Optical Fibre

Three connections and one measurement. Light is coupled into the fibre, spills out of the far end as a cone, and lands on a screen carrying four fixed circles. Slide the screen until the beam matches one of them, then read off how far away it had to move.

Procedure

1. 1.

   Click "Insert Fibre" to place the fibre between the transmitter unit and the NA jig.

2. 2.

   Switch on the mains supply to the transmitter unit.

3. 3.

   Choose one of the jig's four fixed circles — its diameter is w — and slide the screen until the cross-section of the laser beam coincides with it.

4. 4.

   Note the distance L between the screen and the jig at that position, and record the diameter w of the circle it matched.

5. 5.

   Work out the numerical aperture, acceptance angle and acceptance cone from L and w using the formulae below.

6. 6.

   Repeat for the remaining three circles.

7. 7.

   Check and verify the result.