So, this has been on the cards for a long time: should we still be using multimode fibre when it comes to FTTX? The short answer is ‘no’. Singlemode transceivers have typically always been more expensive than multimode tranceivers, however multimode cable has always been considered a little more expensive than singlemode cable. So there has always been a bit of a payoff for choosing one over the other. However, to get the gist of this particular article, we have to understand the exact difference between the two kinds of fibre optic cable and their traditional uses.
What is Multimode Fibre?
Multimode fibre is pretty much a self-explanatory term: data is transmitted down a fibre optic cable via light. In a multimode fibre cable the core is much larger than that of a single-mode fibre. This means that a variety of transmissions can be made down the same length of fibre at the same time. This is because the core is wide enough to accommodate a number of different wavelengths; ie. 850, 953 and 1300nm.
What Is Singlemode Fibre?
Contrary to multimode fibre, singlemode fibre can only transmit information down a single pathdown the cable. This doesn’t mean that one packet of data exists within the cable at any one time: packets of data immediately precede each other. The difference is that traditionally it was believed that multimode would be an easier way to transmit more volumes of data.
The Rise of Singlemode Fibre
The above case did not prove to be true; multimode fibre allows for much more light refraction within the core. This means that the db loss is considerably higher. In some wavelengths a multimode fibre can experience losses of 3.00 db/km, and this is without losses as a result of splices, bends, etc.
Additionally, at the point of transceiver, a multimode fibre suffers from DMD (differential mode delay) as time is taken to determine which wavelength the message is being relayed. At this point in time, the only real reason why multimode fibre is being utilized is due to the cost of singlemode duplex network in comparison to that of a multimode network. The cost can often be double that of a multimode fibre network! Well… that is until now.
Singlemode networks are fast becoming more cost effective than multimode networks. Why? Well for starters, the sheer volume of data that we use nowadays means that the only way fibre can keep up with our demands is by utilising a duplex SM or bidirectional SM network (something that can be scaled up to terabits in future). This means that more singlemode transcievers and SFP modules are required, which in turn means more production, which is resulting in a drop in the cost of production. Furthermore, it is actually more expensive for fibre cable businesses to produce multimode fibre due to the complexity of the cable.
Let’s Conclude
Singlemode fibre is becoming cheaper, and that doesn’t just mean the cable: that includes transceivers and modules too. Secondly, depending on the network design, the scalability of a singlemode fibre network will keep us invested in fixed P2P for the considerable future. The only place where multimode fibre will continue to be used would be on premises networks that require much cheaper modules: think mining (over shorter distances, of course).
Heavitech 