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EETE JANUARY 2013

CONNECTORS & CABLING showing some events found in a typical fibre measurement. cal path is split from one into multiple fibres, the power of the Some events such as splice joints reflect no more light towards light is distributed to each corresponding fibre. This represents the OTDR than the fibre itself does. They follow the trend line a loss of light in each fibre and equates to 3dB each time the of the trace, which shows a gradual decrease in reflected light number of splits doubles (1 x 2 = 3dB loss = power halved – see over the length of the fibre. These are known as non-reflective Table 1). events. As a PON branches out across the region it serves, more and Other physical events, such as connector joints, cracks in more splitters are used, and sometimes they can be so closely the fibre and the fibre end, cause a greater level of light to be spaced that they become difficult for a conventional OTDR reflected to the OTDR and are known as reflective events. The to measure. Anritsu’s OTDRs for PON installations are able to higher level of light returned to the OTDR from reflective events identify closely spaced splitters using short pulse widths, result- momentarily saturates the OTDR’s sensor to a level above ing in high measurement resolution and accuracy, ensuring that the backscattered light that follows it, and the sensor needs the user can see all events in the network - see figures 3 and 4. to recover before it can see beyond the reflective event. The Since these measurements on a PON are fully automated distance it takes for the OTDR to recover is known as the dead and take account automatically of the number of splits, there zone. is no need to train the fibre installer in complex PON network To be more precise, dead zones can be characterised in one architectures in order to produce valid test results. A modern of two ways: a reflective/Fresnel dead OTDR will also provide other features zone is the distance it takes for the which help the inexperienced user test OTDR to be able to see the next reflec- fibre installations effectively. These tive event; an attenuation dead zone include an optical power meter and is the distance it takes for the OTDR optical loss test sets. In addition, a Vis- sensor to recover to a level at which it ible Laser Diode (VLD) can be used to can correctly measure backscatter. In help find pinpoint breaks in the fibre, a high-quality OTDR, dead zones are and a Video Inspection Probe (VIP) very short. can be used to view and save a 400x In addition, fast growth in the de- magnified image of the fibre end face. ployment of PONs, which use multiple Many network owners now require in- levels of splitters in the network archi- stallers to supply an image of the fibre tecture, adds further complexity, and end to prove that all fibre connections requires a more complex calculation to Table 1: how fibre splits lose light in PONs. are clean on installation. correctly measure loss. When the opti- The advantages of hyperboloid contact technology By Bill Henderson Hypertac has been well known in the aerospace, rail and industrial markets as the company that provides the blue printed circuit board connectors incorporating the hyperboloid socket contact technology. What perhaps is less widely known is that Hypertac also provides the very high performance rack and panel connectors for applications such as avionics suite of the Eurofighter aircraft, as well as the heavy duty transpon- ders for the rail Eurobalise system. This relies on the superior fretting corrosion resistance which is a unique characteristic of the hyperboloid socket contact to maintain reliable operational performance during missions. Combined with the filtering and Fig. 1: The hyperboloid socket contact. transient protection technology within these connectors, this places Hypertac at the technology forefront within mil/aero, rail for very high power applications of up to 1000A. The basic con- and industrial markets. struction of the Hyperboloid socket contact is shown in figure 1. The fundamental characteristics available from this design are The Hyperboloid socket contact is a marvel of modern engi- retained across the whole range and offer substantial advan- neering where the basic socket technology can now be scaled tages over the more standard bifurcated socket contact design. from as small as 0.3mm diameter contacts used in very high Furthermore, the socket contact design offers a tremendous frequency coaxial applications up to 40GHz to 30mm diameter opportunity for characteristic optimisation to suit particular ap- plications. For example, the diameter and number of wires used Bill Henderson is Industry Director, Aerospace and Defence at within the hyperboloid cage together with the length of contact Hypertac -www.hypertac.com and the angle of twist can all be varied to optimise insertion 36 Electronic Engineering Times Europe January 2013 www.electronics-eetimes.com


EETE JANUARY 2013
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