Ch 9- Fibre Optic Gyro Compass (to finish)

Question 1

What are the four types of compass systems?

Answer 1

• Magnetic compasses
• GPS compasses
• Gimballed systems
• ‘Strap Down Systems’

Question 2

Does a fibre-optic gyrocompass have moving parts?

Answer 2

No

Question 3

What does a FOG use, and how does this work?

Answer 3

A number of sensors to compute the direction of rotation of the earth, and from this derives the direction of geographical North

Question 4

Does a FOG have a gimbal system?

Answer 4

No

Question 5

Where can a FOG be bolted down?

Answer 5

Any suitable location

Question 6

What type of vessels are FOGs suitable for?

Answer 6

High speed vessel, whose operation requires frequent changes in speed/heading

Question 7

Describe a fibre-optic cable

Answer 7

The core has a higher refractive index than the cladding which causes internal reflection of a beam of light

Question 8

How is the rotation of a fibre optic coil measured?

Answer 8

• Beam of light is split before the two paths are sent in opposite directions around the fibreoptic coil
• Upon return of the beams, the wavelengths are compared using interferometry
• The phase shift is translated into angular velocity
• Thus the rotation of the coil can be measured

Question 9

What is a fibre-optic sensor unit comprised of?

Answer 9

A power source, three fibre-optic coils, level sensors and a processor

Question 10

What effect do fibre optic coils use to measure angular velocity?

Answer 10

Sagnac effect