Modified Fabry-Perot interferometric method for waveguide loss measurement

Abstract

An extension to the Fabry-Perot interferometric method is demonstrated to calculate the optical loss and the reflectivity for optical waveguides simultaneously. The method uses an excitation of the waveguide with a broadband amplified spontaneous emission source (a superluminescent diode in our case) and curve fitting to account for the change of input power, thereby simplifying the measurement procedure. The use of a broadband source as opposed to tunable lasers allows for simultaneous measurements over multiple wavelengths and decreased sensitivity to reflections in the cavity. Further, waveguides of different lengths are measured to calculate the optical loss and the reflectivity simultaneously. It is shown that, if the value for reflectivity is assumed, there could be a large error in the measurement of loss especially for short waveguides. Optical loss for ridge waveguides is measured and compared by using a tunable laser as the input source. The method can be used for a generic case where it is suspected that the input power changes during the measurement.

High index contrast passive potassium double tungstate waveguides

“…2 (b)]. Propagation losses can also be estimated based on the Fabry-Perot fringes induced in the waveguide cavity formed between the input and output end-facets [29][30]. The power reflected from the Fabry-Perot cavity by the end-facets of the waveguides is given by Eq.…”

Hot-wire chemical vapor deposition low-loss hydrogenated amorphous silicon waveguides for silicon photonic devices

“…Based on the analysis of the Raman spectra, the best Gaussian fit of a-Si:H network material with optimal T sub was determined. Preliminary transmission measurements were then conducted on the a-Si:H waveguides deposited at various T sub , with dimensions of 2 μm width and 400 nm height, using the Fabry-Perot [32] method to correlate with the Raman results. The light was coupled into the device by the end-fire coupling approach with a 40× magnification objective lens at the input and output of the waveguide.…”

Method for characterization of Si waveguide propagation loss

“…Where i a ( 1,4) i = are the four inputs and j b ( 1,4) j = the four outputs. The real coefficients t and k account respectively for the field transmission and coupling of the bus to ring directional coupler with the additional condition 2 2 1 t k + = .…”

“…To the authors knowledge there is not a standard for waveguide loss measurement. Commonly used methods are cut back [3], Fabry-Perot loss modulation [4,5], variable length clips [6], and critical coupling configuration with all-pass single microring structures [7]. In this paper we propose a method based on a simple microring structure in and under coupled condition.…”