable can be suitably reduced to conditions or under the conditions of higher temperatures.
Using fiber surface growth “stress cladding layer” and “sealing coating technique”, the life of the optical fiber can be introduced following formula: t2/t1 = 19.36 × 10IRσa7 formula, σa is the applied stress or stress. Σa which can be calculated with the relationship t2/t1. Such fibers life of up to 40 years and could be used for submarine cables and military communications.
Some other studies also shown that manufacturing optical fiber by using germanium (GeO2) and fluorine (F) as a doping agent, and without phosphorus (P2O5) as a dopant, because phosphorus “water (H2O)” good, the fiber susceptible to moisture, causing the core internal P-OH bond absorption attenuation increases, the fiber slowly changing. So long service life of optical fiber to eliminate with phosphorus mixed materials.
In the manufacturing process, pay attention to moisture waterproof cable to reduce residual stresses. The first is the cable core design, be sure to use loose structure to prevent leaving residual stress, Stranded cable when I want to select a reasonable length of fiber, but also can reduce the tensile stress effect; in the cable core is filled with petroleum gel, purpose is to proof, waterproof, anti-hydrogen-containing compound (contaminated liquid) etching; using plastic coated steel, aluminum also to moisture, increased cable resistance to lateral pressure, tensile capacity; some factories in the cable core intervals one meter to add a hot melt adhesive water blocking layer to prevent the cable core longitudinal water penetration; selection of small linear expansion coefficient of the material for the strength of the cable core element, the purpose is to protect the fiber, eliminating the external tension. Finally it should also be noted that each of the manufactured fiber raw material itself must have more than 30 years of life, must have a high stability of the physical properties and chemical properties. Only by strictly controlling the quality of the manufacturing process of the road, it can extend the life of the cable.

Photonic Integrated And High-speed Optical Interconnection Technology

Currently, in the field of active optical devices, high-speed optical communication (40G/100G), broadband access FTTH, 3G and LTE wireless communication, high-speed optical interconnection, chips applied in intelligent Fiber Optic Network, device and module technologies are competing to become the hot spots of development. And the photonic integrated, high-speed optical signal modulation technique, high-speed optical device packaging technology, as the representative of the optical device platform technology are also increasingly being valued by the majority of OC manufacturers.

The Technology Development And Breakthrough Of Active Optical Devices

To meet the growing demand for bandwidth, while continuing to reduce the capital, operation and maintenance expenses, will continue to be the two main driving force to promote the development of optical communication technology. In order to meet the evolving needs of the system, the development of active optical communication device involves many technologies, however, in recent years there are several technologies deserve special attention, including 40G/100G high speed transmission device and module technology, the next generation fiber access technology, ROF (Radio Over Fiber) components and module technology, optical integration technology, high-speed interconnect optoelectronic components and modules, etc.

Optical Integration Technology Is Worth Looking Forward

Optical integrated devices due to its low cost, small, easy to large-scale assembly, high work rate, stable performance and other advantages, as early as the 1970s, it caused the world’s attention and research. In the ensuing three decades, with the rapid development of optical waveguide production technology and a variety of fine processing technology, optical integrated devices are heavily into the business, particularly some optical passive components based on Planar Lightwave Circuit (PLC), such as Planar Lightwave Circuit Splitter, arrayed waveguide grating (AWG) and so on, have become hot products in optical communication on the market. In the field of optical active devices, the active integration products are still far from large-scale commercial, but with the successful development of some advanced technologies such as Dispersion Bridge Grating, active devices based on PLC recently made great progress.

The develop direction of optical integration technology can be divided into two categories: monolithic and hybrid integration. Monolithic integration refers to the semiconductor or optical crystal substrate, over the same production process, integrating all the components together, such as: PIC and OEIC technology; the hybrid integration refers to through different production processes, making part of the components, then assembled in the semiconductor or optical crystal substrate.

Previously, the actual production process of Si-based hybrid integration has been quite complex, but recently, a number of research institutions had improved the traditional hybrid integration technology based on flip, and made great progress. Among them, the most remarkable achievements include two items: The first is the University of California at Santa Barbara, in cooperation with Intel company researched hybrid integrated device based on Wafer level; second is the Ghent University based chip and the wafer hybrid integrated devices.

In recent years, the development of optical integration technology, making it quickly became a very worth looking forward platform technology in optic communication, is expected to be widely applied.

High-speed Optical Interconnection Technology Beyond Imagination

High speed optical interconnection technology is realized by parallel Fiber Transceiver and Ribbon Cable or fiber optic cable. Parallel optical module is based on VCSEL array and PIN array,wavelength of 850nm, suitable for 50/125 μm and 62.5/125 μm multimode fiber. Its electrical interface uses standard MegArray connectors in package, optical interface uses standard MTP/MPO ribbon cable. At present more common parallel optical transceiver module has 4 channels and 12 channels. In the current market, the more common high-speed parallel optical modules include: 4 × 3.125Gb/s (12.5Gb/s) parallel optical module, applications such as high-end computer systems, blade servers short distance interconnection; 12 × 2.725Gb/s (32.7Gb/s) parallel optical module, used in high-end switching equipment as well as backplane connection. Parallel optical module applications are gradually becoming more mature.

