Industry Insights

Testing 400G Coherent Optical Components and Transceivers

2019-08-23  |  4 min read 

In telecommunications and data communications, it is important to optimize coherent optical transmitters for reach, spectral efficiency, and power consumption. Performing common measurements, such as error vector magnitude (EVM), IQ offset, IQ imbalance, quadrature error, and skews is complex in coherent optical signal analysis. To thoroughly test an optical transmitter, it is necessary to stimulate it with complex waveforms using different modulation formats and data sources. It is also important to de-skew and pre-distort input signals to account for any linear impairments in the test setup and measure the true performance of the optical transmitter. A flexible and scalable test solution, comprised of an arbitrary waveform generator (AWG) and an optical modulation analyzer (OMA), ensures fast and accurate testing of optical transceivers.

Testing 400G coherent optical transceivers and its sub-components requires test equipment capable of clean signal generation and analysis. The test equipment also requires a measurement bandwidth of at least 40 GHz. Both the stimulus and analysis side need many different modulation schemes and pulse shapes on four synchronized channels for dual-polarization in-phase and quadrature (IQ) signals. This is provided by instruments based on high-speed digital-to-analog converters (DAC) and analog-to-digital converters (ADC). Software tools that provide a comprehensive set of general-purpose algorithms, including interfaces to work with self-developed specialized algorithms, increase test efficiency.

Coherent Optics Device Test

Optoelectrical components used in coherent optical transmission systems have unique test challenges. For example, to test dual-polarization IQ modulators and intradyne coherent receivers, it is necessary to measure the electrical-to-optical (E/O) and optical-to-electrical (O/E) conversion efficiency, respectively. Characterizing coherent optical devices requires measurements such as bandwidth, gain, imbalances, group delay, and skew. These measurements are complex and time-consuming. Selecting the right test equipment saves valuable time and reduces costs for the development and qualification of coherent optical devices.

For component and device manufacturers, testing is a significant challenge. High-speed silicon that drives the optical transceivers lags the optics by about a year. Test equipment that can generate and analyze 16-QAM 64 Gbaud signals with optical impairments enables manufacturers to test their components and devices for terabit applications today.

Learn how Keysight’s solutions can help you address your optical and photonic test challenges:

• Understand how integrated photonics and new standards drive next-generation DCI, read the white paper Coherent Optical Transforms Data Center Interconnects

• Discover how to accurately and efficiently test your transceivers so you can design the next generation of high-speed interconnects visit Optics and Photonics solutions