focus technique

TECHNICAL FOCUS

How to determine the appropriate bail length for your clamp ?

A clamp’s bail length is directly related to the cable bending performances. The lower the cable bending performance, the shorter the bail length may be. Two configurations have to be distinguished :

SIMPLE ANCHORING

Comment déterminer la bonne longeru d'anse pour sa pince

DOUBLE ANCHORING

Assuming that the angle α due to the ratio cable sag over cable span is minor and cos (x) ≈ 1, the bail length is directly related to the minimum bending radius of the cable and it can be determined by using the following formula:

Comment déterminer la bonne longeru d'anse pour sa pince

Cable tension calculations

Calculation formula for cable tension load

Calcul de tension des câbles

Where
Weight (in kg/m): Apparent weight of one cable meter
Tension (in daN): Calculated tension load applied to the cable and clamp
Span (in m): Distance between two poles
Sag (in m): Vertical distance at the center of the span, usually equal to 1% of the span

For example, for a 96 fibre count distribution cable, whose weight is 0.1kg/m, deployed on a 50 meters span with a sag of 1% (0.5meter), the calculated tension is :

Tension = 0.1 x 5022 / 8 x 0.5 = 62.5daN

Bad weather conditions induce additional load on overhead infrastructures. The ice load increases the cable weight as well as the total surface subject to the wind.

The above formula takes into consideration weather conditions and their impact. Thus, wind and ice loads are integrated in the apparent cable weight calculation :

Cable data is provided by the cable manufacturers, while climatic data can be usually found in national standards for building/ infrastructure. As for example, in the USA, the National Electric Safety Code (NESC) Rule 250B defines 3 regions with typical values for ice thickness, temperature, and wind pressure :

Calcul de tension des câbles

A good knowledge of the topographic parameters (span, gradient of the ground) and of the climatic conditions allows to anticipate the loads and the overloads impacting the overhead infrastructure. This is also the best starting point for choosing the right material, cables and clamps, adapted to the considered area for a qualitative and future-proof network.

Droptic® Bend insensitive fibre

International Telecommunications Union organisation has established several categories of bend insensitive fibres, characterised by macrobending losses. Telenco takes into account the main challenges of last mile connections. To bring reliable solutions for buffer storage in outdoor or indoor boxes, cable running inside buildings or on facades, drops glued or stapled alongside baseboards, Telenco provides only for solutions compliant with ITU recommendations for G.657A2 or G.657B3 fibres.

Quality controls for Droptic® range include the inspection of three wavelengths (1310nm, 1550nm and 1625nm) to ensure that the optical attenuation remains below standard values. This guarantees the optimal use of our fibre products with GPON access network technology and allows the anticipation of future applications with WDM PON or XGPON technologies.

Les câbles Droptic a fibre optique insensible à la courbure

(source: ITU-T G657 recommendation – 11/2016)

Pole banding or drilling: which functional differences ?

As a general rule, two attachment methods are possible to install pole hardware: by performing pole banding applications or by driling the support. The choice between these two solutions is first of all made by considering the pole’s characteristics. For non pre-drilled concrete, metal or composite poles, the pole line hardware can only be mounted by using pole band. However, on wooden poles, cross-arms or brackets can be installed at convenience either by using pole band or by performing drilling applications.

Due to its peripheral tightening, pole band does not alter the original structure of the support and allows the maintain of its exact mechanical properties. The different pole band dimensions and grades meet the various needs of mechanical and corrosion resistance.

When a wooden pole is subject to harsh climatic conditions, its diameter can reduce to a smaller or higher extent. In this particular case, it is advisible to use the drilling method for mounting pole hardware. It is also important to respect a minimum spacing of 5cm between each hole, regardless of the pole’s side and the length of the used material (pass through bolt or lag bolt) Poorly performed drilled holes can reduce the mechanical resistance of a pole, endangering thus all the existant infrastructure as well as the direct neighbouring areas (pedestrians, houses, road crossings, ...).

Which cross-arm for which application ?

Each cross-arm presents a technical specificity enabling to meet the issues of parallel layout overhead lines. The Telenco® 5/07 cross-arm presenting 5 holes is the most compact product solution. Engineered with a 40mm spacing between each hole, this cross-arm is ideal for enabling customer connections in low-density areas and at the end of the network. As for the Telenco® 5/14 cross-arm with 11 holes, this accomodates up to 19 drop clamps or 9 anchor clamps for feeder or distribution networks while occupying a reduced width. Finally, the Telenco® 5/15 cross-arm displays 13 holes with a 60mm spacing for accomodating up to 23 drop clamps or anchoring devices for feeder or distribution network segments. Its greater length enables the creation of an offset reinforced by a Telenco® 5/14 cross-arm.

