Integrated Beam Splitter Offset Ports Stray Light
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Solution Overview
Problem
Optical sensor devices used for high-voltage current and voltage measurements face challenges in achieving metering class accuracy due to temperature dependence and signal instability, particularly in extended temperature ranges.
Innovation Solution
The design incorporates an integrated-optics beam splitter with offset ports and a recess for the quarter-wave retarder, along with a soft adhesive layer to reduce mechanical strain and stray light recoupling, ensuring improved signal stability and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional beam splitter designs are used, then the device structure is simple, but signal instability and temperature dependence occur leading to reduced measurement precision
Solution Approach 1:
The beam splitter is designed with asymmetric port positioning where the sensing-side port is offset from the optoelectronics-side ports. This asymmetric geometry prevents stray light generated at the optoelectronics ports from recoupling into the sensing port, thereby eliminating signal instability while maintaining measurement precision across extended temperature ranges
Solution Approach 2:
The quarter-wave retarder is extracted from the conventional integrated structure and placed in a separate recess on the beam splitter surface. This separation allows the retarder to be positioned independently to introduce the required 90° phase bias without being affected by temperature-dependent stress in the integrated structure, thus improving signal stability
2Device complexity
If integrated-optics beam splitter is used, then device complexity is reduced, but temperature-dependent stress affects measurement precision
Solution Approach 1:
The beam splitter is segmented into distinct functional regions: optoelectronics-side ports for light input/output, a sensing-side port for the measurement path, and a recess for the quarter-wave retarder. This segmentation allows each component to perform its function independently without temperature-dependent stress affecting the overall measurement precision
Solution Approach 2:
The quarter-wave retarder acts as an intermediary element placed in the optical path between the beam splitter and the sensing fiber. It introduces the required 90° phase bias between orthogonal polarization modes without being subject to temperature-dependent stress, thereby maintaining measurement precision while keeping the integrated-optics design simple
3Ease of manufacture
If ports are aligned in conventional design, then manufacturing is easier, but stray light recoupling causes signal instability
Solution Approach 1:
The beam splitter is designed with asymmetric port positioning where the sensing-side port is offset from the optoelectronics-side ports. This asymmetric geometry prevents stray light generated at the optoelectronics ports from recoupling into the sensing port, thereby eliminating signal instability while maintaining measurement precision across extended temperature ranges
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 effectively reduces signal instability and temperature-dependent stress, achieving accuracy within ±0.2% over a temperature range of −40°C to 85°C, enabling metering class accuracy without the need for temperature control.
Implementation Method 1
Light entering the optoelectronics-side entry port is coupled at least partially into the sensing-side port, and light entering the sensing-side port is split at least partially into the optoelectronics-side exit ports
Implementation Method 2
A sensing element whose (e.g. circular and/or linear) birefringence changes as a function of a measurand
Implementation Method 3
The retarder 10 converts the orthogonal linearly polarized light waves exiting from the PMF into left and right circularly polarized waves
Implementation Method 4
The magnetic field of the current introduces a differential phase shift between left and right circularly polarized light waves propagating through the fiber
Data Source
AI summary
The optical interferometric sensor device comprises an integrated beam splitter having a first facet and a second facet with optical ports arranged therein. On the beam splitter, the beam splitting junctions as well as the optoelectronics-side ports and the sensing-side port are arranged with a mutual displacement along the direction of the first facet. This displacement reduces undesired interference effects caused by stray light. Also, a quarter-wave retarder is provided in a recess of the beam splitter with layers of soft adhesive adjacent to it in order to reduce stress.