Optical Imaging for Waveguide Inspection via OFDM
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Solution Overview
Problem
Current methods for testing optical devices like planar waveguides are inefficient as they cannot accurately determine the location and amount of light loss, leading to wasted resources and time, especially since they require physical dissection and cannot differentiate between light in the waveguide and cladding modes.
Innovation Solution
An optical imaging apparatus using Optical Frequency Domain Measurement (OFDM) technology that collects scatter data at multiple locations along the device under test (DUT) over time, allowing for fine time resolution and detection of small amounts of scatter, enabling accurate detection of light loss and propagation through the device without physical dissection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional testing methods are used to test optical devices, then the testing process is simple, but the ability to accurately determine the location and amount of light loss is poor
Solution Approach 1:
The patent segments the optical device into multiple discrete locations along its length, testing each location independently. By dividing the waveguide into N distinct measurement points, the system can identify specific locations of light loss rather than providing only a overall loss measurement, thereby improving measurement precision without requiring overly complex equipment
Solution Approach 2:
The patent introduces an intermediary testing system that includes a light source, detector, and control unit. This intermediary system mediates between the optical device and the measurement process, enabling precise detection of light loss at multiple locations through controlled light injection and detection, while keeping the actual device under test relatively simple
2Productivity
If physical dissection is used to test optical devices, then the testing process is straightforward, but time and resources are wasted
Solution Approach 1:
The patent performs preliminary testing on optical devices before final assembly or deployment. By testing the device at multiple locations while it remains intact, the system can identify defects early in the process, preventing wasted time and resources on devices that would fail anyway. This preliminary action eliminates the need for physical dissection and reassembly
Solution Approach 2:
The patent replaces mechanical testing methods (physical dissection, manual inspection) with an optical-based testing system. The light source and detector system substitutes for mechanical probing, enabling non-contact, non-invasive measurement of light loss at multiple locations simultaneously, thereby dramatically improving productivity and reducing testing time
3Loss of information
If traditional testing methods are used, then the testing process is simple, but the ability to differentiate between waveguide and cladding mode light is poor
Solution Approach 1:
The patent applies local quality by making the testing capability location-specific. The system can selectively test and differentiate light modes at each of the N locations along the optical device. This localized measurement approach provides detailed information about waveguide versus cladding mode light at specific positions without requiring overly complex system-wide modifications
Solution Approach 2:
The patent adds a spatial dimension to the testing process by measuring light loss at multiple locations along the device length. This dimensional expansion transforms a single-point measurement system into a distributed measurement system, enabling differentiation of light modes across the entire device without proportionally increasing system complexity
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
Enables precise detection of light loss and propagation characteristics within optical devices, allowing for rapid identification of problem areas and reducing waste by testing entire wafers of planar waveguides without dicing, with the ability to distinguish between waveguide and cladding mode light.
Implementation Method 1
A light source provides light that is coupled into a device under test (DUT)
Implementation Method 2
which scatters light out of the device at one or more locations along the DUT
Implementation Method 3
A light detector detects a portion of light scattered at each of multiple locations along the DUT
Implementation Method 4
Data is determined using OFDM data processing that corresponds to an amount of light collected at each of the multiple locations along the DUT as a function of time
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
An optical imaging apparatus based on optical frequency domain measurement (OFDM) collects scatter data at multiple locations within or on the DUT as a function of time. A light source launches light into a device under test (DUT) which scatters light at one or more locations along the DUT. A light detector detects a portion of light scattered at each of multiple locations along the DUT. Data is determined using OFDM data processing that corresponds to an amount of light collected at each of the multiple locations along the DUT as a function of time. The data is stored for each of the multiple locations along the DUT. User information is provided that indicates an amount of light scattered at each of the multiple locations along the DUT based on the stored time domain data. The OFDM processing permits fine time resolution (e.g., 0.1 picoseconds) that allows small optical delay distances (e.g., 30 microns) to be resolved and allows for accurate detection of small amounts of scatter (e.g., one trillionth) to be detected simultaneously with the fine time resolution.