Abstract:
The Michelson Interferometer has been the principal interferometer configuration for
Optical Coherence Tomography (OCT) imaging. For OCT applications, in particular
endoscopy, there may be polarisation induced signal fading due to environmental changes
within the sample arm. The most significant cause of polarisation induced fading within
OCT systems is suggested to be due to changes within the optical fibres. The Fizeau
interferometer has been shown to eliminate this polarisation induced fading as the sample
and reference arm experience the same environmental effects. However the Signal to Noise
Ratio (SNR) o f the Fizeau configuration is lower than that o f the Michelson because a
second processing interferometer is required.
An investigation into suitable interferometer configurations for OCT was carried out in
order to increase the performance o f the Fizeau interferometer compared with Michelson
configuration. It was shown theoretically that by using a circulator and balanced
detection, a standard Fizeau interferometer could achieve a signal to noise ratio (SNR) up
to I8dB greater than the conventional Michelson interferometer and a comparable SNR to
the Michelson interferometer optimised for power conservation.
An analysis into the optical components used in OCT systems was carried out and the
optimal Fizeau interferometer design was constructed. The Optimal design was shown to
give an increase o f 26dB compared to the standard Fizeau interferometer relative to
theoretical results using the same optical components. It was experimentally shown that
the use o f an optical circulator within the Fizeau interferometer improves the SNR
compared to the standard configuration.
