-Fiberoptic Cable Testing Per IEC 60794-1-2

8/12/2019 -Fiberoptic Cable Testing Per IEC 60794-1-2

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Fiberoptic Cable Testing MethodsPer IEC 60794-1-2

Synergy Cables

Quality Assurance Department

Written by

Dr. Hanan Yinnon

July 2007


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1. Tensile performance Per IEC-794-1-2 Method E11.1. Object

This measuring method applies to optical fiber cables, which are tested at a particular tensilestrength in order to examine the behavior of the attenuation and the fiber elongation strain as afunction of the load on a cable, which may occur during installation and/or operation.

1.2. SampleThe cable length under test is 150 meters. Additional cable length is needed to connect thefibers to be tested.

1.3. ApparatusThe apparatus consists of: An attenuation measuring apparatus, typically an OTDR. A fiber elongation strain measuring apparatus based on dispersion testing equipment.

A specially designed tensile test machine capable of tensioning 150 meters of optical cable insix legs of 25 meters each. The machine is equipped with a motor for controlled tensioningand a load cell for measuring the actual tension applied on the cable.

Figure 1 shows a typical machine.

Figure 1: Typical Tensile Load Machine

1.4. ProcedureThe cable is wound in the machine over appropriately sized sheaves. The cable ends extend toreach the measuring instruments. A pre-determined number of fibers within the cable areconcatenated by fusion splicing. Typically, two sets of fibers are used, one will serve to measureattenuation change and the other serves for elongation monitoring.After all initial measurements and calibration are carried out, the cable is pulled at a specifiedrate until a pre-determined tension is applied. The cable is laid to rest under tension as perdetail specifications, and then the attenuation and fiber length are measured.This process may involve several tensile levels in order to characterize the entire tensilebehavior of the cable, or be carried out only at the defined maximum allowed tension level.


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1.5. Pass/Fail criteria Under load, the fiber attenuation is not increased more than a predetermined value, typically

0.05 dB over the fiber length measured. Under load, the fiber does elongate by more than a pre-determined value over its initial

length. The allowed elongation under installation load is typically 0.25%.

2. Crush (Compression) Per IEC-60794-1-2 Method E32.1. Object

The purpose of this test is to determine the ability of an optical fiber cable to withstandcompression.

2.2. SampleThe sample is a representative cable length sufficient to carry out the specified test.

2.3. ApparatusThe apparatus allows a sample of cable to be crushed between a flat steel base plate and amovable 100 mm long steel plate. The edges of the movable plate are rounded with a radius ofabout 5 mm. A typical apparatus is shown in Figure 2.

Figure 2: Typical Compressive Load Machine

2.4. ProcedureThe cable sample is mounted between the plates so that lateral movement is prevented, and apre-determined force is applied gradually. The maximum applied force is typically maintainedfor 10 minutes.Two types of measurements may be defined:

The fiber attenuation is measured at the end of the 10-minute period while the cable is stillunder pressure.

The fiber attenuation is measured 5 minutes after pressure release. This requirement isusually carried out at higher compressive loads than the previously described measurement.

2.5. Pass/Fail criteria The attenuation must not change by more than a pre-determined value, typically 0.05 dB. In all cases, the cable elements should not fracture or crack. Signs of compression are not

considered as damage to the cable elements.


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3. Impact Per IEC-794-2-1 Method E43.1. Object

The purpose of this test is to determine the ability of an optical fiber cable to withstand impact.


3.3. ApparatusThe apparatus allows a hammer with a 25 mm rounded edge to drop vertically on a cablesample fixed on a flat steel plate. The apparatus may allow a single or multiple repeatedimpacts to be imparted on the cable sample.The energy of the impact is determined by the drop height and by the weight of the hammer.A typical impact test set-up is shown in Figure 3.

Figure 3: Typical Impact Testing Machine

3.4. ProcedureTwo procedures are commonly used: A repeated impact test whereby the hammer drops on the same location in the cable sample

25 times. The hammer is allowed to drop on 3 different locations in the cable, typically separated by

50 cm from each other. The number of impacts in each location is limited (1 to 3).


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3.5. Pass/Fail criteria The fiber attenuation does not increase by more than a predetermined value, typically 0.05

dB.

In some case, the cable passes the test if there are no fiber breaks. This requirement isusually applied when very high impact energy is used. There are no breaks or cracks in the cable elements. Signs of the impact are considered

normal.

4. Repeated bending (Cyclic Flexing) per IEC-794-1-2 Method E64.1. Object

The purpose of this test is to determine the ability of an optical fiber cable to withstandrepeated bending.


4.3. ApparatusThe apparatus allows a cable sample to be bent backwards and forwards through at an angle of180, the two extreme positions making an angle of 90 on both sides of the vertical, while thesample is subjected to a tensile load. A typical apparatus is shown in Figure 4.The bending arm is designed to permit holding the cable securely during the entire test, withoutcrushing the optical fibers or inducing optical loss. The bending radius is controlled byreplaceable cushioning reels chosen to match the cable bending radius.The apparatus is capable of cycling at a rate of 30 cycles per minute.

