Optical Modulation Analyzers In-depth analysis of complex coherent optical signals

The Keysight N4391C optical modulation analyzer (OMA) enables development of the coherent technologies required to advance performance in modern communication systems, such as those found in and connecting data centers. It consists of a Keysight UXR real-time oscilloscope and a calibrated coherent optical receiver. The N4391C builds on the UXR Series oscilloscope’s industry-leading noise and bandwidth performance and Keysight’s reliable and flexible vector signal analysis (VSA) software.

The most compact OMA solution of its class, the N4391C solves your coherent measurement problems, simplifies your test equipment decision, and protects your investment. It provides independent bandwidth choice for optical measurements using its own coherent receiver and electrical measurements directly at the oscilloscope's ports.

Complex modulated signals are common in long-distance transmission across dense wavelength division multiplexing links. However, newly proposed technologies for intra-data center interconnections use the coherent approach in the O-band, addressing higher data throughput with reduced power consumption. Keysight now provides OMA-coherent receivers for the O-band in addition to coherent receivers that work in the C-band and L-band.

Applications

The demand for higher transmission capability is pushing systems from 64 Gbaud to a proposed 124 Gbaud and even 200 Gbaud. The Keysight N4391C helps you keep pace with the demand for test equipment that can handle the symbol rate classes of transceivers for 800 Gb/s, 1.2 Tb/s, and 1.6 Tb/s, from early advanced research through the development phase.

Not only are symbol rates challenging, but modulation formats are getting more demanding because of higher-order quadrature amplitude modulation, which requires a step up in noise performance. The UXR oscilloscope’s industry-leading effective number of bits (ENOB) performance of 5.4 enables the N4391C to meet this challenge.

The Keysight N4391C provides operating bandwidth up to 110 GHz and myriad options for selecting modulation formats. Options include support for user-defined modulation formats, all at a high ENOB at the highest bandwidths.

Select from Two Frequency Bands

The N4391C comes in two configurations based on the connector type of the UXR oscilloscope: 1.85 mm and 1.0 mm. In either case, the optical coherent receiver has the same connector type as the oscilloscope. It possess internal hardware appropriate for the band, as well as calibration for the full band. It offers factory calibration to 70 GHz for C-band and O-band variants in the 1.85 mm configuration and 110 GHz in the 1.0 mm configuration. The OMA is field upgradable to maximum frequency.

A new feature in the N4391C OMA offering is independent and upgradable optical and electrical bandwidth licensing for the oscilloscope and the OMA itself. This scheme recognizes that the oscilloscope works in two use modes: as part of the OMA system where optical bandwidth is necessary and in standalone oscilloscope operation (optical coherent receiver disconnected) where electrical bandwidth is key. Because the modes are independent, you can enable what your teams need when they need it.

Each of the N4391C's configurations is upgradable to higher bandwidths for both electrical and optical use models. Configurations based on the 1.85 mm connector can be 40 GHz, 50 GHz, 59 GHz, or 70 GHz, upgradable in these steps to a maximum of 70 GHz. Configurations based on the 1.0 mm connector can be 40 GHz, 59 GHz, 70 GHz, 80 GHz, 100 GHz, or 110 GHz, upgradable in these steps to the maximum 110 GHz.