Test and measurement provider ID Photonics has expanded its product range with a new type of automatic bias control (ABC) for complex multi-level coherent optical signals, jointly developed with Fraunhofer Heinrich-Hertz-Institute.
Unlike other products on the market, the bias control is independent of the applied RF signal (constellation), requires no manual tuning for optimal results and features a zero-noise mode for reference measurements, the company claims.
"The industry is currently advancing from standard 100G DP-QPSK technology to modulation formats such as QAM-16 that require multi-level coding," said David Stahl, general manager of ID Photonics. "This step opens up the possibility to flexibly implement a large variety of potential formats and flavours, which all need to be evaluated and selected for network and system designs. A test solution that generates a multitude of optical transmitter signals in a stable and format-independent way is required to help researchers and developers addressing this challenge."
The product is available as a turnkey integrated electro-optic converter instrument that connects to arbitrary waveform generators. Alternatively, a standalone ABC board provides an option for customers who want to build a customised Mach Zehnder modulator device but require a best-in-class automatic bias control feature.
Although AWG instruments are readily available to generate the electrical drive signals, electro-optic converters suffer from inherent drift of the optimal operating point versus time that needs to be compensated. This task is performed by automated bias control circuits via control feedback signals generated in the electro-optic converter.
To control IQ modulators used in coherent optical systems, other products tap the RF components present in the modulated data signal as a feedback signal source. Naturally, this causes a strong dependency on modulation format and test data pattern applied. Thus, control instability is a significant issue and manual adjustment is often required. The new bias controller eliminates all these issues with an RF-signal-independent design.
The bias control portfolio will be on display at the OFC 2015 exhibition, 24-26 March, in Los Angeles, booth #1113.