Keysight N4391B Optical Modulation Analyzer (OMA)


September 18, 2018

  1. Introduction
  2. Customer Problem
  3. How does Keysight solution solve this problem?
  4. Key Features
  5. Additional Information/Images
  6. Related Information

The Keysight N4391B is the next generation optical modulation analyzer (OMA) based on the UXR-Series Infiniium oscilloscopes. It is a compact real-time oscilloscope-based OMA solution which combines industry-leading noise performance and bandwidth with Keysight’s reliable and flexible vector signal analysis (VSA) software.

Customer Problem

Transmitting ever-increasing amounts of information through optical channels has driven the rapid rise of coherent transmission, as well as the need to generate and analyze complex modulated optical signals. The demand for transmission capacity is driving symbol rates to 64 and 100 GBaud. Handling this continual increase in symbol rates requires tools that can address transceiver speed classes of 600 Gbit/s to terabit per second, from advanced research through product development.

Higher-order quadrature amplitude modulation (QAM) formats and techniques, like probabilistic shaping, also place greater demands on test equipment due to required low-noise performance. Designers need detailed insights into complex modulated optical signals at the physical layer to determine signal quality and identify sources of impairment. This is also true for evaluating components that are designed for IQ modulation and demodulation.

How does Keysight solution solve this problem?

The Keysight N4391B optical modulation analyzer, based on the UXR-Series Infiniium oscilloscopes, is uniquely positioned to support these demanding application requirements. The industry leading effective number of bits (ENOB) at operating bandwidths up to 110 GHz, combined with multiple options for pre- or user-defined modulation formats, provide a fully integrated solution specifically designed for these complex challenges.

The N4391B is a compact real-time oscilloscope-based OMA solution, combining four channels up to 110 GHz at full analog bandwidth in a single oscilloscope that is mounted on an optical coherent receiver. The optical coherent receiver has been improved to reach up to 110 GHz through the latest photodiode technology. A 70 GHz version is also available. Each optical coherent receiver integrates an internal tunable narrow-linewidth laser as a local oscillator (LO), inputs and outputs for the LO signal, and a calibrated optical power meter to monitor the input signal power.

Compared to the time-consuming and resource-intensive implementation of a home-grown optical modulation analysis solution, the integrated N4391B provides a fully specified, reliable, and repeatable turn-key test instrument that enables designers to quickly deliver their innovation to the market.

Key Features
  • Industry leading ENOB at bandwidths up to 110 GHz
  • Four channels at full analog bandwidth in one scope frame
  • No synchronization via external cabling required
  • 25 fs (rms) of intrinsic jitter and less than 10 fs of additional inter-channel intrinsic jitter
  • Upgrade options available for lower bandwidth and legacy systems protect customers’ investments

Additional Information/Images
N4391B, OMA, optical modulation analyzer

Keysight N4391B Optical Modulation Analyzer

64 QAM, 64 GBd, optical signal analysis

64 QAM / 64 GBd Optical Signal Analysis

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About Keysight Technologies

Keysight Technologies, Inc. (NYSE: KEYS) is a leading technology company that helps enterprises, service providers, and governments accelerate innovation to connect and secure the world.  Keysight's solutions optimize networks and bring electronic products to market faster and at a lower cost with offerings from design simulation, to prototype validation, to manufacturing test, to optimization in networks and cloud environments. Customers span the worldwide communications ecosystem, aerospace and defense, automotive, energy, semiconductor and general electronics end markets. Keysight generated revenues of $3.2B in fiscal year 2017. In April 2017, Keysight acquired Ixia, a leader in network test, visibility, and security. More information is available at

Related Information

Geri Lynne LaCombe, Americas
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Magda Antone, Europe
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