I think others have already answered the question of entanglement earlier in this thread. But if this fibre is so fragile and you indicate "The fibre I am referring to is 900 microns in diameter and has no strength member, it can be broken by hand with little effort.". What provisions is the designer/installer of the system taking to protect those cables in a day to day normal situation? If above ceiling voids and other spaces, no doubt there will be other installers, service engineers, maintenance staff all in those voids and spaces carrying out maintenance tasks etc and if fibre is indeed so fragile then would it not then suffer damage leading to failure of the data comms it was transferring?

Is that Data critical, whats the impact on loss of those fibres, safety/financial etc, plus somebody having to go out and repair.

Just on that alone I agree with what Alan B suggested should those fibres not be installed within a form of containment, protected from physical damage by another means, or installing in an area of the void/space to prevent ALARP damage. Or if so fragile select a diffrent fibre cable spec.

Cheers GTB

I think others have already answered the question of entanglement earlier in this thread. But if this fibre is so fragile and you indicate "The fibre I am referring to is 900 microns in diameter and has no strength member, it can be broken by hand with little effort.". What provisions is the designer/installer of the system taking to protect those cables in a day to day normal situation? If above ceiling voids and other spaces, no doubt there will be other installers, service engineers, maintenance staff all in those voids and spaces carrying out maintenance tasks etc and if fibre is indeed so fragile then would it not then suffer damage leading to failure of the data comms it was transferring?

Is that Data critical, whats the impact on loss of those fibres, safety/financial etc, plus somebody having to go out and repair.

Just on that alone I agree with what Alan B suggested should those fibres not be installed within a form of containment, protected from physical damage by another means, or installing in an area of the void/space to prevent ALARP damage. Or if so fragile select a diffrent fibre cable spec.

Cheers GTB

So the system in question is for retrospectively installing fibre in domestic settings, as you would install a coaxial cable for other tv and internet services, there are no trays conduit or other intrinsic support systems, no maintenance crews or others services in common voids, nor would the only data that may be classed as critical would be VoIP traffic but at the point of failure due to fire it is no longer a consideration. It is Netflix, emails, and teams’ calls running along skirting boards and walls.

Low breaking strain is relative, it would be difficult to break this fibre accidently, i.e. a child would have difficulty pulling it apart, cutting the fibre with child’s craft scissors would be a possibility. From an optics point of view the laser emerging from a broken fibre is class M1, the beam is divergent and presents no hazard unless observed under optics. The greater hazard is glass, if the cable is pulled apart then there is a possibility of exposed glass and so some kind of containment is appropriate. Given its domestic setting the supplier provides an adhesive that encloses the cable completely and dries clear.  In the event of a fire the adhesive fails at the same time as the fibres structure so the requirements in edition 18 are met. We also place steel clips above egress routes, doors windows etc. It is simple to meet the requirements of the wiring regulations, the challenge is doing so in a way that is acceptable to the domestic customer.

Thanks for the further explanation Timothy. I think your last few words will be the most challenging "Acceptable to the domestic customer".  Beauty is in the eye of the beholder, and a reminder why I never ever got involved in domestic/residential type work. Apart from my own home of course.

GTB