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How to Build a Sagnac Interferometer / Fiber Optic Gyroscope ( FOG )

Doug Marett ( 2010)

Our Instructional Video on YouTube

Some other details of the project:

1) The schematic diagram of the device:

2) A picture of the component parts (a smaller loop is shown for reference in yellow):

The part List: 

These parts are selected for the best match of components using all FC/PC or FC/UPC connectors at the 1310nm wavelength

Part Quantity Source
Laser diode 1 mW 1310 nm with FC/PC connector 1 with case and switch
battery power supply 1.5VDC 1 with RCA connector
PIN photodiode with FC/PC connector 1 diode alone   diode with amplifier
2 x 2 coupler 50:50 with FC/PC connectors 1
fiber optic loop with FC/UPC connectors 100m 1
single polarization/phase controller wheel  1 with mounting leg
mounting platform 1 flat round perforated metal pan 
FC/PC adapters 2 Senko type
D.C. voltmeter 1 multimeter

3. Calibration Test Run:

A fully assembled iFOG with a 100m fiber optic loop is shown below on its mounting platform.

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Other Relevant Information:

Discussion on the theory of the Sagnac interferometer and the Michelson-Gale experiment can be found here.

An interactive Sagnac interferometer simulator can be found here.

The original paper by Georges Sagnac can be found here.

The Dufour and Prunier paper (English Translation) with its detailed analysis of the Sagnac interferometer and how it does not obey relativistic theory can be found here.