Optical Adaptive Filter. Frequency Domain Implementation.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
Pagination or Media Count:
This report presents the results of a feasibility test on an optical adaptive filter, implemented in the frequency domain. The OAFFI is the follow-on to the optical adaptive filter, which was implemented in the time domain. The theory of OAFFI is based on adaptive linear predictions using correlation cancellation loops and optical signal processing OSP using Fourier optics lenses and acousto-optics Bragg cells. A few optical architectures, which form the fundamental building blocks of OAFFI, were built and examined prior to the OAFFI architectures. These fundamental architectures included an Optical Spectrum Analyzer, Optical Excisor two versions and a Liquid Crystal Light Valve. The Optical Excisor used heterodyning principles which in an OSP sense usually involves an interferometer MZI and common path interferometer CPI. OAFFIMZI exhibited phase stability problems in the optical output. To overcome these phase stability problems, the common path interferometer version of OAFFI was built. OAFFICPI overcame the phase stability problems of OAFFIMZI. However, stability problems resulting from positive feedback at various frequencies were observed in OAFFICPI. Nevertheless, OAFFICPI also demonstrated some positive results that should stimulate further investigations.