Information: Selecting Fibre Type

We have talked before about the advantages of using Advance transceiver modules and hopefully made clear that the technical performance of our products is at least as good, if not better, than original vendor’s products. It is important to remember though that the transceiver is only part of the equation when assessing the performance of a fibre optic link – probably the single lowest cost item in any fibre link is the patch lead (or patch cord, patch cable, fly lead or any one of a plethora of alternative names used to describe a short piece of fibre cable with connectors on each end!) and selecting the correct one is just as important as selecting the right SFP module.

It is always best to match the patch lead to the fibre installed in the fixed part of the optical network – the multicore cables that terminate inside panels within the rack. A miss-match here can have serious effects due to increased attenuation and losses. There are some exceptions when miss-matched grades do not pose an issue providing the core size of the fibre is matched. This is only applicable with multimode 50/125 and singlemode 9/125 fibres.

Multimode 50/125, technically referred to as OM2, has the same core size as OM3 and OM4 fibre – 50 microns. OM3 and OM4 are laser optimised, with increasing bandwidth capabilities between the two, but ultimately are backwards compatible with OM2 providing the connecting devices are Gigabit or slower. 10G links and above require laser optimised fibre over the entire length of the link to reach expected performance. What this means though is; if an OM2 backbone is installed you can use an OM3 or OM4 patch lead between the switch and panel on some links.

Similarly, singlemode 9/125 fibre has been improved on over time. OS1 and OS2 grades are identical in core size, 9 microns in this case, and are fully compatible with each other. OS2 fibre was originally designed to perform better in outdoor rated cables, whereas OS1 was typically used in indoor cables. Due to the reduction in manufacturing costs when producing at scale though, generally all singlemode fibres manufactured in the last 5 years or so are OS2 grade. Either way, these grades are interchangeable with no performance hit on the optical link.

With that all covered, a little guide on identifying existing fibres may be useful. Generally the multicore cables in the network are black, so colour here is not a useful indicator. If you can access the cable itself within the rack, normally the entire cable length will be printed with its technical information, including grade and core size. If not, then comparing existing patched in cables may be the best way to go without opening up panels and potentially disturbing existing links. Below is a guide to industry accepted colour codes for patch cable, but beware – not everyone follows the exact same standards and sometimes you do find alternative colours, or even multimode cables in singlemode colour and visa-versa.

Grade Core Size Colour
OM1 62.5/125 Grey or less commonly, Orange
OM2 50/125 Orange
OM3 50/125 Aqua
OM4 50/125 Violet or less commonly, Aqua
OS1/OS2 9/125 Yellow

I put a couple of less common colours in this table. Generally the first colour shown is the accepted norm, but there has been some difficulties with standardisation in the past which lead to some crossover in colours. If you are not 100% sure, patch cable will normally have its grade and core size printed along its length.

Once the fibre type is identified, choosing connectors is a simple process. Below is a set of images detailing each of the most common connectors, and also their receptacles which is normally what you’ll see on a patch panel. Match one end of the patch lead to your panel and the other end to the host device’s connector. GBIC modules use SC, SFP/SFP+ use LC, QSFP use LC or MTP (aka MPO-12). Normally connectors are duplex, in that there are physically two connectors (one for transmit, the other for receive), although Bi-Di (bidirectional) modules use a single connector and MTP is an array.

So now we have identified fibre type, and connector type at both ends of the cable. Armed with this information and a desired length in mind, you can contact your preferred supplier for a quote. Of course, we’d like it if you put Advance at the top of your list! We stock a huge array of lengths, modes and connector types to fulfil almost every requirement imaginable. And if we don’t have the specific lead you need in stock, we can manufacture any custom assembly to demand in our UK based termination facility. Contact us for more information and a quote today.