Polarization Control in Photonic Integrated Circuits
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In optical polarization multiplexed transmission systems, maintaining the orthogonality of polarizations is crucial to prevent signal overlap and noise, but waveguide imperfections and deviations cause polarization state changes, leading to data bit errors.
Innovation Solution
The use of birefringent waveguide structures and birefringent wavelength selective couplers, along with polarization strippers and alignment lasers, to maintain and align the polarization state of optical signals within and between photonic integrated circuits, ensuring orthogonality and minimizing signal interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If waveguide structures are used to transport optical signals, then signal transmission is enabled, but waveguide imperfections and fabrication deviations cause polarization state changes
Solution Approach 1:
The patent introduces a polarization controller as an intermediary device between the waveguide and the polarization beam combiner. This controller actively compensates for polarization state changes caused by waveguide imperfections, ensuring that the polarization states remain orthogonal at the combiner input despite manufacturing variations in the waveguide structures.
Solution Approach 2:
The patent employs adjustable polarization controllers that can dynamically modify polarization state parameters (such as orientation angles) to compensate for deviations. By changing these parameters in real-time or during system calibration, the system maintains orthogonal polarization states despite fixed manufacturing imperfections in the waveguide structures.
2Productivity
If polarization multiplexing is implemented to double transmission capacity, then transmission capacity increases, but polarization orthogonality must be perfectly maintained to prevent signal interference
Solution Approach 1:
Polarization controllers are positioned as intermediary devices between the waveguide outputs and the polarization beam combiner inputs. These controllers ensure that regardless of polarization state changes during propagation, the signals arrive at the combiner with maintained orthogonality, thus enabling reliable polarization multiplexing and doubling of transmission capacity.
Solution Approach 2:
The system incorporates feedback mechanisms through polarization controllers that can monitor and adjust polarization states. This feedback loop ensures that any deviations from orthogonal polarization states are detected and corrected, maintaining the integrity of the polarization multiplexed signals throughout transmission.
3Ease of operation
If optical elements and waveguide structures are added to the system, then signal modulation and transmission are enabled, but polarization state re-orientation occurs due to waveguide bends and junctions
Solution Approach 1:
The polarization controller serves as a mediator that compensates for polarization state changes introduced by necessary optical elements and waveguide structures. While these elements enable signal modulation and transmission functionality, the controller ensures that the polarization states remain stable and orthogonal by actively adjusting for re-orientation caused by waveguide bends, junctions, and other structural features.
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 approach effectively maintains the polarization state of optical signals, reducing noise and data bit errors by ensuring orthogonality and stability throughout the transmission process, thereby enhancing the transmission capacity and reliability of polarization multiplexed signals.
Implementation Method 1
The use of birefringent waveguide structures and birefringent wavelength selective couplers, along with polarization strippers and alignment lasers, to maintain and align the polarization state of optical signals
Implementation Method 2
two optical signals each having a common wavelength, but one of two orthogonal polarizations, may be independently modulated, and then multiplexed together for transmission
Implementation Method 3
an optical coupler configured to accept a first optical signal on a first input and a second optical signal on a second input, the second optical signal having a polarization state
Data Source
AI summary
The present invention provides a system, apparatus and method to maintain the polarization state of an optical signal propagating within a photonic integrated circuit, or from a first photonic integrated circuit to a second photonic integrated circuit. According to various embodiments of the invention, an optical circuit is provided which includes an optical coupler configured to accept a first optical signal on a first input and a second optical signal on a second input, the second optical signal having a polarization state. The optical coupler may combine the first and second optical signals into an optical output signal. A principle axis of a first end of an optical fiber is may be configured to align with the polarization state of the second optical signal, such that a polarization maintaining connection is established. The polarization state may be a TM polarization state, a TE polarization state, or another polarization state. The optical circuit may include birefringent structures, such as birefringent waveguides and birefringent wavelength selective couplers, to further maintain the polarization of optical signals propagating through the photonic integrated circuits.