Design considerations in optical add/drop multiplexers based on grating-assisted null couplers

Abstract

Abstract-The performance of a fully optimized optical add/drop multiplexer (OADM), based on null couplers and tilted Bragg gratings, is studied in detail. It is shown that maximization of the device performance involves three main optimization steps. First, the waveguide asymmetry ( 2 1 ratio) should be optimized in order to minimize the extinction ratio of the unwanted mode at the null coupler waist. Second, the coupler taper shape should be optimized in order to further minimize the aforementioned extinction ratio. Third, the grating tilt angle and relative width can be also optimized to give negligible backreflections at the input port and minimize radiation losses. The results show that the proposed high-performance OADM configuration can meet the stringent telecom specifications.

Optical add-drop multiplexers based on the antisymmetric waveguide Bragg grating

“…However, reflections between forward-and backward-propagating modes of the same profile ͑a ϭ b͒ are still produced in various strengths at different wavelengths. 5,7 Figure 2 illustrates the predicted reflectivity of a TBG when even or odd modes are launched. The tilt of the grating is close to the angle that minimizes the odd-odd reflection (optimum).…”

“…The tilt of the grating is close to the angle that minimizes the odd-odd reflection (optimum). 5 It was predicted theoretically and demonstrated exper- imentally 5,6 that there is no angle that minimizes the even-even reflection without drastically reducing the strength of the desired reflection with mode conversion. The effect of this unwanted even-even reflection can be minimized by choice of the proper input and outports; however, this reflection still produces noise and cross talk and places stringent requirements on the performance of the Y branch.…”

“…[2][3][4][5][6] As shown in Fig. 15, from the input port (narrower branch) several wavelength-division multiplexing (WDM) channels excite the odd mode of the waist.…”

“…However, TBGs produce multiple reflections, only one of which provides the desired mode conversion. [5][6][7] The unwanted reflections produce noise, cross talk, and backreflection, and they place stringent requirements on the performance of the Y branch.…”

A Complete Analytical Analysis and Modeling of Few Mode Non-Uniform Fiber Bragg Grating Assisted Sensing Waveguide Devices

“…The mechanism of FBG is the reflection at the Bragg wavelength and coupling of power from the forwardpropagating mode to the backward-propagating mode. This coupling phenomenon is very important in the case of optical fiber sensors or any other types of devices [11,12]. The widely established approach for the simulation of waveguide devices and grating assisted coupled waveguide devices is the coupled mode theory (CMT), which combines a deep insight into the problem together with a much greater computational simplicity than other numerical methods such as Finite Difference (FD), Finite Element (FE), and Beam Propagation Methods (BPM).…”