Tapered Input Rib Waveguides for Optical Multiplexer Bandwidth
Solution Overview
Problem
Conventional optical multiplexers, particularly Echelle grating multiplexers, face challenges in broadening channel bandwidth without incurring additional losses, as existing methods to increase bandwidth either reduce peak transmission or are ineffective due to alignment errors and temperature drift.
Innovation Solution
The optical multiplexer design features input waveguides with tapered rib portions that decrease in width towards the slab waveguide of the wavelength multiplexer element, broadening the optical mode width and channel bandwidth while maintaining high transmission levels, and can function as both a multiplexer and demultiplexer due to optical symmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the input waveguides are made with different widths than output waveguides to broaden channel bandwidth, then the channel bandwidth is increased, but the peak transmission is reduced due to mode mismatch
Solution Approach 1:
The input waveguide rib portion is made tapered (dynamic width variation) rather than uniform, allowing the mode width to gradually transition and match the slab region mode profile. This dynamic geometric change enables both broad channel bandwidth and high peak transmission by optimizing mode coupling across the waveguide interface.
2Area of stationary object
If rib waveguides are used to extend mode into surrounding etched region, then the mode width is increased, but the mode centre shifts from physical centre reducing peak transmission
Solution Approach 1:
The rib portion is made tapered with varying width along the propagation direction, creating local geometric variations that control the mode profile. The taper ensures the mode centre remains aligned with the physical centre at critical interfaces while still extending the mode width into the slab region for broader channel bandwidth.
3Area of stationary object
If the optical mode width is increased to broaden channel bandwidth, then alignment error tolerance is improved, but transmission efficiency is reduced
Solution Approach 1:
The geometric parameters of the waveguide rib portion are changed by introducing a taper profile. This parameter modification allows the mode width to be increased for better alignment tolerance while the taper design optimizes the mode transformation to maintain high transmission efficiency through improved coupling to the slab region.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design achieves broader channel bandwidth with reduced losses, maintaining high transmission efficiency and enabling the multiplexer to operate effectively over a wide wavelength range, including 1.2 μm, while being compatible with various multiplexing technologies like Echelle and arrayed-waveguide grating multiplexers.
Implementation Method 1
a wavelength multiplexer element, coupled to each input waveguide and the output waveguide, the wavelength multiplexer element comprising a slab waveguide which includes a grating configured to multiplex signals of differing wavelengths
Implementation Method 2
the input rib portion(s) of one or more of the input waveguides are tapered so as to decrease in width in a direction towards the slab waveguide of the wavelength multiplexer element. The tapered width of the input rib portion(s) broaden the optical mode width significantly
Data Source
AI summary
An optical multiplexer. The optical multiplexer comprising: a plurality of input waveguides, each comprising an input slab portion and an input rib portion; an output waveguide, comprising an output slab portion and output rib portion; and a wavelength multiplexer element, coupled to each input waveguide and the output waveguide, the wavelength multiplexer element comprising a slab waveguide which includes a grating configured to multiplex signals of differing wavelengths, received from the input waveguides, into a multiplexed signal, and provide the multiplexed signal to the output waveguide. The input rib portion(s) of one or more of the input waveguides are tapered so as to decrease in width in a direction towards the slab waveguide of the wavelength multiplexer element which is an echelle grating or an arrayed waveguide grating.