Bullets
What goes on inside a chamber? A chamber is a container for spare fibre and for one bullet which contains anything up to 288 joins.
Paul of B4RN explains the procedure of making the fibre joints inside a bullet.
The white plates are holders for a few joints. There are a set of white plates like this in each bullet. And that is all it is, the bullet is just a container for a set of connections. But cunningly designed so that the fibre is protected, the fibres can be worked on independently and there is room for some spare fibre.
This is all the bullet is - a container for lots of join like these. Those are plastic coated joints all lined up in their individual slots. There are 12 completed in the picture. There are 12 other slots on this plate and there are maybe 11 other plates.
Example
This chamber has been opened up. There is a coil of 72f already in there and an empty 16mm duct which will eventually have a 48f fibre in it. The other ducts are all 7mm , one for each of the 4 houses coming off this chamber. Two of the houses have their house fibre already - there is an extra piece of fibre protected inside the extra blue bit of duct, and the extra orange piece.
The bullet will connect all of the 48 fibres in the 48f cable to 48 of the 72 fibres in the 72f. That will leave 24 loose ends. Of these, 2 will be joined to the 2 fibres which are inside that blue duct, and 2 will be joined to the 2 inside the orange duct.
If all of the previous chambers have had their bullets spliced, then, when the bullet is completed in this chamber, those 2 houses will have continuous fibre all the way back to a tray in the cabinet.
The picture shows the chamber ready for fibre to be blown to it, that is all the length of spare 16mm you to need leave at the chamber when you are installing. 7mm should be a lot longer.
This chamber is how B4RN expect to find it – labelled and end capped. It ends up looking like one of the other pictures. It can be completely flooded, this doesn’t matter, because the bullet itself is watertight. (In fact, it wouldn’t matter if the bullet were flooded, it wouldn’t interfere with light passing down the fibre-optics)
This is in central Dent, a particularly busy chamber, where we used 5 sections to give more space. It would be okay with 4, but easier with 5.
It contains about 17 spurs and there are 3 extra bundles of fibre for core that is passing through on other routes
You can see that this chamber would have been okay with 3 sections.
To work on the bullet, it is pulled out of the chamber and fixed in a wooden vice. The correct fibres are located, fused together and tidied back into plastic protective plates inside the bullet. (B4RN use 3 different sizes of bullet, the design of plates varies a bit) This is done in the open air, in a tent or in B4RN’s horse box workroom. It is much better to work in the horse box, so chambers should ideally be located somewhere where you could get this to within say five metres. But wherever the chamber is located it can be worked on, only a few tools are needed.
Two sizes of bullets, opened up and secured in the vice to work on. The fibres are fused together then the spare length of fibre is wound into the plastic tray.
That is one of the plates that lives inside a bullet.
A lot of individual fibres carefully arranged.
When a fibre join is made, the actual join is protected by a plastic sleeve which is melted on round the joint. You can see 4 of these sleeved joints in the holders on the right side of the plate.
To join a 144f cable to another 144f cable would take 2 people a minimum of 4 hours
That’s Bruce having difficulty splicing in the cold.
Joe and Rob splicing a bullet in the B4RN tent
The horse box used at a chamber