Coherent Receiver Geometric Arrangement for Assembly and Loss Reduction
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Solution Overview
Problem
Current coherent receiver modules for DP-QPSK modulation formats face challenges in achieving balanced signal processing over a wide wavelength range, high symbol rate, and extended temperature range due to stringent requirements for phase and time alignment, leading to complex and unreliable assembly processes and high optical loss.
Innovation Solution
An integrated coherent receiver chip with a geometric arrangement where the optical axes of the 90° hybrids are parallel to the input facet, allowing for flexible and efficient optical coupling, reduced chip size, and balanced delays, and eliminating optical waveguide crossings, enabling reliable assembly and improved signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If optical waveguide crossings are used to connect hybrid outputs to differential inputs, then signal routing is achieved, but propagation loss increases and device complexity increases
Solution Approach 1:
The patent removes optical waveguide crossings from the system by reconfiguring the geometric arrangement of photodetectors and hybrids. The photodetectors are positioned such that their electrical outputs can be directly connected to the differential inputs without requiring optical waveguide crossings, thereby extracting the harmful crossing elements from the optical path and eliminating associated propagation losses.
Solution Approach 2:
The patent transitions from a planar two-dimensional layout to a three-dimensional geometric arrangement where photodetectors are positioned at specific angles and distances. This dimensional change allows electrical connections to bypass the need for optical waveguide crossings by utilizing spatial separation and angled positioning, thereby reducing optical loss while maintaining functional connectivity.
2Measurement precision
If stringent phase and time alignment requirements are imposed, then signal processing accuracy is improved, but assembly complexity and reliability deteriorate
Solution Approach 1:
The patent implements local quality by positioning each photodetector at a specific geometric location and angle relative to the hybrids, rather than requiring uniform alignment across all components. This localized geometric optimization allows each detector to naturally receive signals with the correct phase and time relationships, reducing the need for stringent global alignment requirements and improving assembly reliability.
Solution Approach 2:
The patent performs preliminary action by pre-configuring the geometric arrangement of photodetectors and hybrids during the design and fabrication stage. The specific angles and positions are predetermined to inherently provide the required phase and time alignment, so that during assembly, fewer adjustments are needed, thereby improving reliability while maintaining precision.
3Measurement precision
If complex assembly processes are used to meet alignment requirements, then signal processing performance is improved, but manufacturing complexity and time increase
Solution Approach 1:
The patent changes the geometric parameters (angles, distances, positions) of the photodetectors and hybrids to optimize signal processing performance. By carefully selecting these parameters during design, the system achieves high-performance signal processing with a simplified assembly process, as the geometric configuration itself provides the necessary alignment rather than requiring complex post-assembly adjustments.
4Loss of energy
If optical waveguide crossings are eliminated, then propagation loss is reduced, but signal routing complexity may increase
Solution Approach 1:
The patent merges the functions of optical signal routing and electrical signal detection by positioning photodetectors to directly receive optical signals from hybrids without intermediate waveguide crossings. This merging of optical and electrical pathways eliminates the need for separate optical routing structures, reducing propagation loss while maintaining manageable geometric complexity through integrated design.
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 solution enhances the efficiency and reliability of the coherent receiver module by simplifying assembly processes, reducing propagation loss, and minimizing skew between polarization components, while allowing for better thermal management and flexible packaging options.
Implementation Method 1
The 90° hybrid can be realized with either a waveguide mode interference coupler (FIG. 2A) or a 4×4 Multimode Interference (MMI) coupler (FIG. 2B)
Implementation Method 2
two 90° optical hybrids (3007, 3008), eight high speed waveguide photo-detectors (3010)
Data Source
AI summary
Disclosed herein is a monolithically integrated coherent receiver chip which has a geometric arrangement of the on-chip components that significantly improves the performance and the manufacturability of a coherent receiver module for Dual Polarization Quadrature Phase Shift Keyed (DP-QPSK) applications and other optical coherent detection systems. The coherent receiver chip comprises two optical hybrids, three optical inputs and eight electrical outputs with the two optical hybrids oriented perpendicular to the optical inputs and the electrical outputs which are widely spaced and arranged in a co-linear fashion that simplifies module design and assembly. The proposed geometric arrangement also replaces any optical waveguide crossings with vertical electrical-optical crossings and includes electrical transmissions which are used to minimize channel skew. The proposed configuration also has the additional benefit of improved thermal management by separating the module's trans-impedance amplifiers.