At present, the rise of applications such as super computer, cloud computing, short-distance high-speed data communication, directly promoting the rapid development of high-pspeed optical interconnection technology, its size of the market and technology development will beyond people’s imagination.

What are the Advantages and Disadvantages of Fiber Optic Cabling

Fiber optic cabling consists of strands of purified glass, or even plastic, rods that conduct specific wavelengths of light, analogous to the electrons carried along a Copper Ethernet Cable. However, light traveling through glass or plastic is not susceptible to the same problems that metal conductors are; The electromagnetic radiation that results from current traveling through a wire is not present in optical conductors, and optical conductors can be made much smaller than metal ones. Today, we’ll talk about the advantages and disadvantages of fiber optic cable.

advantages and disadvantages of fiber optic cable

Advantages and Disadvantages of Fiber Optic Cable

Everything has its own advantages and disadvantages. Learning the advantages and disadvantages of fiber optic cable, we may know how to select one when buying the cables.

Advantages

There are four advantages of fiber optic cabling, these advantages explain why fiber is becoming the preferred network cabling medium for high bandwidth, long-distance applications:

1. Immunity to Electromagnetic Interference (EMI)

All copper cable network media sharing a common problem: they are susceptible to electromagnetic interference (EMI), fiber optic cabling is immune to crosstalk because optical fiber does not conduct electricity and uses light signals in a glass fiber, rather than electrical signals along a metallic conductor to transmit data. So it cannot produce a magnetic field and thus is immune to EMI.

2. Higher Possible Data Rates

Because light is immune to interference, can be modulated at very high frequencies, and travels almost instantaneously to its destination, much higher data rates are possible with fiber optic cabling technologies than with traditional copper systems. Data rates far exceeding the gigabit per second (Gbps) range and higher are possible, and the latest IEEE standards body is working on 100Gbps fiber based applications over much longer distances than copper cabling. Multimode is preferred fiber optic type for 100-550 meters seen in LAN network, and since single mode fiber optic cables are capable of transmitting at these multi-gigabit data rates over very long distances, they are the preferred media for transcontinental and oceanic applications.

3. Longer Maximum Distances

Typical copper media data transmission by the distance limits the maximum length of less than 100 meters. Because they do not suffer from the electromagnetic interference problems of traditional copper cabling and because they do not use electrical signals that can dramatically reduce the long distance, single-mode fiber optic cables can span 75 kilometers (about 46.6 miles) without using signal-boosting repeaters.

4. Better Security

The Copper cable transmission media is susceptible to eavesdropping through taps. A tap (short for wiretap) is a device that punctures through the outer jacket of a copper cable and touches the inner conductor. The tap intercepts signals sent on a LAN and sends them to another (unwanted) location. Electromagnetic (EM) taps are similar devices, but rather than puncturing the cable,they use the cable’s magnetic fields, which are similar to the pattern of electrical signals. Because fiber optic cabling uses light instead of electrical signals, it is immune to most types of eavesdropping. Traditional taps won’t work because any intrusion on the cable will cause the light to be blocked and the connection simply won’t function. EM taps won’t work because no magnetic field is generated. Because of its immunity to traditional eavesdropping tactics, fiber optic cabling is used in networks that must remain secure, such as government and research networks.

Disadvantages

With all of its advantages, many people use fiber optic cabling. However, fiber optic cabling does have a couple of disadvantages:

1. Higher Cost

The higher cost of fiber optic cabling has little to do with the cable these days. Increases in available fiber optic cable manufacturing capacity have lowered cable prices to levels comparable to high end UTP on a per-foot basis, and the cables are no harder to pull. Ethernet hubs, switches, routers, NICs, and patch cords for UTP are very inexpensive. A high quality UTP-based 10/100/1000 auto-sensing Ethernet NIC for a PC can be purchased for less than $25. A fiber optic NIC for a PC costs at least four times as much. Similar price differences exist for hubs, routers, and switches. For an IT manager who has several hundred workstations to deploy and support, that translates to megabucks and keeps UTP a viable solution. The cost of network electronics keeps the total system cost of fiber-based networks higher than UTP, and ultimately, it is preventing a mass stampede to fiber-to-the-desk.

2. Installation

The other main disadvantage of fiber optic cabling is that it can be more difficult to install. Ethernet cable ends simply need a mechanical connection, and those connections don’t have to be perfect. Fiber optic cable can be much trickier to make connections for mainly because of the nature of the glass or plastic core of the fiber cable. When you cut or cleave (in fiber optic terms) the fiber, the unpolished end consists of an irregular finish of glass that diffuses the light signal and prevents it form guiding into the receiver correctly. The end of the fiber must be polished and a special polishing tools to make it perfectly flat so that the light will shine through correctly.

Conclusion

From the above, we have learnt the advantages and disadvantages of fiber optic cable. Knowing the advantages and disadvantages of fiber optic cable can help us to choose a suitable fiber cable. For more details about fiber cables, please visit FS.COM.

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