Choosing the right optical fiber

Choosing the right optical fiber

We have already talked about Ethernet network cables and the differences between them. The fiber optic is an excellent compromise and the trend is rather in its direction, because the standards now recommend a universal communication infrastructure for all applications and the level of supported services is increasingly demanding.

In the context of new constructions, housing, buildings of all kinds, the UTE C 90-483 guide defines the performance of the installations in 4 levels or grades. Here is the list in order of levels:

  1. Grade 1: UTP cable for the top start 100MHz (ex: coaxial television)
  2. Grade 2: Digital local area network - FTP cable (250MHz)
  3. Grade 3: SFTP / SSTP cable (900MHz)
  4. Grade 4: optical fiber

Advantages of fiber

To cite the advantages, it should be compared to the traditional network cable. Here are the notable advantages:

  • Much less restrictive limitation compared to the distance between elements of an installation: around 2 km while for the Ethernet cable, 100 m represents the limit
  • In single mode, the bandwidth is unlimited (in theory)
  • The fiber is insensitive to electromagnetic interference
  • The transfer speed is significantly higher


The optical fiber is fragile, it must be handled with delicacy and be careful not to exert excessive twists and bends.

Composition of a fiber

The optical fiber is formed of several layers, a glass thread is surrounded by a reflective sheath. Light therefore travels through this wire like digital pulses.

From the inside to the outside, here are the different layers:

  1. the heart or soul allows the circulation of light
  2. the optical sheath protects the fiberglass
  3. the coating mechanically protects the core and the sheath
  4. Kevlar reinforcing fiber acts as protection
  5. the upper sheath contains everything

Multimode and singlemode

There are 2 types of fibers, each type will have a specific use.

La multimode fiber has a larger diameter to allow the passage of several wavelengths of light. It is used on the shortest distances.

La single mode fiber only allows one mode of propagation, it is used over distances greater than 5km.

The more the distance increases, the more the multimode fiber will lose in bandwidth, the speed will be more limited.

It should also be noted that the two fibers are incompatible.

Here is a summary table of the different types of fibers, whether multimode or single-mode:

Fiber typeOS1 / OS2OM1OM2OM3OM4
Diameter9 / 125µ62.5 / 125µ50 / 125µ509 / 125µ50 / 125µ
Distance> 5km<5km<550m<300m<150m
Area of ​​usebuilding linksvideo surveillance and networkvideo surveillance and networkGigabit and DatacenterDatacenter
Debitunlimited100 Mbit / s100Mb / s 1Gb / s10 Gb / s10Gb / s 40Gb / s

Quality of a fiber

The fibers are available in several finishes which allows them to be distinguished in terms of the degree of reflectance.

The polishing of the fibers makes it possible to reach such or such level:

  1. PC polishing (Physical Contact): the reflectance obtained will have a lower resistance of 30dB
  2. UPC (Ultra Physical Contact): better reflectance of - 50 dB
  3. APC (Angled Physical Contact): 60dB gain

That ends this article on fiber optics, now you can read cable purchasing reviews with full knowledge of the elements arranged.

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