Abstract

An edge light emitting diode (ELED) emission spectrum is near Gaussian at 820-nm center wavelength with 33-nm FWHM, promising a short coherence length within the range of feasible titanium indiffused lithium niobate (Ti:LiNbO₃) integrated optics unequal arm Mach-Zehnder interferometer (IOMZ) optical path differences. Interferometric ELED coherence measurements were made in a tilted mirror Michelson interferometer. Fringes were viewed with a near-IR video camera and digital imaging frame store connected to a computer. This apparatus measured all the quantities needed to compute the coherence function (Born and Wolf), which fits a Gaussian function of 6.4-μm standard deviation (SD) and peak value 0.78. We observed interference fringes in the output light of the second of two Michelson interferometers in series whenever any two of the four possible optical path lengths were equal within 3 SDs, 20 μm. These fringes are the reconstructed signal for coherence multiplexing. Proton exchange applied to one side of a symmetric Ti:LiNbO₃ IOMZ can form a 2000-μm optical path difference via changes in the substrate refractive index. From such MZs, we propose to form coherence multiplexing systems of up to ten parallel channels. ELED power attenuated by system Y-junctions, background, and detector noise imposes this channel limit.

© 1988 Optical Society of America