Figure 4: Typical Cyclic Flexing Machine

4.4. ProcedureA cable sample is secured to the bending arm while it is in an upright position. A predeterminedweight is attached to the bottom of the cable sample. The motor is turned on and the armoscillates between the two extreme positions flexing the cable. The number of flexing cyclesdepends on the cable design.


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5.5. Pass/Fail criteria The attenuation must not change by more than a pre-determined value, typically 0.05 dB. The cable should not show any indications of mechanical failure, such as jacket cracks,

armor opening etc.

6. Bend per IEC-60794-1-2 Method E116.1 Object

The purpose of this test is to determine the ability of an optical fiber cable to withstand bendingaround a test mandrel.

6.2 SampleThe sample is a representative cable length sufficient to carry out the specified test.

6.3 ApparatusThe apparatus is a simple mandrel of the specified diameter on which a cable sample can bewrapped tangentially in a close helix. A simple apparatus is shown in Figure 6.

Figure 6: A mandrel and bent cable sample

6.4 ProcedureThe sample is wrapped in a close helix around the mandrel at a uniform rate. Sufficient tensionis applied to ensure that the sample contours the mandrel. The sample is then unwrapped. Acycle consists of one wrapping and one unwrapping.

This test is often performed at low temperature to verify the cable ability to be installed at suchtemperatures without being damaged.

6.5 Pass/Fail criteria The attenuation must not change by more than a pre-determined value, typically 0.05 dB. The cable should not show any indications of mechanical failure, such as jacket cracks.


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7. Temperature Cycling per IEC-60794-1-27.1 Object

This measuring method is designed to determine the stability of the fiber attenuation in cables

submitted to extreme temperature conditions.

7.2 SampleThe sample is a standard cable of a length sufficient to make accurate measurement of theattenuation change. Single mode fiber cables should be at least 500 meters long, andpreferably 1000 m long. Multi-mode fiber cables may be shorter.A sufficient number of fibers distributed over the cable structure are tested, at least one fiberper tube in Loose Tube cables. It is important to test a different fiber in each tube to receive astatistically meaningful estimate of the cable performance under different temperatureconditions.In order to gain reproducible values, the cable sample is placed in the climate chamber as aloose coil or on a reel.

In most cases the tested fibers (from different tubes) are fusion spliced in series and measuredtogether using OTDR. The fusion splices are located outside the climate chamber.

7.3 ApparatusA climate chamber is used of a suitable size to accommodate the sample. The chambertemperature can be controlled to within 3 C of the specified testing temperature.Such a chamber is illustrated in Figure 7.The fiber attenuation may be monitored using a stabilized light source / power metercombination or, preferably, an OTDR.

Figure 7: A Climate Chamber and tested cables


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7.4 ProcedureA typical temperature cycle is depicted in Figure 8. A reference value for attenuation is determined on the cable sample already installed in the

climate chamber and ready for the temperature cycling. The temperature in the chamber is then lowered to the appropriate low temperature TA at

the appropriate rate of cooling. After temperature stability in the chamber has been reached, the sample is exposed to the

low temperature conditions for the appropriate period t1. The temperature in the chamber is then raised to the appropriate high temperature TB at the

appropriate rate of heating. After temperature stability in the chamber has been reached, the sample is exposed to the

high temperature conditions for the appropriate period t1. The temperature in the chamber is lowered to ambient temperature at the appropriate rate

of cooling.This procedure constitutes one cycle. Typically, cables are exposed to 2 such cycles.

Figure 8: A Typical Temperature Cycle

7.5 Pass / Fail CriteriaThe attenuation of the fibers in the cable should not increase by more than a pre-determinedvalue.

8. Water penetration per IEC 60794-1-2 Method F58.1 Object

The purpose of this test is to determine the ability of a cable to block water migration along aspecified length.

8.2 SampleA 1 to 3 meter long representative cable sample is used. A watertight seal is applied to one endof the sample to allow a 1 m height of water to be applied.


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8.3 ApparatusThe apparatus consists of a vertical pipe containing water at a height of 1 meter. The pipe isconnected at its bottom to a flexible tube that allows watertight connection to the cable undertest. See Figure 9 for a basic representation of such a set-up. The cable sample is laid flat and asuitable arrangement is made in order to determine if water leaks from its exposed end.

Figure 9: Water penetration test set-up

8.4 ProcedureThe sample is supported horizontally and a 1 m height of water is applied for 24 h.A water-soluble fluorescent dye or other suitable coloring agent may be used to aid in thedetection of water seepage.

8.5 Pass / Fail CriteriaNo water leaks are detected from the exposed cable end.

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-Fiberoptic Cable Testing Per IEC 60794-1-2