The impact of drop cables and network equipment on the optical budget

When building a FTTH infrastructure, the first concern of telecom operators and installers is to ensure reliable and future-proof subscriber connections. To do so, it is essential to rely on a quality network equipment. Whether it is for a P2P "Point to Point" or Point to Multipoint architecture, the quality of installations is essential, as it ensures a sufficiently powerful optical signal so to allow access to very high speed networks. Thus, between the Fibre Concentration Point (FCP) and the Internet box installed at the customer’s premises, the optical budged is reduced at several strategic points of the architecture as for example, the connection points. Indeed, depending on the technique used to connect the different parts of the network together (Optical Distribution Point, Building Entry Point, Floor Distribution Box and OTO, ...), the optical budget may differ. Here is how each point of the FTTH network architecture can affect the overall optical budget of your fibre deployment:

Type of connection

Optical loss

Field mountable connectors


Mechanical splice


Fusion splice


It should be noted that these values are for indicative purposes only. Depending on the quality of the intervention at the connection points, the optical budget may be cut down beyond the optical costs indicated in the table above. In addition, in order to have an accurate estimate, it is necessary to add an additional attenuation of about 1dB due to the ageing of installations.

dual sheath Droptic LM4 drop cable for easy and reliable FTTH rollouts

Outdoor-indoor cables, a multi-purpose solution to boost the FTTH deployments

Dual sheath cables are an ideal solution for solving the problems related to the optical budget. Indeed, thanks to their double-sheath construction, they bring the optical signal from the ODP to the OTO seamlessly. No splice is thus required at the outdoor-indoor transition points, for instance. This considerably reduces the fibre roll-out times, as well as the CAPEX. Indeed, the use of 2-in-1 drop cables(MC) means that expensive equipment such as optical fusion splicers or optical cleavers can be avoided. Moreover, by using double sheath drop cables, specialised manpower is no longer mandatory for building FTTH infrastructures.

In addition, double jacket optical cables allow for simplified product management, as a single drop cable can be used interchangeably at several points of the FTTH architecture: in overhead layouts, in ducts, on facade or indoors. Offering a real flexibility of use, dual sheathed drops can be however built very differently, offering thus distinct performances. To find your fibre optic cabling solution among the diversity of models, we recommend you to take a close look at the information provided by the cable manufacturer.

Which double sheathed drop cable to choose ?

Combining the fire behavior performance required for indoor cables and the ruggedness specific to an outside plant installation, dual sheath drop cables are however built differently. In the Droptic® family for instance, there are two main dual sheath cable constructions with the LX048DS drop on one hand and the LM4 and LM3 on the other. Here are the main features of these cabling solutions and what makes them different:

  • The Droptic® LX048DS is built as an optical drop cable enabling fast and reliable aerial FTTH/FTTP roll-outs, where spans do not exceed 70m. This drop is designed with a tight or semi-tight structure and an outer diameter of 4.6mm. Thanks to a ripcord placed under the outer sheath, telecom technicians can access an LSZH FR indoor cable with a diameter of 3.6mm. In terms of performances, the LX048DS withstands to a maximum tension load of 800N and offers a crush resistance of up to 500N. This optical drop cable is compatible with Field Mountable Connectors and is available in two different versions: for 1FO or 2x1FO.
  • The Droptic® LM4 is a multi-purpose drop cable: it is used both for outside plant applications, in overhead layouts characterised by spans up to 70m, for installation into ducts on several hundred meters, on facades or for indoor applications. Its diameter has been reduced as compared to the Droptic® LM3 (5mm for the LM4 vs. 6mm for the LM3) for a better wind resistance and discreet cabling installations.
    Unlike LX048DS, the LM4 and LM3 drop cables are built with two ripcords, thanks to which the outer sheaths can be peeled off within a couple of seconds and without using any tools so to access an indoor LSZH FR drop cable (LM1L Ø 2.8mm for LM4 and LM1 Ø 3.3mm for LM3). These optical drops feature in addition swelling yarns, ensuring thus a reliable transmission of the optical signal even if flooding were to occur in the duct where they are installed. Available with different capacities: 1FO, 2FO or 4FO.