Polarization Attenuator Waveguide Offset High-Order Mode
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Solution Overview
Problem
Integrated optical components often suffer from polarization-dependent loss (PDL) due to differences in propagation loss and polarization responses, making it challenging to maintain polarization state consistency in optical fiber links.
Innovation Solution
A polarization attenuator structure comprising a first main waveguide, an offset waveguide, and a second main waveguide, where the offset waveguide excites high-order modes, allowing power redistribution between fundamental and high-order modes, with controlled length and offset to achieve low PDL and high extinction ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional waveguide structures are used, then the device is simple in structure, but polarization dependent loss occurs due to differences in propagation loss between polarization states
Solution Approach 1:
The waveguide structure is divided into three distinct segments: a first main waveguide, an offset waveguide, and a second main waveguide. Each segment serves a specific function in managing polarization states. The offset waveguide segment, with its displaced center line, specifically targets one polarization state for attenuation while allowing the other to pass through with minimal loss, thereby resolving the PDL issue through structural segmentation.
Solution Approach 2:
The offset waveguide introduces a localized structural variation where the center line is displaced relative to the main waveguides. This local geometric modification creates different propagation characteristics for different polarization states within that specific region, enabling selective attenuation without affecting the entire waveguide structure uniformly.
2Reliability
If an offset waveguide is introduced to reduce PDL, then polarization balance is improved, but the device complexity increases
Solution Approach 1:
The offset waveguide is designed with an asymmetric configuration where its center line is deliberately displaced from the center lines of the first and second main waveguides. This asymmetric positioning creates different coupling conditions for orthogonal polarization states, allowing one state to experience attenuation while the other maintains low loss, thus achieving PDL balance through controlled asymmetry.
3Reliability
If the offset waveguide causes high attenuation for one polarization state, then polarizer performance is improved, but the other polarization state may experience unwanted loss
Solution Approach 1:
The offset waveguide is designed to apply partial attenuation to one polarization state rather than complete blocking. By carefully controlling the offset distance and waveguide dimensions, the structure achieves sufficient extinction ratio for the blocked polarization state while ensuring that the transmitted polarization state experiences minimal loss, thus balancing the partial action requirement.
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
The solution achieves a low PDL value ranging from 0 dB to −2 dB and an extinction ratio up to −30 dB, effectively balancing polarization states and reducing signal loss in optical devices.
Implementation Method 1
the offset waveguide excites high-order modes, allowing power redistribution between fundamental and high-order modes
Implementation Method 2
the first main waveguide or the second main waveguide supports fundamental modes, and supports at least one high order mode
Data Source
AI summary
The present disclosure provides a polarization attenuator and a polarization attenuation method to solve the problem of polarization dependent loss of optical devices, or to be used in optical devices or systems as a polarizer structure. The polarization attenuator comprises a first main waveguide, an offset waveguide and a second main waveguide which are arranged in sequence, wherein an output surface of the first main waveguide partially overlaps an input surface of the offset waveguide; an output surface of the offset waveguide partially overlaps an input surface of the second main waveguide; the first main waveguide or the second main waveguide supports fundamental modes and supports at least one high order mode. Meanwhile, the present disclosure further provides the polarization attenuation method comprising following steps: 1) optical signals enter the first main waveguide; 2) the optical signals excite high order modes at a joint of the first main waveguide and the offset waveguide; and 3) the signals are mixed again at a joint of the second main waveguide and the offset waveguide, and power between a fundamental mode and high order modes of the offset waveguide is redistributed between the fundamental mode and the high order mode of the second main waveguide.