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Electrical robustness for optical connectors

PushPull XS SFP
Frank Oudshoorn
Frank Oudshoorn
Global Product Manager, HARTING Customised Solutions
PushPull XS SFP

Fibre optic cables are now the common standard for transmitting high data rates over long distances. The biggest problems for an optical connector are dirt and damage to the optical contact surfaces, particularly if the optical communication takes place in harsh environmental conditions or “outdoors”. A weak or unusable signal can be the result. HARTING gets around this problem with its PushPull XS SFP connectors, simultaneously creating other advantages for the user.

In applications where large amounts of data have to be transmitted over long distances, fibre optic cables are the means of choice. Be it in the field of data and telecommunications or camera-based monitoring of extensive areas of the process industry. Datarates of more than 10Gbit/s or distances over 100 Meters makes the use of optical fibre cables inevitable. Corresponding fibre optic cables are clearly superior to their copper counterparts in these aspects. However, as is well known, there are two sides to every coin. The use of optical communication brings with it new challenges that users of electrical data transmission are not familiar with.

Before now?

In the past, the transceiver was either soldered (SFF) onto the printed circuit board (PCB), or as a pluggable transceiver (SFP) mounted somewhere in the device.

In this setup a short optical patch cord within the device was needed to make the connection from the receptacle on the front panel to the transceiver.

By changing the position of plug-in SFP transceiver directly in the device interface gives us two essential benefits. Firstly, it allows us to plug the incoming cable directly into the transceiver which saves us the device internal, short patch cord, not only for the cost of it but more important it saves us unnecessary attenuation. Secondly, and an even bigger benefit, it allows us to remove and change the transceiver through the front panel of the device, it even allows a media change between an optical LC transceiver and an RJ45 transceiver in the same slot as well.

However, this evolution step also resulted in some previously unknown problems. An SFP transceiver is basically standardised in all three dimensions, which is entirely sufficient at first glance. However, different lengths of the transceiver housings due to tolerances from various transceiver manufacturers resulting in, the electrical connection level to the board and thus the optical contact point can move by up to 7 millimetres.

Previous outdoor connector housings therefore have spring-loaded, protruding optical contacts on the termination side that should compensate for any differences in the plug-in depth and the final contact point caused by a shift in the connector. This, however, leads to two problems. The first problem is the resulting compression of the fibres in the connector.

In the worst case, the signal strength could be decreased at this point as a result of the minimum bend radius not being respected. To counteract this problem, previous connection solutions had to have longer housings. This meant that the fibre in the housing had enough space to compensate for the compression while also observing the minimum bend radius requirements.

The second problem is that this was a solution that needed an unnecessary space – a considerable factor with respect to costs and handling.

HARTING found a way to solve this problem with its new solution. The HARTING PushPull XS SFP connector does not intercept the various deep contact points via the bending of the fibres in the housing, but via the housing itself. For this reason, the connector does not lock at a fixed point, but instead has several locking points that ensure a secure connection across a distance of up to 8 millimetres. The XS SFP thus covers all the commercially available transceiver lengths and enables users to use the SFP transceiver of their choice, thereby always guaranteeing a secure connection regardless of the manufacturer.

Attaching the transceiver directly to the connector means that the final contacting of the optical cable takes place via the electrical copper contacts at the other end of the transceiver. The optical contacts can already be connected before the cables are delivered to the site and there installed outdoors and do not have to be separated for "plugging". This minimizes the risk of contamination or damage. Dust, rain or installation in places that are difficult to access are no longer a problem - because an optical cable is connected via electrical contacts.

The XS SFP's characteristics make it particularly suitable for applications in the process industry such as refineries, large chemical plants or mining facilities and it is most suitable as connecivity system on outoor antennas, Wifi Access pionts or any other outdoor networking equipment.

Simple assembly

For commissioning, only the protective caps have to be removed from the connectors and the holding fixture on the housing. The protective cap of the plug protects the pre-assembled SFP transceiver as well. The PushPull SFP can then be quickly and securely connected with just one simple manual action. Fast and correct assembly is also guaranteed by a clear colour coding system. This is optionally available in various colours and can simply and rapidly identify various related connections and connectors.

The final plug position is indicated by clear acoustic and haptic feedback when the locking lever engages. The “clack” sound tells the user knows that the dust-tight, water-tight connection has been made.

When connected, the housing of the XS SFP, in contrast to other glass fibre connectors, is considerably shorter. This saves weight and the need for an unnecessary large housing. Thanks to the very simple mechanism, the PushPull is extremely fast and reliable in terms of handling, always ensures a secure connection with a tactile and acoustic response and provides an effective seal against foreign bodies and moisture. Thanks to the compact square housing cross section, high packing densities with several connections in housings are readily possible.

Always optic?

In addition to the benefits described above in optical transmission, the PushPull XS offers another advantage. Due to the large length compensation, both optical (LC) and electrical (RJ45) transceivers can be used in the same SFP shaft. This allows users to decide themselves whether classic, coper-based cabling should be used or whether future-proof, high-performance optical cabling is the better option.

And for which applications?

The PushPull XS SFP is a connectivity solution for all kind of technology that use transceivers to connect from any device to an attached cable.

PushPull XS SFP is an outdoor rated IP65 connection system which will show its technical advantages where any outdoor active networking devices needs to be connected with either fiber optic (LCduplex) or copper (RJ45).

It allows plugging in the optical variant with attached transceiver, so in fact plugging in the optical fibers via the copper contacts at the transceivers back. It allows a quick replacement of the transceiver without dismantling the device itself, by just unplugging the PushPull XS SFP, removing the defective transceiver, click on a new one and plug the connector back into the device.

PushPull XS SFP is most suitable to be used as a connection solution on; Wifi access points devices for the use in outdoor, industrial, mining or other similar environments. Outdoor antennas which are connected with the use of a transceiver.

Devices for outdoor networking based on the use of transceivers. (Switches, Routers, Radioheads)

So everywhere where a quick and easy media- or transceiver change in an outdoor and outdoor like environment must be possible.

It is even possible to swap the fibre optic transceiver against a copper RJ45 transceiver and vice versa and using both in the same shaft.

The XS SFP scores in all respects:

  • Optimal fibre guidance and signal transmission
  • best protection of the optical contacts
  • smaller housing than competitors
  • safe and acoustically audible locking
  • IP 67 protected
  • Transceiver and housing compatible to all common suppliers
  • Suitable protective caps for connectors with connected transceiver
  • Protection caps for device flange
  • Ideal solution for Ethernet over long distances
  • Telecommunications, process industry (refinery), mining (underground, above ground)


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