We are going to separate the tutorial into two different parts, the theoretical part, where we will explain all the information we need to know what type of optical fiber to choose for our installation, and the practical part, where we will see all the steps to follow to make the connection between our two switches. Finally, we will carry out a visual and logical check of the connection, leaving the equipment ready for any installation requirement where it has to be placed.
The first thing we should know is that there are two different types of optical fibers, and that each one has its advantages and disadvantages. These two types of fiber are called single-mode fiber and multimode fiber, and although their name expresses a bit the main difference between them, we are going to see all the differences in detail.
Due to the demand for higher speed in data networks, it is necessary to have high-speed connections, and these connections have been significantly improved thanks to the use of fiber optics. Currently in switches, we can use single-mode fiber optic (SMF) and multi-mode fiber optic (MMF) to connect them. Depending on our needs, mainly distance, we will have to choose a type of fiber or another type of fiber. Now we are going to focus on the basic construction, distance and cost of the fiber to make a deep comparison between singlemode and multimode fiber.
Singlemode vs multimode fiber
Single-mode optical fiber is designed to transport light only through the fiber, in transverse mode, only a beam of light is delivered in one way, modifying the wavelength in case of wanting to multiplex and make use of download and upload. In the case of switches, the most normal thing is to have one fiber for download and another fiber for upload, that is, there is no multiplexing
In multimode optical fiber it means that there are several modes of propagation of light, it also allows modifying the wavelength to multiplex it and use the download and upload simultaneously. The main difference between singlemode and multimode optical fibers are the diameter of the fiber core and the distance they allow us to cover.
The diameter of single-mode fiber optic cable is clearly thinner than that of multimode fiber optic. The most normal thing is to find that single-mode optical fiber has a diameter of 9 µm, while the diameter of multimode optical fiber is between 50 µm and 62.5 µm.
Wavelength and light source
The size of the fiber core makes it possible to use low-priced light such as LEDs, or much more expensive such as lasers. Typically single mode fiber optics use a laser or laser diodes to “illuminate” the fiber, the wavelength is typically between 1310nm and 1550nm. Regarding multimode optical fibers, we have lasers but also LEDs which are clearly cheaper, in addition, the wavelength of MMFs are 850 nm and 1310nm.
The main characteristic of fiber optics is that it allows us to cover long distances, unlike the popular BASE-T standards that allow up to 100 meters per segment only. With single-mode or multimode optical fibers, we can reach a distance of several kilometers, although the most normal thing is to have distances of around 550 meters, more than enough to link switches between them.
As you can see, the distance when using fiber optics, depending on the standard used, exceeds 500 meters without problems. The typical speed used with fiber optics is 1Gbps or 10Gbps, but we also have speeds of 25G, 40G and even 100G, the latter ideal for data centers.
Fiber optic cabling cost
The first thing we must bear in mind is that to connect two or more switches with fiber optics, we will need two optical transceivers (one in a switch, and another transceiver in the toro switch) and the corresponding cabling with fiber optics. The most expensive thing we can buy are single-mode fiber transceivers, and they can be twice as expensive as multimode fiber transceivers.
Depending on the distance that we are interested in covering, we will have to choose one version or another, single mode or multimode. We must remember that single-mode fibers are used to interconnect equipment over long distances, but transceivers are clearly more expensive. For example, the 1000BASE-LX standard is single-mode and allows distances of up to 10Km, on the other hand, the 1000BASE-SX standard makes use of multimode fiber and allows distances of up to 550 meters.
If we compare the following models:
- D-Link DEM ‑ 431XT using the 10GBASE ‑ SR standard with MMF fiber, the price is 260 euros.
- D-Link DEM ‑ 432XT using the 10GBase ‑ LR standard with SMF fiber, the price is about 480 euros.
Although there are transceivers from brands like 10GTek that are clearly cheaper than the previous ones, the price difference is up to 50% greater between singlemode and multimode. The single-mode version is worth 36 euros, compared to the multimode version, which is worth 24 euros.
Regarding the fiber cabling itself, the prices are quite similar, the most expensive is the transceiver itself, one of the best websites to buy fiber optic cabling is Cablematic, they also have fiber optic transceivers to buy everything in the same store, it is from our favorite stores to buy network cabling.
As you have seen, depending on the distance we are interested in covering and the budget, we must choose single-mode or multimode fiber optics to make the connections between the switches.