Archive for the ‘Optical fibre cables and light boxes.’ Category

Optical fibres are often used to transmit light if a doctor needs a bright light.

An example of one.
optical fibre cable
The most common arrangement is a light box, an optical fibre cable and a headband. The light box often has two lamps in it so if one of the lamps fails mid procedure you can quickly switch to the reserve one. There will be a transformer to reduce the voltage to suit the lamp.
The optical fibres will be either glass or plastic. I am not an expert on the fibres themselves but I think for short distances plastic is used.
At the front box there is place you plug in the optical fibre cable, the cable will then go to a headband and a lens to concentrate the light where it is wanted.
The cables are made up of a bundle of small optical fibres with an outer silicone rubber covering.

Sometimes the user will complain that the light is not as good as it was. Assuming it is just a reduced light output check the cable.
Plug it in to the light box and unplug it from the headband. Turn on the light box and examine the open end of the optical fibre cable. Do not look directly into it because the light can be vey bright. Look at it from an angle.
With a new or good one you will see an evenly bright and round illuminated end.
If when you look at the end you see some little black spots it means that some of the fibres have broken. Each time a fibre breaks it stops transmitting light and therefore goes black.
To start with the first few breaks will make little difference to the light output but over time with each break the light output will get slightly less.
Eventually the user will complain and you will see lots of dark spots.
Sadly other than making sure that both ends are clean there is nothing you can do about it.
There is no way to repair individual fibres. The cable will have to be replaced.
You can buy a tool to measure the brightness of the light output.

It may be that they complain that there is no light. Start by checking that the light box has power to it and that there is an output from the transformer.
Next check the lamps. You wil probably find that they are both broken, sometimes you can tell because the glass will be blackened.
Replace the lamps and test, there may be a rheostat to alter the brightness of the light, check it works.
That should sort out the problem.

A complete set up can be very expensive and a new cable will also be expensive.
These days it is possible to buy head lamps that are used for all sorts of situations in the home and out and about.
The new LED headlamps can be very bright and quite good enough for the general illumination doctors need for their procedures.

This one uses rechargeable batteries, others may use ordinary batteries. It has an output of 750 lumens. A dedicated medical one may have an output of 120 lumens. I don’t think that the user will really notice much difference. The real difference will be that the dedicated medical one might well cost ten times as much.


In commercial situations such a broadband and data transmission it is possible to repair these cables, they have special diagnostic tools to identify where the break is. It is possible to cut and splice in a new piece of cable. This will be done where there is a major break where say someone has completely or partially cut through the cable.

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