Wich cross arm for wich application

Cable-clamp compatibility for a future-proof network

Considering the sustainability and reliability of the network, it is essential that pole hardware and anchors to be adapted and qualified for the network on which they will be installed. The mechanical connection between the anchor and the cable constitutes therefore an important issue for overhead networks. The compatibility between anchors and cables is checked by carrying out the following qualification tests:

 

  • Tensile tests at the short-term tensile load of the cable (Maximum Allowable Tension) according to EN 60794-1-2 standard - modified Method E1 involving a couple of anchoring devices on a cable length greater than 1 meter. There should be no slippage of the cable inside the anchoring clamps, no deterioration of the cable, nor deterioration of the signal (attenuation less than 0.1dB).
  • Galloping test for anchor clamps according to EN 60794-1-2 standard - Method E1. This consists into applying 10 undulations to cables with a smaller or equal diameter to 6mm (drops), 3 undulations to cables with a greater diameter than 6mm (distribution and feeder cables) and a measurement of optical losses for 300 hours. A test is considered conclusive when registered optical losses are less than 0.1 dB throughout the test.

 

Ensuring the utmost quality for all of our products

For the past 20 years, at Telenco, the product quality is strictly related to the performance of functional tests. Conducted during the product development phase and the production quality control process, these technical evaluations are spread into 2 groups :

MECHANICAL TESTS :

  • Multidirectional tensile tests at room temperature, up to the device breakage. They are performed according to CEI EN 60794-1-2 standard involving dead-ends, suspension devices and a reference cable.
  • Tensile strength tests under permanent load with temperature are also carried out. They are generally performed on at least 200 hours, to check material shrinkage and grip performances at low or high temperature.
  • Long duration Vibration test. Conditions are specified in the EN 60794-1-2 standard - Method E19, on two spans of 40 meters with a reference cable and an optical measurement during at least 300 hours.

ENVIRONMENTAL TESTS :

According to CEI EN 50289-4-17, after an exposure of 1000 hours, the UV resistance is evaluated by the variation of the material’s characteristics and after a Charpy shock test EN ISO 179-2 on test samples. For hot-dip galvanised products, corrosion resistance is directly related to Zinc thickness, according to EN ISO 1461. Measuring the thicknesses enables to guarantee the corrosion resistance. Stainless steel products are put under a salt spray according to CEI EN 60068-2-11 standard. Mechanical performances and aspects are thus evaluated.

Dielectric withstand tests are also carried out to check the insulation level between the cable and the pole hardware.

OTO, FDB - which version to choose ?

In the following cases, the Floor Distribution Box (FDB) is supposed to be already mounted. Optical Telecommunications Outlet (OTO) has to be installed and fibres, connected to deliver fast broadband communications services.

Conclusion:
The choice of FTTH equipment is related to the network architecture and to the criteria defined by the network manager: installation time, optical budget, reliability, environmental impact, etc.

Droptic® LM4 – the drop cable solution enabling ZERO signal loss

In FTTH roll-outs, transitions between outside plant deployments and inside premises installations are nerve centers of the network architecture. Indeed, due to improperly performed splicing applications between outdoor and indoor drops, often optical budgets are overstretched. To avoid this and ensure the fastest speeds to end-users, Droptic® LM4 double sheathed optical drop cable is an effective solution. Designed as a multi-purpose drop cable, the LM4 drop enables simple, fast and reliable outdoor-indoor transitions.

Offering a rugged and watertight construction, the LM4 drop suits for both aerial and duct deployments. In overhead FTTH configurations, LM4 can be installed for spans up to 70m. Moreover, the dimensions of this drop cable have been reduced for better wind behaviour performances and a compatibility with duct installation on several hundred of meters.

Built with a double sheath construction, Droptic® LM4 presents two ripcords that can be used to strip off its HDPE outer sheath in a couple of seconds. Thanks to this operation, a Low Smoke Zero Halogen Flame Retardant LM1L drop cable is reached. This can be used for performing effective indoor applications. No splice is thus required to make the transition between the LM4 drop and the LM1L indoor drop. This functional convenience makes possible a constant transmission of the optical signal from an outdoor distribution point up to the telecommunications outlet without weighing down the optical budget.

  • One drop for aerial, facade, duct and indoor FTTH roll-outs
  • High mechanical performances

 

How to optimise the last mile access network ?

International Telecommunications Union organisation has established several categories of bend insensitive fibres, characterised by macrobending losses. Telenco takes into account the main challenges of last mile connections. To bring reliable solutions for buffer storage in outdoor or indoor boxes, cable running inside buildings or on facades, drops glued or stapled alongside baseboards, Telenco provides only for solutions compliant with ITU recommendations for G.657A2 or G.657B3 fibres.

Quality controls for Droptic® range include the inspection of three wavelengths (1310nm, 1550nm and 1625nm) to ensure that the optical attenuation remains below standard values. This guarantees the optimal use of our fibre products with GPON access network technology and allows the anticipation of future applications with WDM PON or XGPON technologies.