Automated bias control for IQ-Mach Zehnder structures unveiled by ID Photonics

Test and measurement technology developer ID Photonics now offers what it describes as a new type of automatic bias control for complex multi-level signals such as 16QAM. The control offering, jointly developed with Fraunhofer Heinrich-Hertz-Institute, is independent of the applied RF signal (constellation), requires no manual tuning, and features a zero noise mode for reference measurements, according to the company.

ID Photonics will offer the capability packaged in a fully integrated high-end E/O converter instrument that connects to arbitrary waveform generators (AWG). It also will be available as a standalone board for engineers looking to build a customized RF chain and Mach Zehnder modulator device and require an automatic bias control feature.

The company foresees a demand for the product in light of the interest in coherent transmission modulation formats such as 16QAM that require multi-level coding. Evaluating designs using such formats requires a test setup that can create a variety of optical transmitter signals in a stable and format-independent way.

"While arbitrary waveform generator instruments are readily available to generate the electrical drive signals, E/O converters suffer from inherent drift of the optimal operating point versus time that needs to be compensated for," explains David Stahl, general manager of ID Photonics. "This task is performed by automated bias control circuits utilizing control feedback signals generated in the E/O converter.

"For IQ modulators used in advanced systems, previously available solutions tap RF components present from the modulated data signal as a feedback signal source," Stahl continues. "Naturally, this causes a strong dependency on modulation format and test data pattern applied. Thus, instability of the control is a big issue and manual tweaking for each case is required. Our new automated bias control eliminates all these issues by an inherently RF signal independent design providing a best-in-class minimal penalty automated bias control."

ID Photonics will display the new bias control portfolio during OFC March 24-26 in booth #1113.

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