Integrated Photonics

Integrated Photonics Test

Silicon Photonics - Efficient Wafer Level Test

Integrated Photonics, often called Silicon Photonics, promises additional benefits for industrial segments such as Intra Data Center communication and Data Center Interconnects (DCI), Telecom, 5G and Automotive connectivity, High Performance Computing, LIDAR, Sensing and Medical. Notably, optical components for the data center infrastructure design margins and low energy consumption targets are getting under pressure with higher data rates. This adds various forms of device integration.

• Integrated photonics technologies emerge to integrate various optical components, to scale parallel optical channels
• Photonic Integrated Circuit (PIC) technology is a foundation to integrate and co-package electrical silicon devices with optical components
• Chip makers move to selling dies (instead of packaged devices) that are further integrated into multi-die designs
• Opportunities arise to qualify known-good dies
• In the long-term, device integration can lead to a lack of access to devices for test purposes. New ways of testing multi-die and integrated devices need to be developed

Integrated Photonics Test Solution Combining Measurement

Keysight provides test solutions for silicon photonics wafer test:

• With wavelength and polarization dependent measurements with 81606A tunable laser source, N7786B polarization synthesizer, N7745A multiport power meter, and B2902A source measurement unit with N7700A application software
• RF tests with Keysight N4373E Lightwave Component Analyzer
• Wafer probing with FormFactor CM300xi probe station

Keysight’s Photonic Test Solution integrated with PathWave Test driver plugins for instrument and wafer probe control enables.

• Optical to optical and optical to electrical device test
• RF O/E and E/O measurements up to 67 GHz and beyond
• Software plugin with Keysight PathWave Tests for integration on T&M engines
• Automated probe station with FormFactor CM300xi
• Integrated & automated test flow

Swept-Wavelength

Optical Measurement Solutions Tunable laser instruments are used for spectral measurements of optical components and materials. The wavelength dependence is rapidly determined with selectable and very high wavelength resolution. The measurement systems can be flexibly configured to match the requirements of the application. Here we suggest some examples.

Insertion loss measurement (IL)

Combining one or more optical power meters with the tunable laser source (TLS) permits measurement of optical power vs. wavelength. Often this is used to find the ratio of power at the input of a component to the output power, commonly called insertion loss and expressed in dB. While the TLS tunes the wavelength over the chosen range, the power meters periodically sample the power for the desired number of measurement points. These samples are synchronized with the TLS sweep by a trigger signal for accurate association with the corresponding wavelength. Use of multiple power meters allows simultaneous measurement of outputs from multiport components like multiplexers, splitters and wavelength switches. Reflection spectra (return loss) can also be measured, by adding the 81610A return loss module. A setup can combine the 81606A, 81607A or 81608A TLS with power meters from the 816x-series modules or the N774x-series multiport power meters and the free N7700 IL software. Faster sweep speeds, sampling rate and scan repetition are achieved using the N7700 FSIL software option.

Performance considerations

 High wavelength accuracy and repeatability, particularly during fast wavelength scans, is assured with the built-in wavelength monitoring in these laser sources. These “lambda-logging” data are synchronized with the measurement triggers to the power meters. For highest absolute and relative wavelength accuracy the monitor is calibrated with a built-in gas cell reference and uses fast sampling to support the high sweep speeds. InGaAs power detectors are best for such measurements due to the small variation in responsivity over the single-mode fiber wavelength range (1260 to 1630 nm), the high sensitivity and dynamic range. The N7744A and N7745A power meters are especially well adapted to these swept-wavelength measurements with fast sampling rates and high signal bandwidth that allow high-resolution measurements at high sweep speeds without distortion of the measurement trace.