On Wednesday, 25 November 2020 at 10:48:15 UTC, Andy Burns wrote:
Brian Gaff wrote:

I'm not disputing the type used for the link, though
there are boosters at certain distances.
no boosters, it's a passive optical network, there's a splitter
somewhere between the exchange and the homes, but AIUI nothing
electronic at all, distance limit 50 to 60km I believe
However there are also connector losses.
yes, maybe even a deliberate attenuator if the distance is short.

I recently had a fibre leased line installed at an office. The length was
a few km and the total upstream and downstream losses were
0.9 and 0.7dB including all splices and connectors. (Different
wavelengths of infra-red light are used for the two directions, hence
the difference in uplink and downlink losses.

As already mentioned, pre-terminated lengths of fibre for indoor use
(and variants for outdoor use and direct burial) are readily available at
low cost to order with a wide variety of connector types.
There are also lots of standard lengths available from stock.
I have bought 30m lengths of pre-terminated duplex single-mode fibre
from eBay for a few pounds.
You may be thinking of plastic fibre which is used for digital audio. This
has a much shorter maximum range than the glass fibre used for
internet provision.

John